AGU: Geophysical Research Letters

 

Editors' Highlight

Aurora on Jupiter: Strange effects from Io

Io, the innermost large moon of Jupiter, orbits within a plasma torus that forms when neutral atoms in Io's atmosphere are ionized and swept into Jupiter's magnetosphere. This torus is tilted with respect to Jupiter's equator, so at times Io is below or above the torus's core. Io's orbit also crosses Jupiter's magnetic field lines, coupling the moon and the planet's upper atmosphere. This generates an electric current that ultimately produces ultraviolet light emissions in Jupiter's northern and southern polar regions facing Io. Scientists term these aurorae the "Io footprints." In each hemisphere, the footprint consists of a bright spot sometimes followed by secondary spots. To study the Io footprint, Bonfond et al. (2008) analyzed measurements from the Hubble Space Telescope and discovered the systematic appearance of a new faint spot, this time preceding the main bright spot. If Io is orbiting in the southern part of the plasma torus, this leading spot is seen in the northern polar regions, and vice versa. The authors hypothesized that current loops in Jupiter's magnetosphere might accelerate electrons toward the other hemisphere, generating the footprint's leading and secondary signatures.

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