地磁场强度对赤道电激流的地方时和经度分布的影响

本文利用秘鲁和印度地磁台站的观测数据，结合全球电离层-热层模型的模拟结果，研究了地磁场强度的减弱对赤道电激流的地方时和经度分布的影响.这对理解地球空间天气和行星演化具有重要的科学意义.结果表明，当地磁场强度减弱一半时，东向电激流和风发电机电场的峰值时间均提前1 h，而低层大气潮汐使峰值时间延后了1 h.其主要原因是，随着地磁场减弱，E层当地激发和来自低层大气迁移潮汐的上传过程均发生了变化.当磁场减弱50%时，电离层Cowling电导率增加为真实地磁场条件下的3倍，而峰值电激流增加为真实地磁场条件下的1.3倍，这与理论值比较接近，但明显弱于秘鲁和印度地磁台站的长期观测结果.与印度扇区相比，秘鲁扇区的电流随地磁场的减少趋势更加明显，说明地磁场强度的变化对秘鲁扇区的影响更大.磁场强度的减弱对低层大气非迁移潮汐DE3和SE2分量的上传影响并不明显，但增强了电离层E区一波和三波分量的幅度，这导致经度90°和120°的电流峰值随着地磁场的减弱而明显增加.

Effects of geomagnetic field on the local time and longitudinal variations in the equatorial electrojet

The influences of the changes in the geomagnetic field intensity on the local time and longitudinal distributions of the equatorial electrojet(EEJ)are investigated using ground observations and Thermosphere-Ionosphere-Electrodynamics General Circulation Model(TIE-GCM)simulations.When the intensity of the geomagnetic field decreases by half,both the modeled peak EEJ and dynamo electric field occur 1 h earlier.With the low atmospheric tidal input,the peak EEJ shifts 1 h later.This local time shift is due to the fact that the local generation in the E region and the up-propagation of the migrating tides from the lower atmosphere change with the reduced magnetic field.The modeled peak EEJ increases by a factor of 1.3 when the magnetic field is weakened by 50%,which is lower than the observed values at the Peruvian and Indian geomagnetic stations.When the magnetic field is reduced by half,the ionospheric Cowling conductance in the model is about 3 times greater than that of the current true magnetic field.The increase in the observed EEJ intensity with declining magnetic field is more prominent in Peru than in India.The weakening of the magnetic field has little effect on the upward propagation of the DE3 and SE2 components in the lower atmosphere,but it increases the wave-1 and wave-3 components in the model.This causes the peak EEJs at longitudes of 90°and 120°in the model to increase as the magnetic field weakens regardless of the lower atmospheric tidal input.