Japan Geoscience Union Meeting 2022

Presentation information

[E] Oral

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

[P-EM09] Space Weather and Space Climate

Mon. May 23, 2022 3:30 PM - 5:00 PM 302 (International Conference Hall, Makuhari Messe)

convener:Ryuho Kataoka(National Institute of Polar Research), convener:Antti A Pulkkinen(NASA Goddard Space Flight Center), Kaori Sakaguchi(National Institute of Information and Communications Technology), convener:Daikou Shiota(National Institute of Information and Communications Technology (NICT)), Chairperson:Kaori Sakaguchi(National Institute of Information and Communications Technology), Ryuho Kataoka(National Institute of Polar Research)

4:15 PM - 4:30 PM

[PEM09-22] Atmospheric ionization caused by X-rays, solar protons, and energetic electrons in September 2017 space weather event

*Kiyoka Murase1, Ryuho Kataoka1,2, Takanori Nishiyama1,2, Kaoru Sato3, Masaki Tsutsumi1,2, Yoshimasa Tanaka1,2, Yasunobu Ogawa1,2 (1.The Graduate University for Advanced Studies, 2.National Institute of Polar Research, 3.The University of Tokyo)


Keywords:Energetic particle precipitation, Atmospheric ionization

On September 11, 2017, when the proton flux peaked in the geostationary orbit, mesospheric echoes were observed down to ~42 km, the lowest altitude ever observed by the PANSY radar at Syowa Station. The ionization rate calculated via PHITS (Particle and Heavy Ion Transport code System) air-shower simulation using proton fluxes obtained by the GOES satellite peaked at ~40 km, suggesting that the echo power is enhanced by the increase in electron density due to proton precipitation. The estimated intensity of cosmic noise absorption (CNA) from the resultant ionization rate was ~2.8 dB, which consistently explains the maximum intensity of observed CNA of ~3.0 dB. X-ray fluxes observed by the GOES satellite were also used as input data for PHITS to estimate the observed increase in CNA due to the two X-class flares at ~9 and ~12 UT on September 6. At ~1345 UT on the same day, a transient low-altitude echo at <50 km and CNA spike (~2.0 dB) accompanied by Pc1 geomagnetic pulsations were also observed, which is likely a relativistic electron precipitation (REP) event associated with electromagnetic ion cyclotron (EMIC) wave activity. The ionization rate due to the MeV electrons is also evaluated by PHITS. This event provides a rare opportunity to cross-validate the use of PHITS simulation for variable types of inputs (X-rays, protons, and electrons) to evaluate the atmospheric ionization.