| 太阳极紫外辐射对热层大气密度的影响 |
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| 引用本文： | 汪宏波,张明江,熊建宁.太阳极紫外辐射对热层大气密度的影响[J].空间科学学报,2023,43(1):87-100. |
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| 作者姓名： | 汪宏波 张明江 熊建宁 |
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| 作者单位： | 1.中国科学院紫金山天文台 南京 210023 |
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| 基金项目： | 国家自然科学基金项目资助（U1931136） |
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| 摘 要： | 对2001-2021年SOHO卫星的极紫外辐射测量数据，以及CHAMP,GRACE-A和SWARM-C卫星资料推导出的高分辨率大气密度数据进行统计分析，发现大气密度与极紫外测量值的相关系数大于密度与F10.7指数的相关系数，证实极紫外辐射在不同地方时的影响程度存在显著差异，从而驱动大气密度的周日变化。利用三颗卫星的高度差异揭示极紫外辐射对大气密度的加热效应在350～500 km范围随着高度增加而减弱。统计得到极紫外辐射影响在地方时和纬度上的空间差异：对夏季半球的影响大于冬季半球；在白天，对中纬度地区的影响高于赤道和高纬度地区；在夜间，密度对辐射的斜率在夏季半球高纬度地区存在峰值，在冬季半球中纬度存在谷值，模型DTM2000和NRLMSISE00未能准确刻画。为了改进经验模型，提出基于球谐函数的拟合方法，优于主流模型周日效应采用的表达式，对周日效应建模和修正提供有益借鉴。利用昼夜间能量传输和热层大气经向环流机制探讨了统计结果的物理机制。
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| 关 键 词： | 热层大气密度 太阳极紫外辐射 相关性分析 周日效应 |
| 收稿时间： | 2021-12-16 |
Effects of Solar Extreme Ultraviolet Radiation on Thermospheric Neutral Density |
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| Affiliation: | 1.Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 2100232.Key Laboratory of Space Object and Debris Observation, Chinese Academy of Sciences, Nanjing 210023 |
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| Abstract: | The Solar Extreme Ultraviolet (EUV) radiation is well known as the major source of energy of driving the Earth atmospheric motion and transformation. The 10.7 cm solar radio flux (F10.7) instead of EUV measurement is often used in the thermospheric neutral density models, to calculate the thermosphere density and temperature. In this paper, the continuous measurements of EUV from SEM instruments onboard the SOHO satellite during 2001－2021 are directly compared with the densities derived from accelerometers onboard the CHAMP, GRACE-A and SWARM-C satellites, to reveal the essential relation between the solar EUV radiation and the thermosphere density. It is found that the correlation coefficients between the EUV data and the densities are obviously greater than those between the F10.7 indexes and the densities, which proves that the solar EUV radiation is the dominant energy source of heating the thermosphere rather than the radio radiation. From the liner regression slopes at different local time, it is shown that the maximum value occurs at 15:00 LT (corresponding to 14:00－16:00 LT), while the minimum value at 01:00 LT (00:00－02:00 LT), which confirms that the EUV radiation derives the diurnal variation of the thermosphere. According to the statistical results from three satellites with different orbital altitudes, it is indicated that in the 350~500 km altitude region, the heating effect of the EUV radiation at lower altitude is more intense than that at higher altitude (considering absolute variation). Because of the high spatial resolution of the observation of three satellites, the difference in the effect of the EUV radiation at various local time and geographic latitudes can be concluded: the slope in summer hemisphere is greater than that in winter hemisphere; in the dayside, the slope at the mid-latitudes is greater than that at the equator and high latitudes; in the nightside, the maximum of the slope appears at the high latitude of summer hemisphere, which is not described by the thermosphere models such as DTM2000 and NRLMSISE00 yet. In order to improve the modeling of the effect of the EUV radiation, the fitting method of six-order spherical harmonics is proposed. Compared with the formulas of the present models, the spherical harmonics are more valuable in improving the model construction or correction of the EUV effect and the thermosphere diurnal variation. At last, the physical mechanism of statistical results is discussed by considering the energy transmission and meridional circulation in the thermosphere. |
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