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A Model of Homologous Confined and Ejective Eruptions Involving Kink Instability and Flux Cancellation  

Alshaimaa Hassanin   Submitted: 2022-04-24 16:15

In this study, we model a sequence of a confined and a full eruption, employing the relaxed end state of the confined eruption of a kink-unstable flux rope as the initial condition for the ejective one. The full eruption, a model of a coronal mass ejection, develops as a result of converging motions imposed at the photospheric boundary, which drive flux cancellation. In this process, parts of the positive and negative external flux converge toward the polarity inversion line, reconnect, and cancel each other. Flux of the same amount as the canceled flux transfers to a flux rope, increasing the free magnetic energy of the coronal field. With sustained flux cancellation and the associated progressive weakening of the magnetic tension of the overlying flux, we find that a flux reduction of ≈11% initiates the torus instability of the flux rope, which leads to a full eruption. These results demonstrate that a homologous full eruption, following a confined one, can be driven by flux cancellation.

Authors: Alshaimaa Hassanin; Bernhard Kliem; Norbert Seehafer; Tibor Török
Projects: None

Publication Status: published
Last Modified: 2022-04-26 16:10
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Helical Kink Instability in a Confined Solar Eruption  

Alshaimaa Hassanin   Submitted: 2016-09-09 07:47

A model for strongly writhing confined solar eruptions suggests an origin in the helical kink instability of a coronal flux rope which remains stable against the torus instability. This model is tested against the well observed filament eruption on 2002 May 27 in a parametric MHD simulation study which comprises all phases of the event. Good agreement with the essential observed properties is obtained. These include the confinement, terminal height, writhing, distortion, and dissolution of the filament, and the flare loops. The agreement is robust against variations in a representative range of parameter space. Careful comparisons with the observation data constrain the ratio of the external toroidal and poloidal field components to Bet/Bep≈1 and the initial flux rope twist to Φ≈4π. Different from ejective eruptions, two distinct phases of strong magnetic reconnection can occur. First, the erupting flux is cut by reconnection with overlying flux in the helical current sheet formed by the instability. If the resulting flux bundles are linked as a consequence of the erupting rope's strong writhing, they subsequently reconnect in the vertical current sheet between them. This reforms the overlying flux and a far less twisted flux rope, offering a pathway to homologous eruptions.

Authors: Alshaimaa Hassanin and Bernhard Kliem
Projects: TRACE

Publication Status: Astrophys. J., accepted
Last Modified: 2016-09-10 13:39
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A Model of Homologous Confined and Ejective Eruptions Involving Kink Instability and Flux Cancellation
Helical Kink Instability in a Confined Solar Eruption

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