CEDAR 2008 Workshop
Observations at the Plasmaspheric Boundary
Layer with the Mid-latitude SuperDARN radars
Mike Ruohoniemi, Ray Greenwald, and Jo Baker
Department of Electrical and Computer Engineering
Virginia Tech
Blacksburg, VA
Elsayed Talaat and Rob Barnes
The Johns Hopkins University Applied Physics Laboratory
Laurel, MD
Mid-Latitude SuperDARN
Radar builds
– Wallops Island, VA
(2005)
– Hokkaido, Japan
(2006)
– Blackstone, VA
(2008)
Space Weather: Storm-time Expansion of
Ionospheric Electric Fields
Beam 4
12
15
18
June 12,2005
21
00
03
06 UT
June 13, 2005
Doppler time series on northerly directed beam shows equatorward expansion of highlatitude convection to =53. Velocities in excess of 1600 m/s were observed.
Dusk Sector Subauroral Irregularities Near Plasmapause Boundary
Production mechanism
F-region gradient drift inst.
Two-Dimensional Image of SAPS and
SAID (Scan Duration = 49 seconds)
Midnight Sector Subauroral Irregularities Near
Plasmapause Boundary
Wallops Island Radar May 5, 2006 ~0400 UT
Geomagnetic Coordinates Kp=3
=60
=50
Dawn Sector Subauroral Irregularities Near
Plasmapause Boundary
The Quiescent State - Nighttime
Continuous scatter
throughout
nighttime hours
Low Doppler
velocities except for
one brief period
Low spectral widths
Examples of Ionospheric Scatter
From Plasmasphere Boundary Layer
1
2
1
1
1
1
1
2
1
4
3
4
Jan 21, 2006
Beam 4
Jan 22, 2006
Beam 4
Jan 23, 2006
Beam 4
6+
7
8-
6+
Sept 11, 2005
Beam 1
Sources of Ionospheric Irregularities
• Mid to high-latitudes
– Magnetospheric plasma circulation, horizontal electrondensity gradients, Birkeland currents, shear flows,
horizontal temperature gradients.
– Relevant instability processes.
• Gradient Drift instability {E and F region}
• Two-stream instability {E-region}
• Electrostatic Ion Cyclotron instability {E and F region}
• Temperature Gradient instability {F region}
• Kelvin-Helmholtz instability {F region}
• Others ????
Millstone/Wallops Experiment to Identify Source of
Subauroral Irregularities
Wallops: 16 beam Doppler velocity
scan. Millstone Hill is along beam
indicated by the arrow.
MHO: 34 az, (18/28/48 el) + zenith
focused on 55-60 inv @ 300 km
Wallops HF Radar Measurements Along Viewing
Azimuth of Millstone ISR
Millstone Hill Plasma Parameters
22-23 February 2006 2300–0430 UT
Log(Ne)
Zenith
54 inv
Te
Zenith
54 inv
Log(Ne)
48 el
55.5 inv
Te
48 el
55.5 inv
Log(Ne)
28 el
57.0 inv
Te
28 el
57.0 inv
Log(Ne)
18 el
58.2 inv
Te
18 el
58.2 inv
Temperature Gradient Instability is Source of
Plasmapause Irregularities
Sequence of Events
22-00 UT: Poleward motion of ocean scatter
footprint following sunset.
00-0120 UT: Irregularities form in post-sunset
ionosphere. Possibly associated with F-region
gradient-drift instability as reported previously.
0120 UT onwards: Temperature gradient
reverses and steepens. Backscatter intensifies.
Onset of TGI.
Substorm Impacts on the Inner Magnetosphere
•
How do substorms affect inner magnetosphere convection?
• Do substorms contribute to penetration electric fields?
• What types of velocity changes occur?
• What is the local time extent of the effects?
• What are the time delays?
• What is their duration?
Magnetic Observations on April 25, 2008
Kp=3
GOES 12
St. John
Ottawa
Observations with the mid-latitude SuperDARN radars
•
•
•
•
•
Dramatic space weather is observed as the expansion of stormtime electric fields to mid-latitudes
Under less disturbed conditions strong electric fields are
observed in SAPS/SAID events at the equatorward boundary
of the oval
Unexpected sources of irregularities populate the mid-latitude
ionosphere during quiet times – these appear to be associated
with the plasmapause
The plasmapause electric fields, while comparatively small,
exhibit transient behavior
Next step – more extended observations at mid-latitudes to
address the dynamics of the plasmapause and inner
magnetosphere
Mid-Latitude SuperDARN Chain