[A-OS25] 陸域海洋相互作用-惑星スケール物質循環

[AOS25-P01] Ionizing Radiation at the Martian Surface during Young and Current Sun

*山敷 庸亮¹、前原 裕之²、Airapetian Vladimir³、野津 湧太⁴、佐藤 達彦⁵ (1.京都大学大学院総合生存学館、2.国立天文台岡山分室、3.NASAゴダード宇宙飛行センター、4.コロラド大学ボルドー校、5.日本原子力研究開発機構)

キーワード：火星、電離放射線、太陽フレア

The enhanced magnetic activity of the young sun was an important in the atmospheric evolution and dynamics of the early solar system. Lower solar luminosity associated provided planets a cooler atmospheric and surface environment on the early Earth and Martian surfaces and required production of potent greenhouse gasses in their atmospheres. Within these environments, the dose of ionizing radiation from solar energetic particles (SEPs) from the young Sun could have played an important role in the early phases of planetary habitability. Here, we present a theoretical model of the exposure of the early Mars to high fluence and hard spectra SEPs from the young sun by evaluating the possible magnitude and frequency of solar flares by using possible star spot area, derived from their rotational period. We evaluated annual and maximum flare energy in different cases of sunspot areas for 3%, 5% and 10% of their surfaces. The maximum dose at the Martian top of the atmosphere reaches 5.86 x 10³Gy (2.65 x 10²Sv) at the time when the sunspot area is -10% of the solar surface. Early atmospheric condition and possible hydrological cycles could have been affected by this strong ionizing radiation.