Empirical modelling of auroral absorption during disturbed periods of interplanetary coronal mass ejection events
Empirical modelling of auroral absorption during disturbed periods of interplanetary coronal mass ejection events
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DOI：
10.1016/j.jastp.2020.105364
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发表时间：
2020-10
影响因子：
1.9
通讯作者：
O. Ogunmodimu;F. Honary;N. Rogers;I. Richardson;B. Adebisi;V. Nwankwo
中科院分区：
文献类型：
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作者：
O. Ogunmodimu;F. Honary;N. Rogers;I. Richardson;B. Adebisi;V. Nwankwo
与太阳风扰动相关的高能带电粒子降水导致高纬度电离层高频无线电波吸收增强。本研究利用芬兰基尔皮斯耶尔维电离层研究成像Riometer（IRIS）的测量结果，对38.2 MHz宇宙噪声吸收（CNA）进行建模，该测量结果是在太阳活动周期23（1996-2009）期间获得的，与行星际日冕物质抛射（ICME）经过地球有关; ICME是增强地磁活动的主要驱动力。叠加历元分析表明，IRIS的r6吸收与时间曲线取决于ICME到达时间是白天（10-14 MLT）还是夜间（22-02 MLT），吸收峰值分别出现在ICME到达前约2-3 h或ICME到达后约4 h。我们确定的太阳风和IMF参数的组合显示与白天或夜间到达ICME使用叠加历元分析和最小二乘估计方法相关的吸收的最佳相关性。太阳风参数的各种组合（包括体积速度v，密度n，和行星际磁场的北，南分量Bz和SYMH地磁指数），已排名获得最佳的耦合功能与白天和夜间到达ICME的吸收。白天事件的吸收被发现与太阳风动压，SYMH，和北方向的Bz密切相关，而夜间事件的吸收是最密切相关的方向的Bz和SYMH。耦合函数成功地模拟了观测到的吸收，观测到的吸收和模拟的吸收之间的相关系数为~0.7-0.8。
Energetic charged particle precipitation associated with solar wind perturbations causes enhanced high-frequency radiowave absorption in the high-latitude ionosphere. This study models 38.2 MHz cosmic noise absorption (CNA) by utilising measurements from the Imaging Riometer for Ionospheric Studies (IRIS) at Kilpisjärvi, Finland obtained during solar cycle 23 (1996–2009) associated with the passage of interplanetary coronal mass ejections (ICMEs) past Earth; ICMEs are a major driver of enhanced geomagnetic activity. Superposed epoch analysis suggests that the r6absorptionvs.time profile depends on whether ICME arrival occurs in the day-time (10–14 MLT) or night-time (22-02 MLT) for IRIS, with peak absorption occurring ~2–3 h ahead of ICME arrival or ~4 h after ICME arrival, respectively. We determine which combinations of solar wind and IMF parameters show the best correlation with the absorption associated with day-time or night-time arriving ICMEs using superposed epoch analysis and the least squares estimation method. Various combinations of solar wind parameters (including bulk velocity v, density n, and the interplanetary magnetic field north and south components Bz and the SYMH geomagnetic index), have been ranked to obtain the best coupling function for the absorption associated with day- and night-time arriving ICMEs. The absorption for day-time events is found to correlate closely with the solar wind dynamic pressure, SYMH, and the northward direction of the Bz while the absorption for night-time events is most closely related to the direction of the Bz and SYMH. The coupling functions are found to model the observed absorption successfully, with correlation coefficients of ~0.7–0.8 between the observed and modelled absorption.