THE POSSIBLE ROLE OF HIGH-FREQUENCY WAVES IN HEATING SOLAR CORONAL LOOPS

We investigate the role of high-frequency waves in the heating of sola r active region coronal loops. We assume a uniform background magnetic held, and we introduce a density stratification in a direction perpen dicular to this field. We focus on ion compressive viscosity as the da mping mechanism of the waves. We incorporate viscosity self-consistent ly into the equations, and we derive a dispersion relation by adopting a slab model, where the density inside the slab is greater than that outside. Such a configuration supports two types of modes: surface wav es and trapped body waves. In order to determine under what conditions these waves may contribute to the heating of active regions, we solve our dispersion relation for a range of densities, temperatures, magne tic field strengths, density ratios, wavevector magnitudes, wavevector ratios, and slab widths. We find that surface waves exhibit very smal l damping, but body waves can potentially damp at rates needed to bala nce radiative losses. However, the required frequencies of these body waves are very high. For example, the wave frequency must be at least 5.0 s(-1) for a slab density of 10(9.5) cm(-3) a slab temperature of 1 0(6.5) K, a field strength of 100 G, and a density ratio of 5. For a s lab density of 10(10) cm(-3), this frequency increases to 8.8 s(-1). A lthough these frequencies are very high, there is no observational evi dence to rule out their existence, and they may be generated both belo w the corona and at magnetic reconnection sites in the corona. However , we do find that, for slab densities of 10(10) cm(-3) or less, the di ssipation of high-frequency waves will be insufficient to balance the radiative losses if the magnetic field strength exceeds roughly 200 G. Because the magnetic held strength is known to exceed 200 G in many a ctive region loops, particularly low-lying loops and loops emanating f rom sunspots, it is unlikely that high-frequency waves can provide suf ficient heating in these regions.