Atmospheric vertical coupling and space weather in the solar-terrestrial system

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Weekly Seminar

We'll always have an open seminar every Thursday from 10:30 AM - finish

Our weekly seminars will resume on October 8 2026.

*presenters may be changed without notice due to unforeseen circumstances

Please feel free to come and visit us* at :

W1-A-617-1, West 1 Building, 6th Floor, Ito Campus, Kyushu University (Opposite of Huixin-sensei's office)

*Please contact us beforehand if you wish to visit

News / Recent Events

AOGS (August 3–7, 2026)

We participated in the AOGS conference held at the Fukuoka International Congress Center, where we each gave presentations. You can find details about the event here

Maria Gloria Tan Jun Rios: Doctoral Dissertation Defense (July 30, 2026)

Gloria, one of our doctoral students, successfully defended her dissertation.

Visit of Prof. Mamoru Yamamoto (2026/07/23)

Prof. Mamoru Yamamoto from Kyoto University, gave us a talk on Thermospheric density derivation from Starlink Satellites. More infromation about his work can be found here.

IPS/AOGS Commemorative Public Session, “From the Blue Earth to Beyond the Starry Sky” (2026/06/21)

We are pleased to announce the IPS–AOGS Commemorative Public Session, “From the Blue Earth to Beyond the Starry Sky: A Journey Through Earth and Planetary Sciences with Stories and Visualizations,” to be held on June 21, 2026, at the Fukuoka City Science Museum. The event will bring together researchers and science communicators to share insights into Earth, space, and planetary sciences through talks and visual presentations. Prof. Liu will be one of the guest lecturers, and all are welcome to attend. Further details about the event can be found at www.fukuokacity-kagakukan.jp/activity/2026/05/IPSAOGS.html

Our Research

Our chief

Prof. Dr. Liu Huixin

Ph.D. from Max-Planck-Institute for Aeronomy in Germany in 2001. Research Associate at the National Center for Atmospheric Research, US; Alexander von Humboldt fellow at the German Research Center for Geosciences, Germany; JSPS fellow in Hokkaido University, JSPS RPD fellow in Kyoto University before taking up Professor position at Kyushu University in 2011. She is the Vice President of Kyushu Uinviersity since 2023, responsible for international collaboration on research and education.

Research keywords

Space weather, vertical coupling process through out the atmosphere-ionosphere-magnetosphere-sun system, thermosphere, ionosphere, satellite drag, magnetic storms, EISCAT radar, planetary atmosphere

Research Summary

The area between about 80-1000 km above the Earth surface is called the upper atmosphere, including the ionosphere and thermosphere. This is the region where International Space Station, satellites, and rockets fly, hence is the gateway to space. Distrubances of the ionosphere and thermosphere can have severe societal impact on radio communications, gobal positioning system, satellite orbit control and lifetime, space debris, and so on. This is why ionosphere/thermosphere research is the core part of "space weather" research. Space weather involves processes along the Sun-Earth chain, which can be roughly divided into "downward coupling processes driven by the Sun", "upward coupling processes driven by the meteorological weather", "plasma-neutral coupling". We study these coupling processes using ground, satellite observations, along with numerical simulations using whole atmosphere models.

Here is a short animation explaining the tug-of-war between the solar forcing from above and the terrestrial forcing from below using the example of increasing CO2 on space weather impact presented in Liu et al. 2021: https://doi. org/10.1029/2020JA028607.

A_Cosmic_Tug-of-War.mp4

Project Summary

Sun-Driven Space Weather

Atmosphere-plasma Interaction in Weakly Ionized Media

Space Weather Driven by Meteorological Phenomena

Recent Research Highlights

Long‐Term Trends in Sporadic E Critical Frequency Using Multi‐Decadal Ionosonde Data

Trinidad Duran1 and Huxin Liu2 (2026) link to paper

1Instituto de Física del Sur (CONICET‐UNS), Bahía Blanca, Argentina, 2Department of the Earth and Planetary Science, Faculty of Science, Kyushu University, Fukuoka, Japan.

Figure 4. Long‐term foEs trends (kHz/year) for all stations, shown for each local time and month, calculated by filtering solar activity.

In this study we investigate multidecadal trends in the sporadic E critical frequency (foEs) using more than 30 years of manually scaled ionosonde observations from 14 stations spanning low‐, mid‐, and high latitudes in both hemispheres.The results reveal pronounced regional and latitudinal differences. Mid‐latitude stations in the Southern Hemisphere exhibit predominantly positive foEs trends across most local times and seasons, whereas NorthernHemisphere mid‐latitude stations show positive trends mainly during summer and weak or negative trendsduring other seasons. High‐latitude stations generally display negative trends. Removing the influence of thesolar cycle produces only minor changes in the trend estimates, indicating that solar variability is not the primarydriver of the observed long‐term changes. The spatial and seasonal patterns of the trends are consistent withrecent model predictions linking increasing carbon dioxide concentrations to enhanced vertical ion convergencethrough changes in thermospheric wind shear, particularly at mid‐latitudes. These findings highlight theimportance of resolving diurnal and seasonal variability when assessing long‐term ionospheric change.

