Reply to comment by U. Villante and M. Piersanti on 'Statistical analysis of geosynchronous magnetic field perturbations near midnight during sudden commencements'

摘要

We thank Villante and Piersanti [2015 hereinafter referred to as VP] for their comments on our recent paper Park et al. [2014, hereinafter referred to as P14]. The main comment in VP is that geosynchronous magnetic field perturbations near midnight during sudden commencement (SC) can be explained by different combinations of the hinging point distance and current sheet thickness. We basically agree with VP. However, we have question as to whether all SC-associated magnetic field perturbations observed at geosynchronous orbit near midnight can be explained by empirical models developed by Tsyganenko [2002a, 2002b, referred to as T01] in VP and developed by Tsyganenko and Sitnov [2005, referred to as TS05] in P14. It should be noted that T01 and TS05 are not time-dependent models. This indicates that the magnetic field strength and magnetic field vectors of strongly disturbed magnetic field perturbations, which is caused by the passage of interplanetary shock over the Earth's magnetosphere, during a typical SC interval less than ～15 min cannot be easily estimated from both T01 and TS05 models. The models do not provide the distance of the hinging point from Earth and current sheet thickness in the magnetotail as a function of the solar wind dynamic pressure during the SC interval. In particular, the location where the SC-associated current establishes has not been provided from the models. This is a reason that we do not make a quantitative examination whether the SC observation at geosynchronous orbit is consistent with the model field variation (see Figures 7 and 8 in P14).