We investigate slow magneto-acoustic waves that are naturally excited by turbulent convection and investigate their role in the energy balance of a plage region using three dimensional (3D) radiation-MHD simulations. To study slow magneto-acoustic waves traveling along the magnetic field lines, we track 25 magnetic field lines both in space and time inside a strong magnetic element. We calculate velocity component parallel to the background field and compute the temporal power spectra at various heights above the mean solar surface. Additionally, horizontally averaged power spectra for both longitudinal (parallel to the background magnetic field) and vertical (i.e. the component perpendicular to the surface) components of velocity are calculated using time-series at fixed locations. We also degrade our simulation data to compare our results with observations. The velocity power spectra, averaged horizontally over the whole domain, show that low frequency waves may reach into the chromosphere possibly along the inclined magnetic field lines. In addition, the power spectra at high frequencies follow a power law with an exponent close to -5/3, suggestive of turbulent excitation. The horizontally averaged power spectra of vertical component of velocity at various effective resolutions show that the observed acoustic wave energy fluxes are underestimated, by a factor of three even if determined from observations carried out at a high spatial resolution of 100 km. Since the waves propagate along the non-vertical field lines, measuring the velocity component along the line-of-sight, rather than along the field contributes significantly to this underestimate. Moreover, this underestimation of energy flux indirectly indicates the importance of high-frequency waves that have a smaller spatial coherence and are thus more influenced by spatial averaging effect compared to low-frequency waves. Our results show that, in contrast to claims made in the literature, longitudinal waves within magnetic elements carry sufficient energy to heat the chromosphere.

Small-scale coherent vortical motions are ubiquitous in the photosphere. The complex dynamics between vortical flows and magnetic elements are linked to many solar events, e.g. jets and wave generation. One important magnetic structure expected to be driven by atmospheric rotational motions is the twisted magnetic flux tube. In this work, the twisted magnetic flux is defined as a new typology of a solar vortex. We applied forefront methodologies to detect the kinetic and magnetic vortices tubes in realistic magnetoconvection simulations. Both types of vortices are found in the intergranular downflow; magnetic vortices appear mostly in flow shear areas where plasma beta greater than one, whereas the kinetic vortices were detected in low plasma-beta regions. The solar vortices tend to concentrate the magnetic field locally, presenting similar dynamics at different solar atmosphere levels. Based on their plasma magnetic and kinetic energy ratio, we find two distinct magnetic vortex types with different geometries for the magnetic field lines. The kinetic vortices show upward jets and tend to encompass high magnetic fluxes; thereby, their dynamics is mainly dominated by magnetic forces. Due to the high magnetic tension, the vortical motion can only perturb the magnetic lines, and therefore the kinetic vortices are incapable of twisting the magnetic flux tube. We find that the magnetic vortices are created regardless of the existence of vortical motions.

The recent rediscovery of magnetic switchbacks by Parker Solar Probe has led to a strong interest about their origin and nature. In-situ measurements and analysis suggest a lower coronal origin and an Alfvénic nature. Through magnetohydrodynamic (MHD) numerical simulations, we test whether this scenario of switchback origins is plausible. We find that, in contrast to a relatively stable propagation of switchbacks in a uniform medium without gravity, the presence of a gravitationally stratified medium significantly impacts the stability of highly kinked switchbacks. We suggest that switchbacks generated in the deep corona are unlikely to survive out into the solar wind.

It is well accepted that resonant absorption plays an important role in the dynamics of collective modes in solar waveguides. Taking the much-studied kink modes in coronal loops as an example, we perform an examination on resonant absorption from the energetics perspective, the aim being to shed more light on the interplay between the compressional and magnetic energies. We start with a well-established energy conservation law governing arbitrary time-dependent Eulerian perturbations in linear, ideal, finite-beta, gravity-free MHD, where a source term is involved when the equilibrium magnetic field is non-potential. We then specialize to resonantly damped kink modes in a canonical equilibrium configuration, in which coronal loops are seen as straight cylinders and the inhomogeneity is restricted to a transition layer bordering the cylinder. With three-dimensional time-dependent simulations and subsequent eigen-mode computations, we first demonstrate that this source term tends to be non-negligible even when the equilibrium magnetic field deviates only slightly from a potential one. Furthermore, in the inhomogeneous layer, the wave energies tend to be dominated by the magnetic and compressional ones. However, when re-evaluated with the Lagrangian perturbations, the compressional energy becomes negligible unless in the resonant layer. This switch from the Eulerian to the Lagrangian perspective also helps reconcile two apparently competing interpretations for the source term, converging to the notion that the interaction between the equilibrium and the perturbations results effectively in the exchange between the magnetic and compressional energies. Our results are discussed in the context of future spectroscopic measurements capable of resolving the fine-scales resulting from resonant absorption.

Within the last decade, solar physics has moved into a golden era of discovery. A diverse assortment of ground- and space-based facilities, coupled with modern modelling efforts, has helped make rapid progress in the detection, identification, characterisation and understanding of dynamic motions spanning the photosphere through to the corona. Here I will discuss recent wave phenomena detected and benchmarked using an assortment of instruments at the Dunn Solar Telescope in New Mexico, USA. In particular, I will reveal wave activity captured by the Fabry-Pérot IBIS instrument, in addition to the high-cadence ROSA imaging suite. I will highlight the challenges presented when examining these features across a range of atmospheric heights, structural sizes, and ionisation states, before looking towards the future with upcoming next-generation hardware and facilities.  

A generalised model for MHD wave propagation in solar structures is, as of yet, not available. Realistic theoretical models of different possible equilibria are required to better explain the ever increasing number of detailed observations thanks to modern high resolution instruments. This allows magnetoseismology to be conducted and provides more accurate information about local plasma properties. In this work, an innovative numerical approach using classical techniques allows the dispersion diagram and eigenfunctions to be obtained for any arbitrarily-symmetric inhomogeneous equilibrium. The analytic dispersion relation is not required, therefore advancing previous studies which are restricted to analytical investigations. This proposed technique implements the shooting method to match necessary boundary conditions on continuity of displacement and total pressure of the waveguide.  As is the case with any new algorithm, the approach is tested against well-known analytical results for MHD waves in uniform slab. This work is then extended by investigating the behaviour of the dispersion diagrams and wave mode eigenfunctions when the equilibrium plasma density is inhomogeneous and modelled in the form of Gaussian and trigonometric spatial profiles. A further extension investigates the effect that a non-uniform background flow has on the properties of the wave modes. The resulting eigenfunctions of perturbed total pressure and displacement in an inhomogeneous plasma are compared with the uniform model and the physical differences are discussed which have implications for observers.

