Simultaneous UV Images and High‐latitude Particle and Field Measurements During an Auroral Dawn Storm at Jupiter

R. W. Ebert*, T. K. Greathouse, G. Clark, V. Hue, F. Allegrini, F. Bagenal, S. J. Bolton, B. Bonfond, J. E. P. Connerney, G. R. Gladstone, M. Imai, S. Kotsiaros, W. S. Kurth, S. Levin, P. Louarn, B. H. Mauk, D. J. McComas, C. Paranicas, A. H. Sulaiman, J. R. SzalayM. F. Thomsen, R. J. Wilson

*Corresponding author for this work

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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.
Original languageEnglish
Article numbere2021JA029679
JournalJournal of Geophysical Research: Space Physics
Number of pages15
ISSN0148-0227
DOIs
Publication statusPublished - 2021

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