Abstract

The properties of the annual asymmetry in the electron density of the F2-layer maximum NmF2 at noon are analyzed based on the global empirical model of the F2-layer critical frequency median (SDMF2 model). As a characteristic of this asymmetry, we used the R index, i.e., the January/July ratio of the total (at a given and geomagnetically conjugate points) NmF2 density at noon averaged over all longitudes. It was found that the R index decreases with increasing solar activity at low geomagnetic latitudes (Φ < 31°–33°). At higher latitudes, the R index increases with an increase in solar activity. During low solar activity, the main R maximum is located at latitude Φ = 22°–24°. During high solar activity, this R maximum is located at Φ = 64°–66°. At latitude Φ = 22°–24° in the Northern and Southern hemispheres, the longitudinal average NmF2 density in January is higher than that in July for any level of solar activity. At Φ = 64°–66°, an increase in R with increasing solar activity is mainly caused by a January increase in NmF2 in the Northern Hemisphere. The global (average over all latitudes) R index increases with increasing solar activity. Additional analysis showed that the global R index decreases with increasing solar activity in the IRI model both with URSI option and, even more so, with CCIR option. This appears to be due to the limited amount of experimental data on the obtainment of the CCIR and URSI coefficients, especially over the oceans.

中文翻译：

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NmF2 年不对称性对地磁纬度和太阳活动的依赖性

摘要

基于F 2 层临界频率中值的全局经验模型（SDMF2 模型），分析了中午F 2 层最大NmF 2电子密度年不对称性的性质。作为这种不对称性的一个特征，我们使用了R指数，即 1 月/7 月总（在给定和地磁共轭点）中午NmF 2 密度在所有经度上的平均值。发现在低地磁纬度（Φ < 31°–33°），R指数随着太阳活动的增加而降低。在高纬度地区，R指数随着太阳活动的增加而增加。在低太阳活动期间，主要的R最大值位于纬度 Φ = 22°–24°。在高太阳活动期间，此R最大值位于 Φ = 64°–66°。在北半球和南半球的纬度Φ = 22°–24°处，无论太阳活动水平如何，1月份的纵向平均NmF 2 密度均高于7月份。在 Φ = 64°–66° 处，随着太阳活动的增加，R的增加主要是由北半球1 月NmF 2 的增加引起的。全球（所有纬度的平均值）R指数随着太阳活动的增加而增加。额外的分析表明，全局R在 IRI 模型中，无论是使用 URSI 选项，还是使用 CCIR 选项，指数都随着太阳活动的增加而降低。这似乎是由于获得 CCIR 和 URSI 系数的实验数据有限，尤其是在海洋上。