Abstract
Reconnection within planetary magnetotails is responsible for locally energizing particles and changing the magnetic topology. Its role in terms of global magnetospheric dynamics can involve changing the mass and flux content of the magnetosphere. We have identified reconnection related events in spacecraft magnetometer data recorded during Cassini's exploration of Saturn's magnetotail. The events are identified from deflections in the north‐south component of the magnetic field, significant above a background level. Data were selected to provide full tail coverage, encompassing the dawn and dusk flanks as well as the deepest midnight orbits. Overall 2094 reconnection related events were identified, with an average rate of 5.0 events per day. The majority of events occur in clusters (within 3 h of other events). We examine changes in this rate in terms of local time and latitude coverage, taking seasonal effects into account. The observed reconnection rate peaks postmidnight with more infrequent but steady loss seen on the dusk flank. We estimate the mass loss from the event catalog and find it to be insufficient to balance the input from the moon Enceladus. Several reasons for this discrepancy are discussed. The reconnection X line location appears to be highly variable, though a statistical separation between events tailward and planetward of the X line is observed at a radial distance of between 20 and 30R S downtail. The small sample size at dawn prevents comprehensive statistical comparison with the dusk flank observations in terms of flux closure.
Highlights
Magnetic reconnection is the fundamental process by which magnetic fields can reconfigure, and it plays a critical role in shaping planetary magnetospheres
We have presented a new catalog of reconnection-related events, identified using an algorithm which automatically selects deflections in the meridional (Bθ) component of the magnetic field
In order to be selected, the events must fit a polynomial to a sufficient quality, and the size of the deflection must be greater than 1.5× the local RMS of Bθ
Summary
Magnetic reconnection is the fundamental process by which magnetic fields can reconfigure, and it plays a critical role in shaping planetary magnetospheres. Reconnection leads to the mixing of plasma from distinct magnetic regimes such as the solar wind and a planetary magnetosphere. In such a way reconnection has the potential for adding or removing mass from a planetary magnetosphere. In addition to changing the mass contained within the system reconnection has the capacity to modify the amount of open flux contained within the polar caps. On the dayside of a planet it can open magnetic flux, connecting previously closed planetary field lines to the interplanetary magnetic field (IMF). On the nightside of a planet reconnection can sometimes involve the closure of open field lines, those once connected into the IMF
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