No. 205, "Acceleration-region Densities," by Sa"m Krucker and Marina Battaglia. Independent constraints on the densities of ions and non-thermal electrons point to bulk acceleration. See 

http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/Acceleration-region_Densities

Older Nuggets are available at
http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/RHESSI_Science_Nuggets
 (the current series, 2008-present), and at
http://sprg.ssl.berkeley.edu/~tohban/nuggets/ (the original series, 2005-2008).

We publish these at roughly two-week intervals and welcome contributions, which should be related, at least loosely, to RHESSI science.