Comparison of Energetic Electron Fluxes Measured by GPS and THEMIS Spacecraft in the Inner Magnetosphere
Comparison of Energetic Electron Fluxes Measured by GPS and THEMIS Spacecraft in the Inner Magnetosphere
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DOI：
10.1029/2022ja030724
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发表时间：
2022-09
期刊：
影响因子：
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通讯作者：
Reed Curtis;A. Artemyev;D. Vainchtein;A. Kellerman;S. Morley;V. Angelopoulos
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作者：
Reed Curtis;A. Artemyev;D. Vainchtein;A. Kellerman;S. Morley;V. Angelopoulos
空间天气模型的关键要素是内磁层和外辐射带的高能电子通量。通量损耗是由各种损耗过程驱动的：散射到大气中，磁层顶遮蔽。通量增强是由各种加速过程驱动的：局部波粒相互作用，径向输运，等离子体片注入。其中许多进程都是在24小时的时间尺度上进行的。这种中尺度通量的变化并不能很好地被轨道长得多的赤道航天器跟踪。全球定位系统（GPS）星座上的高能电子探测器为探测这种小时尺度的通量变化提供了独特的机会。来自多达23个相同仪器的GPS卫星的测量覆盖了广泛的能量和L壳层范围，具有亚小时的时间分辨率。然而，它们的轨道是倾斜的，因此所有在L壳层>4.3的测量都是偏离赤道的。在这份报告中，我们提出了一个比较赤道THEMIS和非赤道GPS测量全向≤600 keV的电子通量。这样的比较使我们能够推导出使用离赤道GPS通量来推断赤道值的系数。这些系数取决于粒子能量和L壳层。我们展示了一个新的数据集来自GPS测量，并讨论了它如何可以用来调查中尺度动力学的内磁层高能电子通量。
Key elements of space weather models are energetic electron fluxes in the inner magnetosphere and the outer radiation belt. Flux depletion is driven by various loss processes: scattering into atmosphere, magnetopause shadowing. Flux enhancement is driven by various acceleration processes: local wave‐particle interactions, radial transport, plasma sheet injections. Many of these processes operate on ∼ hour timescales. Such mesoscale flux variations are not well traced by equatorial spacecraft with much longer orbits. Energetic electron detectors onboard the Global Positioning System (GPS) constellation provide a unique opportunity for probing such ∼ hour‐scale flux variations. Measurements from up to 23 identically instrumented GPS satellites cover a wide energy and L‐shell range with a subhour time resolution. However, their orbits are inclined and thus all measurements at L‐shell >4.3 are off‐equatorial. In this report, we present a comparison of equatorial THEMIS and nonequatorial GPS measurements of omnidirectional ≤600 keV electron fluxes. Such a comparison allows us to derive coefficients for using off‐equatorial GPS fluxes to infer the equatorial values. These coefficients depend on particle energy and L‐shell. We demonstrate a new data set derived from GPS measurements and discuss how it can be used to investigate mesoscale dynamics of energetic electron fluxes in the inner magnetosphere.