The study of the accumulation of magnetic helicity via emergence of new magnetic flux and/or shearing photospheric motions is considered an important tool for understanding the processes that lead to eruptive phenomena. In a previous work we measured the amount of magnetic helicity injected into the corona through the photosphere in a sample of active regions (ARs) by inferring the apparent motion of photospheric footpoints of magnetic field lines from a time series of MDI full-disk line-of-sight magnetograms \citep{Rom11}. The temporal variation of the maps of magnetic helicity flux was analysed by measuring the fragmentation of the patches characterized by different flux of magnetic helicity. The more fragmented were the maps of the magnetic helicity flux, the higher was the flare and coronal mass ejection (CME) frequency. In order to further investigate the correlation between the number of these patches and the flare and the CME occurrence, another sample of ARs observed with a higher spatial resolution by SDO/HMI has been analyzed. The new results indicate that not only the accumulation of magnetic helicity in the corona, but also its positive and negative fragmentation and distribution should be taken into account to provide a more confident indication of AR complexity and flare/CME productivity.

Spatial distribution of the magnetic helicity flux measured with SDO/HMI in active regions hosting flares and CMEs

ZUCCARELLO, Francesca
2013

Abstract

The study of the accumulation of magnetic helicity via emergence of new magnetic flux and/or shearing photospheric motions is considered an important tool for understanding the processes that lead to eruptive phenomena. In a previous work we measured the amount of magnetic helicity injected into the corona through the photosphere in a sample of active regions (ARs) by inferring the apparent motion of photospheric footpoints of magnetic field lines from a time series of MDI full-disk line-of-sight magnetograms \citep{Rom11}. The temporal variation of the maps of magnetic helicity flux was analysed by measuring the fragmentation of the patches characterized by different flux of magnetic helicity. The more fragmented were the maps of the magnetic helicity flux, the higher was the flare and coronal mass ejection (CME) frequency. In order to further investigate the correlation between the number of these patches and the flare and the CME occurrence, another sample of ARs observed with a higher spatial resolution by SDO/HMI has been analyzed. The new results indicate that not only the accumulation of magnetic helicity in the corona, but also its positive and negative fragmentation and distribution should be taken into account to provide a more confident indication of AR complexity and flare/CME productivity.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.11769/86352
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