Abstract
AbstractWe present Jovian auroral observations from the 2014 January Hubble Space Telescope (HST) campaign and characterize the auroral second oval feature with particular attention to the response to hot plasma injections. The location of the second oval feature lies between the Ganymede and Europa moon footprint contours between 150 and 240° system III longitude, corresponding to a source in the inner magnetosphere between 9 and 13 RJ. At the examined longitudes, this is in the same region of 11–16 RJ known as the pitch angle distribution boundary, beyond which electrons are thought to be scattered into a field‐aligned configuration and cause auroral precipitation. The feature is enhanced in both brightness and longitudinal spread 1–3 days after large hot plasma injections. The precipitating electrons have a higher‐energy and lower flux than the electrons generating large injection signatures. We suggest that wave‐particle interactions are responsible for the scattering of electrons in this region. We also suggest that the plasma injections can act as a temperature anisotropy and particle source to enhance electron scattering into the aurora and the brightness of the second oval feature. Changes to the magnetic field topology around an injection may also generate shear Alfvén waves and therefore accelerate electrons parallel to the magnetic field resulting in precipitation.
Highlights
Jupiter’s aurora is typically divided into three morphological categories based on their position relative to the main auroral emission, known as the main auroral oval; the polar emissions, the main emission itself, and the outer emissions
We suggest that wave-particle interactions are responsible for the scattering of electrons in this region
We suggest that the plasma injections can act as a temperature anisotropy and particle source to enhance electron scattering into the aurora and the brightness of the second oval feature
Summary
Jupiter’s aurora is typically divided into three morphological categories based on their position relative to the main auroral emission, known as the main auroral oval; the polar emissions, the main emission itself, and the outer emissions. Auroral signatures that appear equatorward of the main emission correspond to currents generated planetward of the plasma corotation breakdown region in the magnetosphere. These “outer emissions” have three main forms. These are the moon footprints, the injection signatures, and the second oval. The moon footprints are the most equatorward emissions [Bonfond, 2012]. They are used to validate mapping along magnetic field lines between magnetospheric source regions and the ionospheric auroral signatures, because their location in the magnetosphere is known
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