Quantitative Performance Assessment Of Recent Empirical Geomagnetic Field Models In Outer Radiation Belt Zone

Accuracy of geomagnetic field model has key importance for the theoretical and operational studies about radiation belt. Using magnetic field data measured by Van Allen Probes (VAP) from 2012 to 2018 and GOES15 from 2011 to 2017, this paper quantitatively evaluates performances of three newer empirical external magnetic field models (TS05, TA15, and TA16) in the outer radiation belt (3 similar to 6.6R(E)). The prediction efficiency (PE) is chosen as a measure to quantitatively assess models' performance in various spatial ranges (Lm), under different geomagnetic conditions (Kp), and along with magnetic local time (MLT). Also, theta (the angle between the observed and estimated magnetic field vector) is calculated to evaluate the model's ability to predict the direction of the magnetic field. The results show that with increasing Lm and disturbed level of geomagnetic field, the PE decreases and the 0 increases. The PE at MLT=12-21 is smaller than MLT = 0 - 9 in the range of Lm = 5 similar to 6.5R(E), showing a dawn-dusk asymmetry and indicating that the three magnetic field models can describe the strength of the magnetic field in the dawn sector better than in the sector from afternoon to dusk; at the geosynchronous orbit (Lm similar to 6.6R(E)), PE at MLT=9-15 is greater than at other local times, the day-night asymmetry indicates that the three magnetic field models can well estimate the magnitude of the magnetic field in the dayside, but they may have noticeable errors on the nightside. The theta at MLT = 6 - 12 is smaller than at other local times, showing a day-night asymmetry and indicating that the three magnetic field models can better describe the geomagnetic field configuration in the dayside, but they may have noticeable errors in the nightside. Within the range of Lm similar to 3 similar to 6.5RE, the estimations of TA16 are the closest to the observations from VAP, with PE>0.7 and theta<3 degrees; at the geosynchronous orbit (6.6R(E)), the estimation of TS05 model is the closest to the observations from GOES15 with PE of about 0.75 and theta of about 7 degrees. The relevant research results can provide references for the selection of geomagnetic field models for the on-orbit cross calibration of energetic particles for Chinese spaceborne energetic particle detectors, the study of the dynamic model of energetic particles in the radiation belt, and related theory/application research of the magnetospheric environment.