COMMISSION G: Ionospheric Radio and Propagation(including ionospheric communications and remote sensingof ionised media)(November 2016 – October 2020)
Edited by Mamoru Yamamoto (Kyoto University)
1. Summary
URSI Commission G aims to discuss radio and its propagation in the ionosphere. In addition tothese essential purposes, this commission is to study the ionospheric communications and remotesensing of the ionized media, too. The last purpose includes general research of the ionosphere and/or
the upper atmosphere. We should note that measurement techniques and instruments take importantpart of our research in the commission G.
The ionosphere that overlaps with the upper atmosphere is the transition region from the Earth's
atmosphere to the space. It is a region that is largely affected from both the top and bottom, andcomplex interactions occur. Recently, studies of the other planets are getting more important in our
research community. Researchers from Japan contribute the vast research area of the USRI
Commission G in wide spectrum. Level of the research is also very high. We have variety ofmeasurement instruments on the ground, sounding rocket, and satellites. Region of the studies spreads
from Japan, Asia to the world as well. We have big efforts on modeling (large-scale computer
simulation) and database. Comprehensive analyses of multiple data are also actively conducted.
This report compiles contributions from our committee members. We summarize the research
activities by showing major measurement instruments, observation network, related model/databaseprojects, and future plans that are closely related to the Commission G. We also tried to include URL
to many of our web pages, which we hope to be useful to interested readers. Following are the contentsof our report.
2. Activity Report
2.1. Instruments and measurement techniques
2.1.1 PANSY
2.1.2 EISCAT radar
2.1.3 SuperDARN Hokkaido East / West Radars
2.1.4 MU radar
2.1.5 Equatorial Atmosphere Radar
2.1.6 Ground-based network observations
MAGDAS / PWING project / ISEE Magnetometers / VLF/ELF /New digital receiver for HF Doppler sounding /VHF aeronautical navigation signals / Airglow imagers /SEALION / Planetary atmospheres
2.1.7 GNSS receiver network
2.1.8 Satellite missions
IMAP/VISI / AKATSUKI / HISAKI / ARASE
2.1.9 Sounding rocket experiments
JAXA/ISAS Sounding Rocket SS-520-3 / Rocksat-XN rocket
2.1.10 Instruments for planetary sciences
2.2. Model, database, and multi-instrument analysis
2.2.1 GAIA
2.2.2. Numerical Simulations of Atmospheric Escape12.2.3 IUGONET
2.2.4. Shortwave Propagation Simulator (HF-START) Service
2.2.5. Studies of ionosphere/atmosphere vertical coupling
2.3. On-going and future plans
2.3.1 Masterplan 2014/2017/2020
2.3.2 Telescope PLANETS
2.3.3. FACTORS

2. Activity Report
2.1 Instruments and measurement techniques
2.1.1 PANSYPANSY (Program of the Antarctic Syowa MST/IS Radar) is a project which was started in 2000
to comprehensively study the polar atmosphere with a large aperture atmospheric radar as the main
instrument combined with complementary observation techniques and also with numerical modelingand theoretical works. (PANSY project web page: http://pansy.eps.s.u-tokyo.ac.jp/en/)Continuous full system observation (with 520 kW transmitting power and 1045 array antennas)of the PANSY radar started late September 2015 and is ongoing until 2020. It enables us to capture
various temporal- and spatial-scale phenomena in the Antarctic troposphere, stratosphere, mesosphere,
and thermosphere/ionosphere with high temporal and vertical resolution throughout the year and tocontribute to improving global climate models for better understanding of future climate change.
In addition, the first international campaign based on a combination of GCM (General Circulation
Model) simulations and simultaneous observations by several MST/IS radars over the world including
PANSY and some complementary instruments such as MF (Medium Frequency) and meteor radars,
lidars, imagers, and so on was successfully conducted in the winters of 2017, 2018, 2019, and 2020.
This campaign was named the Interhemispheric Coupling Study by Observations and Modeling(ICSOM: see details at http://pansy.eps.s.u-tokyo.ac.jp/icsom/), and approved as a project for
ROSMIC (Role Of the Sun and the Middle atmosphere/thermosphere/ionosphere In Climate) of
SCOSTEP (Scientific Committee on Solar-Terrestrial Physics) under ICSU (International Council for
Science). It is expected that these international collaborations including the PANSY radar will promotea more accurate understanding of the Antarctic atmosphere and interhemispheric coupling processes.

2.1.2 EISCAT radar
NIPR (National Institute of Polar Research) and Institute of Space-Earth Environmental Research(ISEE), Nagoya University have joined the EISCAT (European Incoherent Scatter) Scientific
Association since 1996 and conducted observations with three incoherent scatter radar systems, at
224 MHz, 931 MHz in Northern Scandinavia and one at 500 MHz on Svalbard. They kept highresearch activity in this period. Examples of research results are as follows. (EISCAT webpage in
NIPR: http://eiscat.nipr.ac.jp/)
Ogawa et al (2019) studied data from the EISCAT radars above Tromsø and Longyearbyen
between 1996 and 2015, and investigated how velocity and flux of ionospheric ion upflows varyduring magnetic storms driven by corotating interaction regions (CIRs) and coronal mass ejections(CMEs). In the daytime, substantial ion upflows last for a few days after the storm onsets under small
CIR storms, whereas they last for only a day under small CME storms. Kawamura et al (2020) studied
the lifetime of O(1S) using the EISCAT UHF radar above Tromsø and a ground-based five-wavelength
photometer to reveal the emission altitude of pulsating aurora (PsA). The emission altitude becomes
lower in the morning side than in the midnight sector, which indicates that the energy of PsA electrons2

