Evolution of magnetic helicity during eruptive flares and coronal mass ejections
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During eruptive solar flares and coronal mass ejections, a non-potential magnetic arcade with much excess magnetic energy goes unstable and reconnects. It produces a twisted erupting flux rope and leaves behind a sheared arcade of hot coronal loops. We suggest that: the twist of the erupting flux rope can be determined from conservation of magnetic flux and magnetic helicity and equipartition of magnetic helicity. It depends on the geometry of the initial preeruptive structure. Two cases are considered, in the first of which a flux rope is not present initially but is created during the eruption by the reconnection. In the second case, a flux rope is present under the arcade in the pre-eruptive state,and the e.ect of the eruption and reconnection is to add an amount of magnetic helicity that depends on the fluxes of the rope and arcade and the geometry.
Priest , E R , Longcope , D W & Janvier , M 2016 , ' Evolution of magnetic helicity during eruptive flares and coronal mass ejections ' Solar Physics , vol 291 , no. 7 , pp. 2017-2036 . DOI: 10.1007/s11207-016-0962-6
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Funding: UK STFC, High Altitude Observatory and Montana State University.
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