scholarly journals A topological analysis of the magnetic breakout model for an eruptive solar flare

2005 ◽  
Vol 461 (2059) ◽  
pp. 2099-2120 ◽  
Author(s):  
Rhona Maclean ◽  
Colin Beveridge ◽  
Dana Longcope ◽  
Daniel Brown ◽  
Eric Priest
Keyword(s):  
Solar Flare ◽  
Magnetic Reconnection ◽  
Topological Analysis ◽  
Null Point ◽  
Topological Approach ◽  
Sunspot Model ◽  
New Class ◽  
Linear Force ◽  
Field Lines

The magnetic breakout model gives an elegant explanation for the onset of an eruptive solar flare, involving magnetic reconnection at a coronal null point which leads to the initially enclosed flux ‘breaking out’ to large distances. In this paper we take a topological approach to the study of the conditions required for this breakout phenomenon to occur. The evolution of a simple delta sunspot model, up to the point of breakout, is analysed through several sequences of potential and linear force-free quasi-static equilibria. We show that any new class of field lines, such as those connecting to large distances, must be created through a global topological bifurcation and derive rules to predict the topological reconfiguration due to various types of bifurcation.

Proton acceleration in three-dimensional non-null magnetic reconnection

2016 ◽  
Vol 82 (5) ◽  
Author(s):  
Z. Akbari ◽  
M. Hosseinpour ◽  
M. A. Mohammadi
Keyword(s):  
Magnetic Field ◽  
Energy Distribution ◽  
Magnetic Reconnection ◽  
Electric Fields ◽  
Three Dimensional ◽  
Null Point ◽  
Proton Acceleration ◽  
Electric And Magnetic Fields ◽  
Field Lines ◽  
The Magnetic Field

In a three-dimensional non-null magnetic reconnection, the process of magnetic reconnection takes place in the absence of a null point where the magnetic field vanishes. By randomly injecting a population of 10 000 protons, the trajectory and energy distribution of accelerated protons are investigated in the presence of magnetic and electric fields of a particular model of non-null magnetic reconnection with the typical parameters for the solar corona. The results show that protons are accelerated along the magnetic field lines away from the non-null point only at azimuthal angles where the magnitude of the electric field is strongest and therefore particles obtain kinetic energies of the order of thousands of MeV and even higher. Moreover, the energy distribution of the population depends strongly on the amplitude of the electric and magnetic fields. Comparison shows that a non-null magnetic reconnection is more efficient in accelerating protons to very high GeV energies than a null-point reconnection.

scholarly journals Jets of energetic particles generated by magnetic reconnection at a three-dimensional magnetic null

2006 ◽  
Vol 2 (14) ◽  
pp. 98-98
Author(s):  
Silvia Dalla ◽  
Philippa K. Browning
Keyword(s):  
Particle Acceleration ◽  
Magnetic Reconnection ◽  
Energetic Particle ◽  
Three Dimensional ◽  
Null Point ◽  
Numerical Code ◽  
Coronal Magnetic Fields ◽  
Field Lines ◽  
Magnetic Null ◽  
Magnetic Null Point

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.

Toward laboratory torsional spine magnetic reconnection

2017 ◽  
Vol 83 (6) ◽  
Author(s):  
David L. Chesny ◽  
N. Brice Orange ◽  
Hakeem M. Oluseyi ◽  
David R. Valletta
Keyword(s):  
Magnetic Reconnection ◽  
Kinetic Parameters ◽  
Three Dimensional ◽  
Limited Range ◽  
Null Point ◽  
Plasma Parameters ◽  
Astrophysical Plasmas ◽  
Current Sheets ◽  
Practical Applications ◽  
Field Lines

