On the mechanism of seasonal and solar cycle N_mF_2 variations: A quantitative estimate of the main parameters contribution using incoherent scatter radar observations

A. V. Mikhailov; L. Perrone

摘要

Seasonal (winter/summer) and solar cycle N_mF_2 variations as well as summer saturation effect in N_mF_2 have been analyzed using Millstone Hill incoherent scatter radar (ISR) daytime observations. A self-consistent approach to the Ne(h) modeling has been applied to extract from ISR observations a consistent set of main aeronomic parameters and to estimate their quantitative contribution to the observed N_mF_2 variations. The retrieved aeronomic parameters are independent of uncertainties in thermosphere and solar EUV empirical models, and this is a distinguishing feature of the present consideration. Different temperatures in winter and in summer in the course of solar cycle overlapped on the O~+ + N_2 reaction rate coefficient temperature dependence result in different N_mF_2 dependences on solar activity: a steep practically linear increase with a tendency to turn up in January (contrary to international reference ionosphere prediction) and a slow increase with a tendency to saturate at high solar activity in July despite increasing solar EUV irradiation. In winter the EUV flux and thermospheric parameters provide approximately equal contributions to the N_mF_2 increase, while in summer the contribution of thermospheric parameters is small. Both in winter and in summer the variations of atomic oxygen [O] are small at the F_2 layer peak, and its contribution is small compared to linear loss coefficient, β. It is shown that the summer saturation effect in N_mF_2 under high solar activity is not just reduced to O/N_2 or EUV flux solar cycle variations but is determined by β via the γ1 temperature dependence. A new mechanism (qualitative) to explain the December anomaly in N_mF_2 is proposed. It is based on the idea that the areas of atomic oxygen production and its loss are spatially separated and that time is required to transfer [O] from one area to the other where [O] associates in a three-body collision. Therefore, under a 7% increase in the 02 dissociation rate due to the Sun-Earth distance decrease in December–January compared to June–July, an accumulation of atomic oxygen should take place in the thermosphere in the vicinity of the December solstice resulting in a 21% N_mF_2 increase, which is close to the observed global December effect.

机译：季节(冬季/夏季)和太阳活动周期N_mF_2变化以及夏季饱和效应分析了N_mF_2使用磨石山非相干散射雷达(ISR)白天观察。Ne (h)建模应用于提取ISR观察一组一致的主航空和估计其参数对观察到的N_mF_2量化贡献变化。是独立的不确定性在运转吗和太阳能EUV实证模型,这是一个特色的礼物考虑。在夏天的太阳活动周期重叠的O ~ + +甲烷反应速率系数的温度依赖性导致不同的N_mF_2依赖性在太阳活动:一个陡峭的几乎线性增加的趋势(与国际1月出现参考电离层预测)和缓慢增加在高饱和的趋势尽管7月太阳活动增加太阳能EUV辐照。thermospheric参数提供大约N_mF_2平等的贡献增加,在夏天thermospheric的贡献参数很小。原子氧[O]的变化很小₂层峰,它的贡献很小相对于线性损耗系数,β。表明,夏季在N_mF_2饱和效应在高太阳活动不仅仅是减少O /甲烷或EUV通量,但太阳周期变化通过γ1温度由β依赖。解释N_mF_2的12月异常建议。原子氧生产及其损失空间上分开,这需要时间[O]从一个地区转移到其他的地方[O]associates三体碰撞。在02离解率增加了7%由于来观察太阳-地球距离减少辛普森相比6原子氧积累应该发生在附近的热大气层冬至导致N_mF_2 21%增加,接近全球观测12月的效果。

On the mechanism of seasonal and solar cycle N_mF_2 variations: A quantitative estimate of the main parameters contribution using incoherent scatter radar observations

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