This paper used the similarities between the ionospheres on Mars and Earth, the most similar of the terrestrial planets, to examine the relative importance of photochemical and transport processes at dawn and dusk. The amount of plasma present in the ionosphere, as measured by the total electron content (TEC), was examined at different locations for both solstice seasons over a solar cycle. Using the rate of change of TEC as a function of solar zenith angle made it possible to compare the plasma production via photoionisation and loss via recombination in the main layer of each planetary ionosphere despite the extreme differences in the total quantity of plasma. This study finds that, at least to first order, the dawn and dusk TEC slopes at Mars are symmetric. This symmetry is interpreted as an indicator of photochemical equilibrium. Deviations from photochemical equilibrium in different geographic and aerographic regions were used to explore the underlying processes responsible for plasma transport. Seasonal and solar cycle variations were also examined at dusk. These variations found that differing interactions with solar forcing mechanisms resulted in a Martian ionosphere with regions that showed evidence of significant transport processes at solar maximum, while at Earth transport processes were most important at solar minimum. In general, the photochemical processes in both ionospheres behave similarly when no magnetic field is considered. The presence or absence of a magnetic field shape the production via photoionisation and loss via recombination processes in both ionospheres, especially when considering plasma transport. This study has notable implications for comparative aeronomy, as a good understanding of how the ionosphere of magnetised and un-magnetised bodies compares is important for characterising planetary environments and atmospheric evolution over long time scales.

中文翻译：

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至日黎明和黄昏时地球和火星TEC的比较

本文利用火星和地球（最相似的类地行星）电离层之间的相似性，研究了黎明和黄昏时光化学和传输过程的相对重要性。通过总电子含量 (TEC) 测量的电离层中存在的等离子体量在太阳周期的两个冬至季节的不同位置进行了检查。使用 TEC 的变化率作为太阳天顶角的函数，可以比较每个行星电离层主层中通过光电离产生的等离子体和通过重组产生的损失，尽管等离子体总量存在极大差异。这项研究发现，至少在一阶，火星的黎明和黄昏 TEC 斜率是对称的。这种对称性被解释为光化学平衡的指标。使用不同地理和航空区域中光化学平衡的偏差来探索负责等离子体传输的潜在过程。还在黄昏时检查了季节性和太阳周期变化。这些变化发现，与太阳强迫机制的不同相互作用导致火星电离层的区域显示出太阳活动极大期的重要传输过程，而地球传输过程在太阳活动极小期时最重要。一般来说，当不考虑磁场时，两个电离层中的光化学过程表现相似。磁场的存在与否会影响两个电离层中通过光电离产生的产物和通过复合过程的损失，尤其是在考虑等离子体传输时。