| Autor: |
Qu, B. H.1 (AUTHOR), Lu, J. Y.1 (AUTHOR) jylu@nuist.edu.cn, Wang, Z. W.2 (AUTHOR), Liu, J. J.3 (AUTHOR), Wang, M.1 (AUTHOR), Li, J. Y.1 (AUTHOR), Zhang, H.1 (AUTHOR) |
| Předmět: |
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| Zdroj: |
Journal of Geophysical Research. Space Physics. Jun2024, Vol. 129 Issue 6, p1-15. 15p. |
| Abstrakt: |
Studies commonly assumed that variations in ionospheric conductance were insignificant and proposed that vorticities can be a reliable proxy or diagnostic for ionospheric field‐aligned currents (FACs). We propose a complete method for measuring FACs using data from the Super Dual Auroral Radar Network radar and the Defense Meteorological Satellite Program. In our method, the FACs are determined by three terms. The first term is referred to as magnetospheric‐origin FACs, while the second and third terms are known as ionospheric‐origin FACs. This method incorporates height‐integrated conductances based on observational data, thereby addressing the limitation of assuming uniform conductances. Different from previous works, we can calculate FACs at a low altitude of 250 km and obtain high‐resolution measurements within observable areas. Another advantage of this method lies in its ability to directly calculate and analyze the impact of ionospheric vorticity and conductance on FACs. We apply this method to obtain FACs in the Northern Hemisphere from 2010 to 2016 and analyze the distributions of height‐integrated conductances and total FACs. Our analysis reveals that the average FACs clearly exhibit the large‐scale R1 and R2 FAC systems. We conduct statistical analysis on magnetospheric‐origin FACs and ionospheric‐origin FACs. Our findings show that within the auroral oval, ionospheric‐origin FACs reach a comparable level to magnetospheric‐origin FACs. However, ionospheric‐origin FACs are significantly minor and almost negligible in other regions. This implies that height‐integrated conductance gradients and vorticities play equally significant roles within the auroral oval, whereas vorticities dominate in other regions. Plain Language Summary: Field‐aligned currents (FACs) refer to current sheets that flow parallel or antiparallel to the geomagnetic field lines in the polar region. Typically, the intensity of FACs is estimated using magnetic perturbation measurements, while the current density is determined by the thickness of current sheets. In this study, we propose another method for calculating FACs based on ionospheric plasma vorticities and conductances. This method allows for FAC calculations at lower altitudes compared to previous methods. Additionally, we investigate the significance of vorticities and height‐integrated conductance gradients on FACs. Our findings reveal that both height‐integrated conductance gradients and vorticities significantly influence FACs in auroral emission areas. However, the influence of vorticities is more pronounced in other areas. Key Points: We proposed a complete method for measuring ionospheric field‐aligned currents (FACs)Within the auroral oval, both height‐integrated conductance gradients and vorticities play equally important rolesIn non‐auroral regions, vorticities take on a dominant role in influencing FACs [ABSTRACT FROM AUTHOR] |
| Databáze: |
GreenFILE |
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