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Relation between fine structure of energy spectra for pulsating aurora electrons and frequency spectra of whistler mode chorus waves
Author(s) -
Miyoshi Y.,
Saito S.,
Seki K.,
Nishiyama T.,
Kataoka R.,
Asamura K.,
Katoh Y.,
Ebihara Y.,
Sakanoi T.,
Hirahara M.,
Oyama S.,
Kurita S.,
Santolik O.
Publication year - 2015
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2015ja021562
Subject(s) - electron , electron precipitation , physics , magnetosphere , ionosphere , spectral line , whistler , computational physics , atomic physics , geophysics , plasma , astronomy , nuclear physics
We investigate the origin of the fine structure of the energy spectrum of precipitating electrons for the pulsating aurora (PsA) observed by the low‐altitude Reimei satellite. The Reimei satellite achieved simultaneous observations of the optical images and precipitating electrons of the PsA from satellite altitude (~620 km) with resolution of 40 ms. The main modulation of precipitation, with a few seconds, and the internal modulations, with a few hertz, that are embedded inside the main modulations are identified above ~3 keV. Moreover, stable precipitations at ~1 keV are found for the PsA. A “precipitation gap” is discovered between two energy bands. We identify the origin of the fine structure of the energy spectrum for the precipitating electrons using the computer simulation on the wave‐particle interaction between electrons and chorus waves. The lower band chorus (LBC) bursts cause the main modulation of energetic electrons, and the generation and collapse of the LBC bursts determines on‐off switching of the PsA. A train of rising tone elements embedded in the LBC bursts drives the internal modulations. A close set of upper band chorus (UBC) waves causes the stable precipitations at ~1 keV. We show that a wave power gap around the half gyrofrequency at the equatorial plane in the magnetosphere between LBC and UBC reduces the loss rate of electrons at the intermediate energy range, forming a gap of precipitating electrons in the ionosphere.