Using 3D MHD simulations, we study the heating effects and the synthetic emissions of transverse oscillation in coronal loops with the presence of radiative cooling. The coronal loop is driven at the footpoint by transverse oscillations, and subsequently the induced Kelvin–Helmholtz instability deforms the loop cross section and generates small-scale structures. Wave energy is transferred to smaller scales where it is dissipated. We find that the heating effects by transverse oscillations are promising balancing the radiative loss. We then transform the simulated straight loop to a semi-torus loop and forward-model the spectrometer and imaging emissions, mimicking the observations of Hinode/EIS and SDO/AIA. We find that the oscillation amplitudes of intensity are different at different slit positions, but the oscillation amplitudes from different spectral lines or channels are almost the same. We also find that the observed Doppler velocities are one order of magnitude smaller than real oscillation velocities in our model due to large column depth. These results are helpful for further understanding the heating effects of transverse oscillations in coronal loops and their observational signatures.

Using the three-dimensional Versatile Electron Radiation Belt (VERB-3D) code, we perform simulations to investigate the dynamic evolution of relativistic electrons in the Earth’s outer radiation belt. In our simulations, we use data from the Geostationary Operational Environmental Satellites to set up the outer boundary condition, which is the only data input for simulations. The magnetopause shadowing effect is included by using last closed drift shell, and it is shown to significantly contribute to the dropouts of relativistic electrons at high L*. We validate our simulation results against measurements from Van Allen Probes. In long-term simulations, we test how the latitudinal dependence of chorus waves can affect the dynamics of the radiation belt electrons. Results show that the variability of chorus waves at high latitudes is critical for modeling of megaelectron volt (MeV) electrons. We show that, depending on the latitudinal distribution of chorus waves under different geomagnetic conditions, they cannot only produce a net acceleration but also a net loss of MeV electrons. Decrease in high‐latitude chorus waves can tip the balance between acceleration and loss toward acceleration, or alternatively, the increase in high‐latitude waves can result in a net loss of MeV electrons. Variations in high‐latitude chorus may account for some of the variability of MeV electrons. We also calculated lifetime using the diffusion coefficients including the effect of high-latitude chorus waves.We also perform simulations for the COSPAR International Space Weather Action Team Challenge for the year 2017.  We ‘fly’ a virtual satellite through our simulation results and compare the simulated differential electron fluxes at 0.9 MeV and 57.27 degrees local pitch-angle with the fluxes measured by the Van Allen Probes. In general, our simulation results show good agreement with observations. We calculated several different matrices to validate our simulation results against satellite observations. 

We show that sub-relativistic/relativistic electron microbursts form the high‐energy tail of pulsating aurora (PsA). Whistler‐mode chorus waves that propagate along
the magnetic field lines at high latitudes cause precipitation bursts of electrons with a wide energy range from a few keV to MeV. The rising tone elements of chorus waves cause individual microbursts of subrelativistic/relativistic electrons and the internal modulation of PsA. The chorus bursts for a few seconds cause the microburst trains of subrelativistic/relativistic electrons and the main pulsations of PsA. Our simulation studies demonstrate that both PsA and relativistic electron microbursts originate simultaneously from pitch angle scattering by chorus wave‐particle interactions along the field line.

The two Van Allen Probes simultaneously recorded a coherently modulated quasiperiodic (QP) emission that persisted for 3 hours. The magnetic field pulsation at the locations of the two satellites showed a substantial difference, and their frequencies were close to but did not exactly match the repetition frequency of QP emissions for most of the time, suggesting that those coherent QP emissions probably originated from a common source, which then propagated over a broad area in the magnetosphere. The QP emissions were amplified by local anisotropic electron distributions, and their large-scale amplitudes were modulated by the plasma density. A novel observation of this event is that chorus waves at frequencies above QP emissions exhibit a strong correlation with QP emissions. Those chorus waves intensified when the QP emissions reach their peak frequency. This indicates that embryonic QP emissions may be critical for its own intensification as well as chorus waves under certain circumstances. The low-earth-orbit POES satellite observed enhanced energetic electron precipitation in conjunction with the Van Allen Probes, providing direct evidence that QP emissions precipitate energetic electrons into the atmosphere. This scenario is quantitatively confirmed by our quasilinear diffusion simulation results.

Loss mechanisms act independently or in unison to drive rapid loss of electrons in the radiation belts. Electrons may be lost by precipitation into the Earth’s atmosphere, or through the magnetopause into interplanetary space. Whilst this magnetopause shadowing is well understood to produce dropouts in electron flux, it is less clear if shadowing continues to remove particles in tandem with electron acceleration processes, limiting the overall flux increase. We investigate the contribution of shadowing to overall radiation belt fluxes throughout a geomagnetic storm. We use new, multi-spacecraft phase space density calculations to decipher electron dynamics during each storm phase and identify features of magnetopause shadowing during both the net-loss and the net-acceleration storm phases. We also highlight two distinct types of shadowing; 'indirect', where electrons are lost through ULF wave driven radial transport towards the magnetopause boundary, and 'direct', where electrons are lost as their orbit intersects the magnetopause.

Oblique whistler mode waves are observed frequently in dayside and dawnside of the Earth’s magnetosphere around the outer radiation belt. Through the nonlinear trapping, by coherent chorus waves, energetic resonant electrons (tens keV) can be accelerated rapidly and become relativistic electrons (a few MeV). Electron acceleration of velocity perpendicular to the background magnetic field of resonant electrons plays an essential role in both cyclotron and Landau resonances. Green’s functions are treated as the results of wave-particle interactions between the target waves and the given electrons. We build up a database of Green’s functions for a great number of electrons interacting with oblique whistler mode chorus emissions. The formation processes of the outer radiation belt electron fluxes interacting with consecutive chorus emissions are traced by applying the convolution integrals for the Green’s functions. We trace the evolution of the radiation belt electron fluxes for a few minutes and find that MeV electrons are generated promptly due to the combination of cyclotron resonance and Landau resonance with oblique chorus waves. We compare the formation processes among waves with different wave normal angles, and the results show that chorus waves with larger wave normal angles can accelerate 10-30 keV electrons to MeV faster. We further compare the precipitation fluxes between parallel and oblique chorus emissions. Our simulation result reveals that oblique chorus emissions lead to more electron precipitation than parallel chorus emissions. Multiple resonances effect in the oblique whistler mode wave-particle interactions is the reason for the greater precipitation.

