标题： 同步轨道磁层顶穿越：必要条件 显示英文标题

标题： Geosynchronous magnetopause crossings: necessary conditions

摘要： 用于选择包含1995年至2001年间638次地球同步磁层边界穿越(GMCs)的169个案例事件的数据是GOES的磁场测量数据和LANL地球同步卫星的等离子体测量数据。 我们使用Psw与Bz坐标空间中的GMC散点图来研究地球同步磁层边界穿越的必要条件。 在这种表示中，上游太阳风条件显示出一个尖锐的包络边界，在该边界下不会发生GMC。 该边界有两个直的水平分支，其中Bz对磁层边界位置没有影响。 第一个分支位于Psw=21 nPa范围内，对应于压力平衡的渐近状态，适用于大正Bz。 第二个分支在非常强的负Bz下渐近地接近Psw=4.8 nPa范围，并且与Bz影响饱和的状态有关。 我们认为这种饱和是由于磁层热压力对磁层边界处的压力平衡有相对较高的贡献。 对于中等负和小正IMF Bz的边界中间区域，可以用双曲正切函数很好地近似。 我们将包络边界解释为地球同步磁层边界上大多数靠近地球("近地点")点发生GMC所需的上游太阳风条件范围。 我们得出结论，偶极子倾斜角和晨昏不对称性会影响"近地点"点的位置。 我们发现该点的aGSM纬度与偶极子倾斜角呈线性关系，斜率约为-0.5。 "近地点"点的aGSM经度随着IMF Bz的增加而减少，速率约为每1 nT减少2角分。 提出了一种预测地球同步轨道"近地点"点磁层边界穿越的经验模型。 显示英文摘要

摘要： The experimental data on GOES magnetic measurements and plasma measurements on LANL geosynchronous satellites is used for selection of 169 case events containing 638 geosynchronous magnetopause crossings (GMCs) in 1995 to 2001. We study the necessary conditions for the geosynchronous magnetopause crossings using scatter plot of the GMCs in the coordinate space of Psw versus Bz. In such representation the upstream solar wind conditions demonstrate sharp envelope boundary under which no GMCs are occurred. The boundary has two strait horizontal branches where Bz does not influence on the magnetopause location. The first branch is located in the range of Psw=21 nPa for large positive Bz and is associated with an asymptotic regime of the pressure balance. The second branch asymptotically approaches to the range of Psw=4.8 nPa under very strong negative Bz and it is associated with a regime of the Bz influence saturation. We suggest that the saturation is caused by relatively high contribution of the magnetosphere thermal pressure into the pressure balance on the magnetopause. The intermediate region of the boundary for the moderate negative and small positive IMF Bz can be well approximated by a hyperbolic tangent function. We interpret the envelope boundary as a range of necessary upstream solar wind conditions required for GMC in the point on the magnetopause located mostly close to the Earth ("perigee" point). We obtain that the dipole tilt angle and dawn-dusk asymmetry influence on the "perigee" point location. We find that the aGSM latitude of this point depends linearly on the dipole tilt angle with the slope about -0.5. The aGSM longitude of the "perigee" point decreases with IMF Bz with a rate of about 2 angular minutes per 1 nT. An empirical model predicting the magnetopause crossing of the geosynchronous orbit in the "perigee" point is proposed.