The Impact of Energetic Particles on the Martian Ionosphere During a Full Solar Cycle of Radar Observations: Radar Blackouts
The Impact of Energetic Particles on the Martian Ionosphere During a Full Solar Cycle of Radar Observations: Radar Blackouts
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雷达观测的整个太阳周期期间高能粒子对火星电离层的影响：雷达停电
DOI：
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Aaron Russell
中科院分区：
文献类型：
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作者：
M. Lester;B. Sánchez–Cano;D. Potts;R. Lillis;M. Cartacci;F. Bernardini;R. Orosei;M. Perry;N. Putzig;B. Campbell;P. Blelly;S. Milan;H. Opgenoorth;O. Witasse;Elena M.M. Redrojo;Aaron Russell
基于对 2006 年至 2017 年在火星快车和火星勘测轨道飞行器上观测到的雷达回波停电的分析，我们首次对火星较低电离层（约 90 公里以下）的电离层进行了长期表征，该区域是轨道现场观测无法到达的区域。当部分观测的预期表面反射部分或完全衰减时，就会发生停电。 60-90公里高度处电离增强，低于主要电离层电子密度峰值，导致雷达信号吸收增加，导致停电。我们发现（a）工作频率在1.8至5 MHz之间的MARSIS比具有更高载波频率（20 MHz）的SHARAD遭受更多停电，（b）停电发生与太阳周期有明显的相关性，（c）停电发生与地壳磁场之间没有明显关系，（d）停电发生在夜间和白天观测期间，尽管峰值发生在夜间较深。对火星大气和 20 至 200 keV 之间的挥发性演化太阳高能粒子电子计数的分析表明，这些电子可能是导致雷达信号衰减的原因。我们研究了电离低层大气并产生可测量的衰减所需的最小 SEP 电子通量。当两个雷达都经历停电时，SEP 电子通量达到最高。根据几个案例研究，我们发现导致停电的平均 SEP 光谱在其较高能量端（即高于 70 keV）尤其增强。
We present the first long‐term characterization of ionization layers in the lower ionosphere of Mars (below ∼90 km), a region inaccessible to orbital in‐situ observations, based on an analysis of radar echo blackouts observed on Mars Express and the Mars Reconnaissance Orbiter from 2006 to 2017. A blackout occurs when the expected surface reflection is partly or totally attenuated for portions of an observation. Enhanced ionization at altitudes of 60–90 km, below the main ionospheric electron density peak, leads to increased absorption of the radar signal, resulting in the blackouts. We find that (a) MARSIS, operating at frequencies between 1.8 and 5 MHz, suffered more blackouts than SHARAD, which has a higher carrier frequency (20 MHz), (b) there is a clear correlation of blackout occurrence with solar cycle, (c) there is no apparent relationship between blackout occurrence and crustal magnetic fields, and (d) blackouts occur during both nightside and dayside observations, although the peak occurrence is deep on the nightside. Analysis of Mars Atmosphere and Volatile EvolutioN Solar Energetic Particle electron counts between 20 and 200 keV demonstrates that these electrons are likely responsible for attenuating the radar signals. We investigate the minimum SEP electron fluxes required to ionize the lower atmosphere and produce measurable attenuation. When both radars experience a blackout, the SEP electron fluxes are at their highest. Based on several case studies, we find that the average SEP spectrum responsible for a blackout is particularly enhanced at its higher energy end, that is, above 70 keV.
将实时测量仪测量结果同化为 30 MHz 极帽吸收模型
影响因子：
3.3
作者：
Rogers N
通讯作者：
Rogers N