Suprathermal electrons (~0.1-10 keV) in the inner magnetosphere are usually observed in a 90°-peaked pitch angle distribution, formed due to the conservation of the first and second adiabatic invariants as they are transported from the plasma sheet. We report a peculiar field-aligned suprathermal electron (FASE) distribution measured by Van Allen Probes, where parallel fluxes are one order of magnitude higher than perpendicular fluxes. Those FASEs are found to be closely correlated with large-amplitude hiss waves, and are observed around the Landau resonant energies. We demonstrate, using quasilinear diffusion simulations, that hiss waves can rapidly accelerate suprathermal electrons through Landau resonance, and create the observed FASE population. The proposed mechanism potentially has broad implications for suprathermal electron dynamics as well as whistler mode waves in the Earth’s magnetosphere, and has been demonstrated in the Jovian magnetosphere.

The triggering process of whistler-mode rising-tone emissions such as chorus in the Earth’s magnetosphere is studied by one-dimensional electromagnetic simulations [1]. We assume a parabolic magnetic field and energetic electrons forming an anisotropic subtracted bi-Maxwellian momentum distribution function. We inject a large amplitude triggering waves at the magnetic equator by oscillating currents with a constant frequency 0.3 of the electron cyclotron frequency externally. By separating forward and backward waves based on the spatial helicity of the whistler-mode waves, we find that the generation region of triggered rising-tone emissions moves upstream of the triggering waves as a self-sustaining process. Being separated from the triggering wave with a constant frequency, a series of triggered wave packets are formed with frequencies gradually increasing from 0.3 to 0.75 of the electron cyclotron frequency. The wave growth of the first triggered wave packet is smooth over the frequency range 0.3-0.5 of the electron cyclotron frequency. Subsequently, the triggered wave packets with short durations are observed with the frequency range 0.5-0.7 of the electron cyclotron frequency. We observe formation of electron holes in the spatial range with the inhomogeneity factor |S| less than 1. The electron hole position continuously moves to smaller absolute values of parallel velocity in velocity phase space, resulting in smooth wave growth and frequency increase in the first triggered wave packet. When a modulation of the first subpacket with a short duration appears in the wave amplitude, some density modulations of the untrapped resonant electrons are observed around the electron holes. Those density modulations cause fluctuations of the resonant current, which enhance the formation of subpackets in space and time. [1] T. Nogi, S. Nakamura, and Y. Omura, “Full particle simulation of whistler‐mode triggered falling‐tone emissions in the magnetosphere”, Journal of Geophysical Research: Space Physics, 125, e2020JA027953, 2020.

In order to analyze the large volume of wave data returned from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) investigation on NASA’s Van Allen Probes, we have developed computational methods to find key characteristics of waves in the Earth’s inner magnetosphere. Using novel signal processing techniques, we have developed autonomous algorithms that can analyze Van Allen Probes waveform observations to determine the characteristics of individual chorus elements. In particular, the methods allow us to determine each individual chorus element as a function of frequency and time. With this characterization, we can derive the frequency/time sweep rate of chorus elements for a large number of events without the need for manual identification of the elements. This enables statistical studies of the properties of the individual chorus elements which has been limited in the past to small numbers of events identified and analyzed by hand. We present the basics of the automated detection technique, describing its current state of evolution as well performance metrics. We also show results of the statistics on the range and character of chorus element sweep rate. In addition we show how chorus power varies with radial position, magnetic latitude, and magnetic local time as well the relation between chorus power and sweep

Dynamical jets are generally found on light bridges (LBs), which are key to studying sunspot decay. So far, their formation mechanism is not fully understood. In this paper, we used state-of-the-art observations from the Goode Solar Telescope, the Interface Region Imaging Spectrograph, the Spectro-polarimeter on board Hinode, and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory to analyze the fan-shaped jets on LBs in detail. A continuous upward motion of the jets in the ascending phase is found from the Hα velocity that lasts for 12 minutes and is associated with the Hα line wing enhancements. Two mini jets appear on the bright fronts of the fan-shaped jets visible in the AIA 171 and 193 Å channels, with a time interval as short as 1 minute. Two kinds of small-scale convective motions are identified in the photospheric images, along with the Hα line wing enhancements. One seems to be associated with the formation of a new convection cell, and the other manifests as the motion of a dark lane passing through the convection cell. The finding of three-lobe Stokes V profiles and their inversion with the NICOLE code indicate that there are magnetic field lines with opposite polarities in LBs. From the Hα -0.8 Å images, we found ribbon-like brightenings propagating along the LBs, possibly indicating slipping reconnection. Our observation supports the idea that the fan-shaped jets under study are caused by magnetic reconnection, and photospheric convective motions play an important role in triggering the magnetic reconnection.

On 25 June 2015, two kinds of chromospheric jets, one is a non-periodic fan-shaped surges, and the other is a fibril group, with an oscillation period of about 4.4 minutes, were observed in two light bridges (LBs) of the active region 12371. At the same time, the two LBs have significant but different photo- spheric convective patterns. In LB1, where the surges are intermittently occurring, there are mainly four convective patterns: 1) grains moving uni-directly along or off the axis of LB1; 2) shearing among grains; 3) being compressed central dark lane; 4) paroxysmal clusters of grains, which is first observed. In addi- tion, the appearance of the surges is highly consistent with the duration of the grain clusters. In contrast, the convection in LB2, where the fibril group oscillates, is relatively gentle and mainly consists of off-axis movement of grains. Where the grain off-axis movement is stronger, the corresponding fibril amplitude is higher. Therefore, it suggests that photospheric convection can indicate the type of chromospheric jets to a certain extent. As for the driving mechanisms of two kinds of jets, we think that there should be a twisted magnetic flux tube lying along LB1, a reconnection with the magnetic field of the core in the sunspot occurring when the grain cluster rushing into; and the lifting of the fibrils is driven by the leaking acoustic waves.

