Research On Influence Of Different Land Use Types On Electromagnetic Field Propagation Of Lightning Stroke

Lightning disasters are constantly threatening the social public security and people's life and property security,affecting our daily production and life.The study of the physical activity process of thunder and lightning and the accurate understanding of the mechanism of thunder and lightning is not only the demand of the development of the Lightning science research,but also the important basis for the scientific protection measures for the masses 'production and life.Based on the actual situation of land use in Hetao of Inner Mongolia,the effects of different land use types on the electromagnetic field propagation of lightning stroke are studied by means of field measurement,modeling analysis and lightning flow engineering model calculation.(1)The characteristics of soil parameters under different land use types were statistically analyzed:the maximum soil resistivity appeared in sandy land,the minimum value appeared in farmland,and the observed value of soil temperature was smaller in different land use types;is because the observation area is located in the Inner Mongolia Bayan Nur City Yellow River irrigated.(2)The influence factors of soil resistivity under different types of land use were analyzed.Three methods of multiple nonlinear regression,least square method and BP neural network were used.The soil electrical conductivity model established by BP neural network had the highest accuracy.(3)Assuming the Earth is an ideal ground for an infinitely large conductivity:the amplitude of the electric field and the magnetic field component of lightning strike stroke decreases with the increase of observation distance,and the rise time increases with the increase of observation distance;the amplitude of vertical electric field decreases with the increase of observation altitude,but the gap becomes smaller with the increase of observation distance.The amplitude of horizontal electric field increases with the increase of observation altitude,the rising time decreases with the increase of observation altitude,while the amplitude of the horizontal field decreases significantly with the increase of observation distance,while the rise time increases with the increase of observation distance;the magnetic field intensity decreases with the increase of observation altitude,but the difference between different observation heights is very small.(4)The influence of soil finite conductivity on the electromagnetic field of lightning return stroke is further studied.The amplitude of horizontal and vertical electric fields in three types of land use increases with time,with the increase of observation height,the amplitude of horizontal electric field in grassland is obviously larger than that of farmland and sandy land after 2?s,and the amplitude difference between farmland and sandy land is not obvious.The variation of magnetic field with observation distance in different land use types,The intensity of magnetic field is negative,but the amplitude of magnetic field intensity decreases with the increase of observation distance,the field intensity of grassland is obviously larger than that of farmland and sandy land,and the gap between field intensity and sandy land is always small.When the observation distance is 0-2km,the farther the observation distance is,the more obvious the increase of the vertical electric field waveform of the finite conductivity decreases,and when the observation distance reaches 2km,the farmland,grassland and sandy land are compared with the infinite conductivity.0.045?s,0.055?s and 0.047?s were reduced by vertical electric field rising along time.(5)To explore the influence of different parameters in the Lightning stroke model on the distribution of electromagnetic field of lightning strike back:When the observation distance is 50m,the effect of the dielectric constant of the type in different land on the horizontal electric field component,the vertical electric field component and the magnetic field component of the electromagnetic field is not obvious.The fitted current value has a significant effect on the electromagnetic field of lightning stroke,the waveform of three electromagnetic field components is similar to that of different land use types;the soil conductivity has a significant effect on the horizontal electric field and the vertical electric field component of the electromagnetic field of lightning stroke,but the influence on the magnetic field component is very small.