Kilometric continuum detected by Geotail

Abstract

A new kind of terrestrial continuum that appears to be generated inside the Earth's plasmasphere has been detected by the Geotail satellite at an orbital distance of 10 to 30 RE in the dayside and evening sectors of the magnetosphere. This previously undetected emission, which will be called "kilometric continuum," is found to consist of slowly drifting narrowband signals at a frequency of 100 to 800 kHz, corresponding to the plasma frequency inside the plasmasphere at an altitude extending down to only a few thousand kilometers in the topside equatorial region of the Earth's ionosphere. Unlike normal continuum, kilometric continuum is found to occur only near the magnetic equator, where it appears to be unrelated to magnetic activity and is emitted within a well-defined beam within only ∼10° of the magnetic equator. Copyright 1999 by the American Geophysical Union.