Multi-wavelength observations of the 2014 June 11 M3.9 flare: temporal and spatial characteristics

Abstract

We present multi-wavelength observations of an M-class flare (M3.9) that occurred on 2014 June 11. Our observations were conducted with the Dunn Solar Telescope (DST), adaptive optics, the multi-camera system ROSA (Rapid Oscillations in Solar Atmosphere) and new HARDcam (Hydrogen-Alpha Rapid Dynamics) camera in various wavelengths, such as Ca~II~K, Mg~I~b$_2$ (at 5172.7 Ang), and H$\alpha$ narrow-band, and G-band continuum filters. Images were re-constructed using the Kiepencheuer-Institut Speckle Interferometry Package (KISIP) code, to improve our image resolution. We observed intensity increases of $\approx$120-150% in the Mg, Ca~K and H$\alpha$ narrow band filters during the flare. Intensity increases for the flare observed in the SDO EUV channels were several times larger, and the GOES X-rays increased over a factor of 30 for the harder band. Only a modest delay is found between the onset of flare ribbons of a nearby sympathetic flare and the main flare ribbons observed in these narrow-band filters. The peak flare emission occurs within a few seconds for the Ca~K, Mg, and H$\alpha$ bands. Time-distance techniques find propagation velocities of $\approx$60 km/s for the main flare ribbon and as high as 300 km/s for smaller regions we attribute to filament eruptions. This result and delays and velocities observed with SDO ($\approx$100 km/s) for different coronal heights agree well with the simple model of energy propagation versus height, although a more detailed model for the flaring solar atmosphere is needed. And finally, we detected marginal quasi-periodic pulsations (QPPs) in the 40--60 second range for the Ca~K, Mg and H$\alpha$ bands, and such measurements are important for disentangling the detailed flare-physics.