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Presentation Mode : All
Conference Day : 06/08/2021
Time Slot : AM2 11:00 - 13:00
Sections : ST - Solar and Terrestrial Sciences










Solar and Terrestrial Sciences | Fri-06 Aug




ST22-PS03-A008 | Invited
Swinging Around the Sun with the Parker Solar Probe: Mission, Discoveries, and Milestones

Nour E. RAOUAFI#+
Johns Hopkins Applied Physics Laboratory, United States


Launched on 12 Aug. 2018, NASA’s Parker Solar Probe is venturing closer to the Sun than any other spacecraft, mapping the last unvisited regions of the solar system. PSP completed seven of its planned 24 elliptical orbits around the Sun. The perihelia realized so far are 35.7 Rsun (orbits 1-3), 27.8 Rsun (orbits 4-5), and 20.3 Rsun (orbits 6-7). On February 20, 2021, PSP flew by Venus for the fourth time setting the mission for another record of 15.97 Rsun from the center of the Sun. The spacecraft incorporates cutting-edge technology to attain new science: PSP crossed a technological barrier by protecting sensitive spacecraft and payload components from intense solar photon radiation. Parker is primarily an exploration mission, and the data returned so far is a treasure trove that holds the potential for breakthrough discoveries. It is breaking new boundaries of space exploration by flying halfway between Mercury and the Sun. Parker is writing a new chapter of space research by revolutionizing our understanding of this mysterious region by answering long-standing questions that puzzled scientists for decades: how the solar wind plasma is heated and accelerated and solar energetic particles accelerated and transported throughout the heliosphere. The analyses of science data show new phenomena and plasma properties not seen before in the solar wind. Several major discoveries have been so far, most of which are mystifying (e.g., magnetic field switchbacks, solar wind tangential flows, solar energetic particles, and the dust-free zone). Some other discoveries concerning the heliospheric dust are also very insightful. I will provide an overview of the mission's scientific findings after two and a half years of operation and the outlook for the upcoming solar encounters.

ST22-PS03-A005 | Invited
The FIREBIRD-II CubeSat Mission

Arlo JOHNSON1#+, Harlan SPENCE2, John SAMPLE1, Mykhaylo SHUMKO1, David KLUMPAR1, Berhard BLAKE3, Sonya SMITH2, Larry SPRINGER1, Alex CREW4
1Montana State University, United States, 2University of New Hampshire, United States, 3The Aerospace Corporation, United States, 4Johns Hopkins University Applied Physics Laboratory, United States


FIREBIRD-II is a United States National Science Foundation funded CubeSat mission designed to study the scale size and energy spectrum of relativistic electron microbursts. The mission consists of two identical 1.5 U CubeSats in a low earth polar orbit, each with two solid state detectors that differ only in the size of their geometric factors and fields of view. Each detector returns high cadence (10’s of ms) measurements of the electron population from 200 keV to >1 MeV across six energy channels. FIREBIRD-II has been in orbit for over 6 years and one unit continues to return high quality data. The long lifetime of the FIREBIRD-II mission has allowed for all primary science objectives to be achieved as well as a variety of additional science beyond the scope of the original mission. We present a summary of the FIREBIRD-II mission, the spacecraft design, and the data products. We then highlight some of the science achievements and ongoing projects enabled by FIREBIRD-II.

ST22-PS03-A009
The MARSU Exoplanet Science Cubesat Project : Studying the Transiting Close-in Exoplanets and the Activity of Young and Low-mass Dwarfs

jean-francois DONATI1#, Driss KOUACH2+, Tianqi CAN1, Pascal PETIT1,2, Claire MOUTOU1, Greg HERCZEG3, Sheng-Hong GU4, Jianning FU5, Michel BLANC6
1Research Institute in Astrophysics and Planetology, France, 2OMP, France, 3Beijing University, China, 4Yunnan Observatory, China, 5Beijing Normal University, China, 6Institute for Research in Astrophysics and Planetology, France


