Based on 16 years of magnetic field observations from CHAMP and Swarm satellites,this study investigates the influence of the Interplanetary Magnetic Field(IMF)Bx component on the location and peak current density of ...Based on 16 years of magnetic field observations from CHAMP and Swarm satellites,this study investigates the influence of the Interplanetary Magnetic Field(IMF)Bx component on the location and peak current density of the polar electrojets(PEJs).We find that the IMF Bx displays obvious local time,seasonal,and hemispherical effects on the PEJs,as follows:(1)Compared to other local times,its influence is weakest at dawn and dusk.(2)In the midnight sectors of both hemispheres,the IMF Bx tends to amplify the westward PEJ when it is<0 in the Northern Hemisphere and when it is>0 in the Southern Hemisphere;this effect is relatively stronger in the local winter hemisphere.(3)At noontime,the IMF Bx intensifies the eastward current when it is<0 in the Northern Hemisphere;in the Southern Hemisphere when it is>0,it reduces the westward current;this effect is notably more prominent in the local summer hemisphere.(4)Moreover,the noontime eastward current shifts towards higher latitudes,while the midnight westward current migrates towards lower latitudes when IMF Bx is<0 in the Northern Hemisphere and when it is>0 in the Southern Hemisphere.展开更多
The ionospheric currents in the polar region are caused mainly by field-aligned currents. The quiet polar current system consists of a pair of current vertices at dawn and dusk. When substorm occurs, however, intense ...The ionospheric currents in the polar region are caused mainly by field-aligned currents. The quiet polar current system consists of a pair of current vertices at dawn and dusk. When substorm occurs, however, intense magnetic disturbances are generated by enhanced polar currents, especially the westward electrojet of a millions Amperes in the auroral oval. The intensity of the auroral electrojet is commonly described by the auroral electrojet indices AL, AU, AE and AO. In this paper the relationship between the polar current system and the auroral electrojet indices is quantitatively studied by means of polar current functions obtained from the data recorded at 71 magnetic stations in the northern polar region during the International Mag- netospheric Study (IMS). Fairly well linear correlation of AL (or AU) with AE index has been found, indicating that AE index multiplied by a proper factor can approximately substitute AL and AU indices. The total polar current, JT, and the strengths of the dawn and dusk current vortices, JT 1 and JT , can be characterized by AE index, an increment of 1nT in AE index corresponding to 2 1000A in JT. A fairly well direct proportion is found between AE and the maximal westward current density, an increment of 1 nT in AE corresponding to 1 A/km of the maximal westward current density at magnetic midnight. The latitudinal profiles of the current density are similar for different local time in night sector. The maximal density of the westward electrojet usually occurs at geo- magnetic latitude 65°—70°around midnight, as for the eastward electrojet, it is around 80°. The analysis shows that for 5-mimute mean values, the saturation values of AE and AL are 700 nT and –500 nT, respectively. Accordingly, a caution should be taken when the indices greater than the saturation values would be used for studying magnetospheric or ionospheric processes.展开更多
基金the National Key Research and Development Program(2022YFF0503700)National Natural Science Foundation of China(42374200)the National Natural Science Foundation of China Basic Science Center(42188101).
文摘Based on 16 years of magnetic field observations from CHAMP and Swarm satellites,this study investigates the influence of the Interplanetary Magnetic Field(IMF)Bx component on the location and peak current density of the polar electrojets(PEJs).We find that the IMF Bx displays obvious local time,seasonal,and hemispherical effects on the PEJs,as follows:(1)Compared to other local times,its influence is weakest at dawn and dusk.(2)In the midnight sectors of both hemispheres,the IMF Bx tends to amplify the westward PEJ when it is<0 in the Northern Hemisphere and when it is>0 in the Southern Hemisphere;this effect is relatively stronger in the local winter hemisphere.(3)At noontime,the IMF Bx intensifies the eastward current when it is<0 in the Northern Hemisphere;in the Southern Hemisphere when it is>0,it reduces the westward current;this effect is notably more prominent in the local summer hemisphere.(4)Moreover,the noontime eastward current shifts towards higher latitudes,while the midnight westward current migrates towards lower latitudes when IMF Bx is<0 in the Northern Hemisphere and when it is>0 in the Southern Hemisphere.
基金supported by the Ministry of Science and Technology of hina(Grant No.G20000784).
文摘The ionospheric currents in the polar region are caused mainly by field-aligned currents. The quiet polar current system consists of a pair of current vertices at dawn and dusk. When substorm occurs, however, intense magnetic disturbances are generated by enhanced polar currents, especially the westward electrojet of a millions Amperes in the auroral oval. The intensity of the auroral electrojet is commonly described by the auroral electrojet indices AL, AU, AE and AO. In this paper the relationship between the polar current system and the auroral electrojet indices is quantitatively studied by means of polar current functions obtained from the data recorded at 71 magnetic stations in the northern polar region during the International Mag- netospheric Study (IMS). Fairly well linear correlation of AL (or AU) with AE index has been found, indicating that AE index multiplied by a proper factor can approximately substitute AL and AU indices. The total polar current, JT, and the strengths of the dawn and dusk current vortices, JT 1 and JT , can be characterized by AE index, an increment of 1nT in AE index corresponding to 2 1000A in JT. A fairly well direct proportion is found between AE and the maximal westward current density, an increment of 1 nT in AE corresponding to 1 A/km of the maximal westward current density at magnetic midnight. The latitudinal profiles of the current density are similar for different local time in night sector. The maximal density of the westward electrojet usually occurs at geo- magnetic latitude 65°—70°around midnight, as for the eastward electrojet, it is around 80°. The analysis shows that for 5-mimute mean values, the saturation values of AE and AL are 700 nT and –500 nT, respectively. Accordingly, a caution should be taken when the indices greater than the saturation values would be used for studying magnetospheric or ionospheric processes.
