Ion composition of substorms during storm-time and non-storm-time periods
Ion composition of substorms during storm-time and non-storm-time periods
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DOI：
10.1016/s1364-6826(02)00013-5
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发表时间：
2002-03
影响因子：
1.9
通讯作者：
A. Korth;R. Friedel;F. Frutos-Alfaro;C. Mouikis;Q. Zong
中科院分区：
文献类型：
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作者：
A. Korth;R. Friedel;F. Frutos-Alfaro;C. Mouikis;Q. Zong
研究了风暴时亚暴(dst=−195nT)和无风暴亚暴(非风暴时亚暴)(dst⩾−30nT)的氧氢比(O+/H+)。在这项研究中，我们使用CRRES粒子和电场数据，以及风暴(DST)和亚风暴(AE)活动的指标，以及来自IMP-8的IMF BZ分量。风暴和亚暴期间粒子向内磁层的注入与近地磁尾中的大尺度风暴或黎明-黄昏电场引起的对流增强是一致的。这种对流的强度与负IMF BZ的大小和持续时间有关，风暴时的BZ都大于非风暴时的BZ。在较大的L值(L=5.0~7.0)范围内，非暴暴期的亚暴对环电流的贡献很小，而暴暴期的亚暴对主环电流的贡献较大。在风暴期间，环电流最大值可以从L=4.5时的平静位置移动到L=3。风暴亚暴的O+/H+比率为100%，而非风暴亚暴的O+/H+比率介于15%和65%之间。暴时亚暴与非暴时亚暴在成分上的明显差异表明，风暴期间，氧离子优先在等离子体片中加速/输运，(2)风暴前条件导致氧捕获边界后方有大量氧离子储存库，或(3)极地电离层外流增强，导致氧离子对流源增加。
The oxygen to hydrogen ratio (O+/H+) is investigated for storm-time substorms (Dst=−195 nT ) and for substorms in absence of storms (non-storm-time substorms) (Dst⩾−30 nT ). For this study we use CRRES particle and electric field data as well as indicators for storm (Dst) and substorm (AE) activity and the IMF Bz-component from IMP-8. Injection of particles into the inner magnetosphere during storms and substorms is consistent with enhanced convection caused by large-scale storm-time or dipolarization dawn–dusk electric fields in the near-Earth magnetotail. The strength of this convection is related to the magnitude and duration of the negative IMF Bz, which are both larger for storm-time substorms than for non-storm-time substorms. Non-storm-time substorms lead to only minor ring current enhancements at large L-values (L=5.0–7.0), while storm-time substorms can contribute the main ring current. During storms the ring current maximum can move in as far as L=3 from its quiet time position at L=4.5. Storm-time substorms have O+/H+ratios of several 100%, whereas non-storm-time substorms show an O+/H+ratio between 15% and 65%. The obvious composition difference between storm-time and non-storm-time substorms indicates that during storms one or a combination of the following factors play a role: (1) oxygen ions are preferentially accelerated/transported in the plasma sheet, (2) pre-storm conditions lead to a large reservoir of oxygen ions tailward of the oxygen trapping boundary, or (3) polar ionospheric outflow is enhanced leading to an increased convection source of oxygen ions.