Japan Geoscience Union Meeting 2024

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P (Space and Planetary Sciences ) » P-EM Solar-Terrestrial Sciences, Space Electromagnetism & Space Environment

[P-EM15] Study of coupling processes in solar-terrestrial system

Wed. May 29, 2024 5:15 PM - 6:45 PM Poster Hall (Exhibition Hall 6, Makuhari Messe)

convener:Mamoru Yamamoto(Research Institute for Sustainable Humanosphere, Kyoto University), Yasunobu Ogawa(National Institute of Polar Research), Satonori Nozawa(Institute for Space-Earth Environmental Research, Nagoya University), Akimasa Yoshikawa(Department of Earth and Planetary Sciences, Kyushu University)

5:15 PM - 6:45 PM

[PEM15-P12] Thermoshperic He variations associated with two storms on February and March, 2023: the NIRAS-2 observations at Longyearbyen (78.1°N, 16.0°E), Svalbard.

*Takanori Nishiyama1,2, Masato Kagitani3, Takuo T. Tsuda4, Tikemani Bag1, Yuki Iwasa5, Yasunobu Ogawa1,2, Fred Sigernes6 (1.National Institute of Polar Research, 2.Department of Polar Science, The Graduate University for Advanced Studies, SOKENDAI, 3.Planetary Plasma and Atmospheric Research Center, Tohoku University, 4.The University of Electro- Communications, 5.National Metrology Institute of Japan, AIST, 6.University centre in Svalbard)

Keywords:metastable Helium atom, upper thermosphere, Ground-based spectroscopic observation, Magnetic strom , Polar Cap, EISCAT Svalbard Radar

Despite the low density of neutral metastable helium, He(23S), in the upper thermosphere and lower exosphere (typically less than 10 atoms cm-3), its bright, ~1 kR, emission signature at 1083 nm makes this airglow feature an attractive potential candidate for remote sensing of the neutral atmospheric temperature and dynamics in this region. Our SWIR imaging spectrograph installed at the KHO Longyearbyen (78.1°N, 16.0°E), NIRAS-2, has a capability to measure the metastable He emission that is blended with Q-branch of OH (5,2) emission. It actually demonstrated that strong enhancement of the He emission took place during twilight conditions when metastable He in the upper thermosphere was sufficiently illuminated. Preliminary analysis was done for He variations associated with two magnetic storms on February and March, 2023. After onset of the February storm, nighttime He column denisty estimated from intensity of the He emission was decreased immediately, and the depression lasted at least a few days. MSIS 2.1calculation can reproduce the He depression above KHO, and suggest that He density at 450 km was reduced to 30% of one during quiet conditions. In this presentation, we would like to show more detailed analysis results.