JpGU-AGU Joint Meeting 2020

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[E] Oral

P (Space and Planetary Sciences ) » P-EM Solar-Terrestrial Sciences, Space Electromagnetism & Space Environment

[P-EM13] Dynamics of Magnetosphere and Ionosphere

convener:Aoi Nakamizo(Applied Electromagnetic Research Institute, National Institute of Information and Communications Technology), Mitsunori Ozaki(Faculty of Electrical and Computer Engineering, Institute of Science and Engineering, Kanazawa University), Akiko Fujimoto(Kyushu Institute of Technology), Yuka Sato(Nippon Institute of Technology)

[PEM13-29] Geomagnetic field and energetic particle oscillations observed at geosynchronous orbit during the growth and expansion phases of a substorm

*Khan-Hyuk Kim1, Hyuck-Jin Kwon1, Jongho Seon1, Uli Auster2, Werner Magnes3, Stefan Kraft4 (1.School of Space Research, Kyung Hee University, Korea, 2.IGeP, TUBS, Mendelssohnstrasse, Braunschweig, Germany, 3.Space Research Institute, OeAW, Graz, Austria, 4.ESOC-ESA, Robert-Bosch-Strasse, Darmstadt, Germany)

Keywords:Substorm, Geosynchronous orbit, Alfven wave

Magnetic field and energetic electron data (E > 175 keV) acquired by GEO-KOMPSAT-2A (GK-2A) geosynchronous spacecraft in the pre-midnight sector have been used to study quasi-periodic magnetic field and particle oscillations during the substorm growth and expansion phases on 6 March 2019. Three types of oscillations are found in the magnetic field and electron flux: (1) ~300-s and (2) ~120-s oscillations during the decrease of the energetic particle flux prior to the expansion phase (i.e., during the substorm growth) and (3) ~60-s oscillations during the substorm expansion. The ~300-s electron flux oscillations have a quadrature relationship with the magnetic field oscillations in the azimuthal component at geosynchronous orbit, indicating the properties of a standing Alfven wave, and are nearly identical to the waveform of the geomagnetic field measured at low latitude (L = ~1.3) ground station. The ~120-s electron flux oscillations were observed just before the substorm onset. They are out of phase with the magnetic field perturbation in the radial component, which is dominant in the pre-midnight sector. There are no ground perturbations corresponding to the ~120-s electron flux oscillations. At the substorm onset, the ~60-s electron flux oscillations were excited, and the first four cycle of the flux oscillations show an in-phase signature of Pi2 oscillations identified at low-latitude ground station. In this study, we discuss how and where the electron flux oscillations are generated during the substorm growth and expansion phases.