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  The evolution of Saturn’s radiation belts modulated by changes in radial diffusion

Kollmann, P., Roussos, E., Kotova, A., Paranicas, C., & Krupp, N. (2017). The evolution of Saturn’s radiation belts modulated by changes in radial diffusion. Nature astronomy, 1, 872-877. doi:10.1038/s41550-017-0287-x.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-002E-A0E0-8 Version Permalink: http://hdl.handle.net/21.11116/0000-0006-FBAA-0
Genre: Journal Article

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Kollmann, P, Author
Roussos, Elias1, Author              
Kotova, A.2, Author              
Paranicas, C., Author
Krupp, Norbert1, Author              
Affiliations:
1Department Planets and Comets, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832288              
2IMPRS on Physical Processes in the Solar System and Beyond, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832290              

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 MPIS_PROJECTS: CASSINI: LEMMS
 MPIS_PROJECTS: CASSINI: MIMI
 Abstract: Globally magnetized planets, such as the Earth1 and Saturn2, are surrounded by radiation belts of protons and electrons with kinetic energies well into the million electronvolt range. The Earth’s proton belt is supplied locally from galactic cosmic rays interacting with the atmosphere3, as well as from slow inward radial transport4. Its intensity shows a relationship with the solar cycle4,5 and abrupt dropouts due to geomagnetic storms6,7. Saturn’s proton belts are simpler than the Earth’s because cosmic rays are the principal source of energetic protons8 with virtually no contribution from inward transport, and these belts can therefore act as a prototype to understand more complex radiation belts. However, the time dependence of Saturn’s proton belts had not been observed over sufficiently long timescales to test the driving mechanisms unambiguously. Here we analyse the evolution of Saturn’s proton belts over a solar cycle using in-situ measurements from the Cassini Saturn orbiter and a numerical model. We find that the intensity in Saturn’s proton radiation belts usually rises over time, interrupted by periods that last over a year for which the intensity is gradually dropping. These observations are inconsistent with predictions based on a modulation in the cosmic-ray source, as could be expected4,9 based on the evolution of the Earth’s proton belts. We demonstrate that Saturn’s intensity dropouts result instead from losses due to abrupt changes in magnetospheric radial diffusion.

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Language(s): eng - English
 Dates: 2018-01-082017
 Publication Status: Published in print
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 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1038/s41550-017-0287-x
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Title: Nature astronomy
Source Genre: Journal
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Publ. Info: London : Springer Nature
Pages: - Volume / Issue: 1 Sequence Number: - Start / End Page: 872 - 877 Identifier: Other: 2397-3366
CoNE: https://pure.mpg.de/cone/journals/resource/2397-3366