Premium
Freja observations of electromagnetic ion cyclotron ELF waves and transverse oxygen ion acceleration on auroral field lines
Author(s) -
Erlandson R. E.,
Zanetti L. J.,
Acuña M. H.,
Eriksson A. I.,
Eliasson L.,
Boehm M. H.,
Blomberg L. G.
Publication year - 1994
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/94gl01363
Subject(s) - physics , cyclotron , atomic physics , electron precipitation , ion , electron , proton , electric field , magnetic field , plasma , computational physics , magnetosphere , nuclear physics , quantum mechanics
Extremely low‐frequency (ELF) magnetic and electric field plasma wave emissions were recorded on 2 October 1993 on auroral field lines by the Magnetic Field Experiment during Freja orbit 4770. The ELF wave frequencies were below the local oxygen gyrofrequency (25 Hz) and between the helium and proton gyrofrequencies (100 to 400 Hz). The ELF waves, interpreted as electromagnetic ion cyclotron (EMIC) waves, were observed in a region of inverted‐V‐type electron precipitation. The EMIC waves were correlated over time with auroral and lower energy (≈100 eV) electrons, which are both possible sources of free energy, and also with transversely accelerated oxygen ions. The waves above the helium gyrofrequency were more closely correlated with the transverse oxygen ion acceleration than the waves below the oxygen gyrofrequency. These observations are consistent with a scenario in which electron beams generate EMIC waves, which then produce transverse oxygen ion acceleration through a gyroresonant interaction.