Dayside magnetodisc reconnection on Saturn
Abstract
Magnetic reconnection is a key process that energises charged particles explosively, generating phenomena such as nebular flares, solar flares, and stunning aurorae. In planetary magnetospheres, magnetic reconnection has often been identified on the dayside magnetopause and in the nightside magnetotail and/or magnetodisc, where thin-current-sheet conditions are conducive to reconnection process. For giant planets, the dayside magnetodisc is usually considered thicker than the nightside due to the compression of solar wind, and thus not an ideal environment for reconnection. However, a recent statistical study of magnetic flux circulation (Delamere et al. (2015), J. Geophys. Res., 120, 4229-4245) strongly suggests that magnetic reconnection must occur throughout Saturn's dayside magnetosphere. Additionally, the existence of energetic plasma presented at the noon sector of giant planetary magnetospheres has not been fully understood. Here we report direct evidence of near-noon reconnection within Saturn's magnetodisc using measurements from the Cassini spacecraft. An ion diffusion region is well defined based on the analysis of the Hall magnetic field and the electron pitch angle distribution. We also discuss extended case studies and find that the energetic heavy ions (several hundreds of keV) can be enhanced locally in the reconnection regions. The measured energetic (10s 100s of keV) electrons and ions and the estimated energy flux within the reconnection region are sufficient to power aurorae at Saturn. The dayside magnetodisc reconnection process that we consider serves as a new mechanism to explain bursty phenomena in the dayside magnetospheres of giant planets.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMSM52A..09G
- Keywords:
-
- 2731 Magnetosphere: outer;
- MAGNETOSPHERIC PHYSICSDE: 5737 Magnetospheres;
- PLANETARY SCIENCES: FLUID PLANETSDE: 6222 Ganymede;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTSDE: 7899 General or miscellaneous;
- SPACE PLASMA PHYSICS