Detection of the southern counterpart of the Jovian northern polar cusp: Shared properties

Abstract

A transient auroral feature in the northern (N) polar region of Jupiter, referred to as an ‘auroral flare’ [Waite et al., 2001], or as the N polar cusp [Pallier and Prangé, 2001], strangely seemed to lack any southern (S) counterpart. Here, using a new HST/STIS dataset, we find a similar bright spot in the south. We suggest that both features are located near the open/closed field line boundary. They remain close to a fixed‐magnetic‐time profile, near noon, as Jupiter rotates. Their brightness varies concurrently in both hemispheres. We thus propose that the conjugate spots are really the Jovian polar cusps, and that their brightening results from transient reconnection processes with the interplanetary magnetic field. A STIS spectrum reveals primary particles penetrating deeply into the atmosphere. It implies that either the particles are very energetic (∼200 keV ‘equivalent‐electron’ energy), or the hydrocarbon layers are significantly uplifted by the power input.