Cluster-C1 observations of non-train magnetic decreases in the solar wind at 1 AU

By using the magnetic field and plasma data of Cluster-C1 from 2001 to 2009, we have investigated the magnetic field and plasma properties around the linear and nonlinear non-train magnetic decreases (MDs) in the solar wind. Compared with the nonlinear non-train MDs, linear non-train MDs occurred in regions with relative low magnetic field strengths and large densities. It is found that the occurrence rate of linear (nonlinear) non-train MDs decreases (increases first, and then decreases) with magnetic field strength increases, and have no significant change (increases first, and then decreases) when the density increased. In addition, the occurrence rates of linear non-train MDs are basically the same from 2001 to 2009 (nearly one solar cycle), however, the occurrence rates of nonlinear non-train MDs have two peaks in 2003 and 2008 respectively.