First LOFAR interferometric observations of an solar X-class flare

Christian Vocks, Leibniz-Institut für Astropysik Potsdam (AIP)

On 7 September 2017, we obtained the first interferometric imaging observations with LOFAR of a series of solar flares, including an X-class event. LOFAR dynamic spectra of these show several type III and a weak type II radio burst. We generate imaging time series from the interferometric data on several frequencies in LOFAR\'s low band, despite the large separation between the Sun and Tau A as external calibration source. We derive radio brightness curves from the imaging observations of the type III event associated with an M-class flare, and compare them to RHESSI X-ray fluxes, while both radio and X-ray intensities increase over several orders of magnitude within seconds. The X-class flare, associated with the type II event, is not accompanied by type III bursts or a strong increase of radio flux. This indicates that the flaring plasma stayed confined in the solar corona.