TY - JOUR

T1 - Kinetic modeling of particle acceleration in a solar null point reconnection region

AU - Baumann, Gisela

AU - Haugbølle, Troels

AU - Nordlund, Åke

PY - 2013/7/10

Y1 - 2013/7/10

N2 - The primary focus of this paper is on the particle acceleration mechanism in solar coronal 3D reconnection null-point regions. Starting from a potential field extrapolation of a SOHO magnetogram taken on 2002 November 16, we first performed MHD simulations with horizontal motions observed by SOHO applied to the photospheric boundary of the computational box. After a build-up of electric current in the fan-plane of the null-point, a sub-section of the evolved MHD data was used as initial and boundary conditions for a kinetic particle-in-cell model of the plasma. We find that sub-relativistic electron acceleration is mainly driven by a systematic electric field in the current sheet. A non-thermal population of electrons with a power-law distribution in energy forms, featuring a power-law index of about -1.75. This work provides a first step towards bridging the gap between macroscopic scales on the order of hundreds of Mm and kinetic scales on the order of cm in the solar corona, and explains how to achieve such a cross-scale coupling by utilizing either physical modifications or (equivalent) modifications of the constants of nature. With their exceptionally high resolution --- up to 135 billion particles and 3.5 billion grid cells of size 17.5\,km --- these simulations offer a new opportunity to study particle acceleration in solar-like settings.

AB - The primary focus of this paper is on the particle acceleration mechanism in solar coronal 3D reconnection null-point regions. Starting from a potential field extrapolation of a SOHO magnetogram taken on 2002 November 16, we first performed MHD simulations with horizontal motions observed by SOHO applied to the photospheric boundary of the computational box. After a build-up of electric current in the fan-plane of the null-point, a sub-section of the evolved MHD data was used as initial and boundary conditions for a kinetic particle-in-cell model of the plasma. We find that sub-relativistic electron acceleration is mainly driven by a systematic electric field in the current sheet. A non-thermal population of electrons with a power-law distribution in energy forms, featuring a power-law index of about -1.75. This work provides a first step towards bridging the gap between macroscopic scales on the order of hundreds of Mm and kinetic scales on the order of cm in the solar corona, and explains how to achieve such a cross-scale coupling by utilizing either physical modifications or (equivalent) modifications of the constants of nature. With their exceptionally high resolution --- up to 135 billion particles and 3.5 billion grid cells of size 17.5\,km --- these simulations offer a new opportunity to study particle acceleration in solar-like settings.

KW - astro-ph.SR

KW - physics.plasm-ph

U2 - 10.1088/0004-637X/771/2/93

DO - 10.1088/0004-637X/771/2/93

M3 - Journal article

VL - 771

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 2

M1 - 93

ER -