A DISTURBANCE IN JUPITER HIGH-SPEED NORTH TEMPERATE JET DURING 1990

During February 1990 a remarkable disturbance developed in the strongest Jovian atmospheric jet located at ≈24°N planetographic latitude. Our telescopic images at visible wavelenghts revealed the outbreak of two bright features with an initial length scale ≈6000km, the first discovered on February 10 and the second a week later. Both resided on the peak of the eastward jet, drifting rapidly with zonal velocities of 165 and 170 m sec-1, respectively. To the west of these bright features a pattern of alternating dark and light spots developed over the next few days. These features moved with a lower mean velocity of 108 m sec-1 and had a mean east-west length of 10,000 km. Their separation in longitude showed a bimodal distribution with peaks at 12,600 and 19,700 km. The disturbance expanded zonally, encircling the whole latitudinal band at 24°N 3 months after its outburst, generating a new temperate belt. We suggest that the two bright spots were the result of a localized convective instability, while the dark spots may reflect a wave disturbance that was generated by the onset of convection. © 1991.