Light bridges (LBs) are bright lanes that divide an umbra into multiple parts in some sunspots. Persistent oscillatory bright fronts at a temperature of 10^5 K are commonly observed above LBs in the 1400/1330 A passbands of the Interface Region Imaging Spectrograph (IRIS). Based on IRIS observations, we report small-scale bright blobs from the oscillating bright front above a light bridge. Some of these blobs reveal a clear acceleration, whereas the others do not. The average speed of these blobs projected onto the plane of sky is 71.7 ±14.7 km/s, with an initial acceleration of 1.9 ±1.3 km/s^2. These blobs normally reach a projected distance of 3-7 Mm from their origin sites. From the transition region images we nd an average projected area of 0.57 ± 0.37 Mm^2 for the blobs. The blobs were also detected in multi-passbands of the Solar Dynamics Observatory, but not in the H images. These blobs are likely to be plasma ejections, and we investigate their kinematics and energetics. Through emission measure analyses, the typical temperature and electron density of these blobs are found to be around 10^5.47 K and 10^9.7 /cm^3, respectively. The estimated kinetic and thermal energies are on the order of 10^22.8 erg and 10^23.3 erg, respectively. These small-scale blobs appear to show three dierent types of formation process. They are possibly triggered by induced reconnection or release of enhanced magnetic tension due to interaction of adjacent shocks, local magnetic reconnection between emerging magnetic bipoles on the light bridge and surrounding unipolar umbral elds, and plasma acceleration or instability caused by upward shocks, respectively.

Rapidly evolving fine-scale jets known as spicules are the most prominent and dynamical phenomena observed in the solar chromosphere. At any given instant, around a few million of these spicules shoot plasma material out from the Sun’s surface. It is highly likely that these spicules play a crucial role in key solar physics mysteries, such as chromospheric and coronal heating and mass supply to the solar wind. Despite intensive delving in the past decades, still, there is no clear consensus on how these small-jets of magnetized plasma originate from the solar surface, nor we understand how exactly they transfer energy into and possibly heat the solar atmosphere. The exact source of these small-scale jets is hard to observe due to the resolution limitations of earlier telescopes. Therefore, they remain poorly understood. Using an unprecedented multi-wavelength and high-sensitive magnetic field observations from the 1.6-m Goode Solar Telescope at the Big Bear Solar Observatory, we strive to reach conclusions on the possible scenario among the many proposed hypotheses of spicule’s origin. We found that the dynamical interaction of magnetic fields in the partially ionized lower solar atmosphere is the precursor of these high-speed jets which subsequently energizes the upper solar atmosphere.

Large- and small-scale jets and upflows observed in the lower atmosphere of quiet Sun (QS) areas  are considered to play an important role in the transfer of mass and energy from the dense chromosphere into the corona. However, their origin and connection to the dynamics of the magnetic fields are not yet well understood and explored.
Type II spicules are a subset of these small-scale phenomena discovered in off-limb Hinode data. They have on-disk counterparts identified with Ca II “straws” and rapid blueshifted excursions (RBEs).The formation process of type II spicules is thought to affect the corona by generating shocks, flows, waves, and currents, which can be linked to other phenomena such as the red–blue asymmetries observed in UV data as well as propagating coronal disturbances. Their detailed physical cause and role in providing mass and energy to the corona remain largely unknown.
The related difficulties in the interpretation of solar data mainly arise from the limited spatial resolution and complexity of the chromosphere. Although appear in regions of seemingly unipolar magnetic fields, recent high resolution data suggest that they may be a product of reconnection. Here we will present recent progress in studying type II spicules facilitated by data from Goode Solar Telescope. Various data sets and approaches to analysis all seem to indicate that these events result from magnetic reconenction driven by rapidly varying small-scale magnetic fields present in highly turbulent solar photosphere.

The umbral oscillations are regarded as an observational phenomenon of the slow MHD waves. Recent observational studies reported that the umbral oscillations were spatially and temporally associated with umbral dots. It is direct observational evidence for the connection between wave generation and small-scale magnetoconvection. In addition, horizontal propagation of the umbral oscillations gives information about the depth of the wave sources. It allows us to conjecture the vertical size of the convection cells. Therefore, the umbral oscillations can be a powerful tool for the investigation of the magnetoconvection inside sunspots, and furthermore, the substructure of sunspots.

In the quiet regions on the solar surface, turbulent convective motions of the granulation play an important role in creating small-scale magnetic structures, as well as in injecting energy into the upper atmosphere. The turbulent nature of granulation can be studied using spectral line profiles, especially line broadening, which contains information on the flow field smaller than the spatial resolution of an instrument. In this study, we analyzed the spectral profiles obtained using the Spectro-Polarimeter of Hinode, and newly found significant line broadening in fading phase of granules. To investigate the mechanism of the line broadening, we performed spectral line inversion with the Stokes Inversion based on Response-function (SIR), comparing two inversion conditions: with and without microturbulence term. There are two possible scenarios to explain the observed spectral line broadening: one is microturbulence of about 1 km/s and the other is complicated gradients of Doppler velocity along the LOS. Although the distributions of temperature and vertical velocity estimated with and without microturbulence term are largely different in fading granules, it is difficult to distinguish them only with Fe I lines. Future multi-line observations with a ground-based telescope such as DKIST can determine the velocity distribution and enable us to resolve the scenarios.

Understanding how magnetohydrodynamic waves are excited in the interior and atmosphere of the Sun is still limited. Over the last few decades, acoustic events observed in the intergranular lanes in the photosphere have emerged as a strong candidate for a wave excitation source. We report our observations of wave excitation by a new type of event: rapidly changing granules. Our observations were carried out by using the Fast Imaging Solar Spectrograph and the TiO 7057Å broadband filter imager of the 1.6m Goode Solar Telescope at the Big Bear Solar Observatory. We identify granules in the internetwork region that undergo rapid dynamic changes such as collapse (event 1), fragmentation (event 2), or submergence (event 3). In the photospheric images, these granules become significantly darker than neighboring granules. After the granules' rapid changes, transient oscillations are detected in both of the photospheric and chromospheric layers. In the case of event 1, the dominant period of the oscillations is close to 4.2 min in the photosphere and 3.8 min in the chromosphere. In addition, in the Ca II - 0.5Å raster images, we observe repetitive brightenings in the location of the rapidly changing granules that are considered the manifestation of shock waves. Based on our results, we suggest that dynamic changes of granules can generate upward-propagating acoustic waves in the quiet Sun that ultimately develop into shocks.

