Dependence of Solar Wind Speed on the Area of Coronal Holes and Saturation Effect

Abstract

Recently, Samara et al. (2022) showed that proportionality between the solar fast wind velocity V from the low latitude coronal holes (CH) and their area S_ch is satisfied only for small-sized CH, while the saturation effect for larger CH is revealed; i.e., a plateau is formed in a V(S_ch) plot. This is explained by the geometric complexity of CH, described by the fractal dimension. Previously, Akhtemov and Tsap (2018, 2019) established that the correlation coefficient between V and S_ch reaches a maximum for a CH located within a fractional area ±10° in longitude and ±40° in latitude. They suggested that this inference is related to the radial propagation of the solar wind and, hence, the increasing of S_ch should not be accompanied by an increase of V for large CH. The presented work provides a detailed comparative analysis of the results obtained by Samara et al. (2022) and Akhtemov and Tsap (2018, 2019). Arguments are given in favor of the model related to the saturation effect with the radial propagation of the fast solar wind.