Saturn's Open‐Closed Field Line Boundary: A Cassini Electron Survey at Saturn's Magnetosphere

Jasinski, Jamie M., Arridge, Christopher S., Bader, Alexander, Smith, Andy, Felici, Marianna, Kinrade, Joe, Coates, Andrew J., Jones, Geraint H., Nordheim, Tom A., Gilbert, Lin, Azari, Abigail R., Badman, Sarah V., Provan, Gabrielle, Sergis, Nick and Murphy, Neil (2019) Saturn's Open‐Closed Field Line Boundary: A Cassini Electron Survey at Saturn's Magnetosphere. Journal of Geophysical Research: Space Physics, 124 (12). pp. 10018-10035. ISSN 2169-9380

JGR Space Physics - 2019 - Jasinski - Saturn s Open‐Closed Field Line Boundary A Cassini Electron Survey at Saturn s.pdf - Published Version

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We investigate the average configuration and structure of Saturn's magnetosphere in the nightside equatorial and high-latitude regions. Electron data from the Cassini Plasma Spectrometer's Electron Spectrometer (CAPS-ELS) is processed to produce a signal-to-noise ratio for the entire CAPS-ELS time of operation at Saturn's magnetosphere. We investigate where the signal-to-noise ratio falls below 1 to identify regions in the magnetosphere where there is a significant depletion in the electron content. In the nightside equatorial region, we use this to find that the most planetward reconnection x-line location is at 20–25 RS downtail from the planet in the midnight to dawn sector. We also find an equatorial dawn-dusk asymmetry at a radial distance of >20 RS, which may indicate the presence of plasma-depleted flux tubes returning to the dayside after reconnection in the tail. Furthermore, we find that the high-latitude magnetosphere is predominantly in a state of constant plasma depletion and located on open field lines. We map the region of high-latitude magnetosphere that is depleted of electrons to the polar cap to estimate the size and open flux content within the polar caps. The mean open flux content for the northern and southern polar caps are found to be 25 ± 5 and 32 ± 5 GWb, respectively. The average location of the open-closed field boundary is found at invariant colatitudes of 12.7 ± 0.6° and 14.5 ± 0.6°. The northern boundary is modulated by planetary period oscillations more than the southern boundary.

Item Type: Article
Additional Information: Funding Information: JMJ was supported by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory administered by Universities Space Research Association (USRA) through a contract with the National Aeronautics and Space Administration (NASA). AB was funded by a Lancaster University FST studentship. NM acknowledges support from the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. AJC acknowledges STFC support via the solar system consolidated grant to UCL‐MSSL. PPO data can be found at . All the data used in this study can be found at NASA's Planetary Data System ( ).
Uncontrolled Keywords: Cassini, Dungey, Magnetosphere, PPO, reconnection, Saturn
Subjects: F300 Physics
F500 Astronomy
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: Rachel Branson
Date Deposited: 07 Nov 2022 11:03
Last Modified: 07 Nov 2022 11:15

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