Start Date/Time: Tuesday, February 14, 2012, 3:30 PM
Ending Date/Time: Tuesday, February 14, 2012, 4:30 PM
Speaker: Dr. Kim Neilsen
Title: "Aeronomy in the Polar Regions"
The upper atmosphere, and near-space environment over the polar regions, are home to a variety of intriguing natural phenomena. The aurora is arguably the most beautiful of the phenomena, fascinating people from all over the world. Another spectacular event, thought for many years to be unique to the high latitudes, is night-shining Noctilucent Clouds (NLC). These clouds occur in the mesopause region at an altitude of 82 km, which sports the coldest environment in the Earth system during the polar summertime. In recent years, NLC sightings have exhibited an apparent progression towards mid-latitudes, which has generated speculation that they may be harbingers of global change in the mesosphere and lower thermosphere (MLT) region The much colder than expected mesopause hosting the NLC is known to be driven by wave dynamics, which transport energy and momentum into the MLT region via coupling with the lower atmosphere. A significant fraction of the propagating wave spectrum is capable of penetrating to higher altitudes, where they contribute significantly to the dynamical state of the thermosphere. In this presentation, I will give an overview of selected processes occurring in the polar mesosphere and thermosphere, and how they couple across atmospheric layers.