Method for creating a three-dimensional magnetic null point topology with an accurate spine axis

AbstractMagnetic reconnection is a candidate mechanism for particle acceleration in a variety of astrophysical contexts. It is now widely accepted that reconnection plays a key role in solar flares, and reconstructions of coronal magnetic fields indicate that three-dimensional (3D) magnetic null points can be present during flares. We investigate particle acceleration during spine reconnection at a 3D magnetic null point, using a test particle numerical code. We observe efficient particle acceleration and find that two energetic populations are produced: a trapped population of particles that remain in the vicinity of the null, and an escaping population, which leave the configuration in two symmetric jets along field lines near the spine. While the parameters used in our simulation aim to represent solar coronal plasma conditions of relevance for acceleration in flares, the fact that the 3D spine reconnection configuration naturally results in energetic particle jets may be of importance in other astrophysical situations. We also compare the results obtained for the spine reconnection regime with those for the other possible mode of 3D reconnection, fan reconnection. We find that in the latter case energetic particle jets are not produced, though acceleration is observed.

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A Fundamental Mechanism of Solar Eruption Initiation

10.5194/egusphere-egu21-10493 ◽

2021 ◽

Author(s):

Chaowei Jiang ◽

Xueshang Feng ◽

Rui Liu ◽

Xiaoli Yan ◽

Qiang Hu ◽

...

Keyword(s):

Source Region ◽

Three Dimensional ◽

Flux Rope ◽

Null Point ◽

Magnetic Flux Rope ◽

Solar Eruptions ◽

Magnetohydrodynamic Simulations ◽

Magnetic Null ◽

Shearing Motion ◽

Magnetic Null Point

<p>Solar eruptions are spectacular magnetic explosions in the Sun's corona and how they are initiated remains unclear. Prevailing theories often rely on special magnetic topologies, such as magnetic flux rope and magnetic null point, which, however, may not generally exist in the pre-eruption source region of corona. Here using fully three-dimensional magnetohydrodynamic simulations with high accuracy, we show that solar eruption can be initiated in a single bipolar configuration with no additional special topology. Through photospheric shearing motion alone, an electric current sheet forms in the highly sheared core field of the magnetic arcade during its quasi-static evolution. Once magnetic reconnection sets in, the whole arcade is expelled impulsively, forming a fast-expanding twisted flux rope with a highly turbulent reconnecting region underneath. The simplicity and efficacy of this scenario argue strongly for its fundamental importance in the initiation of solar eruptions.</p>

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Instability of isolated three-dimensional magnetic null points

Journal of Plasma Physics ◽

10.1017/s0022377898006461 ◽

1998 ◽

Vol 59 (3) ◽

pp. 537-541 ◽

Cited By ~ 1

Author(s):

MANUEL NÚÑEZ

Keyword(s):

Linear Stability ◽

Three Dimensional ◽

Null Point ◽

Static Equilibrium ◽

Flux Surface ◽

Form Part ◽

Magnetic Null ◽

Transverse Oscillations

Although most magnetic neutral points occurring in nature seem to form part of a continuum, recent studies of reconnection have centred on static equilibria in the neighbourhood of an isolated three-dimensional null point. The linear stability of this configuration is studied here. It is found that one may choose a flux surface so that transverse oscillations localized around the surface and polarized within it must grow exponentially in time. This means that any static equilibrium containing an isolated three-dimensional null point is linearly unstable.

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Cluster Observation of Electrostatic Solitary Waves around Magnetic Null Point in Thin Current Sheet

Chinese Physics Letters ◽

10.1088/0256-307x/27/1/019401 ◽

2010 ◽

Vol 27 (1) ◽

pp. 019401 ◽

Cited By ~ 7

Author(s):

Li Shi-You ◽

Deng Xiao-Hua ◽

Zhou Meng ◽

Yuan Zhi-Gang ◽

Wang Jing-Fang ◽

...

