SM043-08
Cassini observations of ionospheric plasma in Saturn's magnetosphere

Tuesday, 15 December 2020: 07:28
Virtual
Marianna Felici1, Sarah Victoria Badman2, Carley Martin3, Licia C Ray4, Howard Todd Smith5, Robert J Wilson6 and Paul Withers1, (1)Boston University, Boston, MA, United States, (2)Lancaster University, Physics Department, Lancaster, United Kingdom, (3)University of Lancaster, Lancaster, United Kingdom, (4)Lancaster University, Department of Physics, Bailrigg, Lancaster, United Kingdom, (5)Applied Physics Laboratory Johns Hopkins, Laurel, MD, United States, (6)University of Colorado Boulder, Boulder, CO, United States
Recorded Presentation
Abstract:
It is well known that the ionosphere is an important mass source at Earth during periods of intense geomagnetic activity, but lesser attention has been dedicated to study the ionospheric mass source at Saturn.

Felici et al. (2016) described an ionospheric outflow event from Saturn's magnetotail, when Cassini was located at about 2200 h Saturn local time at 36 R S from Saturn. During several entries into the magnetotail lobe, a tailward flowing cold ion beam were observed directly adjacent to the plasma sheet and extending deeper into the lobe. The ions appeared to be dispersed, dropping to lower energies with time. The composition showed very low, or consistent with zero, fluxes of water group ions. Ultraviolet auroral observations showed a dawn brightening, and upstream heliospheric models suggested that the magnetosphere was being compressed by a region of high solar wind ram pressure. They considered several configurations for the active atmospheric regions and estimated the corresponding mass rates outflowing the ionosphere.

We have identified new instances in which the ions appear dispersed in energy in the Cassini Plasma Spectrometer Singles (CAPS/SNG) data. For some of these events, in order to establish if these were detections of ionospheric outflow, we conducted an investigation of the location of the spacecraft in respect to the plasma sheet, flow direction, ion composition, aurora and solar wind activity at the times of detections, utilizing the Cassini Magnetometer data, CAPS Time of Flight data, Cassini Ultraviolet Imaging Spectrograph data, ENLIL model results, and, lastly, estimated the number flux.

We will present these new results that show ionospheric outflow events with different characteristics and number fluxes, underlining the variability of this phenomenon and its importance for improving our understanding of ionosphere-magnetosphere coupling at Saturn, the ionosphere as a source of plasma for the magnetosphere, and how much upstream conditions drive the system. Moreover, estimating the atmospheric escape rate at Saturn, a planet with a strong intrinsic magnetic field, would provide useful inputs for better understanding atmosphere erosion in the solar system.

Felici, M., Arridge, C. S., Coates, A. J., Badman, S. V., Dougherty, M. K., Jackman, C. M., Kurth, W. S., Melin, H., Mitchell, D. G., Reisenfeld, D. B., et al. (2016), Cassini observations of ionospheric plasma in Saturn's magnetotail lobes, J. Geophys. Res. Space Physics, 121, 338– 357, doi:10.1002/2015JA021648.

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