X-Ray Observation of Mars at Solar Minimum with Suzaku
X-Ray Observation of Mars at Solar Minimum with Suzaku
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DOI：
10.1093/pasj/63.sp3.s705
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发表时间：
2011-09
影响因子：
2.3
通讯作者：
K. Ishikawa;Y. Ezoe;T. Ohashi;N. Terada;Y. Futaana
中科院分区：
文献类型：
--
作者：
K. Ishikawa;Y. Ezoe;T. Ohashi;N. Terada;Y. Futaana
2008年4月3日至5日，日本朱雀天文台对火星进行了82千秒的X射线观测。已知火星通过太阳X射线的散射以及外逸层中的中性原子与太阳风离子之间的电荷交换来发射X射线。过去的理论研究表明，在整个太阳活动周期中，外逸层中性密度的变化可能高达10倍。为了研究外气层电荷交换发射的潜在变化，在太阳活动极小期用朱雀号对火星进行了观测。在0.2-5 keV的能量带中，在火星的位置没有探测到显著的信号。在0.5-0.65 keV范围内，O VII线通量的2 σ上限为4.3 × 10 ^{-5}$ ph cm$^{-2}$ s$^{-1}$。将这一上限与过去在太阳活动极大期附近进行的Chandra和XMM-Newton观测进行比较，发现太阳活动极小期的外逸层密度不会超过太阳活动极大期附近的密度6-70倍。
Mars was observed in X-rays during April 3-5 2008 for 82 ksec with the Japanese Suzaku observatory. Mars has been known to emit X-rays via the scattering of solar X-rays and via the charge exchange between neutral atoms in the exosphere and solar wind ions. Past theoretical studies suggest that the exospheric neutral density may vary by a factor of up to 10 over the solar cycle. To investigate a potential change of the exospheric charge exchange emission, Mars was observed with Suzaku at solar minimum. Significant signals were not detected at the position of Mars in the energy band of 0.2-5 keV. A 2 sigma upper limit of the O VII line flux in 0.5-0.65 keV was 4.3$\times10^{-5}$ ph cm$^{-2}$ s$^{-1}$. Comparing this upper limit to the past Chandra and XMM-Newton observations conducted near solar maximum, it was found that the exospheric density at solar minimum does not exceed that near solar maximum by more than 6-70 times.