Abstract
Variations in the photospheric magnetic field in the region of solar flares, related to halo coronal mass ejections (HCMEs) with velocities V > 1500, 1000 < V < 1500, and V < 650 km/s, have been studied based on SOHO/MDI data. Using data with a time resolution of 96 min, it has been indicated that on average the 〈B L〉 and 〈|B L|〉 field characteristics increase nonmonotonically during 1–1.5 days before a flare and decrease during 0.5–1 days after a flare for groups of ejections with V > 1000 km/s for all considered HCME groups. Angle brackets designate averaging of the measured B L magnetic field component and its magnitude |B L| within an area with specified dimensions and the center coincident with the projection onto the region where the flare center field is measured. It has been established that a solar flare related to an HCME originates when the 〈B L〉 and 〈|B L|〉 values are larger than the boundary values in the flare region. Based on 1-min data, it has been found for several HCMEs with V > 1500 km/s that the beginning of powerful flares related to ejections is accompanied by rapid impulsive or stepped variations in 〈B L〉 and 〈|B L|〉 near the center of a flare with a size of approximately 4.5°. It has been established that the HCME velocity positively correlates with the |〈B L〉| value at the flare onset.
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Fainshtein, V.G., Popova, T.E. & Kashapova, L.K. Magnetic field dynamics based on SOHO/MDI data in the region of flares related to halo coronal mass ejections. Geomagn. Aeron. 52, 1075–1086 (2012). https://doi.org/10.1134/S0016793212080105
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DOI: https://doi.org/10.1134/S0016793212080105