Dayside transient phenomena are frequently observed upstream from the bow shock (such as Hot Flow Anomalies, foreshock cavities, and foreshock bubbles) and at the magnetopause (such as flux transfer events and surface waves). They play a significant role in the mass, energy and momentum transport from the solar wind into the magnetosphere and impact the global magnetosphere. They are universal phenomena that have been observed at Earth and other planets. The pressure variations associated dayside transient phenomena perturb the magnetopause, transmit compressional waves into the magnetosphere that can excite resonant ULF waves and cause particles to scatter into the loss cone and precipitate into the ionosphere, generate field-aligned currents in the magnetosphere that drive magnetic impulse events in the high-latitude ionosphere, and trigger transient auroral brightenings. This presentation will discuss the great progress made recently toward answering some specific outstanding science questions. Some outstanding questions are listed below. What are the physical differences and relationships between different transient phenomena at the bow shock? What are the formation conditions for the dayside transient phenomena? How does the magnetosphere respond to dayside transient phenomena? How do transient phenomena evolve with time?

A series of intermittent coherent structures was observed in magnetosheath turbulence in the form of magnetic peaks. These magnetic peaks are always accompanied with enhancement of local current density, and three of them are studied in detail because of their intense current density. Based on the magnetic field signals, magnetic curvatures, and the toroidal magnetic field lines, three peaks are identified as magnetic flux ropes. In each trailing part of these three peaks, an extremely thin electron current layer was embedded within a much broader ion-scale current layer. The energy dissipation is evident within the peaks and direct evidence of magnetic reconnection was found within the thinnest electron current layer. The electrons were heated mainly in two regions of magnetic peaks, i.e. the reconnecting current layer by parallel electric field and the trailing edges by Fermi and betatron mechanisms. These results suggest that the ion-scale magnetic peaks are coherent structures associated with energy dissipation and electron heating in the magnetosheath. Thin current layers can be formed in magnetic peaks, and magnetic reconnection can play a significant role for the energy dissipation in magnetic peaks.  

Using particle-in-cell simulations, we investigate onset of magnetic reconnection from a quiescent current sheet in collisionless plasmas. After the current sheet is destabilized by the collisionless tearing mode instability, it proceeds to onset of reconnection, which manifests spontaneous thinning of current sheet and pileup of upstream magnetic flux. Once the current sheet thins to a critical thickness, about two electron inertial lengths, reconnection begins to grow explosively in this electron current sheet. In this stage, the process is governed by the electron dynamics, and only electrons are obviously accelerated. Then, magnetic reconnection expands from the electron scale to the ion scale, and ions are accelerated to about one Alfven speed in the outflow direction.

Magnetic reconnection is the key to fast release of magnetic energy in many space and astrophysical plasma systems, such as during magnetospheric substorms, but little observational information is available to understand exactly how magnetic-to-electron energy conversion occurs in electron-scale diffusion regions (EDRs). It is generally believed that the EDR has an X-type magnetic field geometry around which the energy of anti-parallel magnetic fields is mostly converted to electron bulk-flow energy. We present multi-spacecraft observations in Earth’s magnetotail of an elongated EDR in which, contrary to the standard model of reconnection, the fast energy conversion was caused mostly by magnetic field annihilation, rather than magnetic topology change. The experimental discovery of the annihilation-dominated EDR reveals a new form of energy conversion in the collisionless reconnection process.

Intense electromagnetic waves are often observed in the reconnection current layer in space and laboratory plasmas. The waves near the reconnection x-line potentially have an impact on the magnetic dissipation through anomalous momentum transfer, driving the reconnection process that extends to a large scale. Recent 3D kinetic simulations have also demonstrated intense activities of electromagnetic waves in the thin current layer formed around the x-line. Nevertheless of these evidences in observations and simulations, the generation mechanisms of the waves and their roles in reconnection were poorly understood yet. The present study has carried out a large-scale 3D PIC simulation for the anti-parallel and no guide field configuration. The simulation results suggest that the electron Kelvin-Helmholtz instability (eKHI) plays a primary role in driving intense electromagnetic turbulence in the reconnection current layer, leading to the dissipation and electron heating. The turbulence intensity is significantly enhanced due to the ejection of magnetic islands from the current layer. It is found that the ions hardly react to the turbulence, which indicates that the turbulence does not cause siginificant momentum exchange between electrons and ions resulting in electrical resistivity. It is demonstrated that the dissipation is mainly caused by viscosity associated with electron momentum transport across the current layer. The present results suggest a fundamental modification of the current MHD models using the resistivity to generate the dissipation. In this talk, we will show the generation mechanism of the elecromagnetic waves and their impacts on the magnetic dissipation.

Petschek (PK) reconnection model is widely studied for 60 years and a strong candidate mechanism to explain the solar flares and substorms. In MHD (magnetohydrodynamic) theory, the reconnection process is driven by electric resistivity based on classical Ohm's law, which is generally described as second-order differential magnetic diffusion effect in Faraday's law. Some previous studies suggest that the uniform electric resistivity results in Sweet-Parker (SP) reconnection model rather than PK model, but this suggestion is still a controversial topic.  In this paper, with 2D MHD simulations, the forth-order differential magnetic diffusion effect is compared with the classical second-order differential effect. All the diffusion coefficient examined here is assumed to be uniform in time and space, for both of second-order and forth-order effects. In fact, such forth-order differential magnetic diffusion effect is predicted in the recent 3D plasma kinetic simulations of fast magnetic reconnection process. In another perspective, such higher-order differential magnetic diffusion effect is universally included in the numerical truncation errors of numerical MHD simulations, which prevents the numerical explosions of simulations, where such higher-order differential effect generally leads to stronger damping of shorter wave length. In this paper, it is shown that the forth-order effect tends to change the magnetic reconnection process from SP-like model to PK-like model, in contrast to the second-order effect. This work is important for the cross-scale coupling problem of fast magnetic reconnection process between 3D plasma kinetic simulations and MHD simulations. Also, it is important to consider the numerical error problems universally included in MHD simulation of the reconnection process in extremely-thin current sheet.  

