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Two sources of dayside intense, quasi‐coherent plasmaspheric hiss: A new mechanism for the slot region?
Author(s) -
Falkowski Barbara J.,
Tsurutani Bruce T.,
Lakhina Gurbax S.,
Pickett Jolene S.
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja023289
Subject(s) - hiss , plasmasphere , physics , local time , magnetosphere , geophysics , van allen radiation belt , noon , ionosphere , van allen probes , astrophysics , electron , computational physics , astronomy , plasma , statistics , mathematics , quantum mechanics
A study of dayside plasmaspheric hiss at frequencies from ~22 Hz to ~1.0 kHz was carried out by using 1 year of Polar data. It is shown that intense, dayside plasmaspheric hiss is correlated with solar wind pressure with P > 2.5 nPa. The dayside effect is most prominent in the ~300 to ~650 Hz range. Intense dayside waves are also present during SYM‐H < −5 nT. The latter is centered at local noon, with the greatest intensities in the L = 2 to 3 region. Assuming drift of ~25 keV electrons from midnight to the wave magnetic local time, plasmaspheric hiss is shown to be highly correlated with precursor AE * and SYM‐H * indices, indicating that the hiss is associated with substorms and small injection events. Our hypothesis is that both sets of waves originate as outer zone (L = 6 to 10) chorus and then propagate into the plasmasphere. Fourteen high‐intensity dayside plasmaspheric hiss events were analyzed to identify the wave k , polarization, and the degree of coherency. The waves are found to be obliquely propagating, elliptically polarized and quasi‐coherent (~0.5 to 0.8 correlation coefficient). It is hypothesized that the dayside plasmaspheric hiss is quasi‐coherent because the chorus has been recently generated in the outer magnetosphere and have propagated directly into the plasmasphere. It is possible that the quasi‐coherency of the dayside hiss at L = 2 to 3 may be an alternate explanation for the generation of the energetic particle slot region.