TRACE and Yohkoh Observations of High-Temperature Plasma in a Two-Ribbon Limb Flare

The ability of the Transition Region and Coronal Explorer (TRACE) to image solar plasma over a wide range of temperatures (T_e ~ 10⁴-10⁷ K) at high spatial resolution (05 pixels) makes it a unique instrument for observing solar flares. We present TRACE and Yohkoh observations of an M2.4 two-ribbon flare that began on 1999 July 25 at about 13:08 UT. We observe impulsive footpoint brightenings that are followed by the formation of high-temperature plasma (T_e ≳ 10 MK) in the corona. After an interval of about 1300 s, cooler loops (T_e < 2 MK) form below the hot plasma. Thus, the evolution of the event supports the qualitative aspects of the standard reconnection model of solar flares. The TRACE and Yohkoh data show that the bulk of the flare emission is at or below 10 MK. The TRACE data are also consistent with the Yohkoh observations of hotter plasma (T_e ~ 15-20 MK) existing at the top of the arcade. The cooling time inferred from these observations is consistent with a hybrid cooling time based on thermal conduction and radiative cooling.