Publication Abstracts

Li et al. 2004

Li, L., A.P. Ingersoll, A.R. Vasavada, C.C. Porco, A.D. Del Genio, and S.P. Ewald, 2004: Life cycles of spots on Jupiter from Cassini images. Icarus, 172, 9-23, doi:10.1016/j.icarus.2003.10.015.

Using the sequence of 70-day continuum-band (751 nm) images from the Cassini Imaging Science System (ISS), we record over 500 compact oval spots and study their relation to the large-scale motions. The ∼100 spots whose vorticity could be measured — the large spots in most cases — were all anticyclonic. We exclude cyclonic features (chaotic regions) because they do not have a compact oval shape, but we do record their interactions with spots. We distinguish probable convective storms from other spots because they appear suddenly, grow rapidly, and are much brighter than their surroundings. The distribution of lifetimes for spots that appeared and disappeared during the 70-day period follows a decaying exponential with time constant (mean lifetime) of 3.5 days for probable convective storms and 16.8 days for all other spots. Extrapolating the exponential beyond 70 days seriously underestimates the number of spots that existed for the entire 70-day period. This and other evidences (size, shape, distribution in latitude) suggest that these long-lived spots with lifetime larger than 70 days are from a separate population. The zonal wind profile obtained manually by tracking individual features (this study) agrees with that obtained automatically by correlating brightness variations in narrow latitude bands (Porco et al., 2003). Some westward jets have developed more curvature and some have developed less curvature since Voyager times, but the number of westward jets that violate the barotropic stability criterion is about the same. In the northern hemisphere the number of spots is greatest at the latitudes of the westward jets, which are the most unstable regions according to the barotropic stability criterion. During the 70-day observation period the Great Red Spot (GRS) absorbed nine westward-moving spots that originated in the South Equatorial Belt (SEB), where most of the probable convective storms originate. Although the probable convective storms do not directly transform themselves into westward-moving spots, their common origin in the SEB suggests that moist convection and the westward jet compose a system that has maintained the GRS over its long lifetime.

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BibTeX Citation

  author={Li, L. and Ingersoll, A. P. and Vasavada, A. R. and Porco, C. C. and Del Genio, A. D. and Ewald, S. P.},
  title={Life cycles of spots on Jupiter from Cassini images},

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RIS Citation

ID  - li04200b
AU  - Li, L.
AU  - Ingersoll, A. P.
AU  - Vasavada, A. R.
AU  - Porco, C. C.
AU  - Del Genio, A. D.
AU  - Ewald, S. P.
PY  - 2004
TI  - Life cycles of spots on Jupiter from Cassini images
JA  - Icarus
VL  - 172
SP  - 9
EP  - 23
DO  - 10.1016/j.icarus.2003.10.015
ER  -

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