On the Variability of EMIC Waves and the Consequences for the Relativistic Electron Radiation Belt Population
On the Variability of EMIC Waves and the Consequences for the Relativistic Electron Radiation Belt Population
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DOI：
10.1029/2021ja029754
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发表时间：
2021-11
期刊：
影响因子：
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通讯作者：
J. Ross;S. Glauert;R. Horne;C. Watt;N. Meredith
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文献类型：
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作者：
J. Ross;S. Glauert;R. Horne;C. Watt;N. Meredith
电磁离子回旋(EMIC)波与相对论电子的相互作用影响着辐射带电子向损耗码的扩散，从而使电子丢失到大气中。EMIC波与能量在几MeV或更高的电子之间的波粒相互作用强烈地依赖于波谱和等离子体性质。在这里，我们研究了在范艾伦探测EMIC观测中发现的波谱和等离子体性质随L*的变化。这些结果被用来计算统计反弹和漂移平均扩散系数，其中包括波谱和等离子体密度作为L*和活动的函数的变化，通过平均观测特定扩散系数。在总辐射带模拟中考虑了扩散系数，并探讨了EMIC波的影响。随着L的降低，等离子体频率与电子回转频率之比的分布减小到较低的值。结果是，在L*≤3.75时，很少有电磁波能够与2-3 MeV电子共振，而在较大的L*处，相同能量的电子在高密度区被电磁波扩散。相比之下，足够数量的电磁波能够与较高能量的电子共振，≥4 2$4 2 MeV，在L*≥3 2 5，从而显著影响电子通量的衰变。对EMIC波对电子扩散的磁波参数进行了比较，发现太阳风动压强与Van Allen探测器的观测结果符合得最好。
The interactions between electromagnetic ion cyclotron (EMIC) waves and relativistic electrons are influential in diffusing radiation belt electrons into the loss code from which the electrons are lost into the atmosphere. These wave‐particle interactions between EMIC waves and electrons with energies of a few MeV or more depend strongly on wave spectra and plasma properties. Here we study the variability in wave spectra and plasma properties as a function of L* found during Van Allen Probe EMIC observations. These results are used to calculate statistical bounce and drift average diffusion coefficients that include the variation in wave spectra and plasma density as a function of L* and activity by averaging observation‐specific diffusion coefficients. The diffusion coefficients are included in global radiation belt simulations and the effect of the EMIC waves is explored. The distribution in the plasma frequency to electron gyrofrequency ratio decreases to lower values as L* decreases. As a result, few EMIC waves are able to resonate with 2–3 MeV electrons at L* ≤ 3.75 while electrons of the same energy at larger L* are diffused by EMIC waves in high density regions. In comparison, a sufficient number of EMIC waves are able to resonate with higher energy electrons, ≥4.2 $\ge 4.2$ MeV, at L* ≥ 3.25 to significantly affect the decay in electron flux. EMIC wave parametrisations of electron diffusion by EMIC waves are compared and solar wind dynamic pressure is found to give the best agreement with Van Allen Probe observations.