The lightning very high frequency （VHF） radiation location system based on the short-baseline time-difference of arrival （TDOA） technique provides an effective approach to describe the temporal and spatial develop...The lightning very high frequency （VHF） radiation location system based on the short-baseline time-difference of arrival （TDOA） technique provides an effective approach to describe the temporal and spatial development of lightning discharge in two dimensions with high resolution. A negative single-stroke cloud-to- ground （CG） lightning flash was analyzed in detail using the radiation location results and synchronic fast/slow elec- tric field changes. The long-duration preliminary break- down process appeared to propagate with hi-directional leader channels. The two negative simultaneous discharge channels sloped down with a considerable horizontal com- ponent in the lower positive charge region at speeds of about 105 m s-1. The stepped leader was clearly converted from one channel of the preliminary breakdown process and spread downwards with branches. The speeds of the stepped leaders were about 105 m s -1. The K processes after the return stroke could either directly initiate from the start region with negative polarity lightning discharge, or initiate from a new region in the cloud as negative recoil streamers. All K processes propagated along the preceding electrified channel, while not all K processes initiated from the tips of positive breakdowns. The speeds of the K processes were about 106-107 m s-1.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
Particle bursts （PBs）, the phenomena characterized by short-term increases of particle counting rates （CRs）, were observed by space-borne radiation belt particle detectors. With the electron CR data obtained by Na...Particle bursts （PBs）, the phenomena characterized by short-term increases of particle counting rates （CRs）, were observed by space-borne radiation belt particle detectors. With the electron CR data obtained by National Oceanic and Atmospheric Ad- ministration （NOAA）-18 satellite, the occurrence of PBs in the inner belt （I〈~L〈2 and B〉20.5 gT） were derived for years 2006-2011. The monthly occurrence number of PBs exhibits a strong maximum in northern summer （May-August）. In associ- ation with global lightning data, the seasonal occurrence of PBs is found to be consistent with the lightning activity, especially if only lightning flashes at latitudes 〉20~ are taken into account. The positive correlation between PBs and mid-latitude light- ning discharges indicates the role of lightning-induced whistler waves, and is consistent with the expected pitch-angle scatter- ing by wave-particle interactions. The contribution of lightning is so significant that it forms a non-negligible seasonal back- ground of PBs. If one connects PBs to seismoelectromagnetic emissions （SEME） in attempt to find the earthquake precursor, the lightning background needs to be considered with great care.展开更多
基金supported by the Instrument Developing Project of the Chinese Academy of Sciences (Grant No.YZ201206)the National Natural Science Foundation of China (Grant Nos.40930949 and 41175002)National Science and Technology Support Project (Grant No.2008BAC36B03)
文摘The lightning very high frequency （VHF） radiation location system based on the short-baseline time-difference of arrival （TDOA） technique provides an effective approach to describe the temporal and spatial development of lightning discharge in two dimensions with high resolution. A negative single-stroke cloud-to- ground （CG） lightning flash was analyzed in detail using the radiation location results and synchronic fast/slow elec- tric field changes. The long-duration preliminary break- down process appeared to propagate with hi-directional leader channels. The two negative simultaneous discharge channels sloped down with a considerable horizontal com- ponent in the lower positive charge region at speeds of about 105 m s-1. The stepped leader was clearly converted from one channel of the preliminary breakdown process and spread downwards with branches. The speeds of the stepped leaders were about 105 m s -1. The K processes after the return stroke could either directly initiate from the start region with negative polarity lightning discharge, or initiate from a new region in the cloud as negative recoil streamers. All K processes propagated along the preceding electrified channel, while not all K processes initiated from the tips of positive breakdowns. The speeds of the K processes were about 106-107 m s-1.
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supported by the National Basic Research Program of China("973" Project)(Grant Nos.2012CB957801,2011CB811405)the National Natural Science Foundation of China(Grant Nos.41274155,40904036)+1 种基金the Public Science and Technology Research Funds Projects of Ocean,State Oceanic Administration of China(Grant No.201005017)the Specialized Research Fund for State Key Laboratories
文摘Particle bursts （PBs）, the phenomena characterized by short-term increases of particle counting rates （CRs）, were observed by space-borne radiation belt particle detectors. With the electron CR data obtained by National Oceanic and Atmospheric Ad- ministration （NOAA）-18 satellite, the occurrence of PBs in the inner belt （I〈~L〈2 and B〉20.5 gT） were derived for years 2006-2011. The monthly occurrence number of PBs exhibits a strong maximum in northern summer （May-August）. In associ- ation with global lightning data, the seasonal occurrence of PBs is found to be consistent with the lightning activity, especially if only lightning flashes at latitudes 〉20~ are taken into account. The positive correlation between PBs and mid-latitude light- ning discharges indicates the role of lightning-induced whistler waves, and is consistent with the expected pitch-angle scatter- ing by wave-particle interactions. The contribution of lightning is so significant that it forms a non-negligible seasonal back- ground of PBs. If one connects PBs to seismoelectromagnetic emissions （SEME） in attempt to find the earthquake precursor, the lightning background needs to be considered with great care.
