Experimental study on the variation of atmospheric magnetic field intensity in dust evets, haze events, rainy days, snowy days and thunderstorms

The simultaneous measurement of vertical magnetic field intensity (B_z), three-dimensional electric field (E_x, E_y, E_z), ambient temperature (T), ambient relative humidity (RH), mass concentration (PM_2.5 and PM₁₀) and three-dimensional wind speed (U_x, U_y, U_z) were conducted at Lanzhou, China and Xi'an, China during haze events, dust events, snowfall events, rainfall events and thunderstorms. The hourly mean value and hourly standard deviation of dB_z/dt were used to evaluate the disturbance level of atmospheric magnetic field (AMF) during these weather. The hourly mean value of dB_z/dt in dusty days, rainy days, snowy days and thunderstorms varies evidently compared to that in fair weather, which implies that these weather conditions will effectively affect the variation of AMF. Analysis of E_z and U_xy suggests that the movement of charged particles under the action of horizontal wind will change the average currents in atmosphere and induce a magnetic field, and this induced magnetic field will disturb the variation of AMF. Hence, the induced magnetic fields generated by the movement of charged particles should not be ignored in these complex weather conditions. The analysis of dE_xy/dt shows that the induced magnetic field generated by the change of the electric field can disturb the AMF as well. In addition, hourly standard deviations of dB_z/dt in haze event, snowfall event and thunderstorms are larger than that in fair weather, which means that these events can influence the fluctuation of AMF. The approximate circular motion of charged particles in the horizontal plane under turbulence was discussed to be the main reason for the intense fluctuation of AMF in haze and snowfall events, but the large fluctuation of AMF in thunderstorms maybe attributed to the transient changes of space electric field under lightning.