Photometric monitoring is a method for characterizing stars with variable brightness, like active stars, young stars, and stars with transiting exoplanets.  Space telescopes are ideal tools for continuously observing variable stars, avoiding the drawbacks of ground-based observations. We propose to build an infrared CubeSat-type space photometer working with SPIRou and SPIP, which are ground-based infrared spectropolarimeters/velocimeters at the Canada-France-Hawaii Telescope (Hawaii, in operation), and the Télescope Bernard Lyot (France, to be commissionned in 2022).  The goal of the SPIRou/SPIP CubeSat, nicknamed MARSU (for 'Millimag Astrophotometry of Red SPIRou/SPIP stars as a University space mission'), is to achieve continuous (duty cycle >90%) photometric monitoring in the YJH bands (1-1.8um) for stars up to H~11, at a precision better than 1mmag for up to 10min exposure times, over continuous periods of up to 3months and simultaneously with SPIRou/SPIP observations. With such specifications, MARSU will provide unique opportunities to study young and active dwarfs hosting transiting close-in exoplanets (like the newly discovered K2-33, V1298Tau and Trappist-1) in a way that can compete or even outperform current photometric space probes working at optical wavelengths such as TESS, and for a much smaller cost.  MARSU is managed by IRAP/OMP in France, with financial contributions from the French Space Agency CNES for the design study of the science payload; options are open for broadening the collaboration to Chinese partners, in particular regarding the platform to host the payload, within the framework of the JEWEL Franco-Chinese scientific cooperation programme. Ultimately, the goal is to aim for a fleet of ~10 MARSU-like CubeSats so that a few hundreds of targets can be monitored over the lifetime of the probes, with obvious synergies with large exoplanet missions like ARIEL.

ST22-PS03-A006 | Invited
Korean Scientific Instrument for Commercial Lunar Payload Service

Young-Jun CHOI1,2#+, Chae Kyung SIM1,3, Dukhang LEE1,3, Minsup JEONG1, Sungsoo KIM4
1Korea Astronomy and Space Science Institute, Korea, South, 2University of Science and Technology, Korea, South, 3Korea National University of Science and Technology, Korea, South, 4Kyung Hee University, Korea, South


Korea has the lunar exploration program including Korea Pathfinder Lunar Orbiter (KPLO) which will be rescheduled to launch on 2022 recently and future Lunar Lander near 2030s. Korea Astronomy and Space Science Institute (KASI) and NASA HQ Science Mission Directorate agreed to initiate the exploration working group to develop and support joint science project. some science instruments from Korean community will be provided for US Commercial Lunar Payload Service (CLPS). KASI has selected four instruments, based on scientific merit and technology readiness. In this talk, the scientific justification of successful instruments and conceptual design will be presented.

ST22-PS03-A001 | Invited
Objective of the Instrument Onboard Smart Lander for Investigating Moon and the Planned Lunar Polar Exploration

Makiko OHTAKE#+
Okayama University, Japan


Following up on the successful SELENE (Kaguya) mission, JAXA decided to launch the Smart Lander for Investigating the Moon (SLIM) mission, a demonstration of precision landing technology in FY2022. The SLIM carries one scientific instrument (MultiBand Camera; MBC), which will observe boulders on the lunar surface in 10 bands from visible to infrared wavelength with high spatial resolution (1.3 mm/pixel at 10 m). Target of the MBC observation is the olivine-rich lithology found by SELENE (Kaguya) spectral observation, which is possibly originated from the lunar mantle. To directly investigate this unexplored lithology, one of the small fresh craters named as “Shioli” just outside of the Theophilus crater is selected as a landing site for the SLIM. Engineering model of the MBC has been developed and tested to confirm its capability to investigate mineralogy and chemical composition of the boulders. After the SLIM mission, JAXA is planning a lunar polar exploration mission. Recently, multiple datasets indicate presence of water condensation at the lunar polar region. The goal of this mission is to obtain information for evaluating possibility to use the water as a resource. ISRO and JAXA have been jointly studied this mission, in which each agency will develop a lander and a rover respectively. The rover has a drilling system which can drill the lunar surface regolith up to 1.5 m and bring up regolith samples. In 2020, JAXA selected Japanese mission instruments for the mission. One of the instruments is called resource investigation water analyzer (REIWA). REIWA consist of mainly four subsystems, namely, lunar thermogravimetric analyzer, triple-reflection, aquatic detector using optical resonance, and ISRO sample analysis package (this is a candidate instrument). Also, advanced lunar imaging spectrometer (ALIS) was selected to observe the lunar surface. In this presentation, we discuss objectives, current mission status of these two missions.

