Observations of Chromospheric Evaporation Flows in RHESSI Microflares

We present the analysis of two homologous microflares of GOES class A9 with respect to mass flows in the chromosphere and transition region. Both events show non-thermal emission (evidence for beamed electrons) in RHESSI X-ray spectra. As outlined by observations of the Coronal Diagnostic Spectrometer, we find for the first event downflows in the He I, O V and Ne VI line reaching speeds up to 40 km s^{-1} at the position of chromospheric flare brightenings. On the other hand, upflows with velocities ≲40 km^{-1} are observed for the second microflare. According to hydrodynamic flare simulations, the non-thermal electron energy density F deposited in the chromosphere determines if chromospheric evaporation is `gentle' or `explosive'. Thus, we derive rough estimates for F in our microflares and compare the results to the observed CDS flow properties.