The Statistical Characteristics of Small‐Scale Ionospheric Irregularities Observed in the Martian Ionosphere
The Statistical Characteristics of Small‐Scale Ionospheric Irregularities Observed in the Martian Ionosphere
复制标题
火星电离层观测到的小尺度电离层不规则现象的统计特征
DOI：
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
R. Ergun
中科院分区：
文献类型：
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作者：
C. Fowler;J. Bonnell;J. Huba;L. Andersson;J. Espley;M. Benna;R. Ergun
最近，火星大气与挥发性演化（MAVEN）探测器在火星上发现了磁场强度和电离层密度的小尺度不规则性。研究这些不规则现象可以深入了解热层和电离层之间的相互作用，并可以比较火星、地球和其他行星之间的航空学。这篇论文报告了第一个统计研究，利用3.5年的MAVEN原位测量来描述这些不规则现象，并提供最有可能观察到这些不规则现象的地图。不规则现象最有可能在黎明和黄昏被观测到，在太阳天顶角90°到150°之间，尽管事件一直被观测到午夜。当电离层发电机条件存在时（磁化电子和未磁化离子），不规则性主要发生在地壳磁场区域之外，在海拔~ 130和160 km之间。这些不规则现象在性质上似乎与MHD相似（这与地面静电磁场有有趣的区别），其特征是绝对磁场强度的变化为背景场的5-15%，垂直于5-20公里的磁场长度尺度。虽然MAVEN不能准确地解析相关的密度变化，但我们估计这些变化通常在背景电离层密度的10%到75%之间。当存在时，在电离层峰值上方和下方出现不规则事件的可能性相等。在地球上，不规则事件的发生表现出强烈的季节依赖性；MAVEN的数据集目前太小，无法确定火星季节的任何决定性趋势。
Small‐scale ionospheric irregularities in magnetic field strength and ionospheric density have recently been discovered at Mars by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. Studying these irregularities provides insight into the interaction between the thermosphere and ionosphere and allows for comparative aeronomy between Mars, Earth, and other planets. This paper reports the first statistical study utilizing 3.5 years of MAVEN in situ measurements to characterize these irregularities and to provide maps of where these irregularities are most likely to be observed. Irregularities are most likely to be observed at dawn and dusk, between solar zenith angles of 90° and 150°, although events are observed all the way to midnight. Irregularities occur primarily outside of the crustal magnetic field regions, between altitudes of ∼130 and 160 km, when ionospheric dynamo conditions exist (magnetized electrons and unmagnetized ions). The irregularities appear to be MHD‐like in nature (an interesting difference to their electrostatic terrestrial counterparts), characterized by variations in absolute magnetic field strength of 5–15% of the background field and perpendicular to magnetic field length scales of 5–20 km. Although MAVEN cannot accurately resolve the associated density variations, we estimate these variations to typically be between 10% and 75% of the background ionospheric density. When present, irregularity events appear to occur with equal likelihood above and below the ionospheric peak. At Earth, the occurrence of irregularity events exhibits strong seasonal dependencies; the MAVEN data set is currently too small to identify any conclusive trends as a function of Mars season.
影响因子：
4.8
作者：
Morschhauser, A.;Lesur, V.;Grott, M.
通讯作者：
Grott, M.