When
3:30 p.m., Feb. 12, 2008
Where
Kuiper Space Sciences 308
Dr. William Hubbard, LPL, will discuss: “MMT Observations of Breaking Internal Gravity Waves in Pluto's Sub-microbar Atmosphere.”
Abstract:
An Arizona-MIT team observing on the MMT on Mt. Hopkins recorded a grazing occultation of a star by Pluto on 2007 March 18 at unprecedented signal-to-noise. Data taken simultaneously at 1.6 micrometers (H band) and in the red end of the visible band (about 0.8 micrometers) show large-scale, nearly limb-aligned density fluctuations in Pluto’s atmosphere over a pressure range of ~0.1-0.7 microbars (0.01 to 0.07 Pa; radius range of 1500 to 1350 km). The features are fully resolved and, importantly, achromatic. Their vertical wavelength increases with height, suggesting that a high-frequency cutoff operates on a spectrum of internal gravity waves generated deeper in Pluto’s atmosphere. The data are in agreement with the theory of breaking gravity waves. The waves, which are potentially observable by New Horizons, are perhaps generated by interactions of the atmosphere with Pluto's surface.
Refreshments will be served at 3:15 p.m. in the Atrium.
Abstract:
An Arizona-MIT team observing on the MMT on Mt. Hopkins recorded a grazing occultation of a star by Pluto on 2007 March 18 at unprecedented signal-to-noise. Data taken simultaneously at 1.6 micrometers (H band) and in the red end of the visible band (about 0.8 micrometers) show large-scale, nearly limb-aligned density fluctuations in Pluto’s atmosphere over a pressure range of ~0.1-0.7 microbars (0.01 to 0.07 Pa; radius range of 1500 to 1350 km). The features are fully resolved and, importantly, achromatic. Their vertical wavelength increases with height, suggesting that a high-frequency cutoff operates on a spectrum of internal gravity waves generated deeper in Pluto’s atmosphere. The data are in agreement with the theory of breaking gravity waves. The waves, which are potentially observable by New Horizons, are perhaps generated by interactions of the atmosphere with Pluto's surface.
Refreshments will be served at 3:15 p.m. in the Atrium.
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