Waves, shocks and non-stationary phenomena in the outer solar atmosphere

The successful launch of the Solar and Heliospheric Observatory (SOHO) satellite allows us to address the enigmatic question of chromospheric and coronal heating by giving for the first time high cadence simultaneous observations of the entire solar atmosphere from the photosphere and far into the solar wind. The most striking conclusion to emerge so far from the first year of observations is that even the quiet Sun is very dynamic. In this paper we will consider the dynamics of the chromosphere, transition region and corona and the consequences of the dynamics on the formation of spectral features in these regions of the solar atmosphere. We will present data, - mainly from the SUMER instrument - showing signatures of various non-stationary processes and compare these with the predictions of numerical models of the chromosphere and transition region. The observations seem to support the importance of upwardly propagating acoustic shocks in heating the chromosphere. In addition, certain characteristics of transition region spectral lines may be the signatures of episodic coronal heating. We will also present observations that are more difficult to interpret in tf:rms of current theoretical ideas.