Abstract
Abstract Position measurements of the Great Red Spot (GRS) on recent digital images of Jupiter were carried out to detect the longitudinal and latitudinal motion of the GRS. Its longitudinal oscillating motion may be interpreted as two types. One has a 57-day period and no latitudinal motion, the other has 86 days and probably has latitudinal motion. In 86 days, oscillation, the GRS seems to locate equatorward when it moves relatively westward, and poleward when it moves eastward. Numerical Experiments of the Intermediate Geostrophic (IG) equation show the same results for the motion of an eddy, and that a kind of wave collides with the eddy when it changes relative longitudinal motion from eastward to westward.
Highlights
The longitudinal oscillating motion of the Great Red Spot (GRS) was found by a team from the New Mexico State University around 1970
The 57-day period component and the 86 days are suggested in the oscillating motion of the GRS of Jupiter
Our observation results of 86 days and the numerical experiments suggest that when the GRS moves westward, the latitude of the GRS is relatively low, and that when it moves eastward, the latitude is high
Summary
The longitudinal oscillating motion of the Great Red Spot (GRS) was found by a team from the New Mexico State University around 1970. Asada (1985a) speculated that an eddy oscillated in the latitudinal direction around the latitude of a peculiar westward zonal flow and that this latitudinal motion caused the longitudinal motion due to the zonal flows around the GRS. The amplitude of oscillating motion, 0.8 degree, corresponds to 0.3 arcsec at the disc center of the Jovian image, if the apparent diameter is 42 arcsec. The longitude decreased 2 or 3 degrees in 30 or 40 min This is because the limb or terminator was clicked inner than the actual and the diameter was estimated to be smaller. The measurements of the markings’ position were carried out for longitudes of the east (proceeding) end and west (following) end, and for latitudes of the north and south ends. We made a formal Fourier transformation as follows: ak
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