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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Solar cycle dependence of ion cyclotron wave frequencies
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Solar cycle dependence of ion cyclotron wave frequencies

机译：太阳活动周期依赖离子回旋波频率

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Electromagnetic ion cyclotron (EMIC) waves have been studied for decades, though remain a fundamentally important topic in heliospheric physics. The connection of EMIC waves to the scattering of energetic particles from Earth's radiation belts is one of many topics that motivate the need for a deeper understanding of characteristics and occurrence distributions of the waves. In this study, we show that EMIC wave frequencies, as observed at Halley Station in Antarctica from 2008 through 2012, increase by approximately 60% from a minimum in 2009 to the end of 2012. Assuming that these waves are excited in the vicinity of the plasmapause, the change in Kp in going from solar minimum to near solar maximum would drive increased plasmapause erosion, potentially shifting the generation region of the EMIC to lower L and resulting in the higher frequencies. A numerical estimate of the change in plasmapause location, however, implies that it is not enough to account for the shift in EMIC frequencies that are observed at Halley Station. Another possible explanation for the frequency shift, however, is that the relative density of heavier ions in the magnetosphere (that would be associated with increased solar activity) could account for the change in frequencies. In terms of effects on radiation belt dynamics, the shift to higher frequencies tends to mean that these waves will interact with less energetic electrons, although the details involved in this process are complex and depend on the specific plasma and gyrofrequencies of all populations, including electrons. In addition, the change in location of the generation region to lower L shells means that the waves will have access to higher number fluxes of resonant electrons. Finally, we show that a sunlit ionosphere can inhibit ground observations of EMIC waves with frequencies higher than ～0.5 Hz and note that the effect likely has resulted in an underestimate of the solar-cycle-driven frequency changes described here.
机译：电磁离子回旋波位的研究了几十年,但仍然是一个从根本上重要主题日球物理。来自地球的高能粒子的散射辐射带是许多话题之一激励需要更深层次的理解特点和发生分布海浪。频率,观察在哈雷站南极洲从2008年到2012年,增加大约从2009年最低60%2012年底。兴奋附近的等离子体层顶,Kp的变化从太阳附近太阳能最大驱动增加等离子体层顶侵蚀,有可能将一代区域的位的降低,导致频率越高。然而,等离子体层顶位置的变化意味着它并不足以解释位的变化观察到的频率哈雷。然而,频移的重的离子的相对密度磁气圈(这将是相关的太阳活动)可以考虑增加频率的变化。辐射带动态,转向更高频率往往意味着这些电波用更少的精力充沛的电子互动,虽然在这一过程中所涉及的细节是复杂的和依赖于特定的等离子体和旋转频率的所有人口,包括电子。一代地区意味着降低L贝壳海浪将会获得更高的数字通量的共振电子。阳光照射的电离层可以抑制地面观测位的波的频率高于~ 0.5赫兹和注意的效果可能导致低估的solar-cycle-driven频率变化描述在这里。

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