is higher in the later Magnetic local time (MLT) sector. Takahashi et al (2019) studied relationshipbetween the motion of auroral patches and the polarization electric field generated therein observedwith EISCAT radars, Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA), and an all‐sky
imager. The electron density and the height‐integrated Hall conductance between 80 and 120 km wereenhanced by a factor of 2–4 inside the auroral patches. Enhanced ion velocities due to the polarizationelectric field was also observed in the auroral patches at up to 200‐km altitude.
2.1.3 SuperDARN Hokkaido East / West Radars
SuperDARN (Super Dual Auroral Radar Network) is an international collaboration project bymore than ten countries in the world. In its initial stage, most SuperDARN radars have observed thepolar regions higher than 60 geomagnetic latitude until 2004. The mid-latitude SuperDARN radars
began operation in 2005, and several discoveries have been made using newly constructedSuperDARN radars by several countries in the world such as Japan, USA, UK, Australia and China.
The Hokkaido East / West radars were constructed by Nagoya University in 2006 / 2014, and arelocated in the lowest latitude of the recently constructed radars. Detailed information on these radars
is found from: http://cicr.isee.nagoya-u.ac.jp/hokkaido/index.html
The radars are used for a variety of studies of the magnetosphere and the ionosphere. In January
2017, an international workshop on the review of the accomplishment of the mid-latitude SuperDARN
was held in Nagoya University. 15 participants from 5 countries intensively discussed
accomplishments and future directions of the mid-latitude SuperDARN network. About two years later,a review paper on the mid-latitude SuperDARN was published in the Progress in Earth and Planetary
Science (Nishitani et al., 2019, https://doi.org/10.1186/s40645-019-0270-5). The paper consists of 5scientific sections (convection, ionospheric irregularities, HF propagation, ion-neutral interaction, and
MHD waves), followed by the discussion of future directions.

2.1.4 MU radar
The MU radar is the 46.5-MHz atmospheric radar located in Shigaraki, Shiga, Japan. The radar
can measure atmospheric winds from near the surface to about 20km, and is also useful to measurecoherent and incoherent scatters from the ionosphere. Multi-beam capability with the active-phasedarray antenna is the most power feature of the system, and the various interesting observations wereconducted so far. (MU radar and EAR web: http://www.rish.kyoto-u.ac.jp/mu+ear/english/index.html)
IEEE, an association dedicated to advancing innovation and technological excellence for the
benefit of humanity, is the world’s largest technical professional society. IEEE established theMilestones Program in 1983 to recognize the achievements of the Century of Giants who formed theprofession and technologies represented by IEEE. Each milestone recognizes a significant technicalachievement that occurred at least 25 years ago in an area of technology and having at least regional
impact. In December 2014, IEEE decided to award Milestone to the MU (Middle and Upper
atmosphere) radar as the first large-scale MST (Mesosphere, Stratosphere, and Troposphere) radarwith a two-dimensional active phased array antenna system. The MU radar was established in 1984by Kyoto University with collaboration of Mitsubishi Electric Corporation, and enabled continuous
and flexible observation of the atmosphere, and has contributed to the progress of atmospheric scienceand radar engineering. Its dedication ceremony was successfully held on May 13, 2015 at Shirankaikan,
Kyoto University.
Recent topic of the MU radar is the combination of its radar range-imaging observations of the
turbulence and the direct measurement of the atmospheric parameters by using UAV. Scientists fromUSA and France conducted the observation campaign experiments.
MU radar web: http://www.rish.kyoto-u.ac.jp/mu/en/32.1.5 Equatorial Atmosphere Radar
Equatorial Atmosphere Radar (EAR) is a big atmospheric radar located in West Sumatra,Indonesia. The EAR was established in June 2001, and has continued long-term observations sinceJune 2001. Research Institute for Sustainable Humanosphere (RISH), Kyoto University and National
Institute of Aeronautics and Space (LAPAN) of Indonesia jointly operate the facility that is open toscientists from both countries and from the world. The EAR data are basically opened.
Recent research topic is the joint experiment with EAR and the ultra long-duration balloon
campaign that is named Stratole-2. Stratole-2 is a project to fly super pressure balloon around theequatorial region at an altitude of 18-20 km. Its first flight tests were conducted in 2019 and we joined
the experiment by providing the EAR data. Data analysis from the experiment is underway.
EAR web: http://www.rish.kyoto-u.ac.jp/ear/index-e.html
Stratolle-2 project web: https://strateole2.cnes.fr/en/strateole-2-0

