Coronal nonthermal velocity following helicity injection before an X-class flare

Abstract

We explore the "pre-flare" behavior of the corona in a three-day period building up to an X-class flare on 2006 December 13 by analyzing EUV spectral profiles from the Hinode EUV Imaging Spectrometer (EIS) instrument. We found an increase in the coronal spectral line widths, beginning after the time of saturation of the injected helicity as measured by Magara & Tsuneta. In addition, this increase in line widths (indicating nonthermal motions) starts before any eruptive activity occurs. The Hinode EIS has the sensitivity to measure changes in the buildup to a flare many hours before the flare begins. ©2009. The American Astronomical Society. All rights reserved. Printed in the U.S.A.