Numerical simulation of the effects of a solar energetic particle event on the ionosphere of Mars
Numerical simulation of the effects of a solar energetic particle event on the ionosphere of Mars
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DOI：
10.1029/2011ja017455
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发表时间：
2012-05
影响因子：
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通讯作者：
V. Sheel;S. Haider;P. Withers;K. Kozarev;I. Jun;S. Kang;G. Gronoff;C. S. Wedlund
中科院分区：
文献类型：
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作者：
V. Sheel;S. Haider;P. Withers;K. Kozarev;I. Jun;S. Kang;G. Gronoff;C. S. Wedlund
[1]我们调查电离层的影响，太阳高能粒子（SEP）事件在火星上，特别是1989年9月29日的事件。我们使用它的能谱和稳态电离层模型来模拟离子和电子密度的垂直剖面。电离层对这一大型事件的反应很容易观察到。它导致30-170公里处的电子密度超过104 cm−3，比通常在100公里以下观测到的要大得多。它还使电离层的总电子含量增加了太阳下值的一半，并将造成无线电波的强烈衰减。模拟衰减在5 MHz时为462 dB，这表明SEP事件可以引起足够的衰减（>13 dB），以解释某些MARSIS上部雷达测深仪观测中缺乏表面反射的原因。我们还开发了一个补充的广义方法来研究SEP事件的电离层效应。这种方法预测的阈值强度，SEP事件可能会产生可检测的变化，电子密度分布和无线电波衰减测量。一个比1989年9月29日事件弱一百倍的事件产生的电子密度在80公里处超过3000 cm−3，这应该是可以通过无线电掩星观测测量的，并且引起足够的衰减来消除MARSIS表面反射。然而，虽然在SEP事件期间已经观察到总电子含量的增强，但预测的低空电子密度的增强没有得到观测的证实。
[1] We investigate the ionospheric effects of a solar energetic particle (SEP) event at Mars, specifically the 29 September 1989 event. We use its energy spectrum and a steady state ionospheric model to simulate vertical profiles of ion and electron densities. The ionospheric response to this large event would have been readily observable. It caused electron densities to exceed 104 cm−3 at 30–170 km, much larger than typically observed below 100 km. It also increased the ionosphere's total electron content by half of its subsolar value and would have caused strong attenuation of radio waves. The simulated attenuation is 462 dB at 5 MHz, which demonstrates that SEP events can cause sufficient attenuation (>13 dB) to explain the lack of surface reflections in some MARSIS topside radar sounder observations. We also develop a complementary generalized approach to the study of the ionospheric effects of SEP events. This approach predicts the threshold intensities at which a SEP event is likely to produce detectable changes in electron density profiles and radio wave attenuation measurements. An event one hundred times less intense than the 29 September 1989 event produces electron densities in excess of 3000 cm−3 at 80 km, which should be measurable by radio occultation observations, and causes sufficient attenuation to eliminate MARSIS surface reflections. However, although enhancements in total electron content have been observed during SEP events, predicted enhancements in low altitude electron density were not confirmed by observations.