A new phenomenon occurring in the space environment of the Earth is simulated and observed. Physical processes which were thought to have only a local influence turn out to have surprisingly large effects at global scales.
Under the influence of the solar wind, the magnetic field of the Earth forms a cavity, the magnetosphere, which can interact with the solar wind. A chain of events starting at the interface between the solar wind and the magnetosphere – the magnetopause – triggers waves propagating in the layer of solar wind flowing around the magnetopause. These in turn generate beams of accelerated particles in unexpected regions of the upstream solar wind.
"It was not envisaged before that magnetospheric processes could trigger an interaction with the upstream solar wind", says the first author of the publication, reseacher Yann Pfau-Kempf from the Finnish Meteorological Institute.
This phenomenon is described based on a large-scale simulation run with the world's most precise large-scale magnetospheric model Vlasiator, developed by a Finnish group with funding from the European Research Council. In this project, also observations were found of this hitherto unexplained process.
"This new observation shows that there is phenomena in near-Earth space not observed previously, which we can explain only now that the modelling methods have developed far enough", concludes Yann Pfau-Kempf.
Researchers from the United Kingdom and the United States also participated in the study. The simulation was run on Sisu, the supercomputer maintained by the Finnish CSC – IT Center for Science. The results are reported in a recent article published in the journal Annales Geophysicae.
Researcher Yann Pfau-Kempf, tel. +358 50 4147 241, firstname.lastname@example.org
Pfau-Kempf, Y., Hietala, H., Milan, S. E., Juusola, L., Hoilijoki, S., Ganse, U., von Alfthan, S., and Palmroth, M. (2016), Evidence for transient, local ion foreshocks caused by dayside magnetopause reconnection Annales Geophysicae, 34, 943–959, doi:10.5194/angeo-34-943-2016.
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