第7回極域科学シンポジウム:[OS]宙空圏11月29日（火）統計数理研究所 3階 セミナー室D30

Alexander Kozlovsky

Björn Gustavsson

Carl-fredrik Enell

Daniel Whiter

Kirsti Kauristie

Michael Kosch

Noora Partamies

Tima Sergienko

Urban Brändström

宮岡 宏

小川 泰信

田中 良昌

門倉 昭

National Institute of Polar Research Repository

  ディスクリートアークのオーロラトモグラフィ解析  田中良昌 1、小川泰信 1、門倉昭 1、Björn Gustavsson2、Kirsti Kauristie3、Daniel Whiter4、Carl-fredrik Enell5、 Urban Brändström6、Tima Sergienko6、Alexander Kozlovsky7、Noora Partamies8、宮岡宏 1、Michael Kosch9 1国立極地研究所、総合研究大学院大学極域科学専攻 2トロムソ大学 3フィンランド気象研究所 4サウサンプトン大学 5 EISCAT 科学協会 6スウェーデン宇宙物理研究所 7ソダンキュラ地球物理観測所 8スバールバル大学 9南アフリカ国立宇宙機関   Aurora tomography analysis of discrete arcs  Yoshimasa Tanaka1, Yasunobu Ogawa1, Akira Kadokura1, Björn Gustavsson2, Kirsti Kauristie3, Daniel Whiter4,  Carl-fredrik Enell5, Urban Brändström6, Tima Sergienko6, Alexander Kozlovsky7, Noora Partamies8, Hiroshi Miyaoka1,  and Michael Kosch9 1 National Institute of Polar Research, and Department of Polar Science, SOKENDAI 2 University of Tromsø - The Arctic University of Norway  3 Finnish Meteorological Institute 4 University of Southampton, UK  5 EISCAT Scientific Association 6 Swedish Institute of Space Physics 7 Sodankylä Geophysical Observatory, Finland  8 The University Centre in Svalbard, Norway 9 South African National Space Agency  We present results from auroral computed tomography analysis of discrete arcs observed in Northern Europe on March 14, 2015. Wavy structures in the discrete arcs were detected at 22:15-22:20 UT by three all-sky EMCCD imagers at Tromsø (69.6ºN, 19.2ºE), Norway, Kilpisjärvi (69.0ºN, 20.9ºE), Finland, and Abisko (68.4ºN, 18.8ºE), Sweden, and four wide-view CCD imagers that compose Auroral Large Imaging System (ALIS). We mainly used narrow-band filters centered at a wavelength of 427.8nm for all the imagers. We set an exposure time to 1 or 2 seconds for all the imagers, and a sampling interval was 2 seconds for the EMCCD imagers and 10 seconds for the ALIS imagers. During this period, the EISCAT UHF radar measured the ionospheric parameters along the magnetic zenith at Tromsø. Prior to the tomography analysis, there was a problem with the calibration of imagers because most of the imagers have not regularly been calibrated. Thus, we determined the calibration coefficients for the imagers self-consistently by the cross-validation method. Then, we applied the tomographic inversion technique to the calibrated images from the three all-sky EMCCD imagers. We compared the obtained altitude profile of the 427.8nm emission with the electron density observed by the EISCAT UHF radar. The main results are summarized as follows: (1) The altitude profile of the 427.8nm emission along the magnetic zenith was very similar to the electron density profile before 22:17:30 UT, while they were quite different after 22:17:30 UT. (2) Even for the similar profile cases before 22:17:30 UT, the electron density estimated from the 427.8nm emission by using empirical atmosphere models was smaller by about 0.3-0.4 times than observed with the EISCAT radar. (3) The averaged energy of precipitating electrons was higher around the center of auroral vortices where the total energy flux was also greater. The item (3) can be explained by the Ohm’s law along the field lines, i.e., the relation that the field-aligned current is proportional to the field-aligned potential difference. As for the items (1) and (2), we discuss what causes the difference between the optical tomography results and the EISCAT observation. 

Auroral tomography analysis of discrete arcs

https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=13804&item_no=1&attribute_id=16&file_no=1

Auroral tomography analysis of discrete arcs

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