ST22-PS03-A004
Development of a Triple-reflection Compact Time-of-flight Mass Spectrometer for Lunar Polar Exploration

Yoshifumi SAITO1#+, Naoki YAMAMOTO2, Satoshi KASAHARA3, Shoichiro YOKOTA4
1Japan Aerospace Exploration Agency / Institute of Space and Astronautical Science, Japan, 2Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Japan, 3The University of Tokyo, Japan, 4Osaka University, Japan


 For the purpose of investigating the presence (and amount) of the water (ice) molecules in the regolith 1 to 1.5 m below the lunar surface, a compact neutral particle mass spectrometer is under development. This neutral particle mass spectrometer is designed to be installed on a Moon rover for performing mass analysis of neutral gas generated in the heating chamber. This mass spectrometer not only aims to measure the amount of water molecules included in the lunar regolith but also identify the atoms, molecules and their isotopes up to mass number 200 with mass resolution as high as 100.The mass spectrometer under development is a reflectron that is a Time-Of-Flight mass spectrometer. In order to increase the mass resolution as much as possible within the allocated volume, we have decided to modify the standard reflectron by adding a second reflector that enables triple reflections and doubles the flight length. This newly designed triple-reflection TOF mass spectrometer also has an additional function to select the mass range of the measured particles by changing the temporal pattern of the pulsed high voltage applied to the first and second reflectors. This function is useful, for example, not to measure the carrier gas the amount of which is much larger than that of the target gas. The triple-reflection TOF mass spectrometer can be operated also as a standard reflectron by changing the voltage applied to the analyzer. Triple-reflection mode is suitable for high mass resolution measurement and standard single reflection mode is suitable for high sensitivity measurement.



ST20-A013 | Invited
Observation of Pre-earthquake Signals in Atmosphere-ionosphere Associated M8.1 Kermadec- New Zealand Earthquake Sequence and Tsunami of March 4, 2021. Preliminary Study.

Dimitar OUZOUNOV1#+, Jann-Yenq (Tiger) LIU2, Katsumi HATTORI3
1Chapman University, United States, 2National Central University, Taiwan, 3Chiba University, Japan


We present a preliminary study on the multi-parameter analysts of transient phenomena observed in the Earth's atmosphere-ionosphere environment plausibly associated with the latest New Zealand (NZ) Earthquake (EQ) and Tsunami sequence of March 4, 2021. The M8.1 EQ in the Kermadec Islands region was about 1,000 kilometers from NZ and was the largest in a series of tremors on the same day, including the two earlier M7.4 and M7.1 quakes. The NZ National Emergency Management issued tsunami threats for large Pacific parts. We collect operational data from two satellites, ground data, and models probing the atmosphere, such as 1. Outgoing long-wavelength radiation (OLR obtained from NPOESS) on the top of the atmosphere (TOA); 2. Cloud formations and pattern from NASA EOS and HIMAWARI-8; 3. Weather Data -Temperature, Atm. Pressure and Relative humidity form GOES-5 model; and 4. The electron density variations in the ionosphere via GPS Total Electron Content (GPS/TEC). On Feb 6, 2021, NOAA satellite thermal observations show an increase of OLR over the Kermadec Islands with a maximum near the future epicenter of M8.1 of March 4, 2021. A similar anomaly but with lower intensity was revealed on Feb 26 over Northern Islands. Unusual cloud patterns start appearing on Feb 24 onward. GPS/TEC data-based on the IGS network indicated an increase of electron concentration in the ionosphere twenty-four hours before the beginning of the swarm. We demonstrate that by integrating data from multiple sensors, we could observe the pre-earthquake evolution patterns in the atmosphere-ionosphere environment starting up to 3 weeks before the March 4th EQ swarms.  The temporal and spatial characteristics of pre-earthquake anomalies were developed in the atmosphere three weeks in advance, typical for M8+ types of EQ and associated with the large area but inside the preparation region estimated by Dobrovolsky-Bowman.

