Premium
Propagation of equatorial noise to low altitudes: Decoupling from the magnetosonic mode
Author(s) -
Santolík O.,
Parrot M.,
Němec F.
Publication year - 2016
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 - 10.1002/2016gl069582
Subject(s) - physics , hiss , van allen radiation belt , geophysics , computational physics , plasmasphere , cyclotron , noise (video) , decoupling (probability) , earth's magnetic field , ionosphere , substorm , instability , electron precipitation , magnetosphere , electron , superposition principle , van allen probes , magnetic field , plasma , nuclear physics , mechanics , quantum mechanics , control engineering , artificial intelligence , computer science , engineering , image (mathematics)
Equatorial noise (often phenomenologically described as magnetosonic waves in the literature) is a natural electromagnetic emission, which is generated by instability of ion distributions and which can interact with electrons in the Van Allen radiation belts. We use multicomponent electromagnetic measurements of the DEMETER spacecraft to investigate if equatorial noise propagates inward down to the Earth. Analysis of a selected event recorded under disturbed geomagnetic conditions shows that equatorial noise can be observed at an altitude of 700 km, while propagating radially downward as a superposition of spectral lines from different distant sources observed at frequencies both below and above the local proton cyclotron frequency. Changes in the local ion composition encountered by the waves during their inward propagation disconnect the identified wave mode from the low‐frequency magnetosonic mode. The local ion composition also induces a cutoff which prevents the waves from propagating down to the ground.