The pre-penumbral magnetic canopy in the solar atmosphere

Abstract

Penumbrae are the manifestation of magnetoconvection in highly inclined (to the vertical direction) magnetic field. The penumbra of a sunspot tends to form, initially, along the arc of the umbra antipodal to the main region of flux emergence. The question of how highly inclined magnetic field can concentrate along the antipodal curves of umbrae, at least initially, remains to be answered. Previous observational studies have suggested the existence of some form of overlying magnetic canopy which acts as the progenitor for penumbrae. We propose that such overlying magnetic canopies are a consequence of how the magnetic field emerges into the atmosphere and are, therefore, part of the emerging region. We show, through simulations of twisted flux tube emergence, that canopies of highly inclined magnetic field form preferentially at the required locations above the photosphere.

arXiv commentAccepted for ApJL

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Cited by in corpus (6)

• On the formation of a stable penumbra in a region of flux emergence in the Sun
• Properties of the Umbral Filament Observed in Active Region NOAA 12529
• The role of the chromospheric magnetic canopy in the formation of a sunspot penumbra
• Continuum enhancements, line profiles and magnetic field evolution during consecutive flares
• Onset of penumbra formation
• The formation and decay of sunspot penumbra in Active Region NOAA 12673