Abstract/Summary

Jupiter's auroral regions are marked by considerable spatial and temporal variability, with numerous sources of auroral enhancements, making it difficult to isolate individual causes of emission brightness. Here, we utilize a data set of 13,000 near-infrared images of Jupiter mapped into latitude, longitude and planetary local time to separate out various sources of emission brightening, smoothed over hundreds of hours of integration and tens of days of observing. We show that equatorial emission is well correlated to planetary local time, indicating that equatorial ionospheric emission is dominated by solar Extreme Ultraviolet (EUV) ionization on the dayside of the planet. main auroral emission is strongly anti-correlated with surface magnetic field strength (with a Pearson correlation of −0.90), and is also strongly correlated with planetary local time (changing in brightness in the same way as equatorial emission with a Pearson correlation of 0.93). This is the first time such strong correlations have been shown at Jupiter, and may be the first evidence of such direct correlations at any planet, including Earth. Both of these correlations are thought to ultimately result from changes in ionospheric electrical conductivity driven by changing magnetic field strength and solar EUV ionization. This suggests the aurora is significantly controlled by breakdown in co-rotation currents flowing deep into the ionosphere, and that this deep layer contains an important component of solar ionization. However, polar auroral emission does not correlate well with planetary local time, suggesting much more complex processes drive the varying emission within this region.