ISSN:
1573-093X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract The apparent brightnesses of Titan and Neptune, near 4718 Å and 5508 Å, have changed by up to 10% and 3% respectively since 1972, and are highly correlated, with the variations at Titan apparently lagging those at Neptune by approximately six months. Since these changes are larger than any plausible solar variation in visible light, the implied cause is an intrinsic albedo change resulting from an externally driven alteration in atmospheric chemistry. Such an alteration could result from solar emissions in UV/EUV or the infrared - where large changes are suspected to exist, or from energetic particle precipitation modulated by the solar wind. It is found that traditional solar indices (10.7 cm radio flux, sunspot number, etc.) do not directly measure the causative process, as they tend to lag the brightness variations in phase. Conversely, solar EUV and some characteristics of the solar wind correlate well with the brightness variations and lead those variations in phase. We believe that either feature could be the cause of the albedo changes, but that too little is known both of the observable brightness changes and of the atmospheric chemistry of Titan and Neptune to make a definitive conclusion.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00156877
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