Solar cycle variation of geosynchronous plasma mass density derived from the frequency of standing Alfvén waves
Solar cycle variation of geosynchronous plasma mass density derived from the frequency of standing Alfvén waves
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由阿尔文驻波频率得出的地球同步等离子体质量密度的太阳周期变化
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发表时间：
2010
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通讯作者：
H. Singer
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作者：
Kazue Takahashi;R. Denton;H. Singer
[1]本文研究了地球同步高度等离子体槽中赤道等离子体质量密度ρeq的太阳周变化。密度是间接确定的频率，fT 3，三次谐波的环形阿尔芬驻波检测到超过12年的时间，从1980年至1991年的磁力计上的五个地球同步业务环境卫星（GOES）。在数值求解波动方程时，使用了环境磁场和场线质量分布的实际模型，以将fT 3与ρeq联系起来。在30分钟的时间窗口内扫描磁力计数据，以10分钟的步长向前移动，我们获得了相当于1586天数据的228，382个fT 3样本。fT 3的检出率在午前区最高（约50%），并使用该区的fT 3和ρeq样本来检查它们对F10.7、Kp和Dst的依赖性。总的来说，F10.7与fT 3和ρeq的相关性最高，这意味着太阳紫外线/极紫外线对电离层高度离子产生的控制强烈反映在地球同步轨道的质量密度变化中。使用27天的中位数计算，不包括等离子体膨胀到地球同步轨道和磁暴的时期，我们得到了经验公式fT 3（mHz）= 38 − 0.097F10.7和logρeq（amu cm−3）= 0.42 + 0.0039F10.7，其中F10.7以太阳通量单位10−22 W · m−2 · Hz−1给出。最后一个公式意味着在选定的太阳活动周期中，当27天的F10.7在68-255的范围内时，质量密度在0.05到0.26 amu cm−3之间变化了0.05倍。在极端安静的时期（Kp平均值小于1），等离子体活动可能会延伸到地球同步轨道，而在风暴期间（Dst小于-50 nT），质量密度可能会增加到超过这些值。
[1] We have studied the solar cycle variation of equatorial plasma mass density ρeq in the plasma trough at geosynchronous altitude. The density was indirectly determined from the frequency, fT3, of the third harmonic of toroidal standing Alfven waves detected over a 12 year period from 1980 to 1991 with magnetometers on five Geostationary Operational Environmental Satellites (GOES). Realistic models of the ambient magnetic field and field line mass distribution were used in numerically solving the wave equation to relate fT3 to ρeq. Scanning the magnetometer data in a 30 min time window that moved forward in 10 min steps, we obtained 228,382 fT3 samples equivalent to 1586 days of data. The detection rate of fT3 is highest (∼50%) in the prenoon sector, and fT3 and ρeq samples from this sector were used to examine their dependence on F10.7, Kp, and Dst. Overall, F10.7 exhibits the highest correlation with fT3 and ρeq, implying that the solar UV/EUV control of ion production at the ionospheric height is strongly reflected in mass density variations at geosynchronous orbit. Using 27 day medians computed excluding periods of plasmasphere expansion to geosynchronous orbit and geomagnetic storm, we obtained the empirical formula fT3 (mHz) = 38 − 0.097F10.7 and logρeq (amu cm−3) = 0.42 + 0.0039F10.7, where F10.7 is given in the solar flux units 10−22 W · m−2 · Hz−1. This last formula means that with the 27 day F10.7 in the range of 68–255 in the selected solar cycle, the mass density varied by a factor of ∼5 from ∼5 to ∼26 amu cm−3. During extremely quiet times (Kp averaged using a 3 day time scale <1), for which the plasmasphere may extend out to geosynchronous orbit, and during storm periods (Dst < −50 nT), the mass density may be enhanced beyond these values.