| The ionosphere is an important part of the Earth’s near-Earth space environment,and the study of its state and variation patterns is of great scientific significance.Airglow is an important optical phenomenon in the ionosphere,and the study of its emissive properties can help advance the deep understanding of photochemical and dynamical processes in the ionosphere-middle and upper atmosphere region.The emissive properties of airglow in the far-ultraviolet band are almost independent of complex backgrounds such as boundary layer atmosphere and surface emission,and therefore are often used as observational targets for space-based optical remote sensing of the ionosphere.During magnetic storms,solar wind energy is captured by the Earth’s magnetosphere and enters the Earth from the polar region,interacting with atmospheric particles and producing a series of significant effects in the global thermosphere and ionosphere.The intensity of far-ultraviolet airglow emission and the height of the emission layer change with the perturbation of the ionosphere during this period,while the change of airglow emission also affects the recovery process of the middle and upper atmosphere during this period.It is important to study the changes of far-ultraviolet airglow emission during magnetic storms and to grasp its change pattern to deepen the understanding of the ionosphere-middle and upper atmosphere change mechanism during storms and to improve the accuracy of ionospheric detection by optical remote sensing during storms.In this paper,we use the GUVI OI 135.6 nm L1 C level limb observation data,take the median value of several data obtained from one orbit scan as a result of which one scan,and use 10 days as the period of one magnetic storm event.The variation in the horizontal distribution and vertical distribution of airglow emission intensity during two strong magnetic storms of different durations in October and November 2003 was analyzed by the sliding average method.The main conclusions of this paper are as follows:(1)OI 135.6 nm airglow emission is mainly distributed in the area between 30° in the northern and southern hemispheres at altitudes of 300 to 400 km during the magnetically quiet period,and has a bimodal structure on both sides of the magnetic equator,reflecting the ionospheric equatorial anomaly caused by the fountain effect due to E×B drift in the ionospheric F layer,and the magnetic storms do not destroy the bimodal structure;(2)The intensity of OI 135.6 nm airglow emission increases with the decrease in the Dst index during the magnetic storm,and shows a quasi-positive correlation with the intensity of the magnetic storm,and the increase phenomenon keeps synchronization with the magnetic storm phase from the time point of view.In particular,there is a significant distribution in some latitudes of the northern hemisphere during the main phase at the height of the middle and low thermosphere(100-200 km);(3)The horizontal distribution of the OI 135.6 nm airglow emission intensity during the magnetic storm will have some north-south asymmetry and latitudinal asymmetry,the north-south asymmetry may be caused by the differences in E×B drift,magnetic declination,and neutral wind between different longitudes,and The latitudinal asymmetry is caused by the difference between the period of the GUVI probe’s motion around the Earth and the temporal resolution of the Dst index;(4)The expansion and heating of the ionosphere-thermal layer system due to enhanced space current activity and enhanced thermospheric winds,as well as the disturbance wind field blowing from the polar region to the equator,and the change of circulation patterns in higher regions may be one of the main physical mechanisms affecting the distribution of OI135.6 nm airglow radiation during the storm. |
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