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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Causes of low thermospheric density during the 2007-2009 solar minimum
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Causes of low thermospheric density during the 2007-2009 solar minimum

机译：期间thermospheric密度低的原因2007 - 2009年太阳能最低

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摘要

Satellite drag data indicate that the thermosphere was lower in density, and therefore cooler, during the protracted solar minimum period of 2007-2009 than at any other time in the past 47 years. Measurements indicate that solar EUV irradiance was also lower than during the previous solar minimum. However, secular change due to increasing levels of CO2 and other greenhouse gases, which cool the upper atmosphere, also plays a role in thermospheric climate, and changes in geomagnetic activity could also contribute to the lower density. Recent work used solar EUV measurements from the Solar EUV Monitor (SEM) on the Solar and Heliospheric Observatory, and the NCAR ThermosphereIonosphere-Electrodynamics General Circulation Model, finding good agreement between the density changes from 1996 to 2008 and the changes in solar EUV. Since there is some uncertainty in the long-term calibration of SEM measurements, here we perform model calculations using the MgII core-to-wing ratio as a solar EUV proxy index. We also quantify the contributions of increased CO_2 and decreased geomagnetic activity to the changes. In these simulations, CO_2 and geomagnetic activity play small but significant roles, and the primary cause of the low temperatures and densities remains the unusually low levels of solar EUV irradiance.
机译：卫星拖动数据表明热大气层低密度,因此冷却器,在旷日持久的太阳能最低的时期2007 - 2009比其他任何时候都在过去的47岁年。比在低辐照度也以前的太阳。由于增加的二氧化碳和其他水平温室气体,冷却上氛围,在thermospheric也扮演了一个角色气候和地磁活动的变化也可能导致较低的密度。最近的工作使用太阳能的EUV测量在太阳能和太阳能EUV监控(SEM)格林威治天文台,NCARThermosphereIonosphere-Electrodynamics一般循环模型,找到好的协议从1996年到2008年,密度变化太阳能EUV的变化。扫描电镜的长期校准的不确定性测量,我们执行模型的计算使用MgII太阳能EUV core-to-wing比率代理指数。增加的二氧化碳和地磁下降活动的变化。二氧化碳和地磁活动虽小但玩重要的角色,和的主要原因较低的温度和密度仍然是太阳能EUV辐照度的异常低的水平。

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