Impacts of the GDS 2018 Global Dust Storm on Martian Ionosphere‐Thermosphere Coupling via Atmospheric Tides

Noritsugu Nagata1 , Huixin Liu1,2 , Sonal Jain3 , Scot Rafkin4 , Victoria Hartwick4 , and Hiromu Nakagawa5 (2026) link to paper

1,Department of Earth and Planetary Science, Faculty of Science, Kyushu University, Fukuoka, Japan, 2Quantum and spacetime research institute, Kyushu University, Fukuoka, Japan, 3Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, USA, 4Department of Space Studies, Southwest Research Institute, Boulder, CO, USA, 5Department of Geophysics, Graduate School of Science, Tohoku University, Sendai, Japan.

Figure 3. Mean observed density structures of three neutral (a–f) and three ion (g–l) species as functions of longitude and altitude during 2016 low‐dust period (1st and 3rd rows) and 2018 global‐dust period (2nd and 4th rows). Panels (a, d) show O, (b, e) Ar, (c, f) CO2, (g, j) O+, (h, k) O2 +, and (i, l) CO2 +, averaged over 5 km altitude and 30° longitude bins. The color bars represent the smallest value (neutral: 104.0 cm− 3 , ion: 10− 1.1 cm− 3 ) as blue and the largest value (neutral: 108.6 cm− 3 , ion: 103.1 cm− 3 ) as red.

In this study, we investigate the ionospheric and thermospheric responses to the 2018 Mars global dust storm (GDS 2018) by examining atmosphere–ionosphere coupling through tidal structures. Using Mars Atmosphere and Volatile EvolutioN Neutral Gas and Ion Mass Spectrometer observations, we analyze tidal amplitudes, phases, and inter‐species correlations of longitudinal density variations in neutral (O, Ar, CO₂) and ion (O+, O2+, CO2+) components. Compared with a low‐dust reference period in 2016, we find that (a) neutral density tidal amplitudes are strongly enhanced during GDS 2018 with a clear dependence on species' mass, whereas ion responses are weaker; (b) GDS 2018 introduces species‐dependent planetary‐scale wave structures, including Wave‐1 dominance in O and ions below ∼180 km and Wave‐4 dominance in CO2; and (c) correlations between neutral and ion densities remain high in both periods and become particularly strong above ∼200 km during GDS 2018. These results indicate that neutrals and ions are driven by common wave sources while the dust storm selectively modulates wave amplitudes depending on species and altitude. Our findings highlight the important role of dust‐enhanced tidal forcing in mediating vertical coupling between the Martian lower atmosphere and ionosphere.

A Statistical Study of Polar Cap Patch Occurrence and IMF

Dependence Using GNSS TEC Maps

Qing‐Yu Zhang1,2,3 , Yu‐Zhang Ma1 , Bei‐Chen Zhang2,4, Qing‐He Zhang1,5 , Zan‐Yang Xing1 , Huixin Liu3 , Kjellmar Oksavik6,7 , Xiang‐Cai Chen2,8,9, Ze‐Jun Hu2,8

Yong Wang1 , and Jian‐Ping Wang10 (2026) (link to paper)

1Shandong Key Laboratory of Space Environment and Exploration Technology, Institute of Space Sciences, Shandong University, Weihai, China, 2MNR Key Laboratory for Polar Science, Center for Space Physics and Astronomy, Polar Research Institute of China, Shanghai, China, 3Department of Earth and Planetary Sciences, Kyushu University, Fukuoka, Japan, 4Antarctic Zhongshan Ice and Space Environment National Observation and Research Station, Polar Research Institute of China, Shanghai, China, 5State Key Laboratory of Solar Activity and Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing, China, 6Department of Physics and Technology, University of Bergen, Bergen, Norway, 7Arctic Geophysics, University Centre in Svalbard, Longyearbyen, Norway, 8Arctic Yellow River Earth System National Observation and Research Station, Polar Research Institute of China, Shanghai, China, 9State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, China, 10Instistute of Physics and Optoelectronics Technology, Baoji University of Arts and Sciences, Baoji, China.

(Figure 5) The spatial MLAT‐MLT distributions of polar cap patch occurrence for different IMF clock angle sectors during 2022–2024, binned on a uniformly spaced grid. Each panel shows results for a 45°‐wide clock angle bin centered at (a) θ = 315°, (b) 0°, (c) 45°, (d) 270°, (e) 90°, (f) 225°, (g) 180°, and (h) 135°, as illustrated in the center schematic.

In this paper, we present an automated algorithm for identifying the two-dimensional distribution of polar cap patches from GNSS Total Electron Content (TEC) maps, combining dynamic thresholding with a set of physical constraints. The performance of the algorithm is validated using a well‐documented event, showing close agreement with manual identification in both timing and spatial morphology. Using GNSS TEC data from 2020 to 2024, we analyze the seasonal, universal time (UT), and Interplanetary Magnetic Field (IMF) dependencies of patch occurrence in the northern polar cap. The statistical analysis mainly focuses on solar‐maximum years, during which the algorithm performs more reliably because the higher background TEC facilitates the separation of classical polar cap patches from relatively weak precipitation‐related structures. The resulting occurrence patterns are generally consistent with previous studies. For the year 2023, we further examine the relationship between patch formation and the preceding IMF variations. The statistical analysis reveals that both rapid and large‐amplitude variations in the IMF By and Bz components are closely associated with patch formation. This suggests that IMF‐driven modulation of the convection pattern plays an important role in polar cap patch formation. These results provide new statistical evidence linking IMF variations to patch formation and demonstrate the capability of TEC‐based methods for statistical patch studies. However, the algorithm may underestimate patch occurrence near the dayside source region because newly formed patches may be excluded by the adopted identification criteria, although this does not affect the statistical conclusions of this study.