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R. R. Howell, A. Grocholski, J. L. Gregg, C. Crumrine (U. of Wyoming)
During late May of 1998 one of the periodic brightenings of Loki began and continued till early January of 1999. It was one of the best documented of these brightenings, occurring during the Galileo mission and during a period of intense ground-based monitoring. It was also one of the longer-lived such events, although it reached a somewhat lower flux level than previous brightenings. The figure below shows the 3.44 micron flux as measured using the Jupiter occultation technique. Those measurements show a turn-on transient lasting approximately one month, followed by approximately five months of steady brightness, then finally what may be a turn-off transient lasting an additional month. In addition to these data, observations were also obtained at longer wavelengths using eclipse photometry and also using the occultation technique at 10 microns. Such a multi-wavelength suite of data allows a detailed examination of the nature of the activity. The flow rate required to match the 3.44 micron data, assuming a simple spreading lava flow, is 1100 square meters per second during the initial phase, and 600 during the steady phase. That “source function” can be used to predict the expected flux at longer wavelengths using simple flow models. Such detailed modeling is now underway and the comparisons between those models and the measurements will allow quantitative tests of the simple flow models and also other models for the nature of the Loki brightenings.
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