Felleskollovium: A Magnetic Perspective on the Interior of Saturn
By Professor Michele K. Dougherty
Department of Physics, the Blackett Laboratory, Imperial College London
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Magnetic fields are windows into planetary interiors and Saturn’s internal magnetic field following the Cassini Grand Finale orbital phase continues to surprise us. The unique geometry of these orbits provided an opportunity to measure the internal magnetic field at closer distances to the planet than ever encountered before.
The surprising close alignment of Saturn’s magnetic axis with its spin axis (known about since the early Pioneer 11 observations) has been confirmed, however external effects, observed even around closest approach are masking some of the magnetic field signals from the interior. The varying northern and southern magnetospheric planetary period oscillations and field aligned currents at both high and low latitudes are contributing to the magnetic signals observed.
We show the directly determined northward offset of Saturn’s magnetic equator and its “longitudinal” variations, small-scale yet highly consistent magnetic structures along the latitudinal direction detected along every Grand Finale orbit.
Observational constraints on the electromagnetic induction response from the semi-conducting region and time variation of Saturn’s internal magnetic field will also be presented. We will discuss how these latest measurements provide a new perspective on answering some key questions concerning Saturn’s interior: level of differential rotation, the existence and extent of stable stratification, and the size and nature of the central core.
We also report new features in the external planetary magnetic field, which not only enhanced our view of the auroral current systems but also revealed a new inter-hemispheric currents flowing in the magnetospheric plasma near the inner edge of the D ring.
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Michele Dougherty is Professor of Space Physics at Imperial College London.
Michele has been involved in space exploration for nearly 30 years and in 2008 she became only the second woman in more than a century to be awarded the Royal Society’s Hughes Medal. She is leading unmanned exploratory missions to Saturn and Jupiter and was the Principal Investigator for the magnetometer instrument onboard the Cassini mission to Saturn that that led to the discovery of an atmosphere around one of Saturn’s moons. Michele is also Principal Investigator the magnetometer for the JUpiter ICy moons Explorer (JUICE) of the European Space Agency due for launch in 2022. She has contributed significantly to the UK space sector and was chair for the Science Programme Advisory Committee of the UK Space Agency from 2014 to 2016.
As Head of Department Michele leads one of the largest Physics Departments in the UK with an outstanding reputation for excellence in research, undergraduate education and postgraduate training. Michele is a Fellow of the Royal Society, was awarded the Royal Astronomical Society Geophysics Gold medal in 2017, was awarded a CBE in the 2018 New Year’s Honours List, and was awarded the Institute of Physics Richard Glazebrook Gold Medal and Prize.