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Thermal Trigger for Solar Flares III: Effect of the Oblique Layer Fragmentation  

Leonid Ledentsov   Submitted: 2021-07-09 04:14

We consider the oblique fragmentation of the current layer as a result of the thermal instability described in Ledentsov (Sol. Phys. 296, 74, 2021a). It is shown that the fragmentation transverse to the current is a natural feature of the model. The fragmentation tilt does not exceed a few degrees for realistic preflare parameters of the coronal plasma. As a consequence, oblique fragmentation generally does not have a strong impact on the simulation results, however, extreme changes can reach an order of magnitude. Thus, oblique fragmentation can lead to a decrease in the estimate of the spatial period of the location of elementary energy release in solar flares to 0.1-1 Mm instead of 1-10 Mm obtained earlier.

Authors: Leonid Ledentsov
Projects: None

Publication Status: This is a post-peer-review, pre-copyedit version of an article published in Solar Physics
Last Modified: 2021-07-10 16:23
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Thermal Trigger for Solar Flares II: Effect of the Guide Magnetic Field  

Leonid Ledentsov   Submitted: 2021-05-19 08:45

We investigate the effect of the thermal imbalance on the structural stability of the magnetohydrodynamic model of the preflare current layer (Ledentsov, Sol. Phys. 296, 74, 2021). The piecewise homogeneous model of the current layer is supplemented by a magnetic field longitudinal with respect to the direction of the current. It is shown that the presence of a weak longitudinal field does not change the previously calculated spatial period of the thermal instability in the most expected range of the parameters of the preflare current layer and, moreover, contributes to the formation of the instability. On the other hand, a strong longitudinal magnetic field contributes to the spatial stabilization of the current layer.

Authors: Leonid Ledentsov
Projects: None

Publication Status: This is a post-peer-review, pre-copyedit version of an article published in Solar Physics
Last Modified: 2021-05-19 13:16
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Thermal Trigger for Solar Flares I: Fragmentation of the Preflare Current Layer  

Leonid Ledentsov   Submitted: 2021-03-11 01:45

We consider the effects of the heat balance on the structural stability of a preflare current layer. The problem of small perturbations is solved in the piecewise homogeneous MHD approximation taking into account the viscosity, the electrical and thermal conductivity, and the radiative cooling. Solution of the problem allows the formation of an instability of a thermal nature. There is no external magnetic field inside the current layer in equilibrium state, but it can penetrate inside when the current layer is disturbed. Formation of a magnetic field perturbation inside the layer creates a dedicated frequency in a broadband disturbance subject to thermal instability. In the linear phase, the growth time of the instability is proportional to the characteristic time of radiative cooling of plasma and depends on the logarithmic derivatives of the radiative cooling function with respect to the plasma parameters. The instability results in transverse fragmentation of the current layer with a spatial period of 1-10 Mm along the layer in a wide range of coronal plasma parameters. The role of that instability in the triggering for the primary energy release in solar flares is discussed.

Authors: Leonid Ledentsov
Projects: None

Publication Status: This is a post-peer-review, pre-copyedit version of an article published in Solar Physics
Last Modified: 2021-03-11 10:18
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Abstracts by Author
Thermal Trigger for Solar Flares III: Effect of the Oblique Layer Fragmentation
Thermal Trigger for Solar Flares II: Effect of the Guide Magnetic Field
Thermal Trigger for Solar Flares I: Fragmentation of the Preflare Current Layer

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