The impact of energetic electron precipitation on mesospheric hydroxyl during a year of solar minimum
The impact of energetic electron precipitation on mesospheric hydroxyl during a year of solar minimum
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通讯作者：
Annet Eva Zawedde;H. Nesse Tyssøy;R. Hibbins;P. Espy;L. G. Ødegaard;M. Sandanger;J. Stadsnes
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作者：
Annet Eva Zawedde;H. Nesse Tyssøy;R. Hibbins;P. Espy;L. G. Ødegaard;M. Sandanger;J. Stadsnes
2008年，日冕洞高速太阳风引发了一系列地磁风暴。利用一种新的分析技术，从NOAA/POES 18卫星上的测量中得到了高能电子沉淀通量的改进估计。这些通量被用来量化太阳极小期高能电子沉降（EEP）对Aura卫星测量的中层大气羟基（OH）的直接影响。在冬季，在俄罗斯北部和北美校正地磁纬度向极地55°处观测到OH的局部纵向密度增强。尽管俄罗斯北部的OH增强与这些经度的EEP增加密切相关，但北美增强的强度和位置似乎与EEP无关。这种OH密度的增强可能是由于大气波动动力学引起的垂直运动，这种垂直运动将富含氧原子和氢原子的空气向下输送到大气中部，在那里它在OH的形成中起作用。在南半球，西南极洲上空OH密度的局部增强可以解释为由于地球磁场强度和大气动力学的局部最小值而增强的EEP。我们的研究结果表明，即使在太阳活动极小期，也存在大量的eep驱动的OH生产。然而，为了量化这种影响，需要在背景大气动力学的背景下详细了解降水发生的地点和时间。
In 2008 a sequence of geomagnetic storms occurred triggered by high-speed solar wind streams from coronal holes. Improved estimates of precipitating fluxes of energetic electrons are derived from measurements on board the NOAA/POES 18 satellite using a new analysis technique. These fluxes are used to quantify the direct impact of energetic electron precipitation (EEP) during solar minimum on middle atmospheric hydroxyl (OH) measured from the Aura satellite. During winter, localized longitudinal density enhancements in the OH are observed over northern Russia and North America at corrected geomagnetic latitudes poleward of 55 ∘ . Although the northern Russia OH enhancement is closely associated with increased EEP at these longitudes, the strength and location of the North America enhancement appear to be unrelated to EEP. This OH density enhancement is likely due to vertical motion induced by atmospheric wave dynamics that transports air rich in atomic oxygen and atomic hydrogen downward into the middle atmosphere, where it plays a role in the formation of OH. In the Southern Hemisphere, localized enhancements of the OH density over West Antarctica can be explained by a combination of enhanced EEP due to the local minimum in Earth’s magnetic field strength and atmospheric dynamics. Our findings suggest that even during solar minimum, there is substantial EEP-driven OH production. However, to quantify this e ff ect, a detailed knowledge of where and when the precipitation occurs is required in the context of the background atmospheric dynamics.