Reversed ionospheric convections during the November 2004 storm: Impact on the upper atmosphere
Reversed ionospheric convections during the November 2004 storm: Impact on the upper atmosphere
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2004 年 11 月风暴期间的逆电离层对流：对高层大气的影响
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
S. Solomon
中科院分区：
文献类型：
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作者：
Yue Deng;G. Lu;Y. Kwak;E. Sutton;J. Forbes;S. Solomon
[1]利用电离层电动力学同化制图（AMIE）程序，对2004年11月风暴的一个特定时段（2000 - 2350 UT，11月9日）进行了研究。在这段时间内，IMF Bz强烈地向北沿着高太阳风动压，这是极区形成反向对流的有利条件。事实上，AMIE的输出显示了很长一段时间（> 1小时）在两个半球的强反向对流单体，这是很少观察到的。使用AMIE输出作为国家大气研究中心热层电离层电动力学环流模式的电动力学输入，研究了对热层中性风的影响。电离层对流逆转后，400 km高度中性风分布也发生了相应的变化，极冠区的差异风型也发生了逆转。通过比较差分离子对流和差分中性风的时间变化，发现水平中性风对反向对流的响应具有一定的时滞。中性风响应时间（e-折叠时间）明显具有高度依赖性，从400公里高度的45分钟到200公里高度的近1.5小时不等。垂直分量的涡度有类似的大小和分布，以前的研究在北向Bz条件和改变的迹象时，对流模式被逆转。CHAMP观测到的跨轨风和模拟的中性风之间的比较表现出一般的协议，和CHAMP跨轨风的时间变化表明离子拖曳力对中性风的强烈影响。
[1] Using the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure, a particular period (2000–2350 UT on 9 November) in the November 2004 storm is studied. During this time interval, IMF Bz was strongly northward along with a high solar wind dynamic pressure, favorable conditions to form reversed convection in the polar region. Indeed, the AMIE outputs show strong reversed convection cells in both hemispheres for a long period (>1 h), which have rarely been observed. The impact on the thermospheric neutral wind has been investigated using the AMIE outputs as the electrodynamic inputs of the National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model. After the ionospheric convection reversed, the neutral wind distribution at 400 km altitude changed correspondingly, and the difference wind patterns reversed in the polar cap region. By comparing the temporal variations of the difference ion convection and the difference neutral wind, it is found that horizontal neutral winds respond to the reversed convection with some time delay. The neutral wind response time (e-folding time) clearly has an altitudinal dependence varying from 45 min at 400 km altitude to almost 1.5 h at 200 km. The vertical component vorticity has a similar magnitude and distribution to previous studies in the northward Bz condition and changes the sign when the convection pattern is reversed. Comparison between the CHAMP observed cross-track wind and the simulated neutral wind exhibits a general agreement, and the temporal variations of CHAMP cross-track wind indicate a strong effect of the ion drag force on neutral winds.