Evolution of Photospheric Vector Magnetic Field Associated with Moving Flare Ribbons as Seen by GST

Abstract

The photospheric response to solar flares, also known as coronal back reaction, is often observed as sudden flare-induced changes in vector magnetic field and sunspot motions. However, it remains obscure whether evolving flare ribbons, the flare signature closest to the photosphere, are accompanied by changes in vector magnetic field therein. Here we explore the relationship between the dynamics of flare ribbons in the chromosphere and variations of magnetic fields in the underlying photosphere, using high-resolution off-band Hα images and near-infrared vector magnetograms of the M6.5 flare on 2015 June 22 observed with the 1.6 m Goode Solar Telescope. We find that changes of photospheric fields occur at the arrival of the flare ribbon front, thus propagating analogously to flare ribbons. In general, the horizontal field increases and the field lines become more inclined to the surface. When ribbons sweep through regions that undergo a rotational motion, the fields transiently turn more vertical with decreased horizontal field and inclination angle, and then restore and/or become more horizontal than before the ribbon arrival. The ribbon propagation decelerates near the sunspot rotation center, where the vertical field becomes permanently enhanced. Similar magnetic field changes are discernible in magnetograms from the Helioseismic and Magnetic Imager (HMI), and an inward collapse of coronal magnetic fields is inferred from the time sequence of non-linear force-free field models extrapolated from HMI magnetograms. We conclude that photospheric fields respond nearly instantaneously to magnetic reconnection in the corona.

Partial Eruption, Confinement, and Twist Buildup and Release of a Double-decker Filament

“…The horizontal component of the magnetic field within this source region increases rapidly after the peak of the precursor flare, and then gradually decreases as the main flare and the total unsigned magnetic flux decay. An increase of the horizontal magnetic field component during or after eruptions has been reported, e.g., by and Liu et al (2018a), and suggested to be a back-reaction of the photosphere and inner part of the Sun to the flares or CMEs. Alternatively, Barczynski et al (2019) argued that photospheric horizontal fields are enhanced by the reconnection-driven contraction of sheared flare loops in the corona.…”

Erupting Magnetic Flux Rope Affects Running Penumbral Waves

“…It is postulated that the rotation is driven by a torque arising with the flare-related restructuring of coronal magnetic field. In the same event, Liu et al (2018) found that changes of photospheric fields occur nearly instantaneously at the arrival of the flare ribbon front. In the ribbon-swept sunspot region, photospheric field turns temporarily more vertical, associated with a sudden counterclockwise rotation of field vectors by 12-20 • in azimuth degree (see also Xu et al 2018), and then either recovers or turns more horizontal than before the ribbon arrival.…”

Comparative study of electric currents and energetic particle fluxes in a solar flare and Earth magnetospheric substorm

“…The images of X-ray sources are superimposed on the images made with SDO/AIA in the 131 Å (panels (a, d, g)) and 1600 Å (panels (b, e, h)) channels, and on the nearby 720 s HMI/SDO magnetograms of the line-of-sight magnetic field component (panels (c, f, i)), which is close to the radial magnetic component, B r , because of near the solar disk center location of the flare region. Images in the 131 Å channel predominantly show the flare loops filled with hot plasma heated to temperatures T ∼ 10 MK (∼ 1 keV), while images in the 1600 Å channel show the flare ribbons in the chromosphere and transition region (more details about the flare ribbons in this event were presented by Jing et al 2016;Liu et al 2018). All images also show the position of the magnetic PIL on the photosphere (pink curves), as one of the traditional landmarks of the flare region.…”

“…Various aspects of this flare have already been studied and discussed in more than a dozen works (e.g. Jing et al 2016;Liu et al 2016;Bi et al 2017;Vemareddy 2017;Wang et al 2017;Kuroda et al 2018;Liu et al 2018;Wang et al 2018a;Wheatland et al 2018;Xu et al 2018;Kang et al 2019). The flare attracted widespread attention, first of all, as it was very well observed by a number of modern instruments.…”