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PSI’s Michelle Thomsen Named 2019 Arctowski Medal Recipient

Jan. 23, 2019

michelle thomsen

Michelle Thomsen

Tucson, Ariz. -- The National Academy of Sciences announced that Planetary Science Institute Senior Scientist Michelle Thomsen will receive the 2019 Arctowski Medal for her outstanding contributions to the study of solar physics and solar terrestrial relationships.

Thomsen is receiving the Arctowski Medal in recognition of her “fundamental contributions to our understanding of the relationships between the Sun and its planetary bodies, with a particular emphasis on the physics of collisionless shocks and the dynamics of the planetary magnetospheres of Earth, Jupiter, and Saturn,” the Academy said. Thomsen will receive a bronze medal, a $100,000 prize, and $100,000 to support research in solar physics and solar terrestrial relationships at an institution of her choice.

“I feel very humbled and grateful to the colleagues who nominated me, that they would consider me a suitable candidate. I am also grateful for all the wonderful research opportunities I have had, getting to work with data from amazing space missions and with a host of talented colleagues,” Thomsen said. “I find it particularly pleasing that the selection recognizes that "solar-terrestrial relationships" embraces other planetary magnetospheres as well as the Earth's, providing an even richer set of phenomena to explore.”

Thomsen said the upper atmosphere of the Sun, known as the corona, is extremely hot and expands continuously outward into the Solar System, forming the solar wind, a very fast-flowing gas of charged particles – plasma – carrying magnetic fields generated at the Sun. When the solar wind encounters the Earth or other magnetized planets, like Mercury, Jupiter, and Saturn, a bow shock forms upstream from the planet to slow and deflect the flow around the planetary obstacle. The shocked solar wind flows around but also interacts with planetary magnetospheres to drive a fascinating set of magnetospheric processes, including aurora, trapped radiation belts, and plasma heating and loss.

“I have had the good fortune to study the nature of the bow shock and how it does its job of slowing and deflecting the solar wind. I have also been able to help explore the effect of solar wind variability on magnetospheric populations and processes from the vantage point of satellites in geosynchronous orbit around the Earth,” she said. “I have had the opportunity to investigate similar magnetospheric processes at Jupiter and especially at Saturn, with data from the Cassini spacecraft. Our studies of the outer planets have shown us that while the physics is universal, the relative importance of various physical processes varies a lot depending on the particular properties of any given planetary body, such as size, strength of the magnetic field, rotation rate, and the presence of plasma sources within the magnetospheres, such as moons.”

Thomsen’s pioneering work continues today as a member of the teams studying the influence of solar wind on the magnetospheres of Jupiter and Saturn. “I will continue to study planetary magnetospheres and how they interact with the variable solar wind. I am actually hopeful that the award will benefit other people's work, especially the next generation of space scientists,” Thomsen said.

The Arctowski Medal will be presented to Thomsen at a ceremony on April 28, during the Academy’s 156th annual meeting in Washington, D.C.

The Arctowski Medal was established in 1958 by the bequest of Jane Arctowska in honor of her husband, Henryk Arctowski.

Alan Fischer
Public Information Officer
fischer [at]

Michelle Thomsen
Senior Scientist
mthomsen [at]

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fischer [at] (A. Fischer)

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