ST20-A009
Monitoring of the Underground Rn Flux near the Surface ; As a Source of Lithosphere-atmosphere-ionosphere Coupling

Katsumi HATTORI#+, Kazuhide NEMOTO, Syu KANEKO, Chie YOSHINO, Haruna KOJIMA
Chiba University, Japan


In recent years, radon anomalies preceding large earthquakes have been reported, which are interpreted as a modulation of Rn gas emanation due to stress changes in the earth’s crust. And it is considered one of possible source of Lithosphere-Atmosphere-Ionsphere Coupling. For this verification, we are conducting continuous observations of underground radon concentration (GRC) in Asahi, Chiba Prefecture (June 2014-) and Miho Village, Ibaraki Prefecture (September 2020-), Japan. We have developed the method to estimate the underground Rn flux (GRF) by using the MSSA (Multi-channel Singular Spectrum Analysis) to remove effects of weather factors of temperature and atmospheric pressure. GRF indicates the upward flow of Rn gas near the ground surface. However, GRF may be affected by heavy precipitations. We conducted a statistical analysis of the relationship between the fluctuation of GRF and precipitation. As a result, we found that GRF significantly increased after heavy rainfall events with 20 mm or more in 2 hours. This is caused by both the increase in load due to rainwater and the infiltration of rainwater near the station. Similar tendency is given for Miho station even though the data are very short. Excluding the influence of the above precipitation effects at the Asahi station, we compare the variation of GRF with the seismic activity near the station, we found there are cases where the GRF increases for reverse fault type earthquakes within an epicenter distance of 50 km from the station. This result suggests the possibility of GRF fluctuation due to the earthquake. In future, it is necessary to quantitatively evaluate the relationship between the fluctuation of crustal stress fields and that of GRF at Miho and Asahi stations.

ST20-A010
Development of Broadband LF Antenna System for Pre-Earthquake Electromagnetic Phenomena

Chie YOSHINO1#+, Kenshin MIURA1, Katsumi HATTORI1, Noriyuki IMAZUMI2,3, Takeshi MORIMOTO4, Yoshitaka NAKAMURA5
1Chiba University, Japan, 2The Institution of Professional Engineers, Japan, 3Idemitsu Kosan, Japan, 4Kinki University, Japan, 5Koba City College of Technology, Japan


 Increases in the electromagnetic pulse in the LF band have been reported as one of the electromagnetic phenomena preceding large earthquakes. Before the 1995 Hyogo-ken Nanbu Earthquake (M7.2), Oike et al. reported an increase in the number of pulses, and this phenomenon is considered to be the precursor for the earthquake. On the other hand, it has been suggested that some of these pulse increases are strongly affected by lightning. The issue is to distinguish between electromagnetic pulses caused by lightning and electromagnetic pulses that are precursors to earthquakes. Therefore, we developed the observation system for LF band electromagnetic waves, which can record detailed pulse waveforms, and investigated the relationship between the number of pulses and earthquakes, and analyzed their waveforms to extract the characteristics of the earthquake precursor pulse.
The observation system consists of a capacitive fast antenna with a circular flat plate, a 500 kHz low-pass filter, a 16-bit AD converter, and a PC for data recording. 100 ms data before and after the pulse waveform exceeding the trigger level (V_pp = 6000 [du]) is registered at 4 MHz sampling. The system was installed on the top of the roof of Science Building No. 5, Chiba University. The analyzed period is from May 1, 2018, to May 31, 2019. The details will be shown in the presentation. 

ST20-A008
Seismo-ionospheric Precursors and Ionospheric Space Weathers Observed by China Seismo-electromagnetic Satellite

Jann-Yenq (Tiger) LIU1#+, F.Y. CHANG1, Xuhui SHEN2, Sergey PULINETS3, Katsumi HATTORI4, Dimitar OUZOUNOV5, Valerio TRAMUTOLI6, Michel PARROT7
1National Central University, Taiwan, 2National Space Science Center,CAS, China, 3Space Research Institute (IKI) Russian Academy of Sciences, Russian Federation, 4Chiba University, Japan, 5Chapman University, United States, 6University of Basilicata, Italy, 7National Center for Scientific Research, France


