The decrease in magnetic field strength measured by Rosetta's RPC-MAG instrument during the outburst event on 29 July 2015. This is the first time a 'diamagnetic cavity' has been detected at Comet 67P/Churyumov–Gerasimenko and is thought to be caused by an outburst of gas temporarily increasing the gas flux in the comet's coma, and pushing the pressure-balance boundary between it and incoming solar wind farther from the nucleus than expected under 'normal' levels of activity. Credit: ESA/Rosetta/RPC/IGEP/IC
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