2.1.6 Ground-based network observations
MAGDASMAGDAS is the world network of magnetometer developed and maintained by International
Center for Space Weather Science and Education (ICSWSE), Kyushu University. MAGDAS network
and its observations are well maintained during this period. Since 2016, new observations started at
10 stations in Malysia, Sri Lanka, Peru. One FM-CW radar started observation of the ionosphere from
Huancayo in Peru. Many studies of atmospheric tides, sudden stratospheric warming, various
ionospheric phenomena, and thermosphere-ionosphere coupling are published in international journals.
Number of MAGDAS related publications is 122 during 2016-2020.
MAGDAS related database web: http://data.icswse.kyushu-u.ac.jp/
PWING Project
The PWING stands for "study of dynamical variation of Particles and Waves in the INner
magnetosphere using Ground-based network observations." The PWING project started on April
2016 as a 5-year project of the Grant-in-Aid for Specially Promoted Research of the Japan Society for
the Promotion of Science (JSPS) (16H06286). The PWING project deploy OMTIs all-sky cooledCCD airglow imagers, 64-Hz sampled induction magnetometers, 40-kHz VLF receivers, and 64-Hz
riometers at 8 stations at magnetic latitudes of ~60 degree around the north-pole to cover longitudinalvariation of aurora and electromagnetic disturbances in the inner magnetosphere. About 200 journal
papers have been published related to this project.
PWING web: https://www.isee.nagoya-u.ac.jp/dimr/PWING/en/
ISEE Magnetometers
ISEE, Nagoya University is conducting the ISEE magnetmeter network in order to investigate thePc1 pulsations and geomagnetic field disturbances. The network is expanding now and reaches morethan 15 stations from the equatorial to the polar regions. New induction magnetometers at subauroral
latitudes are deployed by the PWING project in 2017-2018. Various results has been obtained using
these imagers, including propagation of Pc1/electromagnetic ion cyclotron (EMIC) waves near theplasmapause from the magnetosphere to the ionosphere and interaction of EMIC waves with ringcurrent ions to cause isolated proton aurora at subauroral latitudes. The digital data in CDF format areavailable via the ERG science center.
4

ISEE Magnetometers web: https://stdb2.isee.nagoya-u.ac.jp/magne/
VLF/ELF
Institute for Space-Earth Environmental Research (ISEE), Nagoya University has operated nine
VLF/ELF receivers at subauroral latitudes and in Japan. The receivers at subauroral latitudes are
deployed by the PWING project in 2017-2018. They are 40-kHz sampling continuous waveform
measurements. Various results on the magnetospheric VLF/ELF waves, such as chorus and quasiperiodic emissions, has been reported recent years, including their longitudinal extent andmagnetosphere-to-ground propagation. The spectral data are available via the ERG science center.
The raw waveform data are also available upon request.
ISEE VLF/ELF web: https://stdb2.isee.nagoya-u.ac.jp/vlf/
AVON (Asia VLF Observation Network) group has been making continuous measurements of
LF/VLF/ELF waves at Tainan (Taiwan), Saraburi (Thailand), Pontianak (Indonesia), Los Banos(Philippines), and Hanoi (Vietnam) since December 2007. 14 Universities/institutes including Chiba,
Hokkaido, Tohoku Universities and Ashikaga Institute of Technology participate in the AVON project.
The antennas consist of a monopole antenna, a dipole antenna, and an orthogonal loop antenna. The
sampling frequency of LF/VLF transmitter signals is 200 kHz, while that of VLF/ELF waves radiatedfrom lightning discharges is 100 kHz. Recently, the first observation of about 100-s periodic
oscillations of intensity and phase in two LF transmitter signals over Japan at 05:52-05:56 UT on
March 11, 2011 (about 5’ 42” after the main shock onset the M9.0 earthquake) was reported. The 100s LF periodic oscillation was caused by the vertical propagation of the acoustic waves excited by theseismic Rayleigh waves. Tohoku University group is also operating LF/VLF transmitter observation
at Ny-Alesund (Norway), Poker Flat (Alaska), Athabasca (Canada), Zhigansk (Russia) to detect
energetic electron precipitation from inner magnetosphere. These observations are a part of theground-based observation networks for the ERG satellite launched on December 20, 2016.
New digital receiver for HF Doppler sounding
The University of Electro-Communications (UEC) has promoted HFD sounding in Japan. Now,four research institutes (Chiba University, Kibi International University, Nagoya University, National
Institute of Technology, Kitakyushu College) have been cooperating to continue the observations. Dueto the decrease of people who can handle analog circuits, it has become difficult to maintain existing
analog systems. We have developed a digital HFD receiver system using SDR (Software-DefinedRadio), which enables us to develop the receiver without the knowledge of the analog circuit devices.
The new digital receiver is inexpensive and small. Therefore, we can easily deploy new receiving
stations not only in Japan but in other countries. The dynamic range of the new receiver is wider (>130 dB) than that of the previous system. The signal-to-noise ratio has also been significantly
improved by 20 dB. The new digital receivers have been installed in seven stations of the HFD
observation network (as of August 2021) and demonstrated the feasibility of SDR in actual ionosphericobservations.
Project website: http://gwave.cei.uec.ac.jp/~hfd
VHF aeronautical navigation signals
University of Electro-Communications and other groups established a ground-based network ofreceivers of anomalous long-distance propagation of VHF aeronautical navigation signals (108-118
MHz). They were able to image the locations of the sporadic E (Es) layer by mapping the reflection
points of the signals of which source were identified according to the information published foraeronautical operations. It was found that the anomalous propagation in the VHF navigation bandoccur quite frequently, sometimes the strength can be higher than the limit required for airborne
receivers to work properly, and in some special cases it could be stronger than those from nearby
stations. The results were reported to International Civil Aviation Organization (ICAO), and next5

