Ion motion in focus when a comet transforms from hibernating to active

A new doctoral thesis at the Swedish Institute of Space Physics (IRF) and Umeå University explains how the interaction between comet 67P/Churyumov-Gerasimenko and the flow of charged particles from the Sun, the solar wind, becomes complex when the comet approaches the Sun. Anja Möslinger studied the motion of individual ions to explain this complex state.

The physics behind the interaction between a comet and the solar wind changes fundamentally when a comet gets closer to the Sun. While scientists already understand the physical processes of comet-solar wind interaction far away and close to the Sun quite well, the transition between has not been well-studied.

In her thesis, Anja has focused on how the charged particles in a cometary atmosphere, cometary ions, interact with the solar wind ions during this transition period. The results can help us understand what happens when the solar wind meets other objects with atmospheres in the solar system.

I have analyzed how individual ions move to understand how the collection of ions behave and shape the comet magnetosphere. Instead of flowing in a streamlined fashion, some of the solar wind ions whirl in circles like leaves blown off trees during an autumn storm when they encounter the comet atmosphere. How energy is transferred from the solar wind to the cometary atmosphere and how the solar wind slows down during this transition period depends on the motion of these ions”, says Anja Möslinger, PhD student at IRF and Umeå University.

How the solar wind is slowed down around obstacles it encounters is one of the fundamental problems in space physics. In particular the initial deceleration is little understood. Comets are excellent plasma laboratories for scientists to study the evolution of plasma interactions, since their distance to the Sun, and therefore their plasma environments, constantly change.

The thesis is based on data analysis from ESA’s Rosetta mission to comet 67P/Churyumov-Gerasimenko, and simulations using the numerical model Amitis.

Anja Möslinger, raised near Linz, Austria, had her first introduction to comet research in 2020 when working on the design of a particle instrument for the Comet Interceptor mission for her master thesis at IRF in Kiruna.

She will defend her doctoral thesis entitled “ Physics at sub-ion-gyroradius scales near low-activity comets ” at the auditorium at IRF in Kiruna, Sweden, on Friday 15 November, at 09.00. The faculty opponent is Professor Jan Egedal from the University of Wisconsin-Madison, U.S.

Link to the doctoral thesis: http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-230927

Contact: Anja Möslinger, PhD Student , PhD student, IRF and Umeå University