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 EngineeringVirginia TechBlacksburg, VA

Elsayed Talaat and Rob Barnes

The Johns Hopkins University Applied Physics LaboratoryLaurel, 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

12 15 18 21 00 03 06 UT

June 12,2005 June 13, 2005

Beam 4

Doppler time series on northerly directed beam shows equatorward expansion of high-latitude convection to =53. Velocities in excess of 1600 m/s were observed.

Dusk Sector Subauroral Irregularities Near Plasmapause Boundary

Two-Dimensional Image of SAPS and SAID (Scan Duration = 49 seconds)

Production mechanismF-region gradient drift inst.

Midnight Sector Subauroral Irregularities Near Plasmapause Boundary

=60

=50

Wallops Island Radar May 5, 2006 ~0400 UTGeomagnetic Coordinates Kp=3

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

7 8-6+ 6+

1 4 3 4

1 1 1 2

1 2 1 1Jan 21, 2006

Beam 4

Jan 22, 2006Beam 4

Jan 23, 2006Beam 4

Sept 11, 2005 Beam 1

Sources of Ionospheric Irregularities

• Mid to high-latitudes– Magnetospheric plasma circulation, horizontal electron-

density 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

MHO: 34 az, (18/28/48 el) + zenith focused on 55-60 inv @ 300 km

Wallops: 16 beam Doppler velocity scan. Millstone Hill is along beam indicated by the arrow.

Wallops HF Radar Measurements Along Viewing Azimuth of Millstone ISR

Millstone Hill Plasma Parameters 22-23 February 2006 2300–0430 UT

TeZenith54 inv

Te48 el55.5 inv

Te28 el57.0 inv

Te18 el58.2 inv

Log(Ne)Zenith54 inv

Log(Ne)48 el55.5 inv

Log(Ne)28 el57.0 inv

Log(Ne)18 el58.2 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, 2008Kp=3

GOES 12

Ottawa

St. John

Observations with the mid-latitude SuperDARN radars

• Dramatic space weather is observed as the expansion of storm-time 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