[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

*Masahito Nose¹, Keisuke Hosokawa², Reiko Nomura³, Mariko Teramoto⁴, Kazushi Asamura³, Yoshizumi Miyoshi¹, Takefumi Mitani³, Takeshi Sakanoi⁵, Taku Namekawa⁶, Takeshi Kawano⁷, Yoshihiro Iwanaga⁷, Shunichi Tatematsu⁷, Masafumi Hirahara¹, Alexa Halford⁸, Mykhaylo Shumko⁹, Marc Lessard¹⁰, Kristina Lynch¹¹, Nicholaos Paschalidis⁸, Allison Jaynes¹², Matthew McHarg¹³ (1.Institute for Space-Earth Environmental Research, Nagoya University, 2.The University of Electro-Communications, 3.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 4.Kyushu Institute of Technology, 5.Tohoku University, 6.University of Tokyo, 7.Aichi Steel Corporation, 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)

Keywords:MI sensor, Magnetometer, Field-aligned current, Pulsating aurora

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.