update of an ICAO manual on aeronautical radio frequency spectrum will include the anomalous
propagation effects on aeronautical navigation signals.
Reference: Hosokawa, K., J. Sakai, I. Tomizawa, S. Saito, T. Tsugawa, M. Nishioka and M. Ishii, A
monitoring network for anomalous propagation of aeronautical VHF radio waves due to sporadic E inJapan, Earth, Planets and Space, 72, 2020.
Project website: http://gwave.cei.uec.ac.jp/cgi-bin/vor/vhf.cgi
Airglow imagers
ISEE, Nagoya University is conducting the Optical Mesosphere Thermosphere Imagers (OMTI)
in order to investigate the dynamics of the upper atmosphere through nocturnal airglow emissions.
The network is expanding now and reaches more than 20 stations from the equatorial to the polar
regions. The OMTIs consist of ~20 all-sky cooled-CCD imagers, 5 Fabry-Perot interferometers, 3
airglow temperature photometers, and 3 meridian-scanning photometers. They measure twodimensional airglow images in the mesopauseregion and in the thermosphere, wind and temperaturesin the lower thermosphere, and airglow rotational temperatures in the mesopauseregion.
The researcher group conducts a new project PWING (study of dynamical variation of Particles
and Waves in the INner magnetosphere using Ground-based network observations) and establishes
new observation sites (ground-based stations) at 8 locations in northern subauroral region.
OMTI web: http://stdb2.isee.nagoya-u.ac.jp/omti/
PWING web: https://www.isee.nagoya-u.ac.jp/dimr/PWING/en/
SEALIONSEALION is an ionospheric observation network in Southeast Asia to monitor and study theoccurrence and growth of equatorial ionospheric disturbances, especially plasma bubbles. The network
has been setup by National Institute of Information and Communications Technology (NICT) since2003 and has been operated to date by NICT with an international effort by seven institutes in five
Southeast Asian countries. SEALION is one of the few observation bases in the world that is uniquein having conjugate observational points both in the northern and southern hemispheres and aroundthe magnetic equator. In January 2020, a new VHF radar was installed in Chumphon, Thailand, close
to the magnetic equator, which is expected to capture the whole picture of plasma bubble generation.
SEALION data web: https://aer-nc-web.nict.go.jp/sealion/
Planetary atmospheres
Tohoku University and related groups carried out campaign-based large telescope observations ofplanetary atmosphere and ionosphere. Using the infrared high-resolution spectrographs installed on
big-telescopes, such as Subaru/COMICS and IRCS and NASA IRTF/CSHELL, and small-telescopes
Tohoku-60cm and Tohoku-40cm telescopes at the summit of Haleakala, they reported Jupiter’s
infrared auroral and thermospheric emission (Sinclair et al., 2019, Kita et al., 2018, Watanabe et al.,2018), Venus’s mesosphere (Takami et al., 2020), Pluto’s atmosphere (Arimatsu et al., 2020), and longterm volcanic activity of Jupiter’s satellite Io (Sakanoi et al., 2017). Nakagawa et al. (2016) reported
the development of a new Mid-Infrared Laser Heterodyne Instrument (MILAHI) with >10^6 resolving
power at 7–12 μm. These measurement techniques are applied to exoplanets (Ge et al., 2019).
They are also operating the large radio telescope (IPRT) at Iitate, Fukushima, and HF antennas tomeasure planetary and solar radio emission (Kaneda et al., 2018, 2017, Tsuchiya et al., 2019b, 2018c,
Hans et al., 2018). IPRT is a ground-based VHF-UHF radio telescope developed by Tohoku University
and operated since 2000. IPRT has two distinctive radio receivers; one is a low noise and quite stable
receiver tuned at 325MHz and 785MHz, and another one is a 100-500MHz spectro-polarimeter, named
AMATERAS (the Assembly of Metric-band Aperture TElescope and Real-time Analysis System). The
former is mainly used for observing Jupiter’s synchrotron emission with the sensitivity of 0.1Jy, and6enables us to investigate dynamical variations of Jupiter’s deep inner magnetosphere. The latter is used
for observing solar radio bursts with 10ms accumulation time and 61 KHz bandwidth, and enables us
to clarify various micro structure of wave-particle or wave-wave interactions generated in the solar
corona region.
Spacecraft, space telescope and air plane measurement data were also used to understandatmospheres of Mars (Hisaki: Masunaga et al., 2020, 2017, MAVEN: Nakagawa et al., 2020a, 2020b,
Yoshida et al., 2020, Jakosky et al., 2018, Terada et al., 2017, England et al., 2016, Medvedev et al.,2016, TGO/NOMAD: Aoki et al., 2019, Korablev et al., 2018, Vandaele et al., 2018, Mars Express:
Aoki et al, 2018b, Wolkenberg et al., 2018, Noguchi et al., 2017, SOFIA: Aoki et al., 2018a), Juipiter(Hisaki: Hikida et al., 2020, 2018, Kimura et al., 2019, 2018, 2017, Kita et al., 2019a, 2019b, 2016,
Koga et al., 2019, 2018a, 2018b, Tao et al., 2018, 2016, Tsuchiya et al., 2018b, Yoshikawa et al., 2017,
Juno: Clark et al., 2018, Fletcher et al., 2017, HST: Grodent et al., 2018), and Mercury(Messenger:
Aizawa et al., 2020a, 2019b, 2018, Milillo et al., 2020, Murakami et al., 2020) and Venus (Akatsuki:
Nara et al., 2020, Sato et al., 2020, Iwagami et al., 2018, Ogohara et al., 2017, Satoh et al., 2017, 2016,
Ueno et al., 2016).
Modeling studies were used to understand atmospheres of Mars (Kamada et al., 2020, Kuroda etal., 2020, 2019, 2016, Sakai et al., 2018, Terada et al., 2016).
Haleakala long-term monitoring data web: http://c.gp.tohoku.ac.jp/~pparc/data/hal/
IPRT data center web: https://pparc.gp.tohoku.ac.jp/research/iprt/
Radio wave data web: http://c.gp.tohoku.ac.jp/sakura/#data
2.1.7 GNSS receiver network
GEONET (GNSS Earth Observation Network System) is the GPS receiver network over Japanthat is operated by Geospatial Information Authority of Japan (GSI). GEONET consists of 1,300 GPS
