The solar active region photospheric magnetic field evolves rapidly during major eruptive events, suggesting appreciable feedback from the corona. The new high-cadence (90 s or 135 s) vector magnetogram dataset from the Helioseismic and Magnetic Imager (HMI) is suited for investigating these “magnetic imprints”. Observations of an archetypical event, SOL2011-02-15T01:56, show the following trends. Firstly, the horizontal magnetic field component ($B_h$) exhibits permanent, step-like changes with a time scale of several minutes, whereas the radial component ($B_r$) varies less. Secondly, $B_h$ near the main polarity inversion line increases significantly during the earlier phase of the associated flare, whereas $B_h$ in the periphery decreases at later times with smaller magnitudes. Thirdly, transient artifacts coincide with enhanced flare emission, where the Stokes profiles are no longer adequately modeled under standard settings, and the inferred magnetic field becomes unreliable. Our results corroborate previous findings, remove certain ambiguities that arise from line-of-sight only or lower-cadence vector observations, and provide insights on the momentum processes during solar eruption. The dataset may also be useful to the study of sunquakes and data-driven modeling of the solar corona.
X. Sun, J. Hoeksema, Y. Liu, et. al.
Fri, 24 Feb 17
Comments: Submitted to ApJ; Reference for HMI high-cadence vector magnetograms