Ian J. Cohen

LASP
Mentors: Fran Bagenal, Peter Delamere

 

Title: Analysis of possible open field lines as origins for Jovian auroras

 

Abstract:
Since Voyager 1 passed Jupiter in 1979, there has been evidence of Jovian auroras. The question still remains whether the processes that drive the Jovian aurora are similar to those that drive the aurora here on Earth. It is known that processes other than those found at Earth drive emission in two of the three regions of Jovian aurora, the main auroral oval and the satellite-linked footprints. However, there is still some debate as to the drivers for the variable polar emission seen within the main auroral oval. Our study shows that this variable emission is linked to solar activity and might be driven by similar processes as the aurora on Earth.

Using the Khurana [1997, 2005] model of the Jovian magnetic field and a parameterized definition of the Jovian magnetopause created by Joy et al. [2002] that varies with the value of the solar wind dynamic pressure, we searched for field lines that cross the magnetopause and thusly might be candidates for magnetic reconnection that could open the magnetosphere to the interplanetary magnetic field. Although a field line crossing the magnetopause does not necessarily mean reconnection will occur, it is a good starting point for the investigation.

We found that the regions of open field line candidates are well contained within the main auroral oval for four different dipole orientations. We also observed an increase in the number of candidate field lines and the area that they populate when the dynamic pressure was increased and the magnetopause compressed. Our greatest evidence linking solar activity and the variable polar emission was the lack of open field line candidates we found in the dawn-most sectors of the main auroral oval, where Grodent et al. [2003b] observed dark regions in the aurora. This indicates that there is in fact a correlation between the possibly open field lines and the emission.