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Student project at IRF Uppsala

Student Project (15 c)/Studentprojekt (15 hp)

Plasma density characteristics of magnetic holes near the Kronian magnetosphere boundary surfaces

Student: Marlon Bause, Uppsala University
Supervisor: Michiko Morooka
Period: Spring 2020


Localized magnetic field depressions known as magnetic holes are often observed in the interplanetary medium. A number of observations of similar features have been reported, but the mechanisms of their origin have not fully understood yet. The scale size of their structures varies from several to a few thousand proton gyro radii. The characteristic orientations of the magnetic field also vary, and therefore different types of magnetic holes have been suggested. To date, the magnetic holes are classified as either mirror mode structures or magnetic decreases. Despite a large number of papers that report the observational characteristics of the magnetic holes, many identify the feature using only the magnetic field data. This is due to the scale size of the structure combined with the high solar wind speed, resulting in features that can often not be resolved with the limited sampling frequency of plasma instrumentation, while magnetic field instruments can usually obtain the data in high enough time resolution.

The Cassini spacecraft orbited Saturn for almost 17 years and obtained a large amount of data in/near the Kronian magnetosphere, where series of magnetic depletions have been also observed. The Langmuir Probe (LP) onboard Cassini measures the spacecraft potential which can be converted to a measure of the electron density in the outer magnetosphere and solar wind region. When the LP operates in the continuous fix bias voltage mode, it samples the probe current at 512 points every 10 min in the outer magnetosphere and this can be used as a proxy to the electron density. The goal of this project is to investigate the possibility of using LP data for the magnetic hole study, calibrate the data to derive the plasma density near the magnetopause and bow shock regions of Saturn, and characterize the plasma density structure in the magnetic holes.


Final report

last modified on Thursday, 28-Jan-2021 17:41:44 CET