or more stations. This is one of the largest GNSS network of the world, and the data of every 30s is
openedtothepublic.
GEONET
web
page(inJapanese)is,
http://terras.gsi.go.jp/geo_info/geonet_top.html. GEONET is also used for ionospheric monitoring
and research. Two-dimensional TEC maps over Japan have been provided routinely by NICT
(https://aer-nc-web.nict.go.jp/GPS/DRAWING-TEC/). Real-time 3D ionosphere tomography with
GEONET data (every 15 min, 6 min latency) has been operated since 2016(https://www.enri.go.jp/cnspub/tomo3/). It is utilized for real-time regional HF propagation prediction
called HF-START (HF Simulator Targeting for All-users’ Regional Telecommunication). Since 2018,
real-time rate-of-TEC index (ROTI) maps over Japan have been provided every 5 min by ENRI. Oneof the prominent outcome of the real-time ROTI mapping is the study of the Es layer(https://www.enri.go.jp/cnspub/susaito/rocket/recent_roti.html). Daytime Es layer can be detected byprojecting ROTI values at an altitude of 100 km. Furthermore, characteristics of the Es layer such as
orientation and propagation velocity can be estimated.
More application-oriented study is also important with the GNSS use for the ionosphere. ENRI is
leading activities to characterize the spatial gradient in ionospheric TEC for aviation use of GNSS ina framework of ICAO Asia-Pacific region. Ionospheric TEC gradient data fromStates/Administrations in the Asia-Pacific region have been consolidated and a common “threat model”
in the region for the ground-based augmentation system (GBAS) to enable precise approach guidance
for airplanes has been established in 2016. Studies to improve the threat model as well as evaluationof TEC gradients of the background ionosphere are being conducted. Scintillation of GNSS signals
are also of great interest for GNSS community. ENRI has been studying the ionospheric scintillation
effects on GNSS signals from multiple constellations (GPS, GLONASS, Galileo, Beidou, QZSS etc.)
and multiple frequencies (L1, L2, and L5) by using networks in southern Japan and Southeast Asia.
72.1.8 Satellite missions
During the period of 2016-2020, there are several satellite missions conducted by JAXA, and used
for the studies of the ionosphere, magnetosphere and planetary sciences.
IMAP/VISI
Airglow emissions at the lower-thermosphere (O2 762 nm, 95km alt.) and the upper-thermosphere(O 630 nm, 250 km alt.) are measured with IMAP/VISI on the international space station (ISS). Many
concentric gravity wave events in the O2 emission, and equatorial anomaly and plasma bubbles in
O630 nm emission (Perwitasari et al., 2016, Nakata et al., 2018). Characteristics of mesospheric bore
events were precisely examined using statistical data of O2 emission (Hozumi et al., 2019, 2018).
Further, results from simulatnous measurements between IMAP/VISI and DNB was reported (Yue etal., 2019).
IMAP/VISI project web: https://www.iss-imap.org/
AKATSUKIAKATSUKI, also known as the Venus Climate Orbiter (VCO) and Planet-C, is a Japanese (JAXA)
space probe tasked to study the atmosphere of Venus (Sato et al., 2014, 2015). It was launched aboard
an H-IIA 202 rocket on 20 May 2010. The spacecraft was successfully inserted into the Venus’ orbit
by the thrust ejection operation on December 7, 2015. After checking condition of the on-board
instruments, scientific observations started in April 2016, and data analyses are now carrying out (Naraet al., 2020, Sato et al., 2020, Iwagami et al., 2018, Ogohara et al., 2017, Satoh et al., 2017, 2016,
Ueno et al., 2016).
AKATSUKI mission web: http://www.isas.ac.jp/en/missions/spacecraft/current/akatsuki.html
HISAKIHISAKI, also known as the Spectroscopic Planet Observatory for Recognition of Interaction of
Atmosphere (SPRINT-A), is a Japanese ultraviolet astronomy satellite operated by JAXA. The firstmission of the JAXA’s Small Scientific Satellite program was launched in September 2013 on themaiden flight of the Epsilon rocket. HISAKI carries an extreme ultraviolet spectrometer which will be
used to study the composition of the atmospheres and the behavior of the magnetospheres of theplanets of the Solar System, such as Jupiter (Hikida et al., 2020, 2018, Kimura et al., 2019, 2018, 2017,
Kita et al., 2019a, 2019b, 2016, Koga et al., 2019, 2018a, 2018b, Tanaka et al., 2018, Tao et al., 2018,2016, Tsuchiya et al., 2018b, Yoshikawa et al., 2017, Juno: Clark et al., 2018, Fletcher et al., 2017,
HST: Grodent et al., 2018) and Mars (Masunaga et al., 2020, 2017). Campaign-based collaboration
with coordinated satellite measurements between Hisaki and other spacecraft, such as HST and Juno,
carried out.
HISAKI mission web: http://www.isas.ac.jp/en/missions/spacecraft/current/hisaki.html
ARASE
ARASE, also known as Exploration of energization and Radiation in Geospace (ERG), is ascientific satellite to study the Van Allen belts. It was developed by the Institute of Space andAstronautical Science of JAXA. ARASE was launched aboard Epsilon launch vehicle at 11:00:00, 20
December 2016 UTC into apogee height 32250 km, perigee 214 km orbit. Subsequent perigee-up
operation moved its orbit to apogee 32110 km, perigee 460 km of 565 minutes period. After initialchecking for satellite and on-board instruments, JAXA confirmed that every function is working well.
Nominal operation has been started in March 2017, and scientific results for pulsating aurora,
characteristics of chrus waves and ECH waves in the magnetosphere, high-energy electron
precipitations, and development of instruments and onboard software are reported in many papers(Colpitts et al., 2020, Fukizawa et al., 2020, Hosokawa et al., 2020, Inaba et al., 2020, Miyoshi et al.,8

