Dynamics of energetic particles scattered in the solar wind : Magnetohydrodynamics and test-particle simulations
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arXiv
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| Format: | Preprint |
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2024
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| _version_ | 1866909500293775360 |
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| author | Ahmed, Houeibib Filippo, Pantellini Lea, Griton |
| author_facet | Ahmed, Houeibib Filippo, Pantellini Lea, Griton |
| contents | We model the transport of solar energetic particles (SEPs) in the solar wind. We propagated relativistic test particles in the field of a steady three-dimensional magnetohydrodynamic simulation of the solar wind. We used the code MPI-AMRVAC for the wind simulations and integrated the relativistic guiding center equations using a new third-order-accurate predictor-corrector time-integration scheme. Turbulence-induced scattering of the particle trajectories in velocity space was taken into account through the inclusion of a constant field-aligned scattering mean free path $λ_\parallel$. We considered mid-range SEP electrons of $81\:{\rm keV}$ injected into the solar wind at a heliocentric distance of 0.28 AU and a magnetic latitude of $24^{\circ}$. For $λ_\parallel =0.5\:{\rm AU}$, the simulated velocity pitch angle distributions agree qualitatively well with in situ measurements at 1 AU. More generally, for $λ_\parallel$ in the range 0.1 to 1\:AU, an energy-loss rate associated with the velocity drift of about $10\%$ per day is observed. The energy loss is attributable to the magnetic curvature and gradient-induced poleward drifts of the electrons against the dominant component of the electric field. In our case study, which is representative of the average solar wind conditions, the observed drift-induced energy-loss rate is fastest near a heliocentric distance of 1.2 AU. We emphasize that adiabatic cooling is the dominant mechanism during the first 1.5 hours of propagation. Only at later times does the drift-associated loss rate become dominant. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2403_06706 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Dynamics of energetic particles scattered in the solar wind : Magnetohydrodynamics and test-particle simulations Ahmed, Houeibib Filippo, Pantellini Lea, Griton Solar and Stellar Astrophysics Plasma Physics Space Physics We model the transport of solar energetic particles (SEPs) in the solar wind. We propagated relativistic test particles in the field of a steady three-dimensional magnetohydrodynamic simulation of the solar wind. We used the code MPI-AMRVAC for the wind simulations and integrated the relativistic guiding center equations using a new third-order-accurate predictor-corrector time-integration scheme. Turbulence-induced scattering of the particle trajectories in velocity space was taken into account through the inclusion of a constant field-aligned scattering mean free path $λ_\parallel$. We considered mid-range SEP electrons of $81\:{\rm keV}$ injected into the solar wind at a heliocentric distance of 0.28 AU and a magnetic latitude of $24^{\circ}$. For $λ_\parallel =0.5\:{\rm AU}$, the simulated velocity pitch angle distributions agree qualitatively well with in situ measurements at 1 AU. More generally, for $λ_\parallel$ in the range 0.1 to 1\:AU, an energy-loss rate associated with the velocity drift of about $10\%$ per day is observed. The energy loss is attributable to the magnetic curvature and gradient-induced poleward drifts of the electrons against the dominant component of the electric field. In our case study, which is representative of the average solar wind conditions, the observed drift-induced energy-loss rate is fastest near a heliocentric distance of 1.2 AU. We emphasize that adiabatic cooling is the dominant mechanism during the first 1.5 hours of propagation. Only at later times does the drift-associated loss rate become dominant. |
| title | Dynamics of energetic particles scattered in the solar wind : Magnetohydrodynamics and test-particle simulations |
| topic | Solar and Stellar Astrophysics Plasma Physics Space Physics |
| url | https://arxiv.org/abs/2403.06706 |