2018/11/21 by Ian William Hoppock, Ian W. Hoppock, Benjamin D. G. Chandran +4 · 37 citations
Physics and Astronomy · #Astro and Planetary Science #Atomic physics #Computational physics #Cyclotron #Ionosphere and magnetosphere dynamics #Magnetic field #Mechanics #Nuclear physics #Physics #Plasma #Proton #Quantum electrodynamics #Quantum mechanics #Solar and Space Plasma Dynamics #Solar wind #Turbulence #astro-ph.SR #physics.plasm-ph #physics.space-ph
paper · pdf · doi:10.1017/s0022377818001277
published in Journal of Plasma Physics 84(6) (Cambridge University Press) · 22 pages, 5 figures, accepted for publication in the Journal of Plasma Physics
arxiv created 2018/11/21 · openalex created_date 2018/11/29 · openalex publication_date 2018/12/01 · arxiv updated 2019/01/16 · openalex updated_date 2026/08/05
Stochastic heating refers to an increase in the average magnetic moment of charged particles interacting with electromagnetic fluctuations whose frequencies are smaller than the particles’ cyclotron frequencies. This type of heating arises when the amplitude of the gyroscale fluctuations exceeds a certain threshold, causing particle orbits in the plane perpendicular to the magnetic field to become stochastic rather than nearly periodic. We consider the stochastic heating of protons by Alfvén-wave (AW) and kinetic-Alfvén-wave (KAW) turbulence, which may make an important contribution to the heating of the solar wind. Using phenomenological arguments, we derive the stochastic-proton-heating rate in plasmas in which \unicode[STIX]x1D6FDp∼ 1 –30, where \unicode[STIX]x1D6FDp is the ratio of the proton pressure to the magnetic pressure. (We do not consider the \unicode[STIX]x1D6FDp\gtrsim 30 regime, in which KAWs at the proton gyroscale become non-propagating.) We test our formula for the stochastic-heating rate by numerically tracking test-particle protons interacting with a spectrum of randomly phased AWs and KAWs. Previous studies have demonstrated that at \unicode[STIX]x1D6FDp\lesssim 1 , particles are energized primarily by time variations in the electrostatic potential and thermal-proton gyro-orbits are stochasticized primarily by gyroscale fluctuations in the electrostatic potential. In contrast, at \unicode[STIX]x1D6FDp\gtrsim 1 , particles are energized primarily by the solenoidal component of the electric field and thermal-proton gyro-orbits are stochasticized primarily by gyroscale fluctuations in the magnetic field.