Properties of structured coronal mass ejections in solar cycle 23 Original Research Article

The Solar and Heliospheric Observatory has provided to date doubtlessly the best dataset of coronal observations ever taken over the course of a solar cycle. Structured coronal mass ejections, i.e. events with clear white-light fine structures, have been selected from the dataset of the large angle spectroscopic coronagraph during the period 1996–2002. Their source regions in the low corona and photosphere have been deduced by analyzing data from the Extreme-ultraviolet Imaging Telescope and Michelson Doppler Imager onboard the Solar and Heliospheric Observatory and from ground-based Hα measurements. Based on this subset of coronal mass ejections, originally compiled to study their three-dimensional configuration, we have analyzed the variation of their properties during the present solar cycle. These properties include latitude and tilt angle of source regions of coronal mass ejections, position angle of coronal mass ejections, and deviation of coronal mass ejections with respect to their corresponding source regions. The results show a pronounced and systematic confinement of position angles at equatorial latitudes and equatorward deviations during low solar activity. In contrast, fluctuating position angles and deviations in all directions were found at times of high solar activity. A method to explain the observed deflections is presented.