Ionospheric effects of the gravity wave launched by the September 18, 1974, sudden commencement
Ionospheric effects of the gravity wave launched by the September 18, 1974, sudden commencement
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DOI：
10.1029/ja083ia03p00999
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发表时间：
1978-03
影响因子：
--
通讯作者：
R. Roble;A. Richmond;W. Oliver;R. Harper
中科院分区：
文献类型：
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作者：
R. Roble;A. Richmond;W. Oliver;R. Harper
1974年9月18日世界时1434分，一个突然开始的地磁风暴发生了。大约一小时后，马萨诸塞州米尔斯顿山（北纬42.6度，西经71.5度）的非相干散射雷达探测到了一个行进中的电离层扰动，再晚些时候，波多黎各阿雷西博（北纬18.3度，西经66.7度）的非相干散射雷达也探测到了。电子温度，离子温度和电子密度的垂直分布的测量在两个站的干扰的通道期间显示出显着的扰动相比，前一天获得的地磁安静时间值。从热层的时变动力学模型出发，计算了热层重力波的特征。波源被假定为增强的电流和粒子加热的极地帽地区。脉冲加热产生的重力波向赤道方向传播，其特征结构随着向低纬方向传播而发生变化。计算出的中性温度和风的扰动被添加到安静的时间变化的中纬度电离层F区域的一个昼夜模型计算的时间依赖性的特性的电离层在波的通道在两个非相干散射雷达站。通过要求计算的和观测的电离层结构之间的一致性，我们估计了重力波能量源的大小。对于1974年9月18日的事件，我们在总能量输入约为2 × 1015 J，发生在3小时内的情况下，计算的电离层结构和观测的电离层结构之间有相当好的一致性。
A sudden commencement of a geomagnetic storm occurred at 1434 UT on September 18, 1974. A traveling ionospheric disturbance was detected about an hour later by the incoherent scatter radar at Millstone Hill, Massachusetts (42.6°N, 71.5°W), and still later by the incoherent scatter radar at Arecibo, Puerto Rico (18.3°N, 66.7°W). Measurements of the vertical distribution of electron temperature, ion temperature, and electron density made during the passage of the disturbance at both stations showed significant perturbations in comparison to the geomagnetic quiet time values obtained on the previous day. We calculated characteristics of the thermospheric gravity wave from a time-dependent dynamic model of the thermosphere. The wave source is assumed to be enhanced electric currents and particle heating over the polar cap region. The gravity wave generated by the impulsive heating propagates equatorward, and its characteristic structure changes as it progresses to lower latitudes. The calculated neutral temperature and wind perturbations are added to the quiet time variations in a diurnal model of the mid-latitude ionospheric F region to calculate the time-dependent properties of the ionosphere during the passage of the wave over both incoherent scatter radar stations. By requiring agreement between the calculated and observed ionospheric structure we estimated the magnitude of the gravity wave energy source. For the event on September 18, 1974, we obtained reasonably good agreement between the calculated and observed ionospheric structures for a total energy input of about 2 × 1015 J, occurring over a period of 3 hours.