Influence of ion-to-electron temperature ratio on tearing instability and resulting subion-scale turbulence in a low-$β_e$ collisionless plasma
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| Main Authors: | , , , , |
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| Format: | Preprint |
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2023
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| _version_ | 1866914805796831232 |
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| author | Granier, C. Tassi, E. Laveder, D. Passot, T. Sulem, P. L. |
| author_facet | Granier, C. Tassi, E. Laveder, D. Passot, T. Sulem, P. L. |
| contents | A two-field gyrofluid model including ion finite Larmor radius (FLR) corrections, magnetic fluctuations along the ambient field and electron inertia is used to study two-dimensional reconnection in a low $β_e$ collisionless plasma, in a plane perpendicular to the ambient field. Both moderate and large values of the ion-to-electron temperature ratio $τ$ are considered. The linear growth rate of the tearing instability is computed for various values of $τ$, confirming the convergence to reduced electron magnetodynamics (REMHD) predictions in the large $τ$ limit. Comparisons with analytical estimates in several limit cases are also presented. The nonlinear dynamics leads to a fully-developed turbulent regime that appears to be sensitive to the value of the parameter $τ$. For $τ= 100$, strong large-scale velocity shears trigger Kelvin-Helmholtz instability, leading to the propagation of the turbulence through the separatrices, together with the formation of eddies of size of the order of the electron skin depth. In the $τ= 1$ regime, the vortices are significantly smaller and their accurate description requires that electron FLR effects be taken into account. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2311_01539 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Influence of ion-to-electron temperature ratio on tearing instability and resulting subion-scale turbulence in a low-$β_e$ collisionless plasma Granier, C. Tassi, E. Laveder, D. Passot, T. Sulem, P. L. Plasma Physics A two-field gyrofluid model including ion finite Larmor radius (FLR) corrections, magnetic fluctuations along the ambient field and electron inertia is used to study two-dimensional reconnection in a low $β_e$ collisionless plasma, in a plane perpendicular to the ambient field. Both moderate and large values of the ion-to-electron temperature ratio $τ$ are considered. The linear growth rate of the tearing instability is computed for various values of $τ$, confirming the convergence to reduced electron magnetodynamics (REMHD) predictions in the large $τ$ limit. Comparisons with analytical estimates in several limit cases are also presented. The nonlinear dynamics leads to a fully-developed turbulent regime that appears to be sensitive to the value of the parameter $τ$. For $τ= 100$, strong large-scale velocity shears trigger Kelvin-Helmholtz instability, leading to the propagation of the turbulence through the separatrices, together with the formation of eddies of size of the order of the electron skin depth. In the $τ= 1$ regime, the vortices are significantly smaller and their accurate description requires that electron FLR effects be taken into account. |
| title | Influence of ion-to-electron temperature ratio on tearing instability and resulting subion-scale turbulence in a low-$β_e$ collisionless plasma |
| topic | Plasma Physics |
| url | https://arxiv.org/abs/2311.01539 |