We report infrared observations of the microquasar GRS 1915+105 using the NICMOS instrument of the Hubble Space Telescope during 9 visits in April-June 2003. During epochs of high X-ray/radio activity near the beginning and end of this period, we find that the $1.87 $um infrared flux is generally low ($sim 2$ mJy) and relatively steady. However, during the X-ray/radio ``plateau state between these epochs, we find that the infrared flux is significantly higher ($sim 4-6$ mJy), and strongly variable. In particular, we find events with amplitudes $sim 20-30$% occurring on timescales of $sim 10-20$s (e-folding timescales of $sim 30$s). These flickering timescales are several times faster than any previously-observed infrared variability in GRS 1915+105 and the IR variations exceed corresponding X-ray variations at the same ($sim 8s$) timescale. These results suggest an entirely new type of infrared variability from this object. Based on the properties of this flickering, we conclude that it arises in the plateau-state jet outflow itself, at a distance $<2.5$ AU from the accretion disk. We discuss the implications of this work and the potential of further flickering observations for understanding jet formation around black holes.
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