The China Seismo-Electromagnetic Satellite (CSES) with a sun-synchronous orbit at 507 km altitude was launched on 2 February 2018 to observe seismo-ionospheric precursors (SIPs) and ionospheric space weather.  The CSES probes two manifest longitudinal features of 4-peak plasma density and 3 plasma depletions in the equatorial/low-latitudes as well as midlatitude troughs.  CSES plasma probing and the total electron content (TEC) of global ionospheric map (GIM) are used to study SIPs associated with a destructive M7.0 earthquake and its M6.5 and M6.3/M6.9 aftershocks in Indonesia on 5, 17, and 19, August 2018, respectively, as well as to examine ionospheric disturbances induced by an intense storm on 26 August 2018.  Anomalous increases (decreases) in the GIM TEC and CSES plasma density (temperature) appear specifically over the epicenter day 1-5 before the M7.0 earthquake and aftershocks, and however similar TEC and CSES anomalies occur globally in the southern hemisphere during the storm days of 26-28 August 2018.  The CSES ion velocity shows that the seismo-generated electric fields associated with the M7.0 earthquake are 0.06-0.21 mV/m eastward and 0.13-0.14 mV/m downward on 1-3 August 2018, while the penetration electric fields during the storm periods of 26-28 August 2018 are 0.17/0.60 mV/m westward/downward at post-midnight of 02:00 LT and 0.26/0.34 mV/m eastward/upward at post-noon of 14:00 LT.

ST17-A007
Statistical Analysis of EUV Dynamic Spectra and Their Impact on the Ionosphere During Solar Flares

Shohei NISHIMOTO1#+, Kyoko WATANABE1, Hidekatsu JIN2, Toshiki KAWAI3, Shinsuke IMADA3, Tomoko KAWATE4
1National Defense Academy of Japan, Japan, 2National Institute of Information and Communications Technology, Japan, 3Nagoya University, Japan, 4National Institute for Fusion Science, Japan


Solar flares suddenly emit strong multi-wavelength electromagnetic emissions. Among these emissions, X-rays and extreme ultraviolet (EUV) emissions rapidly change the physical composition of the Earth's ionosphere, thereby causing space weather phenomena such as the sudden ionospheric disturbance etc. (Dellinger 1937).  We verify the extent of reproducing the flare emission spectra and their profiles using a newly developed simple method based on the physical process of the flare loop (Kawai et al., 2020). In this method, we convert the soft X-ray light-curves observed during flare events into EUV emission spectra using a one-dimensional hydrodynamic calculation and the CHIANTI atomic database (Dere et al., 2019). We examined the “EUV flare time-integrated irradiance” and “EUV flare line rise time” of the EUV emissions for 21 events by comparing the calculation results of the proposed method and observed EUV spectral data. The proposed method succeeded in reproducing the EUV flare time-integrated irradiance of the Fe VIII 13.1 nm, Fe XVIII 9.4 nm, and Fe XX 13.3 nm, as well as the 5.5-35.5 nm band. For the EUV flare line rise time, there was acceptable correlation between the proposed method estimations and observations for all Fe flare emission lines. In order to examine the effect of flare EUV emission on the ionosphere, we input our calculated flare EUV spectra that mentioned above to the Earth's atmospheric model GAIA (Ground-to-Topside Model of Atmosphere and Ionosphere for Aeronomy; Jin et al., 2011). We compared the total electron content (TEC) variation in the ionosphere reproduced by GAIA with observations for 21 events. We examined in detail the temporal changes in ion densities of major thermosphere species (O+, O2+, N2+ and NO+ ) to clarify which wavelengths in the solar emission spectrum are ionize the atmosphere at which altitude in the ionosphere.

ST17-A008
Relationship Between Solar Flare Spectra and the Dellinger Phenomenon

Kyoko WATANABE1#+, Shohei NISHIMOTO1, Chihiro TAO2, Michi NISHIOKA2
1National Defense Academy of Japan, Japan, 2National Institute of Information and Communications Technology, Japan


