Generation of electric charge associated with the formation of soft hail in thunderclouds
Generation of electric charge associated with the formation of soft hail in thunderclouds
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DOI：
10.1098/rspa.1961.0052
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发表时间：
1961-03
期刊：
影响因子：
--
通讯作者：
J. Latham;B. J. Mason
中科院分区：
文献类型：
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作者：
J. Latham;B. J. Mason
冰晶与模拟冰雹碰撞产生的电荷被测量为它们的温差、晶体的大小和碰撞速度的函数。结果表明，冰雹带电的符号受温度差的影响，当温度高于反弹的冰晶时，冰雹带负电。充电的大小与温度差成正比，但对晶体的尺寸和冲击速度不敏感。在5 ° C的温差下，直径约50 μ的反弹晶体平均产生5 x 10 - 9 e的电荷。S.联合本文还研究了由过冷水滴吸积而成的人工软冰雹颗粒的带电现象。冰雹上的水滴冻结时，伴随着带正电荷的冰屑的喷射，冰雹带负电荷。已经建立了充电和碎片产生率随空气温度、液滴直径和冲击速度变化的方式。在一个典型的实验中，空气温度为-15 °C，直径为80 μ的液滴以10 m s-1的速度撞击，平均产生12个碎片和4 x 10 - 6 e的电荷。S.联合每一滴。直径小于30 μ的液滴几乎不产生碎片，也几乎不带电。这两组实验的结果进行解释的作者的理论下的冰的电荷分离的温度梯度的影响下，并用于计算可能的电荷产生率在雷暴。看来，带电伴随着增长的软冰雹颗粒通过冻结和分裂的过冷液滴是能够产生和分离的电荷在所需的速率约为1 C km-3 min-1，但是，虽然反弹的冰晶通常会充电的冰雹在相同的（负）的意义上，这种机制将有助于雷暴带电只有轻微的。
The electrical charging which results from collisions between ice crystals and a simulated hailstone is measured as a function of their temperature difference, and of the size and impact velocity of the crystals. It is found that the sign of the charging is governed by that of the temperature difference, the hailstone becoming negatively charged if it is warmer than the rebounding crystals. The magnitude of the charging is proportional to the temperature difference but rather insensitive to the size and impact velocity of the crystals. With a temperature difference of 5°C, a rebounding crystal of diameter about 50 μ produces, on average, a charge of 5 x 10-9 e. s. u. The electrification of an artificial pellet of soft hail growing by the accretion of supercooled water droplets (riming) is also investigated. Freezing of the droplets on the hailstone is accompanied by the ejection of positively charged ice splinters, the hailstone acquiring a negative charge. The manner in which the rates of charging and splinter production vary with the air temperature, drop diameter and impact velocity has been established. In a typical experiment, with the air temperature at -15°C, droplets of diameter 80μ impacting at 10 m s-1 freeze to produce, on average, 12 splinters and a charge of 4 x 10-6 e. s. u. per drop. Droplets of diameter less than 30 μ produce few splinters and little charging. The results of both sets of experiments are interpreted in terms of the authors’ theory of charge separation in ice under the influence of a temperature gradient, and are used to calculate probable rates of charge generation in thunderstorms. It appears that the electrification which accompanies the growth of pellets of soft hail through the freezing and splintering of supercooled droplets is capable of generating and separating charge at the required rate of about 1 C km-3 min-1 but, while rebounding ice crystals will usually charge the hailstones in the same (negative) sense, this mechanism will contribute only slightly to thunderstorm electrification.