Diurnal and seasonal variation of electron heat flux measured with the Poker Flat Incoherent‐Scatter Radar
Diurnal and seasonal variation of electron heat flux measured with the Poker Flat Incoherent‐Scatter Radar
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使用 Poker Flat 非相干散射雷达测量的电子热通量的日变化和季节变化
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
B. Watkins
中科院分区：
文献类型：
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作者：
C. Fallen;B. Watkins
使用高级模块化非相干散射雷达进行的测量用于计算阿拉斯加扑克滩上空的平均日电子温度和相应的垂直热通量。我们的结果表明，在2009年和2010年连续12个月内，电子热通量和温度都表现出季节性变化，这是太阳和地磁活动异常安静的时期。电子温度和热通量每天都在变化，白天观察到的幅度比夜间更大。与 20 世纪 60 年代末中纬度地区的测量结果相反，人们发现扑克滩上空的向下热通量随季节变化显着，并且夏季通常比冬季更大。随时间变化的上部电子热通量是描述磁层-电离层耦合的重要参数，它还驱动基于物理的电离层模型中的边界条件。提供了足以用于电离层模型的平均电子热通量和温度的参数化。基于物理的高纬度电离层模型用于证明恒定的热通量边界条件会导致当地午夜附近的电子温度升高，而雷达测量中未观察到这一点。由此产生的电子温度计算不准确导致白天峰值电子数密度高估 15% 以上。应用时变热通量边界条件使模型电子温度和峰值密度与测量结果非常吻合。
Measurements made with the Advanced Modular Incoherent Scatter Radar were used to calculate the average diurnal electron temperature and corresponding vertical heat flux above Poker Flat, Alaska. Our results show that both the electron heat flux and temperature exhibited seasonal variation during 12 consecutive months in 2009 and 2010, a period of exceptionally quiet solar and geomagnetic activity. Both the electron temperature and heat flux varied diurnally, with larger magnitudes observed during the day than night. Contrary to midlatitude measurements from the late 1960s, the downward heat fluxes above Poker Flat were found to vary significantly with season and were typically greater during summer than winter. The time‐dependent topside electron heat flux is an important parameter describing magnetosphere‐ionosphere coupling and it also drives boundary conditions in physics‐based ionosphere models. Parameterizations of the average electron thermal flux and temperature sufficient for use in ionosphere models are provided. A physics‐based high‐latitude ionosphere model is used to demonstrate that a constant heat flux boundary condition leads to an electron temperature increase near local midnight that is not observed in the radar measurements. The resulting inaccuracy in electron temperature calculations leads to more than a 15% overestimate of daytime peak electron number density. Applying a time‐varying heat flux boundary condition brings the model electron temperature and peak density to good agreement with measurements.