HELMET STREAMERS WITH TRIPLE STRUCTURES - WEAKLY 2-DIMENSIONAL STATIONARY STATES

Recent observations of the solar corona with the LASCO coronagraph on board the SOHO spacecraft have revealed the occurrence of triple helme t streamers even during solar minimum, which occasionally go unstable and give rise to particularly huge coronal mass ejections. We present a method to calculate (semi-)analytically self-consistent stationary c onfigurations of triple helmet streamers which can serve as input for stability considerations and dynamical calculations. The method is bas ed on an asymptotic expansion procedure using the elongated structure of the streamers. The method is very flexible and can be used in both Cartesian and spherical geometry. We discuss the effects of magnetic s hear, gravity and field-aligned flow on open field lines. Example solu tions illustrating the influence of each of these features on the solu tion structure are presented.