资源环境科技发展态势分析平台

A new type of polar cap aurora observed in ~ 1500MLT sector, abbreviated as 15MLT‐PCA, is identified on examining the long‐term spectrographic imager observations on the DMSP satellite over the Nothern Hemisphere. Apparent dependencies of 15MLT‐PCA on the solar cycle, season, universal time, and interplanetary magnetic field (IMF) are presented, which indicate that the 15MLT‐PCA occurs in the northern summer under conditions of large dipole tilt angle, long‐lasting positive IMF B_y, and predominant negative B_x. The IMF B_z and other solar wind conditions show less control over the occurrence of 15MLT‐PCA. The particle precipitations of 15MLT‐PCA show magnetosheath‐like or mantle‐like properties with the ions showing clear energy dispersion property. We suggest that the 15MLT‐PCA is caused by reconnection between a twisted lobe field line and an anti‐sunward IMF field line, which differs from the mechanism for High‐latitude dayside aurora (HiLDA) that share some common observational features with the 15MLT‐PCA.