A stringent limit on the amplitude of alfvénic perturbations in high-beta low-collisionality plasmas
It is shown that low-collisionality plasmas cannot support linearly polarized shear-Alfvén fluctuations above a critical amplitude δB⊥/B0 ∼ B-1/2, where β is the ratio of thermal to magnetic pressure. Above this cutoff, a developing fluctuation will generate a pressure anisotropy that is sufficient...
| প্রধান লেখক: | , , |
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| বিন্যাস: | Journal article |
| প্রকাশিত: |
IOP Publishing
2016
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| _version_ | 1826288566614884352 |
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| author | Squire, J Quataert, E Schekochihin, A |
| author_facet | Squire, J Quataert, E Schekochihin, A |
| author_sort | Squire, J |
| collection | OXFORD |
| description | It is shown that low-collisionality plasmas cannot support linearly polarized shear-Alfvén fluctuations above a critical amplitude δB⊥/B0 ∼ B-1/2, where β is the ratio of thermal to magnetic pressure. Above this cutoff, a developing fluctuation will generate a pressure anisotropy that is sufficient to destabilize itself through the parallel firehose instability. This causes the wave frequency to approach zero, interrupting the fluctuation before any oscillation. The magnetic field lines rapidly relax into a sequence of angular zig-zag structures. Such a restrictive bound on shear-Alfvén-wave amplitudes has far-reaching implications for the physics of magnetized turbulence in the high-β conditions prevalent in many astrophysical plasmas, as well as for the solar wind at ∼1 au where β ≳ 1. |
| first_indexed | 2024-03-07T02:15:38Z |
| format | Journal article |
| id | oxford-uuid:a2251b70-9065-4f27-bebc-552d7d268f04 |
| institution | University of Oxford |
| last_indexed | 2024-03-07T02:15:38Z |
| publishDate | 2016 |
| publisher | IOP Publishing |
| record_format | dspace |
| spelling | oxford-uuid:a2251b70-9065-4f27-bebc-552d7d268f042022-03-27T02:18:10ZA stringent limit on the amplitude of alfvénic perturbations in high-beta low-collisionality plasmasJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:a2251b70-9065-4f27-bebc-552d7d268f04Symplectic Elements at OxfordIOP Publishing2016Squire, JQuataert, ESchekochihin, AIt is shown that low-collisionality plasmas cannot support linearly polarized shear-Alfvén fluctuations above a critical amplitude δB⊥/B0 ∼ B-1/2, where β is the ratio of thermal to magnetic pressure. Above this cutoff, a developing fluctuation will generate a pressure anisotropy that is sufficient to destabilize itself through the parallel firehose instability. This causes the wave frequency to approach zero, interrupting the fluctuation before any oscillation. The magnetic field lines rapidly relax into a sequence of angular zig-zag structures. Such a restrictive bound on shear-Alfvén-wave amplitudes has far-reaching implications for the physics of magnetized turbulence in the high-β conditions prevalent in many astrophysical plasmas, as well as for the solar wind at ∼1 au where β ≳ 1. |
| spellingShingle | Squire, J Quataert, E Schekochihin, A A stringent limit on the amplitude of alfvénic perturbations in high-beta low-collisionality plasmas |
| title | A stringent limit on the amplitude of alfvénic perturbations in high-beta low-collisionality plasmas |
| title_full | A stringent limit on the amplitude of alfvénic perturbations in high-beta low-collisionality plasmas |
| title_fullStr | A stringent limit on the amplitude of alfvénic perturbations in high-beta low-collisionality plasmas |
| title_full_unstemmed | A stringent limit on the amplitude of alfvénic perturbations in high-beta low-collisionality plasmas |
| title_short | A stringent limit on the amplitude of alfvénic perturbations in high-beta low-collisionality plasmas |
| title_sort | stringent limit on the amplitude of alfvenic perturbations in high beta low collisionality plasmas |
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