Cloud distance measurement for cosmic ray air shower observation with atmospheric fluorescence telescope

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K03895
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 15020:Experimental studies related to particle-, nuclear-, cosmic ray and astro-physics
• Research Institution: Ritsumeikan University
• Principal Investigator: Okuda Takeshi 立命館大学, 理工学部, 助教 (00610263)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 宇宙線 / 空気シャワー / 雲 / 大気蛍光望遠鏡

Outline of Final Research Achievements

The Telescope Array experiment detects airshowers induced by ultra high energy cosmic rays. The atmospheric Fluorescence telescopic Detector(FD) observes cosmic ray airshower, which is incident very far from the telescope. The observation does not take place in overcast night. However, the cloud status changes quickly and sometimes there are some isolated clouds. For airshower reconstruction, the effect of cloud depends on whether the cloud is foreground or background to airshower. The estimation of exposure with isolated clouds is difficult. And it should be affected more at higher energy event with relatively further from the telescope, which is lower statistics and more important for the ultra high energy cosmic ray physics. Therefore, to test the method for evaluating the correction of exposure, stereo cloud cameras were installed near one of FD sites, and observed the difference of stereo image to measure the distance to cloud.

Free Research Field

宇宙線

Academic Significance and Societal Importance of the Research Achievements

雲の高度は最高でも海抜16kmであり、50km程度の距離内で広角に位置が時間変化する雲の距離を光学的に連続測定している例は見当たらない。気象や大気観測用にはレーダーやレーザーを用いたものはあるがレーザーは大気蛍光観測の障害となり、且つ視野も非常に狭い。また、FDステーションには商用電源がないため、且つ設置コストの問題もありレーダーは運用不可能である。したがってこれらの高価で能動的なシステムではなく安価で受動的なシステムを用いて雲までの距離を広視野で測定するシステムが実現可能かどうかを検証することが今後の大気蛍光望遠鏡観測の高精度化にとって重要である。