Simultaneous UV Images and High-latitude Particle and Field Measurements During an Auroral Dawn Storm at Jupiter
Journal Article
Overview
abstract
We present multi-instrument Juno observations on day-of-year 86, 2017; that link particles and fields in Jupiter’s polar magnetosphere to; transient UV emissions in Jupiter’s northern auroral region known as; dawn storms. Juno ranged from 42ºN - 51ºN in magnetic latitude and 5.8; – 7.8 jovian radii (1 RJ = 71,492 km) during this period. These dawn; storm emissions consisted of two separate, elongated structures which; extended into the nightside, rotated with the planet, had enhanced; brightness (up to at least 1.4 megaRayleigh) and high color ratios. The; color ratio is a proxy for the atmospheric penetration depth and; therefore the energy of the electrons that produce the UV emissions.; Juno observed electrons and ions on magnetic field lines mapping to; these emissions. The electrons were primarily field-aligned,; bi-directional, and, at times, exhibited sudden intensity decreases; below ~10 keV coincident with intensity enhancements up; to energies of ~1000 keV, consistent with the high color; ratio observations. The more energetic electron distributions had; characteristic energies of ~160 – 280 keV and downward; energy fluxes (~70 – 135 mW/m2) that were a significant; fraction needed to produce the UV emissions for this event. Magnetic; field perturbations up to ~0.7% of the local magnetic; field showing evidence of upward and downward field-aligned currents,; whistler mode waves, and broadband kilometric radio emissions were also; observed along Juno’s trajectory during this timeframe. These high; latitude observations show similarities to those in the equatorial; magnetosphere associated with dynamics processes such as interchange; events, plasma injections, and/or tail reconnection.
