An updated climatology of thermospheric neutral winds and F region ion drifts above Millstone Hill
An updated climatology of thermospheric neutral winds and F region ion drifts above Millstone Hill
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DOI：
10.1029/1999ja900345
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发表时间：
1999-11
影响因子：
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通讯作者：
M. Buonsanto;O. Witasse
中科院分区：
文献类型：
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作者：
M. Buonsanto;O. Witasse
1984-1997年期间63个实验的非相干散射雷达数据被用来更新早先发表的关于米尔斯通山离子漂移和中性热层风的气候。数据根据季节、太阳活动、地磁活动和当地太阳时间进行分类。得到的离子漂移模式与以前发表的类似，但我们现在发现，磁活动增加的主要影响是增强了通常夜间向西的离子漂移。对于每个季节/太阳活动水平，对地磁平静条件下的风进行潮汐分解，以提取日平均、日幅度和相位以及半日分量。这些风与米尔斯通山和HWM-93模型之前的结果进行了比较。利用我们扩展的风数据库，现在在夏季和冬季都发现了统计上显著的半日成分，无论是在太阳最高值还是在太阳最低值。我们的平均结果证实了早先发表的结果，即在所有季节，日平均风都是向赤道方向移动的，并且太阳活动周期最小时的日平均风幅比太阳活动周最大时强。由于我们现在使用一个较小的O+，O碰撞频率值，所以在本工作中得到的昼夜振幅比以前发现的要大。最近太阳活动极小值数据(1993-1997年)和上一次太阳活动极小值数据(1984-1986)之间的日平均和日振幅的差异是由于从Millstone Hill电子密度数据推断的EUV通量的差异，这是人们从F10.7指数中没有预料到的。这影响了离子阻力，显然也影响了极紫外线和高纬度热源的相对重要性。
Incoherent scatter radar data from 63 experiments during the period 1984–1997 have been used to update earlier published climatologies of ion drifts and neutral thermospheric winds at Millstone Hill. Data are binned according to season, solar activity, geomagnetic activity, and local solar time. The derived ion drift patterns are similar to those previously published, but we now find that the main effect of the increased magnetic activity is an enhancement of the usual nighttime west-ward ion drift. A tidal decomposition of the winds from geomagnetically quiet conditions is carried out for each season/solar activity level to extract diurnal means, diurnal amplitudes and phases, and semidiurnal components. These winds are compared with previous results at Millstone Hill and the HWM-93 model. Using our expanded wind database, statistically significant semidiurnal components are now found in both summer and winter, at both solar maximum and solar minimum. Our bin-averaged results confirm earlier published findings that at all seasons the diurnal mean winds are more strongly equatorward and the diurnal amplitudes are stronger at solar cycle minimum than at solar cycle maximum. Diurnal amplitudes derived in the present work are larger than those found previously because we now use a smaller value for the O+, O collision frequency. Differences in the diurnal mean and diurnal amplitude between recent solar minimum data (1993–1997) and data from the previous solar minimum (1984–1986) are attributed to a difference in the EUV flux as inferred from Millstone Hill electron density data which one would not expect from the F10.7 index. This affects the ion drag and apparently also the relative importance of the EUV and high latitude heat sources.