Abstract
AbstractThe magnetospheric cusp is a funnel‐shaped region where shocked solar wind plasma is able to enter the high‐latitude magnetosphere via the process of magnetic reconnection. The plasma observations include various cusp signatures such as ion energy dispersions and diamagnetic effects. We present an overview analysis of cusp plasma observations at the Saturnian magnetosphere from the Cassini spacecraft era. A comparison of the observations is made as well as classification into groups due to varying characteristics. The locations of the reconnection site are calculated and shown to vary along the subsolar magnetopause. We show the first in situ evidence for lobe reconnection that occurred at nearly the same time as dayside reconnection for one of the cusp crossings. Evidence for “bursty” and more “continuous” reconnection signatures is observed at different cusp events. The events are compared to solar wind propagation models, and it is shown that magnetic reconnection and plasma injection into the cusp can occur for a variety of upstream conditions. These are important results because they show that Saturn's magnetospheric interaction with the solar wind and the resulting cusp signatures are dynamic and that plasma injection in the cusp occurs due to a variety of solar wind conditions. Furthermore, reconnection can proceed at a variety of locations along the magnetopause.
Highlights
The events are compared to solar wind propagation models, and it is shown that magnetic reconnection and plasma injection into the cusp can occur for a variety of upstream conditions
Chapman and Ferraro [1931a, 1931b] were the first to postulate the idea of the magnetospheric cusp, showing that within the magnetosphere there would be a pair of magnetic “null” points, one in the northern hemisphere and one in the southern hemisphere
We identify the cusp in this example as the region with the lowest energetic-plasma fluxes observed by Magnetospheric Imaging Instrument (MIMI)-Low-Energy Magnetospheric Measurement System (LEMMS), as well as containing part of the depression
Summary
Chapman and Ferraro [1931a, 1931b] were the first to postulate the idea of the magnetospheric cusp, showing that within the magnetosphere there would be a pair of magnetic “null” points, one in the northern hemisphere and one in the southern hemisphere. Due to magnetic tension forces, the reconnected magnetic field line at the lobes convects equatorward and so the ion energy-latitude dispersion observed is opposite to that discussed previously, with the higher-energy ions observed at higher latitudes. The ions observed in the cusp with more antiplanetward pitch angles have already mirrored at low altitudes and traveled a larger field-aligned distance from the reconnection site, compared to ions with a planetward pitch angles which have not yet mirrored In order for this to occur, the ions with an antiplanetward pitch angle must have a higher energy so that their parallel velocity is larger, allowing them to be observed simultaneously. We explore possible solar wind correlations to the observations and present our discussion and conclusions of the survey of observations
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