Small scale transient events in the Solar Corona

Abstract

Solar coronal heating and the energy/mass flow of the solar wind is one of the unsolved but fundamental problems of solar physics. While it has been well established for decades that the corona and solar wind owe their existence to coronal heating, the heating process itself remains unknown other than in broad outline. In recent years it has became increasingly clear that small scale phenomena have a role in maintaining the background temperatures of more than a million degrees Kelvin in the corona and accelerating the solar wind. Indeed, observations of the solar atmosphere outside of active regions have led to the increasing recognition that the chromosphere, transition region and corona of the Sun are threaded with an incredible amount of small-scale, highly dynamic structures, which may have a profound effect on the local dynamics, energy flow and radiative transfer. The rich diversity of the dynamic structures distributed on a fine scale characterizes the highly inhomogeneous appearance of the quite Sun. Over the past, years, apart from the well-known chromospheric features, spicules, many complicated and dynamic ne structures have been discovered in association with the network boundaries, like bi-directional jets (sometimes called 'explosive events'), blinkers, network flares, bright points. However, their interpretation, inter-relationship and relation to the underlying photospheric magnetic concentrations remains ambiguous, because the same feature has a different appearance when observed in different spectral lines and with different instruments. In order to obtain a more quantitative and systematic treatment of the temporal variability in the atmosphere of the Sun, simultaneous observations in diff erent lines with high spatial, spectral and temporal resolution are required.