2020, Kataoka et al., 2020, Martinez‐Calderon et al., 2020, 2019, Masuda et al., 2020, 2018, Nose etal., 2020, 2018, Kasahara S. et al., 2020, 2018, Shiokawa et al., 2020, 2017, Teramoto et al., 2019,
Hashimoto et al., 2018, Hikishima et al., 2018, Kato et al., 2018a, 2018b, Kasahara, Y. et al., 2018,
Kazama et al., 2018, Kotov et al., 2018, Kumamoto et al. 2018, Nagatsuma et al., 2018, Ozaki et al.,2018, Shimbori et al., 2018, Shoji et al., 2018, Seki et al, 2018, Kasaba et all, 2017, Miyoshi et al.,2017). Related to high-energy electron precipitation which cause the ionization at the D-region altitude,
ground-based radio observation data were reported (Hirai et al., 2018, Ohya et al., 2018, Tsuchiya etal., 2018).
ARASE mission web: http://www.isas.ac.jp/en/missions/spacecraft/current/erg.html

2.1.9 Sounding rocket experiments
JAXA/ISAS Sounding Rocket SS-520-3
The SS-520-3 sounding rocket will be launched from the Svalbard Rocket Range in Svalbard,
Norway in 2021 to understand the acceleration mechanism of escaping ions from ionosphere in thecusp region. This rocket will reach over 800 km in order to observe in the dayside cusp region. EISCAT
radar observation from the ground and optical observation will be simultaneously made, too. We will
investigate the heating and acceleration mechanism of the particles by plasma waves which leads tothe outflow of the ionized particles from the in-situ data obtained by this rocket experiment.
Rocksat-XN rocket
The Rocksat-XN rocket is an international student mission with participation from the US,
Norway and Japan. RockSat-X student experiments are developed with an objective of providing
students with an enhanced experience of flying experiments exposed to the space environment. The
RockSat-XN mission was successfully launched from Andoya Space Center, Norway on January 13,
2019. Japanese group named PARM consists of ISAS/JAXA (high-energy electron, and magnetic
field), Tohoku University (Auroral camera), University of Tokyo (medium-energy electron). The
scientific purpose of PARM is to clarify microbursts (temporal precipitation of high-energy electrons)
accoicated with pulsating aurora. They could observe electron precipitations although pulsating
auroral emission was not observed. This project is evolvingly linked to the next rocket mission called
LAMP which is scheduled to be launched in the winter of 2021.
Rocksat-XN web page: https://spacegrant.colorado.edu/national-programs/rocksat-xn
2.1.10 Instruments for planetary sciences
Now Japan operates three spacecrafts HISAKI, AKATSUKI and MIO for planetary sciences. In
addition, researchers are using number of telescopes on the ground. JAXA recently started the futureMars Moon exploration project (MMX), which is going to observe Phobos, Deimos and Martian
atmosphere, and some groups are joining in the core teams for science and instruments. Hokkaido
University operates 1.6m Pirka Telescope that is dedicated for observations of planets(http://sana.ep.sci.hokudai.ac.jp/nayoro/index-en.html). This telescope joins “Optical and Infrared
Synergetic Telescope for Education and Research (OISTER)” that networks telescopes of seven
universities and National Astronomical Observatory of Japan (NAOJ) (Project web page:
http://oister.oao.nao.ac.jp/ (in Japanese)). Tohoku University also plays an important role to study
planets from the ground-based telescope. They were operating a 60-cm telescope (T60) dedicated forplanetary observations at the summit of Haleakala (https://pparc.gp.tohoku.ac.jp/haleakala/). Visible
chronagpraph imager, high-resolusion Echellle spectrograph (VISP), and super-high resolution
heterodyne spectrograph (MIHAHI) are installed on T60 (Sakanoi et al., 2017). They are also
developing a near-infrared imager and Echelle spectrograph. Nakagawa et al. (2016) reports resultsfor Venus atmosphere from this facility after relocation. As shown in the later section (G3.2), the9research group is developing a 2-m telescope called PLANTES in the same location. The study of theplanetary atmosphere is a hot topic in the research field and more data from Japanese satellites andground-based telescopes are now expected.

