一种改进的Kp指数现报模式

An Improved Algorithm for Nowcast of Kp Index

在评估国际常用Kp指数现报模式Takahashi及其应用于中国地磁台站效果的基础上,提出了一种改进的地磁Kp指数现报模式,其可以有效识别地磁规则日变化的逐日变化特性,反映地磁扰动的季节效应和地方时效应,从而提升了Kp指数现报的准确性.采用Takahashi模式开发时所使用的台站数据进行对比,新模式将单站地磁Kp指数现报效率由0.77提升至0.84,多站联合Kp指数现报效率由0.88提升至0.92;采用2000—2006年北京十三陵台站(BMT,磁纬29°N)数据进行评估,Kp指数现报效率由0.70提升至0.80.对Kp指数现报结果的误差分析发现,现报误差存在明显的地方时差异和一定的季节差异,误差随扰动强度变化并在中强磁扰时最大.利用SuperMAG的指数分析表明,Kp台站的经度不均匀分布会对现报效果造成一定影响.

The planetary three-hour-range Kp index is widely used in space weather services.Due to the two weeks＇ time delay of the release of Kp index,the real-time estimation of the Kp index becomes essential for space weather forecasting organizations.In this paper,an improved algorithm for real-time Kp estimation on the basis of Takahashi＇s procedure was developed.The new algorithm improved the accuracy of Kp estimation by distinguishing the day-to-day variations of geomagnetic field＇s regular variation and taking account of both the diurnal and seasonal variations of magnetic disturbance.The statistical result shows that the Prediction Efficiency（PE） increased from 0.77 to0.84 using Fredericksburg＇s data,from 0.88 to 0.92 using the nine stations network＇s data.Using the data from Beijing Ming Tombs observatory（BMT） from 2000 to 2006,the PE increased from 0.70 to 0.80 compared with the Takahashi procedure.The error of the estimations differs from universal time,season and the scale of magnetic disturbance.The RMS error reached maximum for Kp = 7.Analysis of Kp using the SuperMAG indices indicated that the asymmetric distribution of Kp stations affects the Kp nowcast performance.