Influence of relative humidity on the aeolian electric field

We report an experimental measurement of aeolian electric fields in a wind tunnel under different relative humidity, wind speed and temperature. We believe the relative humidity is a crucial factor for aeolian electric field formation. We observed a critical relative humidity, at which the aeolian electric field reaches its maximum value. With an increase in relative humidity up to the critical value, the aeolian electric field linearly increased, but exponentially decreased when the relatively humidity was higher than the critical value. The critical relative humidity depended on the wind speed and increased with the increase of wind speed. Temperature lower than 117 °C was not a key factor to determine the aeolian field as compared to the relative humidity. From the experimental results, we can infer a charging mechanism of sand particles. We believe that collisions between sand particles ionise the moisture around the sand particles to provide the free charges. The free charges transfer between the collisions among sand particles to create a charge.