Spherical field meter to measure the electric field vector-measurements infair weather and inside a dust devil

A spherical field meter has been developed to measure the atmospheric elect ric field vector above the ground surface. Its calibrations in the radial a nd linear electric fields and the method to find out the distortion coeffic ients are described. Extensive measurements of the components of the atmosp heric electric field and the resulting electric field vector in fair weathe r and during the passage of a small dust devil over the spherical field met er are reported. Observations made at Pune (18 degrees 32' N, 73 degrees 51 ' E, 559 m above msl), show that in fair weather the horizontal component o f the electric field may be upto 5% of the vertical component. Variations i n the horizontal components of the electric field when averaged over an int erval of more than 4 s are small and are generally but not always identical to its vertical components. However, at a frequency of few Hertz, variatio ns in the horizontal components may be comparatively larger and generally i ndependent of the vertical components. Observations made during the passage of a small dust devil over the spherical field meter show the development of appreciable horizontal component of electric field above the ground surf ace. These observations demonstrate the capability and reliability of the s pherical field meter to measure the magnitude and direction of the electric field vector. They also demonstrate that the movement of small space charg e pockets close to the surface may cause the development of horizontal comp onent of the electric field. (C) 1999 American Institute of Physics. [S0034 -6748(99)01904-8].