No. 148, Slow Magnetoacoustic Waves in Two-Ribbon Flares, by V. Nakariakov and I. Zimovets. Wave dynamics explains arcade development.

http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/Slow_Magnetoacoustic_Waves_in_Two-Ribbon_Flares

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

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