Collapsing Traps

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Introduction

The coronal magnetic field can undergo large-scale restructurings during a flare or CME. If this restructuring happens [adiabatically], i.e. on scales large compared with the [Larmor motion] of the particles in question, they can gain or lose energy. A "collapsing trap" is exactly the sort of geometry expected from large-scale magnetic reconnection, and so this concept provides a basic mechanism for particle acceleration in a flare or CME. The sketches in Figure 1 show how this might work. There is a lot more detail than needed in the sketches; basically on the left one sees a reconnected magnetic field line "dipolarizing" rapidly, and on the left slowly. This process is the basic element of the standard reconnection models of solar flares, as explained copiously elsewhere among the Nuggets (for example, [here].

Two views of the collapsing magnetic trap following large-scale reconnection. The longer arrows show the field deforming, so rapidly on the left as to induce a fast-mode shock wave ("SW") and more slowly on the right.

Betatron vs First-order Fermi Acceleration

Some Data

Conclusion