Longitude correction method for the field magnetic surveyed diurnal-variation correction

Solar quiet daily variation (Sq) are dependent on local time. Herein, we applied the moving superposition method to separate the Sq component of correction observatory data and performed a time difference correction on the Sq component according to the longitudinal difference between the correction observatory and the field station while maintaining the time of other data components. The data were then reconstructed and used for diurnal-variation correction to improve the accuracy of the daily variations correction resu; lts The moving superposition method employs data of “nonmagnetic disturbance days” obtained 15 d before and after to perform the superposing average calculation on a daily basis, aiming to obtain the Sq of continuous morphological changes. The effect of longitude correction was tested using the observatory record and field survey data. The average correction distance of the test observatories was 2114 km, and the correction accuracies of the H (horizontal component of geomagnetic field), D (geomagnetic declination), and Z (vertical component of geomagnetic field) were improved by 28.4%, 45.0%, and 21.7%, respectively; the average correction distance of the field stations was 2130 km, and the correction accuracies of the F (geomagnetic total intensity), D, I (geomagnetic inclination) components were improved by 35.2%, 26.7%, and 13.9%, respectively. The test results also demonstrated that the longitude correction effect was greater with an increased correction distance.