Effects of Solar Flares on the Ionosphere of Mars: Comparison of Observed and Predicted Electron Density Profiles From 15 to 26 April 2001

IF 2.6 2区 地球科学 Q2 ASTRONOMY & ASTROPHYSICS
Paul Withers, A. G. Cramer, D. J. Pawlowski
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Abstract

Solar flares significantly affect Mars's ionosphere, yet there are few comparisons between observed and simulated densities in the M1 and M2 ionospheric layers during solar flares. Here we compare observed and simulated electron density profiles for the X14.4 solar flare of 15 April 2001 and the M7.8 solar flare of 26 April 2001. We use observations from Mars Global Surveyor radio occultations and simulations from the Mars Global Ionosphere-Thermosphere Model (M-GITM). Due to poor constraints on the solar spectrum incident upon Mars at this time, simulated M2 electron density values were 50% larger than observed. Yet the relative changes in M2 electron density during these two flares were reproduced to 10% accuracy. When accurate solar irradiance data are available, absolute M2 electron density values are simulated accurately. Due to the omission of electron impact ionization from the M-GITM model, the simulated M1/M2 density ratio was under-predicted by a factor of approximately 3. Yet the relative changes in M1 electron density during these two flares were reproduced to 20% accuracy. The model can accurately predict relative changes in M1 and M2 electron densities during a solar flare. If accurate solar irradiance data are available, it can accurately predict absolute changes in M2 electron densities. If a simple parameterization of electron impact ionization were incorporated into the model, then it would likely predict absolute changes in M1 electron densities accurately as well. The M-GITM model is well-suited to studies of time-varying phenomena in the ionosphere of Mars.

太阳耀斑对火星电离层的影响:2001年4月15日至26日观测和预测电子密度剖面的比较
太阳耀斑显著影响火星电离层,然而在太阳耀斑期间,观测到的和模拟的M1和M2电离层密度之间很少有比较。这里我们比较了2001年4月15日的X14.4太阳耀斑和2001年4月26日的M7.8太阳耀斑的观测和模拟电子密度分布。我们使用了来自火星全球探测者的无线电掩星观测和火星全球电离层-热层模型(M-GITM)的模拟。由于此时入射火星的太阳光谱约束较差,模拟的M2电子密度值比观测值大50%。然而,在这两个耀斑期间M2电子密度的相对变化被重现到10%的精度。当有准确的太阳辐照度数据时,可以准确地模拟M2的绝对电子密度值。由于M-GITM模型中遗漏了电子冲击电离,模拟的M1/M2密度比被低估了约3倍。然而,在这两个耀斑期间,M1电子密度的相对变化被重现到20%的精度。该模型能准确预测太阳耀斑期间M1和M2电子密度的相对变化。如果有准确的太阳辐照度数据,它可以准确地预测M2电子密度的绝对变化。如果在模型中加入一个简单的电子碰撞电离参数化,那么它很可能也能准确地预测M1电子密度的绝对变化。M-GITM模型非常适合于研究火星电离层的时变现象。
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来源期刊
Journal of Geophysical Research: Space Physics
Journal of Geophysical Research: Space Physics Earth and Planetary Sciences-Geophysics
CiteScore
5.30
自引率
35.70%
发文量
570
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