Investigation of electron precipitation during an auroral substorm by rocket-borne detectors

Abstract

Results of auroral X ray observations from two rocket-borne detectors launched from Fort Churchill, Manitoba, Canada, into the breakup and postbreakup phases of an auroral substorm are discussed. The X ray intensity measurements obtained during the expansive phase of the substorm indicate the occurrence of widespread low-energy electron precipitation and the softening of the X ray spectrum during the northward movement of the auroral arcs. Electron data obtained by detectors carried on the same rocket indicate, in contrast, localized regions of high-energy precipitation along the leading edge of the northward propagating arcs. During the recovery phase of the substorm, however, the X ray detector registered very soft spectra which are best represented by two different values of the e folding energy, for the low- and high-energy ends. No significant spectral or temporal variation is observed in the low-energy precipitation. But the high-energy component shows large changes in the spectral shape with time. The electron detectors on board the same rocket exhibit similar variations, indicating that the spectral changes in the high-energy component are due to widespread rather than localized precipitation.