The composition in the Earth's ionosphere changes due to X-ray and Extreme ultraviolet (EUV) radiation associated with solar flares. When these radiation reaches the ionosphere D region at lower than 100 km, the ionization and molecular dissociation of atmospheric components in the ionosphere, thereby causing the Dellinger phenomenon (Dellinger 1937). Generally, the Dellinger phenomenon is considered to be caused by the occurrence of M-class or higher solar flares and predicted by using the magnitude of the solar flares. However, reportedly, the Dellinger phenomenon sometimes occurred even in during C-class flares; however, it did not occur even in during X-class flares (e.g. Tao et al., 2020). From these results, it is considered that the flare emissions contributing to the occurrence of the Dellinger phenomenon may also be affected by other emissions. The occurrence of the Dellinger phenomenon can be known by using the minimum reflection frequency (fmin) from vertical incident ionograms. Therefore, we checked the fmin observed in the ionosonde held by the National Institute of Information and Communications Technology at Kokubunji. And then, we statistically compared with the solar flare emission (X-rays and EUVs). When the fluctuation of fmin (about 4,000 events) between 1996 and 2018 was compared with the Geostationary Operational Environmental Satellites (GOES) X-ray intensity, a relationship was seen that was almost in agreement with the results of previous studies (Sato, 1975; Tao et al., 2020). In this paper, we will report the results of statistical comparison of the Dellinger phenomenon (fmin fluctuation) that occurred from 1996 to 2018 with X-ray data. We also report on the results of comparisons between fmin and EUV data which are observed by the Solar and Heliospheric Observatory/Solar EUV Monitor, Project for On-Board Autonomy-2/LYman-alpha RAdiometer, and GOES/EUV Sensors, and discuss the effects of EUV emissions on the Dellinger phenomenon.

ST17-A011
Large-scale Plasma Jets in the Magnetosheath and Auroral Activity

Alexei DMITRIEV#+
Moscow State University, Russian Federation


There are numerous observations of fast and dense plasma streams, so-called jets, propagating inside the magnetosheath. It was found that large-scale jets with duration of minutes can effectively interact with the dayside magnetopause. The interaction is followed by an increase of auroral electrojet (AE) index by up to 100 nT with a time delay of several minutes. The magnetic disturbances are detected first on the dayside and then propagate toward the night side. The jet-related auroral activity is pronounced during quite geomagnetic conditions and can occur under northward orientation of interplanetary magnetic field. We interpret this phenomenon as a complex result of two effects: localized compression of the magnetopause and penetration of the magnetosheath plasma inside the magnetosphere.

ST17-A005
Off-axis Imaging Characteristics of the X-ray Telescope onboard Hinode

Junho SHIN1#+, Ryouhei KANO2, Takashi SAKURAI2, Yeon-Han KIM3, Yong-Jae MOON1
1Kyung Hee University, Korea, South, 2National Astronomical Observatory of Japan, Japan, 3Korea Astronomy and Space Science Institute, Korea, South


Since the launch of Hinode in 2006, the X-Ray Telescope (XRT) has provided us a huge amount of coronal image data with unprecedented high spatial resolution and time cadence, which are used not only for morphological studies of active regions but for the quantitative studies of plasma properties. Hinode/XRT equips the modified Wolter-type grazing incidence (GI) mirror for collecting the lights from the full solar disk area and its neighboring region in 34 x 34 arcmin FOV. The degree of imaging quality of an optical instrument is in general getting worse as it goes away from the center and therefore it is requested to pay more attention when dealing with the data near the periphery of FOV. In this presentation we focus on the issues related to the imaging characteristic of Hinode/XRT, particularly for the data taken from the off-axis region. In order to derive physical parameters of coronal plasma using the data in the region far off from the optical center, it is necessary to perform a series of calibration procedures such as the reduction of scattered lights and the correction of vignetting effect. The light scattered by the roughness of GI mirror surface should be restored in a proper way especially when the data are taken from the faint region over the solar limb and thus the accurate information on the PSF must be essential. It have been revealed from our analysis of over-exposed in-flight data that the scattered light has a power-law distribution and shows an energy dependence. Vignetting is also an important optical characteristics for describing the telescope's performance. We have found that the degree of vignetting varies linearly from the optical center and shows an energy dependence. More results on the interesting off-axis optical characteristics of Hinode/XRT will be discussed in detail.

ST17-A002
On the Walén Relation for Alfvénic Fluctuations in Interplanetary Space

Ya-Hui YANG1#+, Jih-Kwin CHAO2, L. C. LEE3
1National Central University, Taiwan, 2Department of Space Science and Engineering, National Central University, Taiwan, 3Academia Sinica, Taiwan


In the interplanetary space, the majority of the Alfvénic fluctuations cannot satisfy the Walén relation even though the plasma and magnetic field fluctuations are correlated very well. Finding a proper de Hoffman-Teller (HT) wave frame velocity is thus important for characterizing the Alfvénic fluctuations. Recognizing that the Alfvénic fluctuations emanating from different sizes of solar wind streams have their own HT frames, we propose a new scheme called the Wave Frame with Varying Velocity (WFVV) Method by considering the local averaged HT frame to find a time-varying profile of HT frame velocity. By re-examining two Alfvénic events on 2002 October 14 and 17, we show that the WFVV Method can provide the HT frame variation in more detail with a better Walén test result and a smaller convection electric field, particularly for the large solar wind changes associated with directional discontinuities. In addition, we note that the degree of Alfvénicity tends to decrease with an increasing variance of HT frame velocity. We will demonstrate the results of Walén analysis from different schemes and discuss their differences in this presentation.

