地殼磁場對火星熱氧逃脫的影響;The Effect of Crustal Magnetic Fields on the Non-thermal Escape of Hot Oxygen from Mars

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Title:	地殼磁場對火星熱氧逃脫的影響;The Effect of Crustal Magnetic Fields on the Non-thermal Escape of Hot Oxygen from Mars
Authors:	施驊珊;Shih, Hua-Shan
Contributors:	太空科學研究所
Keywords:	火星;熱氧逃逸;地殼磁場;蒙地卡羅模擬;火星氣候演化;Mars;Hot oxygen escape;Crustal magnetic field;Monte Carlo simulation;Martian climate evolution
Date:	2025-07-28
Issue Date:	2025-10-17 11:13:25 (UTC+8)
Publisher:	國立中央大學
Abstract:	火星的大氣逃逸過程是影響其氣候演化的重要機制之一，其中非熱逃逸過程，尤其是熱氧逃逸，在塑造火星上層大氣的結構與動力學特徵上扮演著關鍵的角色。本研究使用三維測試粒子蒙地卡羅（3D test-particle Monte Carlo）模擬方法，結合多流體磁流體力學模型，以定量分析火星地殼磁場對熱氧動態與大氣逃逸速率的影響。我們的研究結果指出，當考慮火星地殼磁場效應時，整體熱氧逃逸速率較無磁場情境約增加了23%。特別是在磁場分布較為活躍的南半球區域，熱氧的區域逃逸速率甚至提升達兩倍左右。這種南北半球顯著的不對稱性，主要源自局部區域中電漿傳輸過程、離子及電子密度分布，以及沿磁場方向的粒子加速機制（field-aligned acceleration）之改變。這些效應使得火星表面局部強磁區域中的熱氧逃逸效率明顯提高。本研究進一步指出，與過去普遍認為磁場具有抑制大氣逃逸、即具防護作用的觀點不同，火星特有的局部地殼磁場在特定條件下反而可能促進大氣逃逸的發生與加速。此一結果為理解火星及其他較弱磁場天體的大氣演化機制，提供了新的視角與研究方向。若考慮早期火星可能曾擁有較現今更強大的全球性磁場，則本研究亦有助於釐清其大氣流失速率隨時間演化的可能路徑與關鍵影響因子。;Atmospheric escape has been a key driver of Mars’ climatic evolution, with non-thermal processes, particularly hot oxygen loss, playing an important role in influencing the structure of its upper atmosphere. In this study, we simulate hot oxygen dynamics using a 3D test-particle Monte Carlo model coupled with a multifluid MHD framework to quantify the effects of crustal magnetic fields on escape rates. Our results show that the inclusion of Mars’ crustal magnetic fields enhances the global hot oxygen escape rate by approximately 23%, with regional increases up to a factor of two in the magnetically active southern hemisphere. This asymmetry is linked to localized modifications of plasma transport, ion/electron distributions, and field-aligned acceleration mechanisms. Contrary to the typical view of magnetic fields as protective barriers, our results reveal that Mars′ localized magnetism can actively facilitate atmospheric escape in specific regions. Recent observations and paleomagnetic data suggest that early Mars may have possessed a stronger, global magnetic field. This work provide a skeleton to explore how changes in magnetic field topology affect atmospheric evolution, offering new insight into Mars′ climatic history and the comparative aeronomy of weakly magnetized planets.
Appears in Collections:	[Graduate Institute of Space Science] Department of Earth Sciences

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