Keyword(s):

Current Sheet ◽

Solitary Waves ◽

Null Point ◽

Thin Current Sheet ◽

Magnetic Null ◽

Magnetic Null Point

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Quasi-periodic Radio Bursts Associated with Fast-mode Waves near a Magnetic Null Point

The Astrophysical Journal ◽

10.3847/1538-4357/aa7d53 ◽

2017 ◽

Vol 844 (2) ◽

pp. 149 ◽

Cited By ~ 19

Author(s):

Pankaj Kumar ◽

Valery M. Nakariakov ◽

Kyung-Suk Cho

Keyword(s):

Null Point ◽

Radio Bursts ◽

Fast Mode ◽

Magnetic Null ◽

Magnetic Null Point

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Spatially Separated Electron and Proton Beams in a Simulated Solar Coronal Jet

The Astrophysical Journal ◽

10.3847/1538-4357/ac2e6d ◽

2021 ◽

Vol 923 (2) ◽

pp. 163

Author(s):

Ross Pallister ◽

Peter F. Wyper ◽

David I. Pontin ◽

C. Richard DeVore ◽

Federica Chiti

Keyword(s):

Particle Acceleration ◽

Particle Deposition ◽

Lower Boundary ◽

Impulsive Phase ◽

Null Point ◽

Solar Photosphere ◽

In Situ Observations ◽

Magnetic Null ◽

Magnetic Null Point

Abstract Magnetic reconnection is widely accepted to be a major contributor to nonthermal particle acceleration in the solar atmosphere. In this paper we investigate particle acceleration during the impulsive phase of a coronal jet, which involves bursty reconnection at a magnetic null point. A test-particle approach is employed, using electromagnetic fields from a magnetohydrodynamic simulation of such a jet. Protons and electrons are found to be accelerated nonthermally both downwards toward the domain’s lower boundary and the solar photosphere, and outwards along the axis of the coronal jet and into the heliosphere. A key finding is that a circular ribbon of particle deposition on the photosphere is predicted, with the protons and electrons concentrated in different parts of the ribbon. Furthermore, the outgoing protons and electrons form two spatially separated beams parallel to the axis of the jet, signatures that may be observable in in-situ observations of the heliosphere.

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Plasma Flow Generation due to the Nonlinear Alfvén Wave Propagation around a 3D Magnetic Null Point

The Astrophysical Journal ◽

10.3847/1538-4357/ac242d ◽

2021 ◽

Vol 922 (2) ◽

pp. 123

Author(s):

S. Sabri ◽

H. Ebadi ◽

S. Poedts

Keyword(s):

Plasma Flow ◽

Current Density ◽

Flow Behavior ◽

Plasma Pressure ◽

Null Point ◽

Oscillatory Behavior ◽

Alfven Wave ◽

Plasma Energy ◽

Magnetic Null ◽

Magnetic Null Point

Abstract The behavior of current density accumulation around the sharp gradient of magnetic field structure or a 3D magnetic null point and with the presence of finite plasma pressure is investigated. It has to be stated that in this setup, the fan plane locates at the xy plane and the spine axis aligns along the z-axis. Current density generation in presence of the plasma pressure that acts as a barrier for developing current density is less well understood. The shock-capturing Godunov-type PLUTO code is used to solve the magnetohydrodynamic set of equations in the context of wave-plasma energy transfer. It is shown that propagation of Alfvén waves in the vicinity of a 3D magnetic null point leads to current density excitations along the spine axis and also around the magnetic null point. Besides, it is pointed out the x component of current density has oscillatory behavior while the y and z components do not show this property. It is plausible that it happens because the fan plane encompasses separating unique topological regions, while the spine axis does not have this characteristic and is just a line without separate topological regions. Besides, current density generation results in plasma flow. It is found that the y component of the current density defines the x component of the plasma flow behavior, and the x component of the current density prescribes the behavior of the y component of the plasma flow.

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