We report on observations of a set of magnetic loops above a region with late-phase flux emergence taken by IRIS, Hinode, and SDO. The loop system consists of many transition-region loop threads that are 5″-12″ in length and ∼0.″5 in width and coronal loops with similar length and ∼2″ width. In the middle of the loop system, there is a clear systematic blueshift of about 10 km s^-1 in the transition region that is consistent with a flux-emerging picture, while a redshift of about 10 km s^-1 in the corona is observed. The nonthermal velocity of the loop system is smaller than that of the surrounding region in the transition region but is comparable that in the corona. The electron density of a transition-region loop is also measured and found to be about 5 × 10¹⁰ cm^-3, a magnitude larger than that in the coronal loops. In agreement with imaging data, the temperature profiles derived from the differential emission measurement technique confirm that some of the loops have been heated to corona level. The expansion of the loops leads to interactions between the loops themselves and with the ambient field, which can drive magnetic reconnection evidenced by multiple intense brightenings, including transition-region explosive events and IRIS bombs in the footpoint region associated with the moving polarity. A set of quasi-periodic brightenings with a period of about 130 s is found at the loop apex. Our observations indicate that the flux emergence in its late phase is much different from that at the early stage. While the observed transition region is dominated by emerging flux, these emerging loops could be heated to corona level, and the heating (if via nonthermal processes) most likely takes place only after they reach the transition region or lower corona.

Emerging flux regions are the locations where a variety of sporadic local heating events are observed. With the aim of understanding such events, we analyze the observational data of emerging AR 12401 obtained by Hinode/SOT and IRIS. Out of the 29 Ca bright points (BPs), seven are situated at the mixed-polarity photospheric background, above which the IRIS UV spectra are strongly enhanced and broadened, indicating the bi-directional jets from low altitude magnetic reconnection. Another 10 BPs are found in unipolar regions at the edges of the emerging flux region. Their UV spectra are in general weak but consistently redshifted at the speeds up to 40 km/s. These observational results support the physical picture that the heating in the region center are due to magnetic reconnection at flux cancellation sites (Ellerman bombs and UV bursts), whereas the peripheral events are due to shocks caused by supersonic downflows along the rising arch filament system.

Coronal loops are building blocks of solar active regions (ARs). However, their formation is not well understood. Here we present direct observational evidence for the formation of coronal loops through magnetic reconnection as new magnetic fluxes emerge to the solar atmosphere. Observations in the EUV passbands of SDO/AIA clearly show the newly formed loops following magnetic reconnection within a vertical current sheet. Formation of the loops is also seen in the Hα images taken by NVST. The SDO/HMI observations show that a positive-polarity flux concentration moves toward a negative-polarity one with a speed of ~0.5 km s^-1 before the apparent formation of coronal loops. During the formation of coronal loops, we found signatures of flux cancellation and subsequent enhancement of the transverse field between the two polarities. We have reconstructed the three-dimensional magnetic field structure through a magnetohydrostatic model, which shows field lines consistent with the loops in AIA images. Numerous bright blobs with a width of ~1.5 Mm appear intermittently in the current sheet and move upward with apparent velocities of ~80 km s^-1. We have also identified plasma blobs moving to the footpoints of the newly formed large loops, with apparent velocities ranging from 30 to 50 km s^-1. A differential emission measure analysis shows that the temperature, emission measure and density of the bright blobs are 2.5-3.5 MK, 1.1-2.3×10²⁸ cm^-5 and 7.9-16.4×10⁹ cm^-3, respectively. Power spectral analysis of these blobs indicates that the magnetic reconnection is inconsistent with the turbulent reconnection scenario.

White-light flares (WLFs), first observed in 1859, refer to a type of solar flare showing an obvious enhancement of the visible continuum emission. This type of enhancement often occurs in most energetic flares, and is usually interpreted as a consequence of efficient heating in the lower solar atmosphere through nonthermal electrons propagating downward from the energy release site in the corona. However, this coronal-reconnection model has difficulty in explaining the recently discovered small WLFs. Here we report a C2.3 WLF, which is associated with several observational phenomena: a fast decrease in opposite-polarity photospheric magnetic fluxes, the disappearance of two adjacent pores, significant heating of the lower chromosphere, a negligible increase of the hard X-ray flux, and an associated U-shaped magnetic field configuration. All these suggest that this WLF is powered by magnetic reconnection in the lower part of the solar atmosphere rather than by reconnection higher up in the corona.

We carry out radiation magnetohydrodynamics (RMHD) simulations for the sunspot formation. It is thought that the magnetic field is created deep in the convection zone, and thermal convection transports the magnetic flux to the surface of the Sun. Due to the significant spatial and temporal differences between the deep convection zone and the near-surface region, calculations in these layers have been separated. We developed the new RMHD code that can simultaneously deal with low and high Mach number situations in these regions. With the new code, we carry out a series of RMHD simulations of the sunspot formation in an unprecedentedly deep domain covering the whole depth of the convection zone. Large-scale convection in the deep layer of the Sun distorts the flux tube and creates sunspots at the solar surface. We find several possible influences of the bottom boundary condition on the simulation results in the previous shallow simulations. We also find that the thermal convection occasionally creates delta-type sunspots and complicated magnetic features at the surface. These results show the importance of the deep convection structure for investigating the sunspot formation at the surface.

We develop a method to predict the horizontal velocity field from the radiation intensity and vertical velocity on the solar surface using neural networks. We can observe thermal convection on the solar photosphere as a mottled pattern called granulation. The thermal convection is related to various phenomena such as the dynamo and the generation of the wave. While the line-of-sight (LOS) velocity can be observed by the Doppler effect, we cannot observe the velocity perpendicular to the LOS. There are methods to estimate the horizontal flow on the solar surface by tracking the time variation of the observation images called local correlation tracking. However, these require at least two or more images. On the other hand, many magnetohydrodynamic (MHD) simulations are carried out and reproduce the observations well. By using simulations, we can obtain physical quantities that cannot be observed. In this study, we use the results of our own MHD simulations to train neural networks, and this network predicts the unobservable horizontal velocity field from the observable intensity and vertical velocity field. By using only the convolution layer, images of any size can be applied, and the prediction is fast. The correlation coefficient between the simulation and the prediction is about 0.65, and this method can be applied to observations.

Solar coronal cavities are dark structures with a rarefied density compared with surrounding streamers. They are often observed as a component of the classic three-part structure of a coronal mass ejections (CME), quiescent cavities are observed mostly in the polar crown regions and may be long-lived. Some of the quiescent cavities may finally erupt as a CME. Cavities possess a characteristic “lagomorphic” structure, observed in linear polarisation observations, which can be explained with the flux rope model. Cavities are hotter than surrounding streamer, and the temperature remains stable.We present statistical analysis of all cavities observed by Coronal Multichannel Polarimeter (CoMP). These observations reveal that all cavities observed over a long time possess “lagomorphic” structure, therefore flux rope model is appropriate for polar-crown prominence cavities. Based on forward modelling we show that visibility of the structure in the linear polarisation depends on the orientation of the structure. We also present Differential Emission Measure (DEM) analysis of previously quiescent cavities during the eruption.  

