HR: 0830h
AN: U31B-0009    [PDF]
TI: Auroral Infrasound Observed at I53US at Fairbanks, Alaska
AU: Wilson, C R
EM: crw@gi.alaska.edu
AF: Geophysical Institute, 903 Koyukuk Dr., Fairbanks, AK 99775-7320 United States
AU: * Olson, J V
EM: jvo@gi.alaska.edu
AF: Geophysical Institute, 903 Koyukuk Dr., Fairbanks, AK 99775-7320 United States
AB: In this presentation we will describe two different types of auroral infrasound recently observed at Fairbanks, Alaska in the pass band from 0.015 to 0.10 Hz. Infrasound signals associated with auroral activity (AIW) have been observed in Fairbanks over the past 30 years with infrasonic microphone arrays. The installation of the new CTBT/IMS infrasonic array, I53US, at Fairbanks has resulted in a greatly increased quality of the infrasonic data with which to study natural sources of infrasound. In the historical data at Fairbanks all the auroral infrasonic waves (AIW) detected were found to be the result of bow waves that are generated by supersonic motion of auroral arcs that contain strong electrojet currents. This infrasound is highly anisotropic, moving in the same direction as that of the auroral arc. AIW bow waves observed in 2003 at I53US will be described. Recently at I53US we have observed many events of very high trace velocity that are comprised of continuous, highly coherent wave trains. These waves occur in the morning hours at times of strong auroral activity. This new type of very high trace velocity AIW appears to be associated with pulsating auroral displays. Pulsating auroras occur predominantly after magnetic midnight (10:00 UT at Fairbanks). They are a usual part of the recovery phase of auroral substorms and are produced by energetic electrons precipitating into the atmosphere. Given proper dark, cloudless sky conditions during the AIW events, bright pulsating auroral forms were sometimes visible overhead.
DE: 3384 Waves and tides
DE: 3399 General or miscellaneous
DE: 7209 Earthquake dynamics and mechanics
SC: U
MN: 2003 Fall Meeting