The internal structure of prominences appearing as twisted tubes was studied. The sample embraced 15 stable and 13 eruptive prominences, exposing patterns which possibly reflect a helical configuration. The equivalent pitch angles (0) of twisted fine structure features were measured. In some cases the evolution of the internal structure was followed and 49 independent measurements of the parameter were performed in total The results are presented in the plane relating the parameter ~9 and the normalized prominence height. The eruptive prominences occupy the region characterized by 0 > 50 ~ and h > 0.8d, where h and d are the prominence height and the footpoint half-separation, respectively. All prominences characterized by h < 0.6d or by 0 < 35 ~ were stable. Such a result is in good agreement with an order of magnitude treatment of the forces acting in a curved magnetic tube, anchored at both ends in the photosphere.

Abstract. Full-disc solar images obtained with the Extreme Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) are used to analyse solar differential rotation by tracing coronal bright points for the period June 4, 1998 to May 22, 1999. A method for the simultaneous determination of the true solar synodic rotation velocity and the height of the tracers is applied to data sets analysed with interactive and automatic methods. The calculated height of coronal bright points is on average 8000-12000 km above the photosphere. Corrected rotation velocities are transformed into sidereal ones and compared with results from the literature, obtained with various methods and tracers. The differential rotation profile determined by coronal bright points with the interactive method corresponds roughly to the profile obtained by correlating photospheric magnetic fields and the profile obtained from the automatic method corresponds roughly to the rotation of sunspot groups. This result is interpreted in terms of the differences obtained in the latitudinal distribution of coronal bright points using the two methods.

Abstract. Full-disc solar images obtained with the Extreme Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) were used to analyse solar differential rotation determined by tracing coronal bright points. Two different procedures were developed and compared: an interactive and an automatic method. The interactive method is based on the visual tracing of coronal bright points in consecutive images using computer programs written in the Interactive Data Language (IDL). The automatic method relies on the IDL procedure "Regions Of Interest (ROI) segmentation" which is used to detect and follow bright points in triplets of consecutive images. The test-results obtained applying both methods by different persons who performed tracing are presented and compared. The advantages and disadvantages of the two methods are discussed.

Abstract. Full-disc solar images obtained with the Extreme Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) were used to analyse solar differential rotation determined by tracing coronal bright points. Two different procedures were developed and compared: an interactive and an automatic method. The interactive method is based on the visual tracing of coronal bright points in consecutive images using computer programs written in the Interactive Data Language (IDL). The automatic method relies on the IDL procedure "Regions Of Interest (ROI) segmentation" which is used to detect and follow bright points in triplets of consecutive images. The test-results obtained applying both methods by different persons who performed tracing are presented and compared. The advantages and disadvantages of the two methods are discussed.