Magnetic Field and Energetic Particle Flux Oscillations and High‐Frequency Waves Deep in the Inner Magnetosphere During Substorm Dipolarization: ERG Observations. Issue 9 (7th September 2021)

• Record Type: Journal Article
• Authors: Miyashita, Yukinaga; Chang, Tzu‐Fang; Miyoshi, Yoshizumi; Hori, Tomoaki; Kadokura, Akira; Kasahara, Satoshi; Wang, Shiang‐Yu; Keika, Kunihiro; Matsuoka, Ayako; Tanaka, Yoshimasa; Kasahara, Yoshiya; Teramoto, Mariko; Jun, Chae‐Woo; Asamura, Kazushi; Kazama, Yoichi; Tam, Sunny W. Y.; Wang, Bo‐Jhou; Yokota, Shoichiro; Kumamoto, Atsushi; Tsuchiya, Fuminori; Shoji, Masafumi; Kurita, Satoshi; Imajo, Shun; Shinohara, Iku
• Is Part Of: Journal of geophysical research. Volume 126:Issue 9(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-09-07
• Subjects: dipolarization -- ballooning instability; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2020JA029095
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Using Exploration of energization and Radiation in Geospace (ERG or Arase) spacecraft data, we studied low‐frequency magnetic field and energetic particle flux oscillations and high‐frequency waves deep in the inner magnetosphere at a radial distance of ~4–5 R E during substorm dipolarization. The magnetic field oscillated alternately between dipole‐like and taillike configuration at a period of ∼ 1 min during dipolarization. When the magnetic field was dipole‐like, the parallel magnetic component of the Pi2 waves was at trough. Both energetic ion and electron fluxes with a few to tens of kiloelectronvolts enhanced out of phase, indicating that magnetosonic waves were in slow mode. Field‐aligned currents also oscillated. These observations are consistent with signatures of ballooning instability. In addition, we found that broadband waves from the Pi1 range to above the electron cyclotron frequency tended to appear intermittently in the central plasma sheet near dipole‐like configuration. Plain Language Summary: Dipolarization is an important magnetospheric process for substorm onset and development, but its mechanism has not been well understood yet. Using spacecraft data, we studied low‐frequency magnetic field and energetic particle flux oscillations and high‐frequency waves deep in the inner magnetosphere during substorm dipolarization. The present results will shed light on instabilities causing substorm dipolarization. Key Points: The magnetic field and particle fluxes oscillated deep in the inner magnetosphere during substorm dipolarization These signatures are consistent with those of ballooning instability Simultaneously high‐frequency waves appeared intermittently near dipole‐like configuration