Continuous observation of geomagnetic total-field at the underground laboratory in Huainan city,China and its time-varying characteristics
Underground laboratory has become a new platform and research hotspot for geomagnetic observation due to its advantage of"ultra-clean"geomagnetic background with small electromagnetic interference.In order to evaluate the geomagnetic environment in the underground laboratory in Huainan city,China,and to understand the time-varying characteristics and the coupling between the ground and underground of geomagnetic total-field,we carried out a long-term continuous observation of geomagnetic total-field synchronously in the underground roadway(-848 m)and the surface(+22 m)in 2022.We analyzed the power spectrum,the wavelet spectrum and the variation characteristics of the observed geomagnetic total-field data and compared them with those of the Mengcheng geomagnetic station near Huainan city.The results show that:(1)the geomagnetic environment at underground stations with no(or weak)magnetic interference is clean and is comparable to the Mengcheng geomagnetic station,and thus is suitable for the high-precision,long-term,continuous observation of the geomagnetic field;(2)the underground geomagnetic observation can effectively filter the electromagnetic interference due to industrial and human activities on the ground,and its time variation of geomagnetic total-field is coupled well with that of the Mengcheng geomagnetic station;(3)the underground geomagnetic observation can clearly record the time-varying information of geomagnetic total-field including calm variation,magnetic storms with different periods and geomagnetic pulses,which can provide geomagnetic constraints for studies of earth system science.