Pre-flare heating around the temperature minimum region found right prior to an X-class flare

Flare producing active region NOAA 9026 (June 2000) provided us with a rare opportunity to study a twisted magnetic flux rope and its rapidly-untwisting motions causing a strong flare. From the analyses of the evolution of this region we found for the first time clear evidence of pre-flare heating or energy release from the upper photosphere through the lower chromosphere starting about two hours before an X-class coronal flare. We conclude that the pre-flare energy release was caused by magnetic field reconnection in the lower atmosphere, where the emergence of a twisted magnetic flux rope was abruptly enhanced by the kink instability.