Large Sunspot Groups and Great Magnetic Storms: Magnetic Suppression of CMEs

• Published in: The Astrophysical journal 2022-10, Vol.938 (2), p.136
• Main Authors: Cliver, Edward W., Pötzi, Werner, Veronig, Astrid M.
• Format: Article
• Language: English
• Subjects: Astrophysics; Coronal mass ejection; Geomagnetic storms; Magnetic storms; Solar active regions; Solar activity; Solar coronal mass ejections; Solar filament eruptions; Solar flares; Solar-terrestrial interactions; Space weather; Stellar coronas; Storms; Sunspot groups; Sunspots
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ac847d

A solar spot group with a large area is not a requirement for a great magnetic storm. Nearly half (14/30) of all storms with a minimum Dst value ≤−300 nT from 1932–2014 originated in spot groups with corrected areas ≤1000 millionths of a solar hemisphere ( μ sh) on the day of the associated eruption. Over the same interval, spot groups with area 3000–4000 μ sh were ∼250 times more likely to give rise to a great storm than those with areas from 100–1000 μ sh, with the high percentage of great storms originating in small spot groups attributed primarily to the much higher occurrence frequency of such groups. Above ∼3500 μ sh, the ability of a spot group to produce a great storm appears to drop abruptly. For the 1932–2014 interval, we find that for the 71 days when a spot group had a measured daily area of 3000–3500 μ sh, five great storms were observed versus none for the 67 times when a group spot with an area from 3500 to ∼6000 μ sh was observed on the Sun. This is consistent with recent studies indicating that large spot groups on the Sun and stars can suppress coronal mass ejections.