SMALL $H_3^+$ EMISSION PATCHES IN THE VICINITY OF JUPITER'S AURORAL REGIONS

We examined a total of 166 images of $3.5{\mu}m\;H_3^+$ emission in the auroral regions of Jupiter observed with the Protocam on IRTF in 1991 and 1992, and found that 30 images contain a clearly isolated small emission patch in the vicinity of the northern auroral regions. Two different time sequences of the images show the small patches at the dusk limb in the range of System III longitudes from $270^{\circ}\;through\;0^{\circ}\;to\;90^{circ}$. The small patches in one sequence of the images, which were taken at 10 phase between $240^{\circ}\;and\;260^{\circ}$, may be related to the 10 flux tube, similarly suggested by Connerney et al. (1993). However, the small patches in the other sequence are separated from Io as much as $80^{\circ}$ in longitude. The positions of the small patches in both sequences are deviated equatorward from the 10 footprint oval by $5^{\circ}-8^{\circ}$ latitude in the longitudinal range of $270^{\circ}-360^{\circ}$. A significant modification is required in current Jovian magnetic field models near the Jupiter's surface if the small patches are produced at the foot of the 10 flux tube.