Relative contributions of H+ and O+ to the ring current energy near magnetic storm maximum
Relative contributions of H+ and O+ to the ring current energy near magnetic storm maximum
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DOI：
10.1029/2001ja000155
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发表时间：
2002-04
影响因子：
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通讯作者：
M. Greenspan;D. Hamilton
中科院分区：
文献类型：
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作者：
M. Greenspan;D. Hamilton
[1] 接近磁暴峰值时，O+ 与 H+ 对环流能量的贡献之比 U(O+)/U(H+) 取决于太阳 EUV 通量和风暴大小。与太阳风源相比，该比率为电离层等离子体源的重要性提供了下限，因为只有电离层提供 O+，而太阳风和电离层都提供 H+。我们使用主动磁层粒子示踪探测器 (AMPTE) CCE 航天器上的 CHEM 离子光谱仪进行的测量来评估风暴最大值附近的 U(O+)/U(H+)。 CHEM 在 4 年多的时间里测量了每电荷能量范围 1.5–300 keV/e 的赤道离子成分，从太阳极小期到第 22 太阳周期的大部分上升阶段。因此，我们的数据集很大，包括 67 个最小 Dst 值小于 -50 nT 的磁暴。为了估计 O+ 和 H+ 对环电流能量的贡献，我们将沿 CCE 轨迹的每个离子能量密度的局部测量值乘以适当的偶极子 L 壳体积，并对从 2 到 7 的 L 值求和。我们使用双线性回归来评估 U(O+)/U(H+) 对太阳 EUV 通量（由 F10.7 参数化）和风暴大小（由最小 Dst 值 Dstmin 参数化）的依赖性。我们发现 F10.7 和 Dstmin 都是 U(O+)/U(H+) 的重要（且几乎独立）预测因子。 67 场风暴中只有 4 场的 U(O+)/U(H+) > 1。四场风暴中的两场相当小，|Dstmin| < 100 nT，但具有高 F10.7 值。这表明，当太阳 EUV 通量较高（即接近太阳极大值）的小风暴期间以及整个太阳周期的非常大的风暴期间，O+ 有时可以贡献大部分环流能量。
[1] Close to the peak of a magnetic storm, the ratio of the O+ to the H+ contribution to the ring current energy, U(O+)/U(H+), depends on both solar EUV flux and storm size. This ratio provides a lower limit on the importance of the ionospheric plasma source compared to the solar wind source since only the ionosphere supplies O+ while both the solar wind and the ionosphere supply H+. We have used measurements from the CHEM ion spectrometer on the Active Magnetospheric Particle Tracer Explorers (AMPTE) CCE spacecraft to assess U(O+)/U(H+) near storm maximum. CHEM measured equatorial ion composition over the energy per charge range 1.5–300 keV/e for more than 4 years, from solar minimum through much of the rising phase of Solar Cycle 22. Thus our data set is large, including 67 magnetic storms with minimum Dst values less than −50 nT. To estimate the O+ and H+ contributions to the ring current energy, we have multiplied local measurements of each ion's energy density along the CCE trajectory by the appropriate dipole L shell volume and summed over L values from two to seven. We have used a bilinear regression to assess the dependence of U(O+)/U(H+) on solar EUV flux, parameterized by F10.7, and storm size, parameterized by minimum Dst value Dstmin. We have found that both F10.7 and Dstmin are important (and nearly independent) predictors of U(O+)/U(H+). Only four storms of 67 had U(O+)/U(H+) > 1. Two of the four were fairly small, with |Dstmin| < 100 nT but with high F10.7 values. This shows that O+ can sometimes contribute the majority of the ring current energy during small storms when the solar EUV flux is high (i.e., near solar maximum) as well as during very large storms throughout the solar cycle.