Hot flow anomalies at Saturn's bow shock

• Published in: Journal of Geophysical Research: Space Physics 2009-08, Vol.114 (A8), p.n/a
• Main Authors: Masters, A., McAndrews, H. J., Steinberg, J. T., Thomsen, M. F., Arridge, C. S., Dougherty, M. K., Billingham, L., Schwartz, S. J., Sergis, N., Hospodarsky, G. B., Coates, A. J.
• Format: Article
• Language: English
• Subjects: bow shock; Earth sciences; Earth, ocean, space; Exact sciences and technology; hot flow anomalies; Saturn
• ISSN: 0148-0227; 2156-2202
• DOI: 10.1029/2009JA014112

We present evidence for the occurrence of hot flow anomalies (HFAs) at Saturn's bow shock. A survey of Cassini magnetic field and electron data taken upstream of the dawn flank bow shock is carried out in order to identify Kronian HFAs. Seventeen events are identified that were all associated with energization of the solar wind electrons and satisfied the majority of the conditions for HFA formation. The majority of the events possessed a central cavity of rarefied plasma; however, for two of the events the central cavity was over dense, possibly indicating that these examples were at an early stage of formation. For the event that occurred on 8 November 2004 the calculation of ion moments is possible, revealing an ion temperature increase by a factor of ∼800 in the central region of the event that was associated with a significant deflection of the solar wind bulk flow. The spatial extent of the event was ∼4.6 Saturn radii in the direction normal to the current sheet underlying the event. Pressure calculations imply that the heated central region was expanding at the time of the encounter. We conclude that the 8 November 2004 event was a spacecraft encounter with an HFA at Saturn's bow shock and we propose that the other 16 events identified by the survey were also HFA encounters. These observations suggest that HFAs are a solar‐system‐wide phenomenon.