Space weather influences on atmospheric electricity
Space weather influences on atmospheric electricity
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DOI：
10.1002/wea.2323
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发表时间：
2014-09-01
期刊：
影响因子：
1.9
通讯作者：
Nicoll, K. A.
中科院分区：
文献类型：
--
作者：
Nicoll, K. A.
大气电力是地球物理科学的一个古老话题，可以追溯到17世纪50年代，当时富兰克林和达利巴德证实了雷暴中存在电力。随后，观测到即使是很好的条件也被带电，在晴朗的天气条件下，在地面附近观察到向下的垂直大气电场，量级为~100V/m。20世纪20年代卡内基号地球物理勘测船的开创性电学测量表明，电场的日变化与世界时而不是当地时间一致，因此“晴朗气候场”的起源仍然未知。这种特征变化仍然被称为卡内基曲线，随后被证明与全球雷暴区的日变化相似。这支持了由CTR Wilson(威尔逊1929；哈里森，2011年)提出的“全球大气电路”的想法，通过该电路，雷暴中的电荷分离维持了世界各地的大范围洋流和晴朗的气候场，目前已被Blakes lee等人(2014)证实。图1表示GEC。地球表面和较低的电离层(大约在60公里高度)被表示为球形电容器的两个相反带电的“电极”，其中空气提供了泄漏的介质。来自雷云、雨和闪电的电荷转移不断地将电离层带电到比地球表面高出250千伏的电离层势，即所谓的电离层势。大气空气是由于团簇离子的存在而导电的，团簇离子主要来自银河系宇宙射线、GCR、来自太阳系以外的高能氢或氦原子核(~GeV能量)，也来自地表附近的地球自然放射性。当GCR进入地球大气层时，它们与大气分子相互作用时会产生一连串的离子。空气的导电性质意味着电离层和地球表面之间的电势差与回流电流有关，这被称为空气-地球传导电流密度，Jc。这种垂直电流在晴朗的地区流动，在电离层和地面之间。在垂直维度上，欧姆定律将Jc与Vi和单位面积柱从电离层到表面的总阻力Rc联系在一起
Atmospheric electricity is a venerable topic of geophysical science, dating back to the 1750s when Franklin and Dalibard established the presence of electricity in thunderstorms. Subsequently even fine conditions were observed to be electrified, and a downward vertical atmospheric electric field of magnitude~ 100V/m observed near the surface during fair weather conditions1. The origin of the “fair weather field” remained unknown the pioneering electrical measurements of the geophysical survey ship Carnegie in the 1920s, which demonstrated a diurnal variation in the electric field aligned with universal time rather than local time. This characteristic variation remains known as the “Carnegie Curve” and was subsequently demonstrated as similar to the diurnal variation in global thunderstorm area. This supported the idea of a “Global atmospheric Electric Circuit”(GEC), postulated by CTR Wilson (Wilson 1929; Harrison, 2011), through which charge separation in thunderstorms sustains large scale current flow around the world and the fair weather field, now confirmed by Blakeslee et al (2014). Figure 1 represents the GEC. The Earth’s surface and the lower ionosphere (at approximately 60km altitude) are represented as two oppositely charged “electrodes) of a spherical capacitor, within which air provides a leaky dielectric. Charge transfer from thunderclouds, rain and lightning continuously electrify the ionosphere to a potential 250kV more positive than Earth’s surface, known as the ionospheric potential, Vi.Atmospheric air is conductive due to the presence of cluster ions, which are created primarily from Galactic Cosmic Rays, GCRs, highly energetic Hydrogen or Helium nuclei (~ GeV energy) from outside our solar system, and also, near the surface, from Earth’s natural radioactivity. As GCRs enter Earth’s atmosphere, they create a cascade of ions as they interact with atmospheric molecules. The conductive nature of air means that the potential difference between the ionosphere and the Earth’s surface is associated with a return current, known as the air-Earth conduction current density, Jc. This vertical current flows globally in fair weather regions, between the ionosphere and the surface. In the vertical dimension, Ohms’ law relates Jc to Vi and the total resistance of a unit area column of air from the ionosphere to the surface, Rc, by