Whistler-mode emissions on the OGO 1 satellite

Abstract

Magnetospheric observations of whistler‐mode emissions were made by the OGO 1 satellite over the frequency range 0.3 to 100 kHz. Taken during the geomagnetically quiet period from September 1964 through May 1965, the data cover geocentric distances from 2 to 24 RE and geomagnetic latitudes in the range ±50°. Emissions are found within L ∼ 10 at all local times except for L > 5 in the midnight‐to‐dawn sector, with intensity peaking at L ∼ 4 and L ∼ 9 near 10 hours local mean time. Their spectra resemble those of chorus and mid‐latitude hiss observed on the ground. An important new result is the observation that the upper‐frequency limit of most of these emissions is proportional to the minimum electron gyrofrequency along the magnetic fieldline passing through the satellite. This is interpreted to mean that the source of these emissions lies close to the equatorial plane. Estimates of the average intensity of these emissions agree with the intensity required to explain the precipitation of electrons through pitch‐angle scattering by whistler‐mode waves. Emissions observed on the dayside beyond L = 8 are burst‐like, and their occurrence tends to decrease with increasing radial distance. The location of the maximum intensity in this region agrees with that found for 1‐kev electron fluxes, giving strong support to theories of generation based on electron cyclotron resonance. No emissions were observed beyond the estimated position of the shock boundary.

Slot region electron loss timescales due to plasmaspheric hiss and lightning‐generated whistlers

“…Plasmaspheric hiss is observed in high density regions associated with the plasmasphere [Dunckel and Helliwell, 1969;Russell et al, 1969;Thorne et al, 1973] and plasmaspheric plumes [Chan and Holzer, 1976;Cornilleau-Wehrlin et al, 1978;Parrot and Lefeuvre, 1986]. Plasmaspheric hiss intensifies during storms and substorms but can also persist during relatively quiet conditions Thorne et al, 1974Thorne et al, , 1977Meredith et al, 2004].…”

Radio Sky Mapping from Satellites at Very Low Frequencies

“…The upper cut-off frequency is always well below the local electron gyrofrequency [36,37,42]. On the other hand, most of the hiss band is above the local proton gyrofrequency, in a frequency range where only the whistler mode exists.…”

Self‐Consistent Theory of Triggered Whistler Emissions

“…(see also eqs. (7-12) through (7)(8)(9)(10)(11)(12)(13)(14)). The numerical difficulty associated with the phase equation can be seen rather clearly from equation (6-7).…”

“…The terms on the right hand side of eq. (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) scale respectively like (dropping the fourth),…”

“…First we neglect the linear damping and the divergence of the group velocity (as higher order in the E"/ expansion as outlined below). The field amplitude is written a, = ETrAeiw, (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) where ET is the field of the triggering wave, so that A is a dimensionless, order unity, slowly varying amplitude. We then scale the velocity to V, = cno/w 1 Note that the slowly varying wave phase W is included with 0, 4 in computing the nonlinear current, so that frequency shifts, bw = -80/Ot , away from the triggering frequency, w = -Oi/ t, are included in the non-linear current.…”