New method developed for studying ions around comets in space


Sofia Bergman’s dissertation offers scientists unique opportunities to study low-energy ions in space. lÃ¥g energi. Photo credit: Institutet för rymdfysik

Sofia Bergman, Swedish Institute for Space Physics (IRF) and Umeå University, defended her doctoral thesis on low-energy ions around comet 67P / Churyumov-Gerasimenko on November 26, 2021. The observation of low energy ions is notoriously difficult because their properties are greatly influenced by the spacecraft that is observing them. Sofia has developed new methods for this. With their work, scientists can study low-energy ions around comets and in a variety of other locations in the solar system.

Comets have a neighborhood of plasma which contains a large number of ions with low energies. In order to understand the physical processes around the comet, it is necessary to understand the properties of these low-energy ions.

Since low-energy ions are difficult to measure, Sofia Bergman developed a new method in her dissertation to analyze measurements of these ions around comet 67P / Churyumov-Gerasimenko.

“A spacecraft interacts with its surroundings, which leads to an accumulation of charges on the surface of the spacecraft. This is problematic when measuring low-energy ions, since the ions are influenced by the spacecraft before they are detected and change both their energy and their direction of flight. We want to know the original properties of the ions before they were influenced by the space probe, which is now possible with the method that I developed in my thesis, ”explains Sofia Bergman.

In the dissertation, data from the ion mass spectrometer ICA (Ion Composition Analyzer) of the IRF on board Rosetta was analyzed. ICA can measure the energy and direction of movement of ions at very low energies, but due to the influence of spacecraft potential on the measurements, the low energy data from ICA has been difficult to interpret.

“For the first time we have now been able to determine the flow directions of low-energy ions observed by ICA on comet 67P / Churyumov-Gerasimenko,” says Sofia Bergman. “The results were surprising. We see a large amount of ions flowing inwards to the comet’s nucleus instead of outwards as expected. “

Comets are interesting to study if we are to understand how the solar wind interacts with various bodies in the solar system. The comets’ elliptical orbits cause the environment around them to change dramatically. As the distance from the comet to the sun changes, we can watch a magnetosphere form around the comet. Low-energy ions are not only important for this interaction in comets:

“The method I developed in my thesis can also be used to study low-energy ions around other bodies in the solar system. The analysis of such ions has so far been very limited due to the difficulties in interpreting the measurements, ”says Sofia Bergman.

Sofia Bergman was born and raised in Borlänge, Sweden.

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