In ultraviolet (UV) spectropolarimetric observations of the solar corona, the existence of magnetic field, solar wind velocity and temperature anisotropies modify the linear polarization associated with resonant scattering. In this paper, we forward model expected signals in the Lyman-α line in order to establish the different roles played by these physical effects. Unlike previous empirical models or global models, which present blended results of the above physical effects, the analytic model adopted here can be adjusted to test the roles of different effects separately. We find that the impact of all three effects is most evident in the rotation of the linear polarization direction. In particular: 1) a magnetic field on the order of several Gauss modifies the linear polarization at low coronal heights, rotating the linear polarization direction either clockwise or counter-clockwise when the angle between the magnetic field and the local vertical is greater or less than the van Vleck angle, which is consistent with the result of Zhao et al. (2019, Paper I hereafter). 2) Solar wind velocity, which increases with height, has a significant effect at higher coronal heights, rotating the linear polarization direction in an opposite fashion to the magnetic effect. 3) Temperature anisotropies are most significant at lower heights where the magnetic field departs from the radial, and follow the pattern of the magnetic effect, opposite to the Doppler dimming. The fact that the three effects operate differently in distinct spatial regimes opens up the possibility for using linear polarization measurements in UV lines to diagnose these important physical characteristics of the solar corona.

Magnetoseismology, a technique of magnetic field diagnostics based on observations of magnetohydrodynamic (MHD) waves, has been widely used to estimate the field strengths of oscillating structures in the solar corona. However, previously magnetoseismology was mostly applied to occasionally occurring oscillation events, providing an estimate of only the average field strength or one-dimensional distribution of field strength along an oscillating structure. This restriction could be eliminated if we apply magnetoseismology to the pervasive propagating transverse MHD waves discovered with the Coronal Multi-channel Polarimeter (CoMP). Using several CoMP observations of the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of the plasma density and wave phase speed in the corona, which allow us to map both the strength and direction of the coronal magnetic field in the plane of sky. We also examined distributions of the electron density and magnetic field strength, and compared their variations with height in the quiet Sun and active regions. Such measurements could provide critical information to advance our understanding of the Sun's magnetism and the magnetic coupling of the whole solar atmosphere.

In this work we will describe Hinode/EIS measurements of coronal magnetic fields in active regions and before and during flares using the newly developed Magnetically-Induced Transition (MIT) technique. We will compare measurements to magnetic field extrapolations, as well as discuss the importance of these measurements for flare forecasting.

Measurements from the Van Allen Probes mission clearly demonstrated that the radiation belts cannot be considered as a bulk population above approximately electron rest mass. Ultra-relativistic electrons (~>4Mev) form a new population that shows a very different morphology (e.g. very narrow remnant belts) and slow but sporadic acceleration. We show that acceleration to multi-MeV energies can not only result of a two-step processes consisting of local heating and radial diffusion but occurs locally due to energy diffusion by whistler mode waves. Local heating appears to be able to transport electrons in energy space from 100s of keV all the way to ultra-relativistic energies (>7MeV). Acceleration to such high energies occurs only for the conditions when cold plasma in the trough region is extremely depleted down to the values typical for the plasma sheet. There is also a clear difference between the loss mechanisms at MeV and multi MeV energies. The difference between the loss mechanisms at MeV and multi-MeV energies is due to EMIC waves that can very efficiently scatter ultra-relativistic electrons, but leave MeV electrons unaffected. We also present how the new understanding gained from the Van Allen Probes mission can be used to produce the most accurate data assimilative forecast. Under the recently funded EU Horizon 2020 Project Prediction of Adverse effects of Geomagnetic storms and Energetic Radiation (PAGER) we will study how ensemble forecasting from the Sun can produce long-term probabilistic forecasts of the radiation environment in the inner magnetosphere.

Electromagnetic ion cyclotron (EMIC) waves have long been known to drive the scattering loss of relativistic electrons from the radiation belts into the Earth's upper atmosphere. In recent years, however, there has been growing evidence to suggest that EMIC can cause the loss of not only relativistic electrons, but also sub-relativistic electrons down to energies of only a few hundred keV. At these lower energies, EMIC waves have access to much larger trapped electron populations, and thus have the potential to drive sufficient electron precipitation to be a significant source of ionisation in the upper atmosphere.
In this presentation we first describe an apparent contradiction between studies of trapped and precipitation electron fluxes in the presence of EMIC wave activity. We demonstrate a simple resolution to this contradiction, and show that that a purely relativistic trapped flux response to EMIC wave activity is not necessarily mutually exclusive with strong sub-MeV electron precipitation measurements.
We also present results from the Sodankylä ion-chemistry model, which we use to investigate the impact of EMIC-driven electron precipitation on atmospheric chemistry. We show that EMIC-driven electron precipitation can drive significant ionisation in the Earth's atmosphere above 40 km, leading to the loss of mesospheric ozone. We compare these results with existing geomagnetic activity proxies used as drivers of modern coupled-climate models, suggesting that EMIC-driven electron precipitation is not currently being accounted for in these models.

Precipitating electrons and protons from the aurora and large solar eruptions are known sources of nitric oxide in the high-latitude mesosphere and lower thermosphere. This NO formation by precipitating energetic particles initiates a chain of chemical-dynamical coupling processes significantly affecting polar stratospheric ozone, and impacting atmospheric dynamics possibly down to tropospheric weather systems. Consequently, this “geomagnetic forcing” is increasingly studied in global chemistry-climate model experiments to quantify the natural forcing of the climate system. There is emerging evidence that electrons accelerated in the radiation belts contribute significantly to this geomagnetic forcing; however, their frequency, intensity and energy range are still uncertain.  In this presentation, we will provide a summary about the state-of-the art of the geomagnetic forcing with a focus on the emerging role of precipitating magnetospheric electrons.

