Deuteron whistler and trans-equatorial propagation of the ion cyclotron whistler

Abstract

New ion cyclotron whistlers which have the asymptotic frequency of one half the local proton gyrofrequency, G p 2 , and the minimum (or equatorial) proton gyrofrequency, G pm , along the geomagnetic field line passing through the satellite have been found in the low-latitude topside ionosphere from the spectrum analysis of ISIS VLF electric field data received at Kashima, Japan. Ion cyclotron whistlers with asymptotic frequency of G pm or G pm 2 are observed only in the region of B m > B 2 or rarely B m > B 4 , where B is the local magnetic field and B m is the mini magnetic field along the geomagnetic field line passing through the satellite. The particles with one half the proton gyrofrequency may be the deuteron or alpha particle. Theoretical spectrograms of the electron whistlers ( R-mode) and the ion cyclotron whistlers ( L-mode) propagating along the geomagnetic field lines are computed for the appropriate distributions of the electron density and the ionic composition, and compared with the observed spectrograms. The result shows that the ion cyclotron whistler with the asymptotic frequency of G p 2 is the deuteron whistler, and that the ion cyclotron whistlers with the asymptotic frequency of G pm or G pm 2 are caused by the trans-equatorial propagation of the proton or deuteron whistler from the other hemisphere.