Cusp observation at Saturn's high-latitude magnetosphere by the Cassini spacecraft

J M Jasinski; C S Arridge; L Lamy; J S Leisner; M F Thomsen; D G Mitchell; A J Coates; A Radioti; G H Jones; E Roussos; N Krupp; D Grodent; M K Dougherty; J H Waite

doi:10.1002/2014GL059319

Cusp observation at Saturn's high-latitude magnetosphere by the Cassini spacecraft

Geophys Res Lett. 2014 Mar 16;41(5):1382-1388. doi: 10.1002/2014GL059319. Epub 2014 Mar 10.

Authors

J M Jasinski¹, C S Arridge¹, L Lamy², J S Leisner³, M F Thomsen⁴, D G Mitchell⁵, A J Coates¹, A Radioti⁶, G H Jones¹, E Roussos⁷, N Krupp⁷, D Grodent⁶, M K Dougherty⁴, J H Waite⁸

Affiliations

¹ Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London Dorking, Surrey, UK ; Centre for Planetary Sciences, UCL/Birkbeck London, UK.
² LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris 6, Université Paris Diderot Meudon, France.
³ Blackett Laboratory, Department of Physics, Imperial College London London, UK.
⁴ Planetary Science Institute Tucson, Arizona, USA.
⁵ Applied Physics Laboratory, Johns Hopkins University Laurel, Maryland, USA.
⁶ Laboratoire de Physique Atmosphérique et Planétaire, Institut d'Astrophysique et de Géophysique, Université de Liége Liege, Belgium.
⁷ Max-Planck-Institut für Sonnensystemforschung Göttingen, Germany.
⁸ Southwest Research Institute, Space Science and Engineering Division San Antonio, Texas, USA.

Abstract

We report on the first analysis of magnetospheric cusp observations at Saturn by multiple in situ instruments onboard the Cassini spacecraft. Using this we infer the process of reconnection was occurring at Saturn's magnetopause. This agrees with remote observations that showed the associated auroral signatures of reconnection. Cassini crossed the northern cusp around noon local time along a poleward trajectory. The spacecraft observed ion energy-latitude dispersions-a characteristic signature of the terrestrial cusp. This ion dispersion is "stepped," which shows that the reconnection is pulsed. The ion energy-pitch angle dispersions suggest that the field-aligned distance from the cusp to the reconnection site varies between ∼27 and 51 R_S . An intensification of lower frequencies of the Saturn kilometric radiation emissions suggests the prior arrival of a solar wind shock front, compressing the magnetosphere and providing more favorable conditions for magnetopause reconnection.

Key points: We observe evidence for reconnection in the cusp plasma at SaturnWe present evidence that the reconnection process can be pulsed at SaturnSaturn's cusp shows similar characteristics to the terrestrial cusp.

Keywords: Cassini; cusp; dispersion; plasma; reconnection.