Abstract
Magnetic reconnection at the magnetopause (MP) energises ambient plasma
via the< release of magnetic energy and produces an “open”
magnetosphere allowing solar wind particles to directly enter the
system. At Saturn, the nature of MP reconnection remains unclear. The
current study examines electron bulk heating at MP crossings, in order
to probe the relationship between observed and predicted reconnection
heating proposed by Phan et al. (2013) under open and closed MP, and how
this may pertain to the position of the crossings in the Δβ-magnetic
shear parameter space. The electron heating for 70 MP crossings made by
the Cassini spacecraft from April 2005 to July 2007 was found using 1d
and 3d moment methods. Minimum variance analysis was used on the
magnetic field data to help indicate whether the MP is open or closed.
We found better agreement between observed and predicted heating for
events suggestive of locally ‘open’ MP. For events suggestive of locally
‘closed’ MP, we observed a cluster of points consistent with no electron
heating, but also numerous cases with significant heating. Examining the
events in the Δβ-magnetic shear parameter space, we find 83% of events
without evidence of energisation were situated in the ‘reconnection
suppressed’ regime, whilst between 43% to 68% of events with
energisation lie in the ‘reconnection possible’ regime depending on the
threshold used. The discrepancies could be explained by a combination of
spatial and temporal variability which makes it possible to observe
heated electrons with different conditions from the putative
reconnection site.