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

Abstract

A spherical field meter has been developed to measure the atmospheric electric field vector above the ground surface. Its calibrations in the radial and linear electric fields and the method to find out the distortion coefficients are described. Extensive measurements of the components of the atmospheric electric field and the resulting electric field vector in fair weather and during the passage of a small dust devil over the spherical field meter are reported. Observations made at Pune (18°32'N, 73°51'E, 559 m above msl), show that in fair weather the horizontal component of the electric field may be upto 5% of the vertical component. Variations in the horizontal components of the electric field when averaged over an interval 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, variations in the horizontal components may be comparatively larger and generally independent 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 surface. These observations demonstrate the capability and reliability of the spherical field meter to measure the magnitude and direction of the electric field vector. They also demonstrate that the movement of small space charge pockets close to the surface may cause the development of horizontal component of the electric field.