hui-xuan qiu1, de-sheng han1✉, hui-ting feng1, run shi1, su zhou2, and y-l.zhang3
1 state key laboratory of m arine geology, school of ocean and earth science, tongji university, shanghai, china
2 school of electronics and com m unication engineering, guiyang university, guiyang,china
3 the johns hopkins university applied physics laboratory, laurel, m d, usa
✉email: handesheng@ tongji.edu.cn
abstract：
taking advantage of the high spatial-resolution and global coverage of dmsp/ssusi observations, we investigated the critical interplanetary factors in controlling the cusp auroral emission by dividing the midday auroras into the gap (weak emission) and non-gap (intense emission) events. although the cusp auroral intensity is essentially determined by a parameter related to the imf direction, imf magnitude (|by|),and solar wind speed (v), we found that the cusp aurora is statistically weak during the southward imf but intense when the v and imf |by| are greater. further, we confirmed that even with v > 600km/s, the intense-aurora event still shows a minimum occurrence near the imf |by| = 0. however, when the imf |by| is greater, the v becomes less significant for the intense-aurora occurrence. these results demonstrate that the imf |by| is critical in controlling the cusp auroral intensity, most likely by producing an electricfield through.
