Investigating the relation between Coronal Holes and CMEs during the Rise, Maximum and Declining Phases of the Solar Cycle 23
Abstract
In a study on the interaction between Coronal holes (CHs) and inter planetary coronal mass ejections (ICMEs) during the declining phase of solar cycle 23, Gopalswamy et al. [2009] showed that coronal holes (CHs) act as a magnetic wall that constrains the CME propagation. The CME trajectories are significantly affected when the eruptions occur in close proximity to CHs. Here, we investigate the influence of coronal holes on the propagation of CMEs through considering both ICMEs categories with and without flux rope structures during the rise and maximum phases of the solar cycle 23. We also, compare the results obtained with that of the declining phase and of the driverless shocks reported previously by Gopalswamy et al. [2009]. A list of ICMEs that are not classified as MCs has been developed from the Interplanetary (IP) shock list of the solar cycle 23 via selecting all disk center events (central meridian distance 15o ) that have been observed to be (MC s) which leaves us with another list includes the non MC events. The influence of the CHs is computed as a fictitious force that depends on the CH area, the distance between the CH and the eruption region, and the magnetic field within the CH at photospheric level. The open magnetic field distribution on the Sun is obtained for the MCs and non MCs solar events studied during the rise and maximum phases in addition to four magnetic cloud events were not included in Goplaswamy et al. [2009]. This open filed distribution is obtained through performing a potential field source surface extrapolation to the corona up to a heliocentric distance of 2.5 Rs. The Correlation Coefficient (CC) between the duration of the ICMEs and the resultant influence parameter F of the coronal holes is determined in the case of MCs and non MCs for rise, maximum and declining phases. The results show that the correlation coefficient in the case of magnetic cloud (MCs) events is very high at the rise phase ( 0.84) which confirms the correspondence between the non radial motion during the rise phase of the solar cycle and the higher magnetic field strength in the solar regions of the polar coronal holes existed in this phase. The difference between measured position angle (MPA) and the influence position angle (FPA) where F is pointing, () for the non MCs in the rise and maximum phases is found to be 34o and 35o ; respectively which is consistent with that for driverless shocks given by Gopalswamy et al. [2009] (where 37o ). These results together with the average influence parameter value (F av 2.53 G) for the declining phase which is found to be the highest compared to the other two phases and also to the MCs average values suggest that the non MCs are resembling in their behavior the driverless shocks (which have been proven by Gopalswamy et al., 2009 to be deflected by the near by CH s away from the Sun-Earth line) and that the non MCs may have flux rope structure as the MCs do have but this structure is hidden from observation due to the deflection by CH s. This finding may have bearing on the idea that all CMEs may be flux ropes and the difference is only due to the viewing angle variation.
- Publication:
-
38th COSPAR Scientific Assembly
- Pub Date:
- 2010
- Bibcode:
- 2010cosp...38.1918S