SIGNATURES OF GLOBAL MODE ALFVEN RESONANCE HEATING IN CORONAL LOOPS

The Yohkoh Soft X-Ray Telescope (SXT) observations of active region co ronal loops transient brightening is analyzed, and the scaling of the thermal energy release with loop lengths is found to be E(th) similar to L(1.60+/-0.09). The numerically determined scaling of the global mo de heating rate for the resonant absorption of Alfven waves, H similar to L, is found to agree with the heating rate deduced from the observ ed thermal energy scaling, provided that the magnetic field scales as B similar to L(-0.70+/-0.05) and the waves are driven with a omega(-1) spectrum. Previous analytical and numerical studies have shown that t he heating due to resonant absorption of Alfven waves is most efficien t at the global mode frequency. In agreement with these studies, we su ggest that coronal loop transient X-ray brightenings occur when a give n length coronal loop is perturbed at its global mode frequency by ran dom footpoint motions, which results in more efficient heating of the loop.