THE HEATING OF SOLAR MAGNETIC-FLUX TUBES - I - ADIABATIC LONGITUDINALTUBE WAVES

We study the formation of shocks and shock heating by adiabatic longit udinal tube waves in solar magnetic flux tubes of different shape. Mon ochromatic waves with periods between 20 and 160 s and energy fluxes r anging from 1.10(7) to 1.10(9) erg cm(-2)s(-1) were considered. It is found that the tube shape is of critical importance for the heating of flux tubes. Constant cross-section tubes show large heating, whereas exponentially spreading tubes show little or no heating at all. In tub es of intermediate shapes (''wine-glass tubes''), the heating is essen tially restricted to those regions, where the tube has attained its ma ximum diameter. This finding is in good agreement with the observation that the chromospheric network can still be seen well above the canop y height. In tubes of lower field strength, the shock formation is del ayed and heating is reduced.