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Measurement of the coronal magnetic field is a crucial ingredient in understanding the nature of solar coronal phenomena at all scales. We employed STEREO/COR1 data obtained during a deep minimum of solar activity in February 2008…

Solar and Stellar Astrophysics · Physics 2014-05-06 M. Kramar , V. Airapetian , Z. Mikić , J. Davila

We use extensive 3D resistive MHD simulations to study how large-scale current sheets will undergo fast reconnection in the high Lundquist number $S$ limit (above $\sim 10^4$), when the system is subject to different externally driven…

Solar and Stellar Astrophysics · Physics 2022-04-06 Yang Liping , Li Hui , Guo Fan , Li Xiaocan , Li Shengtai , He jiansen , Zhang Lei , Feng Xueshang

During eruptive flares, vector magnetograms show increasing horizontal magnetic field and downward Lorentz force in the Sun's photosphere around the polarity-inversion line. Such behavior has often been associated with the implosion…

Solar and Stellar Astrophysics · Physics 2019-06-05 Krzysztof Barczynski , Guillaume Aulanier , Sophie Masson , Michael S. Wheatland

Fully kinetic two-dimensional particle-in-cell simulations are used to study electron acceleration at high-Mach-number nonrelativistic perpendicular shocks. SNR shocks are mediated by the Weibel instability which is excited because of an…

High Energy Astrophysical Phenomena · Physics 2020-04-15 Artem Bohdan , Martin Pohl , Jacek Niemiec , Sergei Vafin , Yosuke Matsumoto , Takanobu Amano , Masahiro Hoshino

This paper considers the current distributions that derive from finite amplitude perturbations of line-tied magnetic fields comprising hyperbolic field structures. The initial equilibrium on which we principally focus is a planar magnetic…

Solar and Stellar Astrophysics · Physics 2015-06-19 I. J. D. Craig , D. I. Pontin

We report a newly found two-stage mechanism of electron acceleration near X-lines of 3D collisionless guide-field magnetic reconnection in the non-relativistic regime typical, e.g., for stellar coronae. We found that after electrons are…

Plasma Physics · Physics 2018-09-11 P. A. Muñoz , J. Büchner

The discovery of rapid synchrotron gamma-ray flares above 100 MeV from the Crab Nebula has attracted new interest in alternative particle acceleration mechanisms in pulsar wind nebulae. Diffuse shock-acceleration fails to explain the flares…

High Energy Astrophysical Phenomena · Physics 2015-06-17 Benoit Cerutti , Gregory R. Werner , Dmitri A. Uzdensky , Mitchell C. Begelman

In this paper we present a two-dimensional, time dependent, numerical simulation of a reconnection current layer in incompressible resistive magnetohydrodynamics with uniform resistivity in the limit of very large Lundquist numbers. We use…

Astrophysics · Physics 2009-10-31 Dmitri A. Uzdensky , Russell M. Kulsrud

Magnetic reconnection, a fundamentally important process in many aspects of astrophysics, is believed to be initiated by the tearing instability of an electric current sheet, a region where magnetic field abruptly changes direction and…

Solar and Stellar Astrophysics · Physics 2020-03-11 James Leake , Lars Daldorff , James Klimchuk

Numerical MHD simulations of 3D reconnection events in the solar corona have improved enormously over the last few years, not only in resolution, but also in their complexity, enabling more and more realistic modeling. Various ways to…

Solar and Stellar Astrophysics · Physics 2012-11-07 G. Baumann , K. Galsgaard , Å. Nordlund

Sudden destabilisations of the magnetic field, such as those caused by spontaneous reconnection, will produce waves and/or flows. Here, we investigate the nature of the plasma motions resulting from spontaneous reconnection at a 3D…

Plasma Physics · Physics 2016-01-29 Julie E. H. Stevenson , Clare E. Parnell

Magnetic reconnection in the partially ionized solar chromosphere is studied in 2.5-dimensional magnetohydrodynamic simulations including radiative cooling and ambipolar diffusion. A Harris current sheet with and without a guide field is…

Solar and Stellar Astrophysics · Physics 2015-09-24 Lei Ni , Bernhard Kliem , Jun Lin , Ning Wu

Coronal heating has been a long-standing conundrum in solar physics. Parker's conjecture that spontaneous current singularities lead to nanoflares that heat the corona has been controversial. In ideal magnetohydrodynamics (MHD), can genuine…

Plasma Physics · Physics 2017-08-30 Yao Zhou

Fast magnetic reconnection is defined by the topology of the magnetic field lines changing on a timescale that is approximately an order of magnitude longer than the topology-conserving ideal-evolution timescale. Fast reconnection is an…

Plasma Physics · Physics 2022-05-18 Allen H Boozer

Many magnetic structures in the solar atmosphere evolve rather slowly so that they can be assumed as (quasi-)static or (quasi-)stationary and represented via magneto-hydrostatic (MHS) or stationary magneto-hydrodynamic (MHD) equilibria,…

Solar and Stellar Astrophysics · Physics 2017-03-15 Dieter H. Nickeler , Thomas Wiegelmann , Marian Karlicky , Michaela Kraus

Forced magnetic reconnection, a reconnection event triggered by external perturbation, should be ubiquitous in the solar corona. Energy released during such cases can be much greater than that which was introduced by the perturbation. It is…

Solar and Stellar Astrophysics · Physics 2019-02-27 Max Potter , Philippa Browning , Mykola Gordovskyy

Magnetic reconnection is a fundamental process in a laboratory, magnetospheric, solar and astrophysical plasma, whereby magnetic energy is converted into heat, bulk kinetic energy and fast particle energy. Its nature in two dimensions is…

Solar and Stellar Astrophysics · Physics 2021-06-09 Ting Li , Eric Priest , Ruilong Guo

In a recent work Grappin et al. [1] have shown that low- frequency movements can be transmitted from one footpoint to the other along a magnetic loop, thus mimicking a friction effect of the corona on the photosphere, and invalidating the…

Solar and Stellar Astrophysics · Physics 2014-11-20 A. Verdini , R. Grappin , M. Velli

The three-dimensional (3D) coordinates of stereoscopically triangulated loops provide strong constraints for magnetic field models of active regions in the solar corona. Here we use STEREO/A and B data from some 500 stereoscopically…

Solar and Stellar Astrophysics · Physics 2015-06-05 Markus J. Aschwanden , Jean-Pierre Wuelser , Nariaki V. Nitta , James R. Lemen , Marc L. DeRosa , Anna Malanushenko

We investigate the 3D stationary flow of a weakly conducting fluid in a cubic cavity, driven by the Lorentz force created by two permanent magnets and a weak constant current. Our goal is to determine the conditions leading to efficient…