Revisiting the determination of the coronal heating function from Yohkoh data

Results on the coronal heating function seem to strongly depend on the empl oyed type of multitemperature modeling along the line of sight. Instruments with broadband temperature filters cause more temperature confusion than t hose with narrowband temperature filters. A possible bias of broadband filt ers is the hydrostatic weighting of multitemperature loop systems, which mi mic a temperature increase with altitude and thus yield a preference for lo optop heating. In this Letter we revisit a loop system previously analyzed by Priest et al., for which they found that the coronal heating is likely t o be uniform in the temperature range between 1.6 and 2.2 MK. As an alterna tive scenario, we use standard hydrostatic solutions here (with vanishing c onductive flux in the transition region). We show that hydrostatic solution s with a uniform heating function throughout the corona and transition regi on lead to unphysical solutions for the column depth and the altitude of th e loop footpoints, while a footpoint-heating model yields acceptable physic al solutions for a heating scale height of s(H) approximate to 13 +/- Mm. T he positive temperature gradient with height (which is also found in filter - ratio temperatures of other Yohkoh data) can be explained by the hydrosta tic weighting bias resulting from hot loops (T-max approximate to 2.6 MK) e mbedded in a cooler (T-max approximate to 1.0 MK) background corona.