2.2. Model, database, and multi-instrument analysis
2.2.1 GAIA
Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy (GAIA) is a global
physics model of the Earth's whole atmospheric regions from the troposphere to the topsidethermosphere as well as the ionosphere. The model has been developed under the collaboration
between Kyushu University, Seikei University and NICT since 2007, in aiming to understand theprocess of vertical coupling in the Earth's atmosphere both for the short and long terms, to understandthe process of occurrence, growth and decay of upper atmospheric disturbances due to solar flares andmagnetic storms, and to build a base model for numerical space weather prediction.
Some of the recent studies using GAIA can be found in the research of long-term verticalatmospheric coupling (Tao et al., 2017; Liu et al., 2017, 2020), equatorial ionospheric disturbances(Yamamoto et al., 2018; Shinagawa et al., 2018, 2020; Ghosh et al., 2020), and global magnetic field
variations (Fujita et al., 2018).
GAIA project web: https://gaia-web.nict.go.jp/index_e.html

2.2.2. Numerical Simulations of Atmospheric EscapeTohoku University group and related researchers have developed electromagnetic hybrid (particle
ions/fluid electrons) and magnetohydrodynamic (MHD) simulation codes that comprehensively
describe the interaction between the solar wind and the ionosphere of unmagnetized planets. They
have been clarifying the physical mechanisms and pathways by which the ionized atmospheres ofplanetary origin removed into space. There simulation results are compared with satellite andspacecraft data and ground-based telescope data in which Tohoku University group leads orparticipates, in order to elucidate the ionization/neutral atmospheric escape and evolution of theatmosphere of Mars, Venus, and exoplanets, and to understand the conditions for the establishment of
habitable planets.

2.2.3 IUGONET
Global phenomena observed in the Earth’s upper atmosphere are the results of many complex
processes, such as the energy and momentum input from the Sun (e.g., solar radiation and solar wind),the energy and momentum transport by atmospheric waves from the lower atmosphere, and various
internal phenomena (e.g., electromagnetic energy transport, plasma convection, chemical reaction).
To understand the mechanism of the long-term variation in the upper atmosphere, therefore, it isimportant to analyze various data (e.g., wind velocity and temperature in the atmosphere, auroral
images, geomagnetic field, solar activity index, etc.) obtained by the global ground-based network
observation.
The Inter-university Upper atmosphere Global Observation NETwork (IUGONET) project started
in 2009 (Abe et al., 2014; Yatagai et al., 2014, 2015). The objective of the project is to establish a
metadata database of various ground-based observation data covering a wide region from the Sun to
the Earth; this will encourage more studies on the mechanisms of long-term variations in the upper10

