Abstract
AbstractWe present ground‐based observations of Jupiter's H3+ aurorae over four nights in April 2016 while the Juno spacecraft was monitoring the upstream interplanetary magnetic field. High‐precision maps of auroral H3+ densities, temperatures, and radiances reveal significant variabilities in those parameters, with regions of enhanced density and emission accompanied by reduced temperature. Juno magnetometer data, combined with solar wind propagation models, suggest that a shock may have impacted Jupiter in the days preceding the observation interval but that the solar wind was quiescent thereafter. Auroral H3+ temperatures reveal a downward temporal trend, consistent with a slowly cooling upper atmosphere, such as might follow a period of shock recovery. The brightest H3+ emissions are from the end of the period, 23 April. A lack of definitive signatures in the upstream interplanetary magnetic field lends supporting evidence to the possibility that this brightening event may have been driven by internal magnetospheric processes.
Highlights
Planetary aurorae are a visible manifestation of a coupling process between an atmosphere and the nearby space environment
We present ground-based observations of Jupiter’s H3+ aurorae over four nights in April 2016 while the Juno spacecraft was monitoring the upstream interplanetary magnetic field
Auroral brightenings in the ultraviolet (UV) have been found to correlate with multiple sources: interplanetary shock arrivals associated with magnetospheric compression events [e.g., Nichols et al, 2007; Clarke et al, 2009], which modify the observed auroral morphology [Nichols et al, 2009]; internally driven aurorae associated with mass loading and related plasma circulation [Bonfond et al, 2012; Kimura et al, 2015]; and a third source causing UV aurorae to vary independently of both solar wind pressure and Io mass loading [Clarke et al, 2009; Badman et al, 2016]
Summary
Planetary aurorae are a visible manifestation of a coupling process between an atmosphere and the nearby space environment. At Earth, this coupling process extends to the Sun, as auroral enhancements are strongly correlated with changes in upstream solar wind conditions that disturb the terrestrial magnetosphere. Both a southward turning of the interplanetary magnetic field (IMF) and a solar wind dynamic pressure pulse can drive global auroral brightening events [e.g., Elphinstone et al, 1996; Chua et al, 2001]. We report on new observations of Jupiter’s H3+ aurorae spread across 11 days in April 2016 when Juno was monitoring the upstream IMF
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