Flux Cancellation and the Evolution of the Eruptive Filament of 2011 June 7

Abstract

We investigate whether flux cancellation is responsible for the formation of a very massive filament resulting in the spectacular 2011 June 7 eruption. We analyse and quantify the amount of flux cancellation that occurs in NOAA AR 11226 and its two neighbouring ARs (11227 & 11233) using line-of-sight magnetograms from the Heliospheric Magnetic Imager. During a 3.6day period building up to the filament eruption, 1.7 × 10 21 Mx, 21% of AR 11226's maximum magnetic flux, was cancelled along the polarity inversion line (PIL) where the filament formed. If the flux cancellation continued at the same rate up until the eruption then up to 2.8 × 10 21 Mx (34 % of the AR flux) may have been built into the magnetic configuration that contains the filament plasma. The large flux cancellation rate is due to an unusual motion of the positive polarity sunspot, which splits, with the largest section moving rapidly towards the PIL. This motion compresses the negative polarity and leads to the formation of an orphan penumbra where one end of the filament is rooted. Dense plasma threads above the orphan penumbra build into the filament, extending its length, and presumably injecting material into it. We conclude that the exceptionally strong flux cancellation in AR 11226 played a significant role in the formation of its unusually massive filament. In addition, the presence and coherent evolution of bald patches in the vector magnetic field along the PIL suggests that the magnetic field configuration supporting the filament material is that of a flux rope.

Simulating the Coronal Evolution of AR 11437 Using SDO/HMI Magnetograms

“…The amount of flux canceled is very similar to that found in Yardley et al (2017) despite the difference in methods used to calculate the magnetic flux. This is also consistent with previous studies such as Green et al (2011), Baker et al (2012), and Yardley et al (2016. The AR also rotates clockwise during this period.…”

Correcting the effect of magnetic tongues on the tilt angle of bipolar active regions

“…López Fuentes et al (2000) reported their existence for the first time in a rotating bipolar AR and they were later observed in many other examples (see e.g. Luoni et al 2011;Mandrini et al 2014;Valori et al 2015;Yardley et al 2016;Vemareddy & Démoulin 2017;Dacie et al 2018;López Fuentes et al 2018). They also have been found in numerical simulations of emerging FRs (Archontis & Hood 2010;Cheung et al 2010;MacTaggart 2011;Jouve et al 2013;Rempel & Cheung 2014;Takasao et al 2015).…”

The Life Cycle of Active Region Magnetic Fields

“…High decay rates have indeed been measured in complex active regions where not only small flux concentrations but spot-size magnetic fields cancel (e.g. 5 ⇥ 10 20 Mx day 1 cancellation rate found in AR 11226 by Yardley et al, 2016; see also Sterling et al, 2010).…”

“…U-loop, see van Driel-Gesztelyi et al 2000) subsurface geometry, or multiple major flux emergence episodes in an active region, which drive large flux concentrations towards the internal inversion line, significantly increasing the cancellation rates there (Yardley et al 2016). The presence of active regions in the vicinity of emerging flux, if they are favorably oriented, can lead to increased cancellation rates along the external boundaries and shortened active-region lifetimes.…”

“…Small-scale flux emergence episodes within either polarity may take place, but as long as the emerging flux is inferior to the flux of the ageing active region, complexity is only temporarily introduced. As such secondary flux emergence episodes are expected to bring up equal amounts of positive and negative fluxes (although see Wang & Shi 1993;Yardley et al 2016, for examples when does not appear to be the case) and cancellation processes between the ageing and new flux remove equal amount of fluxes, these smaller-scale flux emergence episodes only temporarily increase the total flux present.…”