Pre-acceleration in the Electron Foreshock. II. Oblique Whistler Waves
Thermal electrons have gyroradii many orders of magnitude smaller than the finite width of a shock, thus need to be pre-accelerated before they can cross it and be accelerated by diffusive shock acceleration. One region where pre-acceleration may occur is the inner foreshock, which upstream electron...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/acaec8 |
| _version_ | 1827827830567731200 |
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| author | Paul J. Morris Artem Bohdan Martin S. Weidl Michelle Tsirou Karol Fulat Martin Pohl |
| author_facet | Paul J. Morris Artem Bohdan Martin S. Weidl Michelle Tsirou Karol Fulat Martin Pohl |
| author_sort | Paul J. Morris |
| collection | DOAJ |
| description | Thermal electrons have gyroradii many orders of magnitude smaller than the finite width of a shock, thus need to be pre-accelerated before they can cross it and be accelerated by diffusive shock acceleration. One region where pre-acceleration may occur is the inner foreshock, which upstream electrons must pass through before any potential downstream crossing. In this paper, we perform a large-scale particle-in-cell simulation that generates a single shock with parameters motivated from supernova remnants. Within the foreshock, reflected electrons excite the oblique whistler instability and produce electromagnetic whistler waves, which comove with the upstream flow and as nonlinear structures eventually reach radii of up to 5 ion-gyroradii. We show that the inner electromagnetic configuration of the whistlers evolves into complex nonlinear structures bound by a strong magnetic field around four times the upstream value. Although these nonlinear structures do not in general interact with cospatial upstream electrons, they resonate with electrons that have been reflected at the shock. We show that they can scatter, or even trap, reflected electrons, confining around 0.8% of the total upstream electron population to the region close to the shock where they can undergo substantial pre-acceleration. This acceleration process is similar to, yet approximately three times more efficient than, stochastic shock drift acceleration. |
| first_indexed | 2024-03-12T03:38:06Z |
| format | Article |
| id | doaj.art-cb67ff8b0feb4a2a8cf4e8e0dd19a053 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T03:38:06Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-cb67ff8b0feb4a2a8cf4e8e0dd19a0532023-09-03T13:07:59ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0194411310.3847/1538-4357/acaec8Pre-acceleration in the Electron Foreshock. II. Oblique Whistler WavesPaul J. Morris0https://orcid.org/0000-0002-8533-8232Artem Bohdan1https://orcid.org/0000-0002-5680-0766Martin S. Weidl2https://orcid.org/0000-0002-3440-3225Michelle Tsirou3https://orcid.org/0000-0003-3417-1425Karol Fulat4https://orcid.org/0000-0001-6002-6091Martin Pohl5https://orcid.org/0000-0001-7861-1707Deutsches Elektronen-Synchrotron DESY, Platanenallee 6, D-15738 Zeuthen, Germany ; paul.morris@desy.deDeutsches Elektronen-Synchrotron DESY, Platanenallee 6, D-15738 Zeuthen, Germany ; paul.morris@desy.de; Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching, GermanyMax-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching, GermanyDeutsches Elektronen-Synchrotron DESY, Platanenallee 6, D-15738 Zeuthen, Germany ; paul.morris@desy.deInstitute of Physics and Astronomy, University of Potsdam , D-14476 Potsdam, GermanyDeutsches Elektronen-Synchrotron DESY, Platanenallee 6, D-15738 Zeuthen, Germany ; paul.morris@desy.de; Institute of Physics and Astronomy, University of Potsdam , D-14476 Potsdam, GermanyThermal electrons have gyroradii many orders of magnitude smaller than the finite width of a shock, thus need to be pre-accelerated before they can cross it and be accelerated by diffusive shock acceleration. One region where pre-acceleration may occur is the inner foreshock, which upstream electrons must pass through before any potential downstream crossing. In this paper, we perform a large-scale particle-in-cell simulation that generates a single shock with parameters motivated from supernova remnants. Within the foreshock, reflected electrons excite the oblique whistler instability and produce electromagnetic whistler waves, which comove with the upstream flow and as nonlinear structures eventually reach radii of up to 5 ion-gyroradii. We show that the inner electromagnetic configuration of the whistlers evolves into complex nonlinear structures bound by a strong magnetic field around four times the upstream value. Although these nonlinear structures do not in general interact with cospatial upstream electrons, they resonate with electrons that have been reflected at the shock. We show that they can scatter, or even trap, reflected electrons, confining around 0.8% of the total upstream electron population to the region close to the shock where they can undergo substantial pre-acceleration. This acceleration process is similar to, yet approximately three times more efficient than, stochastic shock drift acceleration.https://doi.org/10.3847/1538-4357/acaec8Supernova remnantsShocks |
| spellingShingle | Paul J. Morris Artem Bohdan Martin S. Weidl Michelle Tsirou Karol Fulat Martin Pohl Pre-acceleration in the Electron Foreshock. II. Oblique Whistler Waves The Astrophysical Journal Supernova remnants Shocks |
| title | Pre-acceleration in the Electron Foreshock. II. Oblique Whistler Waves |
| title_full | Pre-acceleration in the Electron Foreshock. II. Oblique Whistler Waves |
| title_fullStr | Pre-acceleration in the Electron Foreshock. II. Oblique Whistler Waves |
| title_full_unstemmed | Pre-acceleration in the Electron Foreshock. II. Oblique Whistler Waves |
| title_short | Pre-acceleration in the Electron Foreshock. II. Oblique Whistler Waves |
| title_sort | pre acceleration in the electron foreshock ii oblique whistler waves |
| topic | Supernova remnants Shocks |
| url | https://doi.org/10.3847/1538-4357/acaec8 |
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