atmosphere. Also, they developped a software to ease comparison between various types of systems.
IUGONET would be important for future study of complicated nature of the ionosphere.
Project web: http://www.iugonet.org/index.jsp?lang=en
2.2.4. Shortwave Propagation Simulator (HF-START) Service
To provide propagation information of the HF-band radio waves, the service of shortwave
propagation simulator (HF Simulator Targeting for All-users' Regional Telecommnications; HFSTART) has been started in cooperation with National Institute of Information and Communications
Technology (NICT), Chiba University, and Electronic Navigation Research Institute, National
Institute of Maritime, Port and Aviation Technology (ENRI). In this web site, users can calculate a
propagation path between any two points. The three-dimensional ionospheric electron density
distribution is necessary to calculate the propagation path. For the calculation of propagation paths inJapan, the electron density distribution derived by tomography using GNSS TEC data provided by
ENRI is used. For the global propagation paths, we use the electron density distribution derived fromthe IRI model or GAIA simulation results. Since all the data of electron density are provided in almost
real-time, propagation paths can be also determined in almost real time. By specifying the date andtime, users can also calculate the propagation paths for any date and time in the past. HF-START has
been featured in magazines and SNS for amateur radio operators, and improvements such as estimationof reception strength are expected in the future.
Website https://hfstart.nict.go.jp/
2.2.5. Studies of ionosphere/atmosphere vertical coupling
During this period, we have made two major progresses in understanding the vertical coupling
processes in the Earth's atmosphere.
First, the thermosphere and ionosphere have been found to respond to the El-Nino Southern
Oscillation (ENSO), with periodic changes in the thermosphere and ionosphere density. Using a seriesof model simulation, we have revealed the mechanism behind this to be mainly related to tidal
modulations during ENSO. Particularly during the intense 2015/2016 ENSO event, our analysis shows
large DW1 tidal enhancement with peak amplitude of 7.4 K (74%) higher than that under neutral (nonENSO) conditions. For the first time, we successfully quantified the relative contribution of tidal
generation and propagation to the observed tidal enhancement. The tidal generation via tidal heating
is found to contribute 0.5 K (7%) of the enhancement, while tidal propagation contributes to theremaining 6.9 K (93%) of the enhancement. Our study further suggests that the overlapping of the2015 El Niño with the eastward phase of the QBO induced the large enhancement of the DW1. Thesefindings have been highlighted in AGU EOS news letter (Liu et al, 2017, Kogure & Liu 2021).
Second, we have mapped the global gravity wave distribution in the bottom ionosphere for the
first time using LEO satellite observations. The analysis reveals pronounced features on their global
distribution and seasonal variability: (1) A prominent three-peak longitudinal structure exists in allseasons, with stronger perturbations over continents than over oceans. (2) Their seasonal variationconsists of a primary semiannual oscillations (SAO) and a secondary annual oscillation (AO). The
SAO component maximizes around solstices and minimizes around equinoxes, while the AO
component maximizes around June solstice. These GW features resemble those of EPBs in spatial
distribution but show opposite trend in climatological variations. This may imply that stronger
medium-scale GW activity does not always lead to more EPBs. Possible origins of the bottomside
GWs are discussed, among which tropical deep convection appears to be most plausible. Thesefindings have been picked up by newspaper (日刊工業新聞)

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2.3. On-going and future plans
2.3.1 Masterplan 2014/2017/2020
Research Institute for Sustainable Humanosphere (RISH), Kyoto University, National Institute ofPolar Research (NIPR), Institute for Space-Earth Environmental Research (ISEE), Nagoya University,and International Center for Space Weather Science and Education (ICSWSE), Kyushu University
proposed the research project “Coupling process in the solar-terrestrial system” to the meeting. We
study the solar energy inputs into the Earth and the response of Geospace (magnetosphere, ionosphere,
and atmosphere) to the energy input by installing large atmospheric radars with an active phased array
antenna at the equator and the Arctic regions. One is Equatorial MU (EMU) radar by RISH in Sumatera
Island, Indonesia, and the other is EISCAT_3D by NIPR in northern Scandinavia under international
collaborations. We also develop the global observation network that is jointly conducted by ISEE andICSWSE. This project has been successfully selected as one of highest-priority projects in Masterplan
2014/2017/2020. We will keep applying this project to the SCJ Masterplan which next selection will
be in 2023.
Project web: https://www.rish.kyoto-u.ac.jp/masterplan2020/

2.3.2 Telescope PLANETS“PLANETS (Polarized Light from Atmospheres of Nearby ExtraTerestrial Systems)” is a project
to develop a new telescope dedicated to the planetary science by the international collaboration by
Tohoku University, University of Hawai'i Institute for Astronomy (IfA), the Kiepenheuer Institute for
Solar Physics (KIS) and Universidade Estadual de Ponta Grossa (Sakanoi et al., 2018). The telescope
is characterized by a high-contrast optical system provided by a low-scattering off-axis main mirror,
adaptive-optics (AO), and stable atmospheric conditions of an observatory site at a high-altitude. The
scattering light of PLANETS is estimated to be more than 10 times better than that of a normal large
telescope. A major scientific target is to detect faint emissions of gasses erupted from Jovian satellites
Io and Europa. Another major scientific target is the escaping gases surrounding planets. The project
is now underway, and expects the first light in Japan in 2021, and this will be installed at Haleakala in2022.
Project web: https://www.planets.life/planets-telescope/
http://www.ifa.hawaii.edu/haleakalanew/planets/
2.3.3. FACTORSFACTORS stands for Frontiers of Formation, Acceleration, Coupling, and Transport Mechanisms
Observed by the Outer Space Research System, which is going to be proposed as a next-generation
multi-satellite formation flight mission now selected as the working group of ISAS/JAXA. Major
scientific targets are: 1) energy transport in the magnetosphere-ionosphere (MI) coupling system andtheir relationship to small-scale auroral phenomena, 2) particle transport in the MI system by ion
outflow, and 3) neutral-ion coupling in the auroral thermosphere. Multi-satellite observation of smallscale plasma parameters and simultaneous auroral imaging data in the altitude range from ~300 km to4000 km enables us to understand dynamical spatial and time variations of Alfvenic wave acceleration,
field-aligned current, particle distribution function and small-scale auroral emission. Related with thisproject, small-scale auroral dynamics using the past satellite missions and ground-based data werecarried out (Nishimura et al., 2020, Fukuda et al., 2016, Nakamura et al., 2016, Sato et al., 2016)12