A qualitative analysis of the diameter of the spherical head of a long positive Jet streamer above thundercloud is presented in this paper under uniform atmospheric condition for streamers of less than 7 km length. In...A qualitative analysis of the diameter of the spherical head of a long positive Jet streamer above thundercloud is presented in this paper under uniform atmospheric condition for streamers of less than 7 km length. In this study, an attempt is made to replicate laboratory-based point electrode discharge model for jet streamers originating above the thunderclouds. In laboratory conditions, it is not possible to produce huge electrode potentials which could be the reason that the streamers generated under the controlled lab environment have diameter of the order of only a few centimeter and length of a few millimeter. On the other hand, the thunderclouds carry huge electrical charges, for example 50 C, which can produce huge electrical potentials of the order of several hundred MeV. Such huge potential can act as the potential of a point electrode which may be capable of producing very large and thicker streamers above the thunderclouds. So, a leader mechanism of streamer initiation is assumed in calculations as the tip of conducting leader channel can act as point electrode carrying huge cloud potential to generate large streamers. It is found in this study that as the streamer moves larger distance away from the electrode (leader tip), the diameter of the streamer head decreases. Higher the potential of the electrode (leader tip), thicker is the streamer and more slowly the diameter decreases. Also, it is also found in our calculations that for higher electrode (leader tip) potential lower is the altitude of initiation of streamers.展开更多
A lightning warning system （LWS） which can predict the possibility of lightning strike and the position of lightning discharge was developed. The LWS uses the electric field intensity at the ground as a parameter to...A lightning warning system （LWS） which can predict the possibility of lightning strike and the position of lightning discharge was developed. The LWS uses the electric field intensity at the ground as a parameter to warn the possibility of lightning strikes. A planar shutter type electric field mill （EFM） with a rotating vane is studied to measure the electric field. From a calibration experiment, the sensitivity of the EFM was adjusted to 0.15 V/kV/m, and this covers the ranges from 200 V/m to 20 kV/m. Magnetic field waveform is detected by a crossed loop coil and an integral amplifier. Frequency bandwidth of the circuit ranges from 5 kHz to 1.2 MHz. The polarity of lightning discharges is discriminated by electric field component. After fixing the polarity, we can calculate the direction and distance of lightning discharge by the peak and the zero cross time of the detected magnetic field waveform.展开更多
From analysis of observational data of thunderstorms in Gansu,China,it was deduced that the electric structure of thunderclouds in this region is often positive charge in the upper,main negative in the middle layer an...From analysis of observational data of thunderstorms in Gansu,China,it was deduced that the electric structure of thunderclouds in this region is often positive charge in the upper,main negative in the middle layer and another positive charge,large in magnitude and extensive in dimension,in the lower part.Intra- cloud discharges often take place between the main negative charge and lower positive charge instead of upper. Case analysis of 6 intracloud discharges in two storms on August 3 and 4,1986 shows that the centers of these discharges and the dipole moments destroyed were at the altitude of 3.8—6 km msl(7.6—-13.5℃)and 18— 40 C km,respectively.展开更多
文摘A qualitative analysis of the diameter of the spherical head of a long positive Jet streamer above thundercloud is presented in this paper under uniform atmospheric condition for streamers of less than 7 km length. In this study, an attempt is made to replicate laboratory-based point electrode discharge model for jet streamers originating above the thunderclouds. In laboratory conditions, it is not possible to produce huge electrode potentials which could be the reason that the streamers generated under the controlled lab environment have diameter of the order of only a few centimeter and length of a few millimeter. On the other hand, the thunderclouds carry huge electrical charges, for example 50 C, which can produce huge electrical potentials of the order of several hundred MeV. Such huge potential can act as the potential of a point electrode which may be capable of producing very large and thicker streamers above the thunderclouds. So, a leader mechanism of streamer initiation is assumed in calculations as the tip of conducting leader channel can act as point electrode carrying huge cloud potential to generate large streamers. It is found in this study that as the streamer moves larger distance away from the electrode (leader tip), the diameter of the streamer head decreases. Higher the potential of the electrode (leader tip), thicker is the streamer and more slowly the diameter decreases. Also, it is also found in our calculations that for higher electrode (leader tip) potential lower is the altitude of initiation of streamers.
文摘A lightning warning system （LWS） which can predict the possibility of lightning strike and the position of lightning discharge was developed. The LWS uses the electric field intensity at the ground as a parameter to warn the possibility of lightning strikes. A planar shutter type electric field mill （EFM） with a rotating vane is studied to measure the electric field. From a calibration experiment, the sensitivity of the EFM was adjusted to 0.15 V/kV/m, and this covers the ranges from 200 V/m to 20 kV/m. Magnetic field waveform is detected by a crossed loop coil and an integral amplifier. Frequency bandwidth of the circuit ranges from 5 kHz to 1.2 MHz. The polarity of lightning discharges is discriminated by electric field component. After fixing the polarity, we can calculate the direction and distance of lightning discharge by the peak and the zero cross time of the detected magnetic field waveform.
基金This work was supported by the National Natural Science Foundation of China.
文摘From analysis of observational data of thunderstorms in Gansu,China,it was deduced that the electric structure of thunderclouds in this region is often positive charge in the upper,main negative in the middle layer and another positive charge,large in magnitude and extensive in dimension,in the lower part.Intra- cloud discharges often take place between the main negative charge and lower positive charge instead of upper. Case analysis of 6 intracloud discharges in two storms on August 3 and 4,1986 shows that the centers of these discharges and the dipole moments destroyed were at the altitude of 3.8—6 km msl(7.6—-13.5℃)and 18— 40 C km,respectively.
