Premium
Right‐hand polarized 4 f ce auroral roar emissions: 1. Observations
Author(s) -
LaBelle J.,
Chen Y.
Publication year - 2016
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja022890
Subject(s) - darkness , coalescence (physics) , latitude , physics , ionosphere , atmospheric sciences , optics , geophysics , astronomy
A receiving system installed at Sondrestrom, Greenland, was used to monitor all detectable auroral radio emissions at the fourth harmonic of the electron cyclotron frequency (called 4 f c e roar emissions) between May 2015 and March 2016. Of 88 events detected, 86 occurred during daylit conditions and were left‐hand polarized. Two occurred during darkness conditions and were right‐hand polarized. The left‐hand and right‐hand polarized events had entirely different frequency distributions. One of the right‐hand polarized 4 f c e emissions occurred at the same time as and at exactly twice the frequency of a second harmonic emission (2 f c e roar). The occurrence rate of 4 f c e emissions during premidnight hours under daylit conditions at Sondrestrom is 5%, comparable to previously reported occurrence rates of 2 f c e roar in darkness conditions at optimum latitudes of occurrence, but the occurrence rate of 4 f c e emissions during dark conditions is much lower, suggesting that if the right‐hand polarized events arise from coalescence of 2 f c e waves, only for a small fraction of nighttime 2 f c e roar emissions does such a process yield 4 f c e emissions detectable at ground level.