Helium in the Earth’s foreshock: a global Vlasiator survey
- 1Department of Physics, University of Helsinki, Finland
- 2Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Mexico City, Mexico
- 3Southwest Research Institute, San Antonio, Texas, USA
- 4University of Texas San Antonio, San Antonio, USA
- 5University of Colorado Boulder, Boulder, Colorado, USA
- 6Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI, USA
- 7LPP, CNRS, École Polytechnique, Sorbonne Université, Université Paris-Saclay, Observatoire de Paris, PSL Res Université, Institut Polytechnique de Paris, Palaiseau, France
- 8School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, Stockholm, Sweden
- 9Finnish Meteorological Institute, Helsinki, Finland
- 1Department of Physics, University of Helsinki, Finland
- 2Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Mexico City, Mexico
- 3Southwest Research Institute, San Antonio, Texas, USA
- 4University of Texas San Antonio, San Antonio, USA
- 5University of Colorado Boulder, Boulder, Colorado, USA
- 6Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI, USA
- 7LPP, CNRS, École Polytechnique, Sorbonne Université, Université Paris-Saclay, Observatoire de Paris, PSL Res Université, Institut Polytechnique de Paris, Palaiseau, France
- 8School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, Stockholm, Sweden
- 9Finnish Meteorological Institute, Helsinki, Finland
Abstract. The foreshock is a region of space upstream of the Earth's bow shock extending along the interplanetary magnetic field. It is permeated by shock-reflected ions and electrons, low-frequency waves, and various plasma transients. We investigate the extent of the He2+ foreshock using Vlasiator, a global hybrid-Vlasov simulation. We perform the first numerical global survey of the helium foreshock, and interpret some historical foreshock observations in a global context.
The foreshock edge is populated by both proton and helium field-aligned beams, with the proton foreshock extending slightly further into the solar wind than the helium foreshock, and both extend well beyond the ULF wave foreshock. We compare our simulation results with MMS HPCA measurements, showing how the gradient of suprathermal ion densities at the foreshock crossing can vary between events. Our analysis suggests that the IMF cone angle and the associated shock obliquity gradient can play a role in explaining this differing behaviour.
We also investigate wave-ion-interactions with wavelet analysis and show that the dynamics and heating of He2+ must result from proton-driven ULF waves. Enhancements in ion agyrotropy are found in relation to, e.g., the ion foreshock boundary, the ULF foreshock boundary, and specular reflection of ions at the bow shock. We show that specular reflection can describe many of the foreshock ion VDF enhancements. Wave-wave-interactions deep in the foreshock cause decoherence of wavefronts, allowing He2+ the be scattered less than protons.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(14453 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
Journal article(s) based on this preprint
Markus Battarbee et al.
Interactive discussion
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RC1: 'Battarbee et al., 2020, Helium in the Earth’s foreshock: a global Vlasiator survey', Jeffrey Broll, 27 Jun 2020
- AC2: 'Response to referee comment 1 by Jeffrey Broll', Markus Battarbee, 04 Aug 2020
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RC2: 'Referee Repart on Batterbee et al.', David Sibeck, 29 Jun 2020
- AC1: 'Response to referee comment 2 by David Sibeck', Markus Battarbee, 04 Aug 2020
Peer-review completion
Interactive discussion
-
RC1: 'Battarbee et al., 2020, Helium in the Earth’s foreshock: a global Vlasiator survey', Jeffrey Broll, 27 Jun 2020
- AC2: 'Response to referee comment 1 by Jeffrey Broll', Markus Battarbee, 04 Aug 2020
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RC2: 'Referee Repart on Batterbee et al.', David Sibeck, 29 Jun 2020
- AC1: 'Response to referee comment 2 by David Sibeck', Markus Battarbee, 04 Aug 2020
Peer-review completion
Journal article(s) based on this preprint
Markus Battarbee et al.
Model code and software
Vlasiator: hybrid-Vlasov simulation code M. Palmroth and the Vlasiator team https://doi.org/10.5281/zenodo.3640593
Video supplement
Supplementary Video A M. Battarbee https://doi.org/10.5446/46641
Supplementary Video B M. Battarbee https://doi.org/10.5446/46638
Supplementary Video C Battarbee, Markus https://doi.org/10.5446/46639
Supplementary Video D M. Battarbee https://doi.org/10.5446/46640
Markus Battarbee et al.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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