SOLARNET Conference: The Many Scales of the Magnetic Sun

Chromospheric emission observed using the Ca II K and H resonance lines is generally well correlated with photospheric magnetic fields. However, a fraction of the stronger chromospheric emission is found to originate over regions of low magnetic flux densities in the photosphere. Here we present the results from our recent study which aims at understanding the physical mechanisms responsible for the strong emission or brightenings over the weak field regions. For this, we use high resolution and high cadence observations in the Ca II H line taken by the Sunrise Filter Imager (SuFI) along with the photospheric magnetograms recorded by the Imaging Magnetograph eXperiment (IMaX), both instruments onboard the first flight of the balloon-borne observatory SUNRISE. We find that while some of the chromospheric brightenings associated with weak fields are located at the peripheries of strong field regions, others can be associated with flux emergence or interactions between weak opposite polarity magnetic fields. The latter can be organized either in two opposite-polarity patches, or in a variety of mixed polarity features.