Mars's induced magnetosphere can degenerate.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39294383.
- Also identified by DOI 10.1038/s41586-024-07959-z and PMC identifier 11446820.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The interaction between planets and stellar winds can lead to atmospheric loss and is, thus, important for the evolution of planetary atmospheres<sup>1</sup>. The planets in our Solar System typically interact with the solar wind, whose velocity is at a large angle to the embedded stellar magnetic field. For planets without an intrinsic magnetic field, this interaction creates an induced magnetosphere and a bow shock in front of the planet<sup>2</sup>. However, when the angle between the solar wind velocity and the solar wind magnetic field (cone angle) is small, the interaction is very different<sup>3</sup>. Here we show that when the cone angle is small at Mars, the induced magnetosphere degenerates. There is no shock on the dayside, only weak flank shocks. A cross-flow plume appears and the ambipolar field drives planetary ions upstream. Hybrid simulations with a 4° cone angle show agreement with observations by the Mars Atmosphere and Volatile Evolution mission<sup>4</sup> and Mars Express<sup>5</sup>. Degenerate, induced magnetospheres are complex and not yet explored objects. It remains to be studied what the secondary effects are on processes like atmospheric loss through ion escape.