[P-EM16] [EE] Physics of Inner Magnetosphere Coupling

[PEM16-04] Initial results of the magnetic field experiment by the magnetometer (MGF) for the ARASE (ERG) mission

*Ayako Matsuoka¹, Mariko Teramoto², Reiko Nomura¹, Masahito Nose³, Akiko Fujimoto⁴, Yoshimasa Tanaka⁵, Manabu Shinohara⁶, Yoshizumi Miyoshi², Kazuo Shiokawa², Tsutomu Nagatsuma⁷ (1.Research Division for Space Plasma, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 2.Nagoya University, 3.Kyoto University, 4.Kyushu University, 5.National Institute of Polar Research, 6.National Institute of Technology, Kagoshima College, 7.National Institute of Information and Communications Technology)

Keywords:Geospace, Radiation belt, magnetic field

The acceleration process of the charged particles in the inner magnetosphere is considered to be closely related to the deformation and perturbation of the magnetic field. Accurate measurement of the magnetic field is required to understand the acceleration mechanism of the charged particles, which is one of the major scientific objectives of the ARASE (ERG) mission. We designed a fluxgate magnetometer which is optimized to investigate following topics;
(1) accurate measurement of the background magnetic field - the deformation of the magnetic field and its relationship with the particle acceleration.
(2) MHD waves - measurement of the ULF electromagnetic waves of frequencies about 1mHz (Pc4-5), and investigation of the radiation-belt electrons radially diffused by the resonance with the ULF waves.
(3) EMIC waves - measurement of the electromagnetic ion-cyclotron waves of frequencies about 1Hz, and investigation of the ring-current ions and radiation-belt electrons dissipated by the interaction with the EMIC waves.
A fluxgate magnetometer (MGF) was built for the ARASE satellite to measure DC and low-frequency magnetic field. The design is based on MGF-I, one of the magnetometers for BepiColombo MMO, Mercury orbiter, which would also suffer high radiation on the Mercury orbit.
The requirements to the magnetic field measurements by ARASE was defined as (1) accuracy of the absolute field intensity is within 5 nT (2) angular accuracy of the field direction is within 1 degree (3) measurement frequency range is from DC to 60Hz or wider. MGF measures the vector magnetic field with the original sampling frequency of 256 Hz. The dynamic range is switched between +/-8000nT and +/- 60000nT according to the background field intensity.
The MGF initial checkout was carried on January 10th 2017, three weeks after the launch of ARASE. The MGF normal performance and downlinked data were confirmed. The MAST for the sensor was deployed on 17th January.
The initial results of the magnetic field observation and data examination will be shown in the presentation.