HRTS Time Series Observations: Chromospheric and Coronal Heating

Abstract

We have studied HRTS time series observations of solar network boundaries, cell interiors, sunspot and active regions. The results show that the intensities of C IV, Si II, Fe II and UV continuum in these features fluctuate constantly, sometimes with large amplitudes of a factor of 2 in 30 sec. Downflow velocities are most common in the transition region. The only place where there are noticeable upflows is in the cell interior. Often neighboring emission features show temporal changes independent of each other, implying a “correlation” length of less than 2″. The observations do not show evidence of regular periodic waves. However, there is evidence that temporal variations in the temperature minimum region, the chromosphere, and the transition region follow each other, indicating some “excitation” agent propagating at a speed > 500 km sec^-1. The heating occurs irregularly in time, perhaps due to energy releases in locally stressed magnetic fields.