资源环境科技发展态势分析平台

Magnetosheath high-speed jets-localized dynamic pressure enhancements typically of similar to 1 Earth radius in size-impact the dayside magnetopause several times per hour. Here we present the first in situ measurements suggesting that such an impact triggered magnetopause reconnection. We use observations from the five Time History of Events and Macroscale Interactions during Substorms spacecraft in a string-of-pearls configuration on 7 August 2007. The spacecraft recorded magnetopause in-and-out motion during an impact of a magnetosheath jet (V-N similar to -300km/s along the magnetopause normal direction). There was no evidence for reconnection for the preimpact crossing, yet three probes observed reconnection after the impact. We infer that the jet impact compressed the originally thick (60-70 d(i)), high magnetic shear (140-160 degrees magnetopause until it was thin enough for reconnection to occur. Magnetosheath high-speed jets could therefore act as a driver for bursty dayside reconnection.