Abstract
AbstractMagnetosonic waves are commonly observed in the vicinity of the terrestrial magnetic equator. It has been proposed that within this region they may interact with radiation belt electrons, accelerating some to high energies. These wave‐particle interactions depend upon the characteristic properties of the wave mode. Hence, determination of the wave properties is a fundamental part of understanding these interaction processes. Using data collected during the Cluster Inner Magnetosphere Campaign, this paper identifies an occurrence of magnetosonic waves, discusses their generation and propagation properties from a theoretical perspective, and utilizes multispacecraft measurements to experimentally determine their dispersion relation. Their experimental dispersion is found to be in accordance with that based on cold plasma theory.
Highlights
Electromagnetic equatorial noise, or magnetosonic waves (MSW) as they are more commonly referred to, consists of intense electromagnetic emissions that occur close to the magnetic equator of the terrestrial magnetosphere
Using data collected during the Cluster Inner Magnetosphere Campaign, this paper identifies an occurrence of magnetosonic waves, discusses their generation and propagation properties from a theoretical perspective, and utilizes multispacecraft measurements to experimentally determine their dispersion relation
Since the dispersion relation of MSW and resonance condition essentially define the relationship between the resonant energy and either the pitch angle or wave normal angle, any deviation from the cold plasma dispersion would result in a marked change in the energy/pitch angle ranges that are affected by these waves [Mourenas et al, 2013]
Summary
Electromagnetic equatorial noise, or magnetosonic waves (MSW) as they are more commonly referred to, consists of intense electromagnetic emissions that occur close to the magnetic equator of the terrestrial magnetosphere. Perraut et al [1982] were able to correlate their observations of MSW with the appearance of peaks in the energy spectra of 90∘ pitch angle protons (ring-like ion distributions), suggesting this as the source of free energy for the growth of these waves. These authors used this theoretical model to investigate the dispersion characteristics of the observed waves. While these emissions are observed to occur within a few degrees of the magnetic equator, detailed analysis by Santolík et al [2002] and Nemec et al [2005] has shown that they tend to reach a maximum intensity at a latitude 2–3∘ above the equator, a point corresponding to the minimum magnetic field strength along the magnetic field line
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