Photo Credit: Jan Curtis, UAF, GI |
CEDAR 2000 Workshop
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Photo Credit: NASA and Space Telescope Science Institute |
| Workshop Description
Aurora and airglow are optical emissions induced, directly or indirectly, by electron and ion precipitation and by photochemical processes, respectively. They are signatures of the atmospheric constituents and of the energetics that excite them. As a result, the analysis of airglow and aurora allows us to infer information on atmospheric composition, energy input to the atmosphere, and magnetospheric source regions. Validation of models and a better theoretical understanding of aurora and airglow on Earth have been achieved through numerous in-situ and remote sensing observations and via laboratoryexperiments. Airglow and auroral emissions have also been observed on other planets
and moons in the solar system. The expertise acquired in terrestrial
aeronomy can contribute significantly to studies of atmospheric emissions
on other worlds. At the same time, Earth's aeronomy can benefit from
the diversity encountered in probing similar processes throughout the solar
system. This workshop gives us an opportunity to see the context of terrestrial
optical issues from the view of comparative studies.
Workshop Report
The planets, moons and comets of the solar system offer a diverse set of emissions from atmospheres that are both similar to and remarkably different from the terrestrial system studied by the CEDAR community. To begin this first-of-its-kind workshop at CEDAR, Stan Solomon (University of Colorado) provided an overview of the many mechanisms that can excite airglow emissions, and of the physical parameters (e.g.,composition and temperature) that can be determined from optical signatures. Specific examples dealt with the 6300 Å and 5577 Å emissions that occur on Earth, Venus and Mars. Tom Slanger (SRI International) then presented sample observational results made possible by high spectral resolution methods using the new Keck telescope to observe new terrestrial bands and 5577 Å emission seen for the first time from Venus. Dirk Lummerzheim (Geophysical Institute) provided a transition to the study of aurora by showing how energetic electrons provoke strong ultraviolet emissions in the Earth's atmosphere and those of all the giant planets, of the non-magnetized Venus and of the jovian moon Ganymede. The companion issue of optical signatures produced by protons and heavy ions precipitating into planetary atmospheres was then treated both observationally and via modeling by Marina Galand. Harald Frey (Berkeley) then took the unifying theme of optical signals from a planet and generalized it to the topic of using such signatures to identify possible extra-terrestrial sites that could sustain life. Audience participation was active on this final topic and in the subsequent discussion of how planetary and terrestrial studies, when done in comparative mode, bring insights and context to atmospheric science investigations regardless of their location in the solar system. Encouraged by the number of participants and enthusiasm for more involvement by CEDAR colleagues, the convenors will set up a new website dealing with "Comparative Aeronomy in the Solar System". We will use the ~ 80 names and e-mail addresses provided by the workshop sign-up sheet for initial distribution of information. If you want to be added to the list and/or have suggestions and comments to make, please send information to mgaland at bu.edu. For more information about the CEDAR 2000 workshop and other CEDAR related topics, visit the CEDAR Homepage. |