Bremsstrahlung X rays from Jovian auroral electrons

Abstract

The spectrum of X rays from the planet Jupiter is calculated according to an auroral electron beam model. The electrons are assumed to be accelerated by a field‐aligned potential drop and penetrate into the atmosphere as a Maxwellian beam of primaries which are scattered, degraded in energy, and merged with a population of ionization secondaries having a power law energy distribution. The soft X rays observed by the Einstein Observatory satellite are due to bremsstrahlung from the secondary electrons in the H2 atmosphere. A good match to the X ray data is obtained if the power law spectral index of the secondary electrons, γe, is ≃2, yielding a power law slope for the photon flux γX = γe + 1 ≃ 3. The X ray intensity is best reconciled with a beam of primaries having a characteristic energy 30–100 keV and penetrating the homopause with an auroral energy flux typically of 10–20 ergs cm−2 s−1 but no greater than 50 ergs cm−2 s−1.