Magnetic reconnection is a fundamental energy conversion mechanism in nature. Major attempts to study this process in controlled settings on Earth have largely been limited to reproducing approximately two-dimensional (2-D) reconnection dynamics. Other experiments describing reconnection near three-dimensional null points are non-driven, and do not induce any of the 3-D modes of spine fan, torsional fan or torsional spine reconnection. In order to study these important 3-D modes observed in astrophysical plasmas (e.g. the solar atmosphere), laboratory set-ups must be designed to induce driven reconnection about an isolated magnetic null point. As such, we consider the limited range of fundamental resistive magnetohydrodynamic (MHD) and kinetic parameters of dynamic laboratory plasmas that are necessary to induce the torsional spine reconnection (TSR) mode characterized by a driven rotational slippage of field lines – a feature that has yet to be achieved in operational laboratory magnetic reconnection experiments. Leveraging existing reconnection models, we show that within a${\lesssim}1~\text{m}^{3}$apparatus, TSR can be achieved in dense plasma regimes (${\sim}10^{24}~\text{m}^{-3}$) in magnetic fields of${\sim}10^{-1}~\text{T}$. We find that MHD and kinetic parameters predict reconnection in thin${\lesssim}20~\unicode[STIX]{x03BC}\text{m}$current sheets on time scales of${\lesssim}10~\text{ns}$. While these plasma regimes may not explicitly replicate the plasma parameters of observed astrophysical phenomena, studying the dynamics of the TSR mode within achievable set-ups signifies an important step in understanding the fundamentals of driven 3-D magnetic reconnection and the self-organization of current sheets. Explicit control of this reconnection mode may have implications for understanding particle acceleration in astrophysical environments, and may even have practical applications to fields such as spacecraft propulsion.

Dynamic non-null magnetic reconnection in three dimensions. I. Particular solutions

2006 ◽  
Vol 462 (2074) ◽  
pp. 2877-2895 ◽  
Author(s):  
Antonia Wilmot-Smith ◽  
Gunnar Hornig ◽  
Eric Priest
Keyword(s):  
Magnetic Reconnection ◽  
Kinematic Model ◽  
Three Dimensional ◽  
Momentum Equation ◽  
Null Point ◽  
Three Dimensions ◽  
Diffusion Region ◽  
Ideal Solution ◽  
Ideal Solutions ◽  
Field Lines

A stationary model of three-dimensional magnetic reconnection in the absence of a null point is presented, with a non-ideal region that is localized in space. Analytical solutions to the resistive magnetohydrodynamic equations are obtained, with the momentum equation included so that the model is fully dynamic, and thus extends the previous kinematic solutions. A splitting of variables allows solutions to be written in terms of a particular non-ideal solution, on which ideal solutions may be superposed. For the non-ideal solution alone, it is shown that only the field lines linking the diffusion region are affected by the reconnection process, and counter-rotating flows above and below the diffusion region are present. It is only the dimensions of the diffusion region along the reconnection line that are important for the reconnection rate. Many features of the previous stationary kinematic model are also observed here.

scholarly journals Onset of magnetic reconnection in a collisionless, high- plasma

2019 ◽  
Vol 85 (1) ◽  
Author(s):  
Andrew Alt ◽  
Matthew W. Kunz
Keyword(s):  
Magnetic Reconnection ◽  
Collisionless Plasma ◽  
High Plasma ◽  
Tearing Modes ◽  
Associated Production ◽  
Pressure Anisotropy ◽  
Low Threshold ◽  
Collisionless Reconnection ◽  
Field Lines ◽  
The Impact

In a magnetized, collisionless plasma, the magnetic moment of the constituent particles is an adiabatic invariant. An increase in the magnetic-field strength in such a plasma thus leads to an increase in the thermal pressure perpendicular to the field lines. Above a$\unicode[STIX]{x1D6FD}$-dependent threshold (where$\unicode[STIX]{x1D6FD}$is the ratio of thermal to magnetic pressure), this pressure anisotropy drives the mirror instability, producing strong distortions in the field lines on ion-Larmor scales. The impact of this instability on magnetic reconnection is investigated using a simple analytical model for the formation of a current sheet (CS) and the associated production of pressure anisotropy. The difficulty in maintaining an isotropic, Maxwellian particle distribution during the formation and subsequent thinning of a CS in a collisionless plasma, coupled with the low threshold for the mirror instability in a high-$\unicode[STIX]{x1D6FD}$plasma, imply that the geometry of reconnecting magnetic fields can differ radically from the standard Harris-sheet profile often used in simulations of collisionless reconnection. As a result, depending on the rate of CS formation and the initial CS thickness, tearing modes whose growth rates and wavenumbers are boosted by this difference may disrupt the mirror-infested CS before standard tearing modes can develop. A quantitative theory is developed to illustrate this process, which may find application in the tearing-mediated disruption of kinetic magnetorotational ‘channel’ modes.

