摘要
本文选取了第24太阳活动周2010年1月至2014年9月期间的快速、大角宽日冕物质抛射(CME)事件,结合不同约束条件下Richardson(2014)太阳高能粒子(SEP)强度经验模型输出结果,分析了 CME属性、先行CME(pre-CME)、Ⅱ型射电暴等观测特征对SEP强度的影响,探讨了 SEP事件的产生及其强度与这些特征的关系.主要结论如下:1)快速CME前13 h内是否存在pre-CME对模型预测效果和快速CME是否产生SEP事件有明显影响,但pre-CME的数量对模型输出结果没有明显改善.2)相比于无Ⅱ型射电暴伴随的快速CME而言,伴随Ⅱ型射电暴的CME爆发产生SEP事件的误报占比明显更低(42％),以此为约束条件,可更加突显大SEP事件(如峰值≥0.01 pfu/MeV)的模型预测值与观测值的关联;如果考虑射电增强,则SEP事件的误报占比可进一步下降至29.4％,模型预测效果显著提升.3)Ⅱ型射电暴的起始频率和结束频率对误报占比的影响不大,以此作为条件约束对模型预测效果提升不明显.4)如考虑Ⅱ型射电暴的细分类型作为模型约束条件,伴随多波段Ⅱ型射电暴的CME比单一波段事件具有更好的模型预测效果,如m-DH-km Ⅱ型射电暴事件,具有较低的误报占比(35.4％),准确率较高.研究结果显示,除了 CME的速度和角宽参数外,pre-CME、Ⅱ型射电暴及其增强、多波段类型等特征作为CME产生SEP事件的约束条件,SEP预测强度与观测强度具有较好的一致性,可以获得较优的模型预测效果.这也进一步表明了伴随有pre-CME、多波段Ⅱ型射电暴及其增强的快速大角宽CME更容易产生SEP事件,这些特征可作为SEP-rich类CME的辨别信号.
Abstract
Based on the multiple-vantage observations of STEREO,SOHO,wind and other spacecraft,the fast and wide coronal mass ejections(CME)during the 24th solar cycle from January 2010 to September 2014 are selected in this paper.Using the outputs of Richardson's(2014)empirical model of solar energetic particle(SEP)intensity under different conditions,the effects of its associations such as CME,pre-CME,and type Ⅱradio bursts,on SEP intensity are analyzed,and the relationship between SEP event and these characteristics is also discussed.The main conclusions are as follows.1)The presence or absence of pre-CME within 13 h before fast CME significantly improves the model prediction effect and has a significant influence on whether fast CME produces SEP event.Compared with the events without pre-CMEs,the events with pre-CMEs have a low proportion of false alarms(FR:47.7％vs.70％).However,the number of pre-CMEs does not improve the model output.2)CMEs with type-Ⅱ radio bursts have significantly lower FR to generate SEP events than fast CMEs without type-Ⅱ radio bursts(42％vs.68％).And selecting type-Ⅱ radio bursts as a constraint will filter out some small/weak SEP events,the relationship between model predictions and observations especially for large SEP events(e.g.Ip≥0.01 pfu/MeV)will stand out.Moreover,if the type-Ⅱ radio enhancement is taken into account,FR can be further reduced to 29.4％,and the proportion of hits can be further increased(HR:48.5％),and the model prediction is significantly improved.3)The larger the start frequency of type Ⅱ radio bursts,the smaller the end frequency is,and FR decreases slightly,but at the same time,a large number of SEP events are excluded by this condition,and the results show that the constraints on the start/end frequency of type-Ⅱ radio bursts do not improve the model predictions distinctly.4)If the sub-classification of type-Ⅱ radio bursts is considered as the model constraint,the CMEs associated with multi-band type-Ⅱ radio bursts have better model predictions than those with single-band events.For example,m-DH-km type-Ⅱ radio bursts have lower FR(35.4％)and higher HR(48％),and the accuracy of empirical model is higher.In summary,we find that in addition to the velocity and angular width of CME,the associations of pre-CME,type Ⅱ radio bursts and their enhancement,and multi-band sub-classification are the favorable conditions for CME to generate SEP events.The SEP intensities obtained by the empirical model have better consistency with the observations,and better predictions can be obtained.This investigation indicates that SEP events are more likely generated by fast and wide CMEs accompanied by pre-CMEs,multi-band type Ⅱ radio bursts and their enhancements,which seem to serve as discriminative signal for SEP-rich and SEP-poor CMEs.
维普
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