Measurements of the electrical properties of dust storms

Characteristics of the electrification in dust storms have been studied by making field observations at different places in the southwestern United States. Measurements consisted of the atmospheric electric potential gradient at ground level, space charge and wind speed (both at 1.25 meters above the ground), atmospheric temperature and relative humidity, and size distribution of dust particles at ground level. It has been observed that during dust storms both signs of potential gradient can occur at ground level, and any sign of potential gradient can be associated with the same or opposite sign of space charge at 1.25 meters above the ground. Potential gradients of many kilovolts per meter are not uncommon during these dust storms, and sometimes these high values can be sustained for many minutes, The space charge values at 1.25 meters above the ground associated with these high values of potential gradient can be as high as 105–106 el cm−3. In some dust storms the polarities of potential gradient and space charge have been observed to change if the blowing dust, rather than reach high altitudes, is raised because of low wind speeds only to lower levels. Size distributions of different types of dust particles collected at ground level are also given.