Auroral field-aligned currents (FACs), which are thought to be highly related to particle precipitations, are an important transport mechanism for energy and momentum between the magnetosphere and ionosphere. In this presentation, we derived FACs from DMSP satellites. The magnetic latitude versus local time distribution of FACs from DMSP shows comparable dependences with previous findings on the intensity and orientation of interplanetary magnetic field (IMF) By and Bz components, which also confirms the reliability of the DMSP FAC data set. With simultaneous measurements of precipitating particles from DMSP, we further investigate the relation between large-scale FACs and precipitating particle energy flux. Our result shows that precipitation electron and ion fluxes both increase in magnitude and extend to lower latitude for enhanced southward IMF Bz, which is similar to the behavior of FACs. Under weak northward and southward Bz conditions, the location of the R2 current maxima, at both dusk and dawn sides and both hemispheres, are found to be close to the maxima of the particle energy fluxes; while for the same IMF conditions, R1 currents are displaced further to the respective particle flux peaks. Largest displacement (about 3.5⁰) is found between the downward R1 current and ion flux peak at the dawn side. Our results suggest that there exist systematic differences in the peak locations of electron/ion precipitation and large-scale upward/downward FACs, with FAC peaks enclosing the particle energy flux peaks in auroral band at both dusk and dawn sides. Our comparisons also found that particle precipitation at dawn and dusk and in both hemispheres maximizes near the mean R2 current peaks. The particle precipitation maxima closer to the R1 current peaks are lower in magnitude, which is opposite to the known feature that R1 currents are on average stronger than R2 currents.

Earth's ionosphere represents a complex and dynamic region characterized by increased concentration of charged particles. Changes in ionospheric density can affect the propagation of electromagnetic signals thus disrupting navigation and positioning. The existing models of ionospheric density rarely meet the accuracy requirements due to being either only climatological (physical models), or using the time and spatial averaging (empirical models). Here we present a continuous empirical three dimensional (3D) model of electron density at heights 130-900 km. Since the ionosphere is a data rich environment it is essential to use all of the collected observations. We use the radio occultation data from various spacecraft, together with in situ data by CHAMP and CNOFS missions and observations from GRACE-KBR, for over 18 years of data. We discuss the application of deep learning to efficiently handle the entire dataset comprising billions of data points. In order to analyze, which features result in the best model performance, we employ a number of ML-based feature selection techniques and discuss the optimal combination of inputs, and their physical meaning. The resulting model gives accurate predictions of electron density in the Earth's ionosphere and yields >90% correlation on the validation data. The model has a wide range of applications for the scientific purposes, space weather monitoring and industrial applications such as positioning and navigation.

We conduct observational and modeling studies of thermospheric composition responses to weak geomagnetic activity (non-geomagnetic storms). We found that the thermospheric O and N₂ column density ratio (∑O/N₂) in part of the Northern Hemisphere measured by Global-scale Observations of the Limb and Disk (GOLD) exhibited large and long-lived depletions during weak geomagnetic activity in May and June 2019. The depletions reached 30% of quiet time values, extended equatorward to 10°N, and lasted more than 10 hours. Furthermore, numerical simulation results are similar to these observations and indicate that the ∑O/N₂ depletions were pushed westward by zonal winds. The ∑O/N₂ evolution during weak geomagnetic activity suggests that the formation mechanism of the ∑O/N₂ depletions is similar to that during a geomagnetic storm. The effects of weak geomagnetic activity are often ignored, but, in fact, are important for understanding thermosphere neutral composition variability and hence the state of the thermosphere-ionosphere system.

Observations by the GOLD mission are able to follow spatial and temporal changes in thermospheric composition, density and temperature and in ionospheric structure and peak density, providing fundamental information for understanding the Thermosphere-Ionosphere system. GOLD images the Earth from geostationary orbit at 47.5° W longitude, observing on a ≤30-minute cadence from 06:10 to 0:40 UT (03:00-21:30 LT at the satellite). Observations performed include limb scans; stellar occultations; and images the sunlit and nightside disk.  These data provide simultaneous, synoptic imaging of the composition and temperature near 160 km for the first time, as well as follow the temporal development of the nighttime ionosphere over the Atlantic and South America every evening. Recent observations of geomagnetic storms and solar eclipses have produced some surprising results. These observations are providing significant tests of current models, tests that may lead to advances in the capabilities of global-scale models of the thermosphere and ionosphere system. Observations also clearly show the presence of waves in the thermosphere, as well as indications at multiple spatial of the influence of waves and tides propagating from lower altitudes. Examples of these observations, as well as their potential for advancing models of the thermosphere-ionosphere system, will be presented and discussed.

This study investigates the underlying physics of equatorial plasma bubbles (EPBs) on 11 December 2019, under solar minimum conditions. The Global‐scale Observations of the Limb and Disk (GOLD) ultraviolet nightglow images exhibit a periodic distribution of reduced emissions related to EPBs. Remarkably, FORMOSAT‐7/COSMIC‐2 (F7/C2) observes a significant altitudinal difference of ~45 km in the bottomside ionosphere between two nearly collocated electron density profiles before the onset of EPBs, indicating the presence of an upwelling. Distinct ionospheric perturbations are also observed in F7/C2 and ground‐based Global Positioning System observations, suggesting that gravity waves may contribute to the upwelling. Simulations with SAMI3/ESF are further carried out to evaluate the upwelling growth and pre‐reversal enhancement (PRE) effect on EPB development. Simulations reveal that the crests of upwellings show a localized uplift of ~50 km, and EPBs only develop from the crest of upwellings. The uplift altitude of upwellings is comparable to the F7/C2 observations and the post‐sunset rise in moderate solar conditions. The polarization electric field (E_p) developed within the upwellings can drive vertical E_p × B drifts of ~32–35 m/s, which are comparable to the PRE vertical E × B drifts. We find that the PRE alone cannot drive EPBs without upwelling growth, but it can facilitate the upwelling growth. Observations and simulations allow us to conclude that upwelling growth could play a vital role in the formation of EPBs.

Equatorial ionosphere can react to substorm events via direct penetrating electric field.   In the past, the thermosphere and ionosphere model driven by the high empirical ion convection models lacked the dynamic high latitude input to properly simulate the penetrating electric field and equatorial response.   The recently developed magnetospheric and ionospheric coupling model GTR (GAMERA-TIEGCM-RCM) aims to resolve the issue.   We will simulate recent substorm events to examine the penetrating electric field effect.    Additionally, we will use the observations from recent missions such as GOLD, COSMIC 2, and ICON to validate the simulation results.  These three missions provide unprecedented coverage of the equatorial ionosphere including ion density profiles, UV images, ion drift, and neutral winds.   The ion drift and neutral winds are particularly important for understanding the equatorial dynamo.