[P-EM15] Dynamics of Magnetosphere and Ionosphere

[PEM15-20] Thermospheric Radiative Emission Response to Interplanetary Shock

*Tikemani Bag^1,2、Yasunobu Ogawa¹、V. Sivakumar³、Vir Singh⁴ (1.National Institute of Polar Research, Tokyo、2.Center for Environmental Remote Sensing, Chiba University, Japan、3.S. V. Raman Researchers Roadmap, Westville, Durban 4000, South Africa、4.Department of Physics, Indian Institute of Technology Roorkee, India)

キーワード： Interplanetary Shock, Magnetosphere-ionosphere-thermosphere coupling, Radiative cooling, Geomagnetic quiet period

When an interplanetary (IP) shock reaches Earth's magnetosphere, it compresses the magnetic field, triggering geomagnetic activity that affects the magnetosphere ionosphere thermosphere system, including auroras, particle precipitation, thermospheric heating, and atmospheric composition changes. A Superposed Epoch Analysis (SEA) technique is applied to investigate the response of thermospheric Nitric Oxide (NO) emission to IP shock by using observations from SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) instrument onboard the TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics) satellite during geomagnetically quiet periods. Measurements from AMPERE (Active Magnetosphere and Planetary Electrodynamics Response Experiment) show intensified field-aligned currents during IP shocks, with a stronger southern hemispheric response as compared to the Northern Hemisphere. Observations from DMSP (Defense Meteorological Satellite Program) spacecraft indicate an early and significant enhancement in precipitating particle flux below 1keV, while higher-energy particles respond at a later time. A notable pre-event increase in NO density by an order of magnitude is observed at around 130 km due to low-energy particle precipitation. Although atomic oxygen and nitrogen densities decrease by approximately 40% at the same altitude, thermospheric temperature increases by about 100K at 400 km. The results reveal a linear increase in high-latitude NO emission, driven by rapid particle precipitation and thermospheric heating following the IP shock. These findings highlight the coupling between the solar wind, magnetosphere, and thermosphere, offering key insights into space weather effects on Earth's upper atmosphere.