Physical Processes Driving the Response of the F2 Region Ionosphere to the 21 August 2017 Solar Eclipse at Millstone Hill
Physical Processes Driving the Response of the F2 Region Ionosphere to the 21 August 2017 Solar Eclipse at Millstone Hill
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DOI：
10.1029/2018ja025479
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发表时间：
2019-04
期刊：
影响因子：
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通讯作者：
Wenbin Wang;Tong Dang;J. Lei;Shunrong Zhang;Binzheng Zhang;A. Burns
中科院分区：
文献类型：
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作者：
Wenbin Wang;Tong Dang;J. Lei;Shunrong Zhang;Binzheng Zhang;A. Burns
高分辨率热层-电离层-电动力学大气环流模式已被用于研究Millstone Hill（42.61°N，71.48°W，最大遮蔽：63%）F2区域电子密度（Ne）对2017年8月21日美国大日食的响应。模式结果的诊断分析表明，日食引起的扰动风直接通过沿沿着场线传输等离子体来引起F2区Ne的变化，间接地通过产生增强的O/N2比来引起F2区Ne的变化，O/N2比有助于在最大遮蔽之后的F2峰处和以下的电离层的恢复。双极扩散对等离子体压力梯度的变化作出反应并改变Ne分布。风输送和双极扩散从日食的早期阶段开始起作用，并显示出强烈的时间和高度变化。F2峰以上的F2区电子密度的恢复主要是由风传输和双极扩散;当日食后在较低的F2区产生更多的离子时，两者都将等离子体从F2峰以下移动到更高的高度。当月影进入、最大化和离开一个特定的观测地点时，该地点的扰动风改变方向，它们对F2区域电子密度的影响也各不相同，从在日食期间向下推动等离子体到在日食后将其向上输送到顶侧电离层。在Millstone Hill非相干散射雷达观测中，太阳辐射变暗、成分变化、风输运和双极扩散等化学过程共同导致了电离层顶侧响应的时间延迟和非对称特性（Ne快速下降和日食效应缓慢恢复）。
The high‐resolution thermosphere‐ionosphere‐electrodynamics general circulation model has been used to investigate the response of F2 region electron density (Ne) at Millstone Hill (42.61°N, 71.48°W, maximum obscuration: 63%) to the Great American Solar Eclipse on 21 August 2017. Diagnostic analysis of model results shows that eclipse‐induced disturbance winds cause F2 region Ne changes directly by transporting plasma along field lines, indirectly by producing enhanced O/N2 ratio that contribute to the recovery of the ionosphere at and below the F2 peak after the maximum obscuration. Ambipolar diffusion reacts to plasma pressure gradient changes and modifies Ne profiles. Wind transport and ambipolar diffusion take effect from the early phase of the eclipse and show strong temporal and altitude variations. The recovery of F2 region electron density above the F2 peak is dominated by the wind transport and ambipolar diffusion; both move the plasma to higher altitudes from below the F2 peak when more ions are produced in the lower F2 region after the eclipse. As the moon shadow enters, maximizes, and leaves a particular observation site, the disturbance winds at the site change direction and their effects on the F2 region electron densities also vary, from pushing plasma downward during the eclipse to transporting it upward into the topside ionosphere after the eclipse. Chemical processes involving dimming solar radiation and changing composition, wind transport, and ambipolar diffusion together cause the time delay and asymmetric characteristic (fast decrease of Ne and slow recovery of the eclipse effects) of the topside ionospheric response seen in Millstone Hill incoherent scatter radar observations.