Methods for estimating regional auroral electron energy deposition from ground-based optical measurements.
Tuesday, September 29, 2015
Donald L Hampton1, Mark Conde2, Michael Jason Ahrns1, Kristina A Lynch3, Matthew D Zettergren4, Stephen Roland Kaeppler5 and Michael J Nicolls5, (1)University of Alaska Fairbanks, Fairbanks, AK, United States, (2)University of Alaska Fairbanks, Space Physics, Fairbanks, AK, United States, (3)Dartmouth College, Hanover, NH, United States, (4)Embry-Riddle Aeronautical Univ, Daytona Beach, FL, United States, (5)SRI International Menlo Park, Menlo Park, CA, United States
Abstract:
Auroral electron precipitation forms a complex and dynamic energy input into the high-latitude ionosphere and thermopshere. Rapid changes in plasma density due to electron impact ionization create correspondingly rapid changes in conductivity which in turn change the magnitude and altitude profile of magnetospheric current closure in the E- and F-region. Modeling these changes in the ionosphere and their effects on current closure requires detailed input over wide regions. In support of the AMISR PINOT campaign and several rocket campaigns (CASCADES-2, MICA, ASSP) we have investigated several methods using purely ground-based optical measurements to determine the characteristics of auroral input in geometries away from magnetic zenith. The use of the N2+ first negative emissions at 427.8 nm reproduces the total energy flux over a wide region, but alone does not indicate the altitude profile of this energy deposition. Determining the energy distribution of the precipitating electrons via automation has been more difficult, especially when observing away from magnetic zenith. The method makes use of the temperature variations observed in a wide-field Fabry-Perot interferometer (Scanning Doppler Imager, SDI) when observing the atomic oxygen green-line emission (557.7 nm). The rapid variations in temperature observed by the SDI during active aurora is due to variations in emission altitude (due to average energy variations) sampling along the steep temperature curve of the lower thermosphere. By comparing the measured temperature to a model temperature profile (MSIS) the emission altitude is found and matched to emission profiles calculated with an electron transport code. Comparing both methods to in-situ and ISR measurements show that the profile method is more accurate, but is harder to automate. A successful automated method for producing energy deposition maps of reasonable resolution over a wide geographic area will certainly require a hybrid of ground-based and orbital optical data as well as in-situ particle measurements, and ISR data.
