Two Classes of Auroral Infrasound at I53US

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Two Classes of Auroral Infrasound at I53US

• By Charles R. Wilson, John V. Wilson, Curt
  Szuberla and Daniel L.Osborne,
• Geophysical Institute, University of Alaska,
  Fairbanks AK

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Huge AIW Bow Wave signal at I53US at1549 UT,
04/14/03 during magnetic storm
Trace velocity 0.602 km/s, Az 276 deg, Cij
0.916
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Uncertainty in Vel and Theta for AIW at I53US
April 14,2003,(Dr.Curt Szuberla)
Vel 614 m/sec /- 60 m/sec
Azimuth 276.5 /- 5.8 deg.
Uncertainty Ellipse in Velocity Space
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Three component Magnetometer traces at Fairbanks
April 14, 2003 Strong magnetic bay at 1200 to
1600 UT
Time of Huge AIW
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All-SKY camera images at 30 second intervals at
Fairbanks
Zenith crossing At 0951 UT
AIW Bow wave at 0959 UT
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Bow Wave model for AIW signals fromsupersonic
aurora electrojet arcs
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(I53US)
Inuvik N.W.T.
Auroral Oval
Azimuths of arrival of AIW at each hour of UT at
I53US
Direction of supersonic motion of Source auroral
arcs for AIW as a Function of UT time
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MCCM
AIW signals
Trace velocity
Azimuth of arrival
April 14,2003 auroral infrasound event of AIW
Bow-Wave Type
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Vel 1.03 km/s
AZ 347 deg.
Vel 0.875 AZ 316
Vel 0.643 AZ 283
Vel 0.871 AZ 280
April 14, 2003 AIW associated with
auroral-electrojet supersonic motions
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Azimuth versus Trace velocity In meters/sec
AIW Bow Wave Signals
Mean trace velocity for Bow Wave AIW Signals is
0.865 km/sec
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New Type of Pulsating Aurora AIW

• Pulsating Aurora
• An Example of a Typical All Sky TV Camera Capture
  of Pulsating Aurora. Image Circle Is About 160
  Degrees Edge to Edge (fisheye lens). Images are
  played in real speed, at 15 fps, the BW image
  utilizes all visible light.

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Pulsating Aurora from GI/UAs Ester Dome
Observatory
East
West
North
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Three images of pulsating Aurora patches above
I53US On March 6, 2003 , images taken At 20
second intervals at 1225 to 1226 UT
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Vel 1.213 Az 144 deg
Peak-to-peak amplitude 0.3 Pascal
I53US Pulsating Aurora Infrasound March 06,
2003, 1225 to 1243 UT
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abs(fft) March 6 P-AIW signal
44.8 sec
32.2 sec
20.8 sec
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Vel 1.517 km/sec Az 202 deg.
P-AIW from March 06, 2003 at I53US 1600 to 1620
UT
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MCCM detector output for March 6, 2003at I53US
showing both MAW from 180 degand high velocity
P-AIW signals from all azimuths
MCCM
MAW signals
High Velocity P-AIW signals
Velocity
Azimuth
MAW signals
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East
North
South
West
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MAW at I53US 03/06/2003 2000 to 2020 UT
March 6,2003, 2000 to 2020 UT
Simultaneous MAW Event
Velocity 0.497 km/sec, Az 181
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Trace velocity m/sec versus Azimuth for MAW And
for high velocity P-AIW signals 06/03/2003
MAW
P-AIW
P-AIW
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Other high velocity infrasound putative pulsating
aurora events

• Two examples, on Dec 15 and 25, 2002 at I53US,of
  infrasonic signals during magnetic storm/auroral
  events with the same signal characteristics of
  very high trace velocity, widely scattered
  azimuth of arrival, and similar spectra. There
  was no photographic aurora data available of
  visible pulsating auroral patches during these
  two events.

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15 December
Phase-aligned 0verlay All 8 sensors
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abs(fft) Dec 15 P-AIW signal
41.5 sec
31.2 sec
25.4 sec
17.5 sec
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Uncertainty in Velocity and Azimuth for
highvelocity auroral infrasound event Dec 15,2002
Vel 2.941 km/sec /- 0.938 km/sec
Azimuth 130 /- 17 deg.
Uncertainty Ellipse in Velocity Space
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MCCM
Trace Velocity Km/sec
Azimuth
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East
North
South
West
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Phase-Aligned Pulsating Aurora Infrasound I53US
12/15/02twenty minutes of data at 12,15,18 and
21 hours UT
Vel
3.35 km/sec
Az 127
Vel
5.26 km/s
Az 171
Vel 1.48 km/s
Az 229
Vel 1.00 km/s
Az 129
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Auroral Infrasound signal azimuths observed at
Pullman Washington, Boulder Colorado and
Washington DC Thousands of kilometers away from
the source region