[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-09] Field-aligned currents associated with pulsating auroral patches: Observation with Magneto-Impedance Magnetometer (MIM) onboard Loss through Auroral Microburst Pulsations (LAMP) sounding rocket

*能勢 正仁¹、細川 敬祐²、野村 麗子³、寺本 万里子⁴、浅村 和史³、三好 由純¹、三谷 烈史³、坂野井 健⁵、滑川 拓⁶、河野 剛健⁷、岩永 吉広⁷、立松 俊一⁷、平原 聖文¹、Halford Alexa⁸、Shumko Mykhaylo⁹、Lessard Marc¹⁰、Lynch Kristina¹¹、Paschalidis Nicholaos⁸、Jaynes Allison¹²、McHarg Matthew¹³ (1.名古屋大学 宇宙地球環境研究所、2.電気通信大学、3.宇宙航空研究開発機構宇宙科学研究所、4.九州工業大学、5.東北大学、6.東京大学、7.愛知製鋼株式会社、8.NASA Goddard Space Flight Center、9.University of Maryland、10.University of New Hampshire、11.Dartmouth College、12.University of Iowa、13.US Air Force Academy)

キーワード：磁気インピーダンスセンサー、磁力計、沿磁力線電流、脈動オーロラ

We made observations of magnetic field variations in association with pulsating auroras with the magneto-impedance sensor magnetometer (MIM) carried by the Loss through Auroral Microburst Pulsations (LAMP) sounding rocket that was launched at 11:27:30 UT on March 5, 2022 from Poker Flat Research Range, Alaska. At an altitude of 200–250 km, MIM detected clear enhancements of the magnetic field by 15–25 nT in both the northward and westward components. From simultaneous observations with the ground all-sky camera, we found that the footprint of LAMP at the 100 km altitude was located near the center of a pulsating auroral patch. The auroral patch had a dimension of ~90 km in latitude and ~25 km in longitude, and its major axis was inclined toward northwest. These observations were compared with results of a simple model calculation, in which local electron precipitation into the thin-layer ionosphere causes an elliptical auroral patch. The conductivity within the patch is enhanced in the background electric field and as a result, the magnetic field variations are induced around the auroral patch. The model calculation results can explain the MIM observations if the electric field points toward southeast and one of the parameters adopted from the previous studies becomes about half the value. We conclude that a pulsating auroral patch is fundamentally associated with a one-pair field-aligned current that consists of downward (upward) currents at the poleward (equatorward) edge of the patch. This current structure is maintained even if the auroral patch is latitudinally elongated.