scholarly journals Formation of coronal rain triggered by impulsive heating associated with magnetic reconnection

2019 ◽  
Vol 630 ◽  
pp. A123 ◽  
Author(s):  
P. Kohutova ◽  
E. Verwichte ◽  
C. Froment
Keyword(s):  
Magnetic Reconnection ◽  
Thermal Instability ◽  
Flux Rope ◽  
Coronal Loops ◽  
Rain Event ◽  
Subsequent Formation ◽  
Standard Models ◽  
Field Lines ◽  
Impulsive Heating ◽  
Coronal Rain

Context. Coronal rain consists of cool plasma condensations formed in coronal loops as a result of thermal instability. The standard models of coronal rain formation assume that the heating is quasi-steady and localised at the coronal loop footpoints. Aims. We present an observation of magnetic reconnection in the corona and the associated impulsive heating triggering formation of coronal rain condensations. Methods. We analyse combined SDO/AIA and IRIS observations of a coronal rain event following a reconnection between threads of a low-lying prominence flux rope and surrounding coronal field lines. Results. The reconnection of the twisted flux rope and open field lines leads to a release of magnetic twist. Evolution of the emission of one of the coronal loops involved in the reconnection process in different AIA bandpasses suggests that the loop becomes thermally unstable and is subject to the formation of coronal rain condensations following the reconnection and that the associated heating is localised in the upper part of the loop leg. Conclusions. In addition to the standard models of thermally unstable coronal loops with heating localised exclusively in the footpoints, thermal instability and subsequent formation of condensations can be triggered by the impulsive heating associated with magnetic reconnection occurring anywhere along a magnetic field line.

scholarly journals IMAGING AND SPECTROSCOPIC OBSERVATIONS OF MAGNETIC RECONNECTION AND CHROMOSPHERIC EVAPORATION IN A SOLAR FLARE

2014 ◽  
Vol 797 (2) ◽  
pp. L14 ◽  
Author(s):  
Hui Tian ◽  
Gang Li ◽  
Katharine K. Reeves ◽  
John C. Raymond ◽  
Fan Guo ◽  
...  
Keyword(s):  
Solar Flare ◽  
Magnetic Reconnection ◽  
Spectroscopic Observations ◽  
Chromospheric Evaporation

scholarly journals Statistical Properties of Magnetic Separators in Model Active Regions

2000 ◽  
Vol 195 ◽  
pp. 443-444
Author(s):  
B. T. Welsch ◽  
D. W. Longcope
Keyword(s):  
Active Region ◽  
Solar Corona ◽  
Magnetic Reconnection ◽  
First Principles ◽  
Magnetic Charge ◽  
Active Regions ◽  
Heating Rates ◽  
X Ray ◽  
Field Lines ◽  
Charge Topology

“Transient brightenings” (or “microflares”) regularly deposit 1027 ergs of energy in the solar corona, and account for perhaps 20% of the active corona's power (Shimizu 1995). We assume these events correspond to episodes of magnetic reconnection along magnetic separators in the solar corona. Using the techniques of magnetic charge topology, we model active region fields as arising from normally distributed collections of “magnetic charges”, point-like sources/sinks of flux (or field lines). Here, we present statistically determined separator (X-ray loop) lengths, derived from first principles. We are in the process of statistical calculations of heating rates due to reconnection events along many separators.

A loop-top hard X-ray source in a compact solar flare as evidence for magnetic reconnection

Nature ◽  
1994 ◽  
Vol 371 (6497) ◽  
pp. 495-497 ◽  
Author(s):  
S. Masuda ◽  
T. Kosugi ◽  
H. Hara ◽  
S. Tsuneta ◽  
Y. Ogawara
Keyword(s):  
Solar Flare ◽  
Magnetic Reconnection ◽  
X Ray
Sign in / Sign up

Export Citation Format

Share Document