In a recent ACPD article, M. Sinnhuber and co-authors use MIPAS observations to investigate the impact of energetic particle precipitation on the NO_x budget in the stratosphere and lower mesosphere during a period of high solar and geomagnetic activity (October 2003-March 2004). They show that in the winter hemisphere the indirect effect of auroral electron precipitation due to downwelling of upper mesospheric/lower thermospheric air exceeds the direct impact of a very large solar proton event by nearly one order of magnitude. Although a direct effect of electron precipitation on NO_x cannot be ruled out, it is lower than 3ppb from 40-56km altitude, and lower than 6ppb from 56-70km altitude. The full abstract can be found here.