Filamentary structure on the Sun from the magnetic Rayleigh–Taylor instability

Abstract

Magnetic flux emerges from the solar surface as dark filaments connecting small sunspots with opposite polarities. The regions around the dark filaments are often bright in X-rays and are associated with jets. This implies plasma heating and acceleration, which are important for coronal heating. Previous two-dimensional simulations of such regions showed that magnetic reconnection between the coronal magnetic field and the emerging flux produced X-ray jets and flares, but left unresolved the origin of filamentary structure and the intermittent nature of the heating. Here we report three-dimensional simulations of emerging flux showing that the filamentary structure arises spontaneously from the magnetic Rayleigh-Taylor instability, contrary to the previous view that the dark filaments are isolated bundles of magnetic field that rise from the photosphere carrying the dense gas. As a result of the magnetic Rayleigh-Taylor instability, thin current sheets are formed in the emerging flux, and magnetic reconnection occurs between emerging flux and the pre-existing coronal field in a spatially intermittent way. This explains naturally the intermittent nature of coronal heating and the patchy brightenings in solar flares.

Break up of returning plasma after the 7 June 2011 filament eruption by Rayleigh-Taylor instabilities

“…Modes with k = 0 are unaffected by the field, with the consequence that the instability acts to form sheets aligned with the field (Isobe et al 2005). Here, however, the magnetic field orientation in the cold plasma and in the warm plasma will not, in general, be aligned.…”

“…In the Crab, the main fingers are thought to be the result of the magnetic Rayleigh-Taylor (RT) instability (Hester et al 1996). RT has also been invoked to explain filamentary structure (Isobe et al 2005) and prominence bubbles (Berger et al 2011) on the Sun.…”

Large-scale 3D MHD simulation on the solar flux emergence and the small-scale dynamic features in an active region

“…Fan 2001; Archontis et al 2004). Note that some calculations using flux sheets showed multiple separations via similar instabilities (Isobe et al 2005;Archontis & Hood 2009).…”

Formation of Ellerman bombs due to 3D flux emergence

“…The region between the loops L3 and L4 (marked with an arrow, at t = 70 and t = 90) is where current density increases, followed by an enhancement of the temperature in the corona. The 3D interaction between an emerging twisted flux tube (or flux sheet) and a pre-existing field in the corona has been studied in more detail by Archontis & Hood (2008), Galsgaard et al (2005) and Isobe et al (2005).…”