Galactic Cosmic Rays at Mars and Venus: Temporal Variations from Hours to Decades Measured as the Background Signal of Onboard Microchannel Plates
Galactic Cosmic Rays at Mars and Venus: Temporal Variations from Hours to Decades Measured as the Background Signal of Onboard Microchannel Plates
复制标题
火星和金星的银河宇宙射线：作为机载微通道板的背景信号测量的从几小时到几十年的时间变化
DOI：
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发表时间：
2022
影响因子：
4.9
通讯作者：
S. Barabash
中科院分区：
文献类型：
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作者：
Y. Futaana;M. Shimoyama;M. Wieser;Stefan Karlsson;H. Andersson;H. Nilsson;Xiao;A. Fedorov;N. André;M. Holmstrom;S. Barabash
微通道板（MCP）是广泛用于对空间中的颗粒进行计数的部件。使用的背景计数从MCP的火星快车和金星快车轨道运行超过17年和8年，分别，我们研究了银河宇宙线（GCR）的内太阳系的特征。火星和金星的MCP背景计数，在太阳活动周期的时间尺度上，表现出明确的太阳黑子数的相关性。我们的结论是，所测量的MCP背景计数包含GCR信息。在火星上使用MCP背景计数测量的GCR特征显示出与地球上太阳活动周期24的测量结果一致的特征。在火星上，太阳黑子数量和MCP背景计数之间的时间差被发现是109个月。沿着轨道记录的较短期背景数据（时间尺度为几个小时）也显示，由于行星吸收了GCR粒子，背景计数明显减少。由于沿轨道沿着可见的行星尺寸变化，我们开发了一个模型，将GCR对MCP背景计数的贡献与MCP玻璃中放射性元素的β衰变引起的内部贡献分开。我们对火星GCR吸收特征的统计分析表明，火星对GCR粒子的有效吸收半径大于行星半径100 km。然而，原因仍然是一个悬而未决的问题。
A microchannel plate (MCP) is a component widely used for counting particles in space. Using the background counts from MCPs on the Mars Express and Venus Express orbiters—operating over 17 yr and 8 yr, respectively—we investigated the galactic cosmic ray (GCR) characteristics of the inner solar system. The MCP background counts at Mars and Venus, on a solar cycle timescale, exhibited clear anticorrelation with the sunspot number. We concluded that the measured MCP background counts contained GCR information. The GCR characteristics measured using the MCP background counts at Mars showed features consistent with measurements on Earth in Solar Cycle 24. The time lag between the sunspot number and the MCP background counts was found to be ∼9 months at Mars. The shorter-term background data recorded along the orbits (with a timescale of several hours) also showed evident depletion of the background counts, due to absorption of the GCR particles by the planets. Thanks to the visible planetary size change along an orbit, we developed a model to separate the GCR contribution to the MCP background counts from the internal contribution caused by the β-decay of radioactive elements in the MCP glass. Our statistical analysis of the GCR absorption signatures at Mars implies that the effective absorption radius of Mars for the GCR particles is >100 km larger than the radius of the planet. However, the cause remains an open question.