Simulation of field-aligned H + and He + dynamics during late-stage plasmasphere
Simulation of field-aligned H + and He + dynamics during late-stage plasmasphere
复制标题
后期等离子体层场对准 H 和 He 动力学模拟
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
J. Fedder
中科院分区：
文献类型：
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作者：
J. Krall;J. Huba;J. Fedder
用NRL电离层程序SAMI-2(SAMI-2是电离层的另一种模式)模拟了模式风暴后3-L 4的等离子体层长时间(天)的再填充过程。充填依赖于上层H~+和He~+离子的补给，H~+充填速率随F_(10.7)指数的增大而减小，而He~+充填速率一般随F_(10.7)指数的增大而增大。早期和晚期的再充注都受到从较暖的地磁半球到较冷的地磁半球的净离子流动的影响。当这些流动很强时，“冬季氦膨胀”增加He+再充注率的能力被抑制。如果不包括中性风，充气率会下降，通常是原来的两倍。在大多数情况下，后期He+再充注与H+再充注成正比，典型的He+/H+密度比最小时为2%，最大时为10%。对于较高的F10.7值，He+再充注表现出很强的日变化，以至于在后期再充注过程中，He+/H+密度比的变化高达2倍。最后，如果等离子体层不受干扰，在L=3和L=4的情况下，H+密度可以再充满长达5周和10周，饱和密度比典型观测密度大近一个数量级。这证实了在这些L值处的等离子体层很少达到饱和。
The refilling of the plasmasphere for 3 L 4 fol- lowing a model storm is simulated over long times (days) using the NRL ionosphere code SAMI2 (Sami2 is Another Model of the Ionosphere). Refilling is dependent on the sup- ply of topside H + and He + ions with the result that H + re- filling rates decrease and He + refilling rates generally in- crease with increasing F 10.7 index. Both early- and late- stage refilling are affected by net ion flows from the warmer to the colder geomagnetic hemisphere. When these flows are strong, the ability of the "winter helium bulge" to increase He + refilling rates is suppressed. When neutral winds are not included, refilling rates fall, typically by a factor of two. In most cases, late-stage He + refilling is proportional to H + refilling, with typical He + /H + density ratios of 2% for so- lar minimum and 10% for solar maximum. For high values of F 10.7, He + refilling exhibits a strong diurnal variation so that the He + /H + density ratio varies by as much as a factor of two during late-stage refilling. Finally if the plasmasphere is left undisturbed, the H + density can refill for as long as five weeks at L=3 and ten weeks at L=4, with saturation densities nearly an order of magnitude greater than typical observed densities. This confirms that the plasmasphere at these L values rarely obtains saturation.