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Identification of the dominant ULF wave mode and generation mechanism for obliquely propagating waves in the Earth's foreshock
Author(s) -
Strumik M.,
Roytershteyn V.,
Karimabadi H.,
Stasiewicz K.,
Grzesiak M.,
Przepiórka D.
Publication year - 2015
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 - 10.1002/2015gl064915
Subject(s) - physics , foreshock , magnetosphere , computational physics , geophysics , spacecraft , magnetic field , instability , mechanics , astronomy , geology , seismology , quantum mechanics , aftershock
We discuss mechanisms of the generation of ultralow frequency (ULF) upstream waves in the terrestrial foreshock that are essential for the acceleration of ions in space plasmas. The analysis is based on global hybrid kinetic simulations of the magnetosphere that provide realistic environment for the growth of the ULF waves in a quasi‐radial configuration of the interplanetary magnetic field. We focus on a long‐debated problem of the generation mechanism of oblique and parallel ULF waves and provide quantitative arguments in favor of the ion/ion cyclotron resonant instability. We also show that parallel propagating waves are predominantly generated in this configuration, but geometrical effects related to the phase space density in wave vector space lead to apparent predominance of obliquely propagating waves. Correspondence between the results outlined above and previously published experimental claims is thoroughly discussed and our results are shown to be consistent with spacecraft measurements.