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Gravity and Pressure‐Gradient Currents Using Ionospheric Electron Density Measurements From COSMIC Satellites
Journal of Geophysical Research: Space Physics ( IF 2.6 ) Pub Date : 2020-10-09 , DOI: 10.1029/2020ja028401
J. Sreelakshmi 1 , Geeta Vichare 1
Affiliation  

The gravity‐driven and pressure‐gradient currents coexist in the ionosphere, and their effects are significant in there, rather than at the outside of the ionosphere; and can be important while studying the ionospheric currents using low‐Earth‐orbiting (LEO) satellite measurements. Maute and Richmond (2017, https://doi.org/10.1002/2017JA024841) (MR17) have demonstrated that above the F region peak, directions of these two coexisting currents are opposite and the net magnetic effects along the ambient magnetic field are nonsignificant. In the view of the diamagnetic corrections being applied to the LEO magnetic field measurements to account for the pressure‐gradient currents, it is imperative to examine the proposition of MR17. In the present paper, we have estimated the gravity and pressure‐gradient currents, using altitude profiles of electron density obtained from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)‐1 satellite cluster. In order to get the latitudinal profiles of magnetic field variations at a fixed local time (LT) using COSMIC data, it is required to combine either different days at a fixed longitude or all the longitudes on a fixed day, thus compromising with either days or longitudes. It is found that the net magnetic field is significant in the low‐latitude region, which increases with solar flux and decreases with altitude. The magnetic field effects show strong LT dependence and are significant in the noon to evening sector. The comparison of the present estimates with the diamagnetic corrections emphasizes that correcting for only one current can introduce unviable errors and thus supports the suggestion of MR17.

中文翻译:

利用COSMIC卫星的电离层电子密度测量重力和压力梯度电流

在电离层中共存有重力驱动和压力梯度流,它们的影响在电离层中而不是在电离层外部很明显。并且在使用低地球轨道(LEO)卫星测量研究电离层电流时可能很重要。Maute和Richmond(2017,https://doi.org/10.1002/2017JA024841)(MR17)证明了F以上在区域峰值处,这两个并存电流的方向相反,并且沿环境磁场的净磁效应不明显。考虑到将反磁校正应用于LEO磁场测量以解决压力梯度电流,必须检查MR17的主张。在本文中,我们使用了从气象,电离层和气候星座观测系统(COSMIC)-1卫星群获得的电子密度的高度剖面,估算了重力和压力梯度电流。为了使用COSMIC数据获得固定本地时间(LT)的磁场变化的纬度分布,需要将固定经度的不同日期或固定日的所有经度组合在一起,因此折衷于天数或经度。结果发现,低纬度地区的净磁场很大,它随太阳通量的增加而随高度的增加而减小。磁场效应显示出很强的LT依赖性,并且在从午夜到傍晚的时间段中非常重要。当前估计值与反磁性校正的比较强调,仅校正一个电流会引入不可行的误差,因此支持MR17的建议。
更新日期:2020-10-20
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