Attention is given to problems which arise when an attempt is made to use observational material to clarify the mechanisms responsible for the heating of the chromosphere in a late-type star, in order to derive a clearer physical view of the nature of a chromosphere, its relation to the underlying photosphere, and the overlying corona. Problems

High resolution H alpha and white light observation of the birth of 73 active regions (AR) were used to check models of sunspots. It is concluded that large AR result from the emergence of a compact and twisted flux rope, while the small ones are produced by the clustering of flux tubes by supergranular motions.

Potassium line data from observatories in Hawaii and Spain were used to establish the authenticity of complex solar oscillation signals. Combination of the two data sets yields precise frequency, amplitude and phase determinations. Analyses of individual lines indicate possible decay and excitation of individual modes and suggest lifetimes for the

The nonlinear development of the kink instability of a magnetic flux tube initially lying in mechanical equilibrium in the deep convection zone is presented. The unstable evolution is started by a small-amplitude sinusoidal perturbation of the shape of the flux tube in a vertical plane. As a result of the development of the instability, the lower

Single-epoch multifrequency data for the BL Lac objects OI 90.4 and 3C 66A, spanning radio through ultraviolet wavelengths, are presented, as well as other measurements relevant to intensity and spectral-shape variability. Both BL Lac objects exhibit spectral curvature in the infrared-to-ultraviolet region, a properity that is inferred to be usual