<p>In July 2017, the MMS constellation was in the magnetotail with an apogee of 25 Earth radii<br>and an average inter-satellite distance of 10 km (i.e. at electron scales). On 23 July around<br>16:19 UT, MMS was located at the edge of the current sheet which was in a quasi-static<br>state. Then, MMS suddenly entered in the central plasma sheet and detected the local onset<br>of a small substorm as indicated by the AE index (~400 nT). Fast earthward plasma flows<br>were measured for about 1 hour starting with a period of quasi-steady flow and followed by<br>a saw-tooth like series of fast flows associated with dipolarization fronts. This plasma<br>transport sequence finished with a flow reversal still occurring close to the magnetic<br>equator. In the present study, we investigate the energy conversion processes at ion and<br>electron scales for these different phases with particular attention on the processes in the<br>vicinity of the dipolarization fronts.</p>