Cross-satellite calibration of high-energy electron fluxes measured by FengYun-4A based on Arase observations

We use the High-energy Electron Experiments(HEP)instrument onboard Arase(ERG)to conduct an energy-dependent cross-satellite calibration of electron fluxes measured by the High Energy Particle Detector(HEPD)onboard FengYun-4A(FY-4A)spanning from April 1,2017,to September 30,2019.By tracing the two-dimensional magnetic positions(L,magnetic local time[MLT])of FY-4A at each time,we compare the datasets of the conjugate electron fluxes over the range of 245–894 keV in 6 energy channels for the satellite pair within different sets of L×MLT.The variations in the electron fluxes observed by FY-4A generally agree with the Arase measurements,and the percentages of the ratios of electron flux conjunctions within a factor of 2 are larger than 50%.Compared with Arase,FY-4A systematically overestimates electron fluxes at all 6 energy channels,with the corresponding calibration factors ranging from 0.67 to 0.81.After the cross-satellite calibration,the electron flux conjunctions between FY-4A and Arase show better agreement,with much smaller normalized root mean square errors.Our results provide a valuable reference for the application of FY-4A high-energy electron datasets to in-depth investigations of the Earth’s radiation belt electron dynamics.

On the possibility of predicting flare index and CME velocity using vector magnetograms

In this paper,106 active regions(ARs)in the visible solar hemisphere in solar cycle 24 whose maximum sunspot groups’areas were larger than 400μh were selected.The association of their flare index(Iflare),largest flare magnitude(Mflare),and fastest coronal mass ejection(CME)velocity(VCME)with the vector magnetic field parameters were examined,and attempts were made to predict Iflare,Mflare,and VCME using the vector magnetograms.Iflare and Mflare were found to have a good correlation with the total photospheric free magnetic energy density(Efree),the length of the magnetic neutral line with a steep horizontal magnetic gradient(LNL),and the area with strong magnetic shear(Aψ).Iflare and Mflare were also found to have a best correlation with Efree.However,VCME displayed a moderate correlation with these three magnetic field parameters with a best correlation with Aψ.Thus,Efree and Aψappear to be the best parameters that can be used to predict Iflare(Mflare)and VCME,respectively.Hence,the multiple linear regression fit is proposed more suitable to predict Iflare and Mflare because of the stronger forecasts obtained than those by the linear fit with one magnetic field parameter for Iflare and Mflare.However,the VCME forecasts are better obtained through the linear fit with Aψ.The majority of the ARs without any CMEs never produced any flare larger than X1.0 while having a relatively lower Efree,shorter LNL,and smaller Aψ.This suggests that the larger the largest flare in an AR is,the faster the fastest CME produced by the AR will be.