HOW IMPORTANT ARE ELECTRON BEAMS IN DRIVING CHROMOSPHERIC EVAPORATION IN THE 2014 MARCH 29 FLARE?

We present high spatial resolution observations of chromospheric evaporation in the flare SOL2014-03-29T17:48. Interface Region Imaging Spectrograph observations of the Fe XXI lambda 1354.1 line indicate evaporating plasma at a temperature of 10 MK along the flare ribbon during the flare peak and several minutes into the decay phase with upflow velocities between 30 and 200 km s(-1). Hard X-ray (HXR) footpoints were observed by the Ramaty High Energy Solar Spectroscopic Imager for two minutes during the peak of the flare. Their locations coincided with the locations of the upflows in parts of the southern flare ribbon but the HXR footpoint source preceded the observation of upflows in Fe XXI by 30-75 s. However, in other parts of the southern ribbon and in the northern ribbon, the observed upflows were not coincident with an HXR source in time or space, most prominently during the decay phase. In this case evaporation is likely caused by energy input via a conductive flux that is established between the hot (25 MK) coronal source, which is present during the whole observed time-interval, and the chromosphere. The presented observations suggest that conduction may drive evaporation not only during the decay phase but also during the flare peak. Electron beam heating may only play a role in driving evaporation during the initial phases of the flare.