The dayside ionospheres of Mars and Venus: Comparing a one-dimensional photochemical model with MaRS (Mars Express) and VeRa (Venus Express) observations
The dayside ionospheres of Mars and Venus: Comparing a one-dimensional photochemical model with MaRS (Mars Express) and VeRa (Venus Express) observations
复制标题
DOI：
10.1016/j.icarus.2014.01.028
复制
发表时间：
2014-05
期刊：
影响因子：
3.2
通讯作者：
K. Peter;M. Pätzold;G. Molina‐Cuberos;O. Witasse;F. González‐Galindo;P. Withers;M. Bird;B. Häusler;D. Hinson;S. Tellmann;G. Tyler
中科院分区：
文献类型：
--
作者：
K. Peter;M. Pätzold;G. Molina‐Cuberos;O. Witasse;F. González‐Galindo;P. Withers;M. Bird;B. Häusler;D. Hinson;S. Tellmann;G. Tyler
火星和金星下部电离层的电子密度分布主要依赖于太阳x射线和EUV通量以及太阳天顶角。在观测到的电离层主要层的峰值电子密度和总电子含量（TEC）的增加中可以清楚地看到太阳通量增加的影响。建立了“大气电离”（IonA）模型，将“火星快车”上的火星和“金星快车”上的VeRa无线电科学实验进行的电离层探测观测结果与模拟的火星和金星电离层电子密度剖面进行比较。这是在实际观测条件下完成的（太阳通量、太阳天顶角、行星坐标），从电离层基地到~ 160公里高度。IonA使用电离层高度的中性大气模型（火星气候数据库（MCD） v4.3）；来自SOLAR2000数据库的0.5-95 nm波长范围（x射线到EUV）的太阳通量信息。在选定的MCD情景（背景大气）下模拟的火星电子密度剖面与IonA剖面的比较表明，所有情景都能再现火星电离层的一般行为。MCD的“低太阳通量/清晰大气”和“低太阳通量/MY24”情景（平均而言）最符合火星的一组观测结果，尽管实际的火星大气在电离层高度似乎仍然略冷一些。对于金星来说，基于VIRA的VenusGRAM模型太有限，无法用于IonA模拟电子密度分布。V2峰值电子密度和TEC随太阳天顶角的变化规律一般可以得到再现，但在太阳极紫外光通量低或高的情况下，峰值密度和TEC要么过高，要么过低。当太阳天顶角小于45°时，模拟的V2峰高度平均有系统地低估了5 km，当太阳天顶角大于60°时，模拟的V2峰高度上升。后者与观察到的行为相反。解释是，VIRA和VenusGRAM仅适用于高太阳活动，尽管与最近太阳活动增加到高值的太阳周期的VeRa观测结果也非常不一致。金星电子密度曲线的观测值与模拟值之间的差异证明，在电离层高度真正遇到的金星大气比VIRA预测的密度更大，但局部温度更低。
The electron density distributions of the lower ionospheres of Mars and Venus are mainly dependent on the solar X-ray and EUV flux and the solar zenith angle. The influence of an increasing solar flux is clearly seen in the increase of the observed peak electron density and total electron content (TEC) of the main ionospheric layers. The model “Ionization in Atmospheres” (IonA) was developed to compare ionospheric radio sounding observations, which were performed with the radio science experiments MaRS on Mars Express and VeRa on Venus Express, with simulated electron density profiles of the Mars and Venus ionospheres. This was done for actual observation conditions (solar flux, solar zenith angle, planetary coordinates) from the bases of the ionospheres to ∼160 km altitude. IonA uses models of the neutral atmospheres at ionospheric altitudes (Mars Climate Database (MCD) v4.3 for Mars; VenusGRAM/VIRA for Venus) and solar flux information in the 0.5–95 nm wavelength range (X-ray to EUV) from the SOLAR2000 data base. The comparison between the observed electron density profiles and the IonA profiles for Mars, simulated for a selected MCD scenario (background atmosphere), shows that the general behavior of the Mars ionosphere is reproduced by all scenarios. The MCD “low solar flux/clear atmosphere” and “low solar flux/MY24” scenarios agree best (on average) with the MaRS set of observations, although the actual Mars atmosphere seemed to be still slightly colder at ionospheric altitudes.For Venus, the VenusGRAM model, based on VIRA, is too limited to be used for the IonA simulation of electron density profiles. The behavior of the V2 peak electron density and TEC as a function of solar zenith angle are in general reproduced, but the peak densities and the TEC are either over- or underestimated for low or high solar EUV fluxes, respectively. The simulated V2 peak altitudes are systematically underestimated by 5 km on average for solar zenith angles less than 45° and the peak altitudes rise for zenith angles larger than 60°. The latter is the opposite of the observed behavior. The explanation is that VIRA and VenusGRAM are valid only for high solar activity, although there is also very poor agreement with VeRa observations from the recent solar cycle, in which the solar activity increases to high values. The disagreement between the observation and simulation of the Venus electron density profiles proves, that the true encountered Venus atmosphere at ionospheric altitudes was denser but locally cooler than predicted by VIRA.