ST18-A006
Interhemispheric Conjugacy of Concurrent Onset and Poleward Traveling Geomagnetic Responses for Throat Aurora Observed Under Quiet Solar Wind Conditions

HuiTing FENG1+, Desheng HAN2#
1GFZ, Germany, 2Tongji University, China


Throat auroras frequently observed near local noon have been confirmed to correspond to magnetopause indentations, but the generation mechanisms for these indentations and the detailed properties of throat aurora are both not fully understood. Using all‐sky camera and magnetometer observations, we reported some new observational features of throat aurora as follows. (1) Throat auroras can occur under stable solar wind conditions and cause clear geomagnetic responses. (2) These geomagnetic responses can be simultaneously observed at conjugate geomagnetic meridian chains in the Northern and Southern Hemispheres. (3) The initial geomagnetic responses of throat aurora show concurrent onsets that were observed at all stations along the meridians. (4) Immediately after the concurrent onsets, poleward moving signatures and micropositive bays were observed in the X components at higher‐ and lower‐latitude stations, respectively. We argue that these observations provide evidence for throat aurora being generated by low‐latitude magnetopause reconnection. We suggest that the concurrent onsets reflect the instantaneous responses of the reconnection signal arriving at the ionosphere, the followed poleward moving signatures reflect the antisunward dragging of the footprint of newly opened field lines, and the micropositive bays may result from a pair of field‐aligned currents generated during the reconnection. This study may shed new light on the geomagnetic transients observed at cusp latitude near magnetic local noon.

ST06-A011
Ionospheric Echoes of Semantic Segmentation in Digital Ionograms Using Deep Watershed Transform

Hao-Wei HSU#+, Chia-Hsien LIN
National Central University, Taiwan


The ionosphere is mainly affected by space weather, including solar flares, coronal mass ejections, high-speed solar wind, corotating interaction regions, etc. Ionospheric disturbances reduce the accuracy of GNSS. In modern society, real-time monitoring of the ionosphere is an important issue. When we monitor the ionosphere in real time, the challenge is that there is a big amount of data that needs to be processed. We use artificial intelligence (AI) for quickly semantic segmentation of digital ionograms. Even the ionograms have low SNR, Deep Watershed Transform(DWT) can provide very good results. We collected 2109 ionograms to test DWT performance, it takes less than five minutes to evaluate all dataset and get more than 60% of accuracy.The work was performed as part of NCU AI group: Chang Y.-C., Dmitriev A., Hsieh M.-C., Hsu H.-W., Huang G.-H., Li Y.-H., Lin C.-H., Lin Y.-C., Mendoza M., Tsai L. C., Tsogtbaatar E.

ST06-A015
Ionospheric Echoes Detection in Digital Ionograms Using Mask Region-based Convolutional Neural Network (mask Rcnn)

Yu-Ciang LIN#+
National Central University, Taiwan


The Ionosphere disturbance is mostly affected by space weather such as solar flares, solar energetic particles, coronal mass ejections, corotating interaction regions even high-speed solar wind from coronal holes. However, ionosphere disturbances can affect the accuracy of GNSS operation so that it's important to monitor and predict space weather in real time. Because these challenges require a huge number of data to analyze, we use artificial intelligence (AI) to help us do semantic segmentation of digital ionograms. Mask Region-Based Convolutional Neural Network (Mask RCNN) is one of the algorithms to work on digital ionograms. We use 2109 ionograms to test the performance of Mask RCNN, and even the ionograms above Taiwan have low Signal to Noise Ratio (SNR) Mask RCNN can provide good results.The work was performed as part of NCU AI group: Chang Y.-C., Dmitriev A., Hsieh M.-C., Hsu H.-W., Huang G.-H., Li Y.-H., Lin C.-H., Lin Y.-C., Mendoza M., Tsai L.-C., Tsogtbaatar E.