Plasmaspheric Bulge

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Ionospheric EffectsduringSevere Geomagnetic
StormsJohn FosterMIT Haystack Observatory
NASA CDAW Mar. 14, 2005
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Ionosphere / Storm Effects

• Ionospheric Conductivity (E F Region) Affects
  Magnetospheric Currents
• Cold Plasma Redistribution Alters I-T Flywheel
  Coupling and Energy Dissipation
• Cold Plasma in Msph Alters W-P Interactions
• Plasmaspheric Material Injected into Tail and
  Plasma Sheet as Erosion Plumes Enter Cusp
• I-M Coupling in SAPS Affects Ring Current
  Development

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Visualizing the Initial Stages of an Ionospheric
Storm
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GPS samples the ionosphere and plasmasphere to an
altitude of 20,000 km
TEC is a measure of integrated density in a 1 m2
column 1 TEC unit 1016 electrons m-2
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Stormtime Ionosphere

• The low and mid-latitude ionosphere is strongly
  perturbed during geomagnetic disturbances
• Low-latitude cold plasma is carried throughout
  the M-I system by disturbance electric fields.
• Storm Enhanced Density (SED) forms at Equatorward
  Edge of Ionospheric Trough
• Ionospheric conductance shapes magnetospheric
  electric fields (e.g. SAPS Sub-Auroral
  Polarization Stream)

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Todays Weather NEXRADObservations of Storm
Front over N. America
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Analysis Understanding are Well Developed
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Space Weather Storm Fronts (GPS TEC Observations)
Foster et al. GRL 2002
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IS Radar Observes Storm Enhanced Density
Millstone Hill IS Radar
Foster, JGR, 1993
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Ionos Storm Characteristics are Repeatable
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WG3 Questions Ionospheric Storms

• 1) What Happens during the first 60 min of a
  Storm?
• 2) What is the Source of the SED at Mid
  Latitudes?
• 3) What are the Impacts of Neutral Wind Effects?
• 4) How is the Plasma Bulge Created?
• 5) Can Models Describe the O/N2 Changes?
• 6) Why is there a Longitude Dependence of the TEC
  response to storms?

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WG3 Data Sets Characterize Ionospheric Effects
and Address the Mechanisms Behind Them
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Spin Up of Neutrals in E Region during
SuperstormsMillstone Hill Lower Thermosphere
Observations
Goncharenko et al, JGR, 2004
(cf. G. Siscoe CDAW tutorial)
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Space Weather Effectsof Ionospheric Cold Plasma
Redistribution

• Steep Mid Latitude TEC Gradients
• Radiation Belt Modification - Greatly Eroded
  Plasmasphere - Loss of Radiation Belt Particles
• Ionospheric Irregularities Scintillation
• Equatorial / Low-Latitude Ionospheric
  Perturbation (Spread F)
• Ionospheric Perturbation at Polar Latitudes -
  Polar Tongue of Ionization

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SED Plume forms Polar Tongue of Ionization
GPS TEC Map
Merged SuperDARN/DMSP Convection
Foster et al., JGR 2004
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Space Weather Severe TEC Gradients over CONUS
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IMAGE EUV observationsSED Plumes accompany
Plasmasphere Erosion
April 11, 2001
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Extreme Space WeatherOct 2003
SuperstormSevere Plasmasphere Erosion
(EUV images courtesy J. Goldstein)
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TEC Plume Mapped to Equatorial Plane
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Space Weather Radiation Belt ModificationHigh-En
ergy Electrons 17 Oct.-1 Dec.
(Courtesy D. Baker)
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Regions of Wave-Particle Interactions
(Courtesy D. Baker)
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Energetic Ion Precipitation on Plume Field Line
SAPS
plasmapause
EMIC Waves
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Destabilization of Ion Wavesin Detached Plasma
Regions
Sub-Auroral Polarization Stream
N Hemis L2.5
6 sec period
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What Drives the Erosion Plume?Sub-Auroral
Polarization Stream (SAPS)

• Strong Stormtime Electric Fields appear
  between the plasmasheet and the plasmapause
• Statistical Studies indicate the Persistence and
  Predictability of the Polarization Stream
• Storm Enhanced Density is formed where the
  Polarization Stream overlaps the Plasmasphere
• Polarization Electric Fields Structure the Outer
  Plasmasphere forming Plasmaspheric Tails

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Sub-Auroral Polarization Stream
DMSP F15 6 April 2000
21 MLT
Plasmapause
Plasmasheet
2-Cell Convection
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Magnetospheric DriverDisturbed Ring
Currentdrives FAC intoSub-Auroral Ionosphere
EXTENDING TO PLASMASHEET
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Ring Current / SAPS/ SED Plume(Sub Auroral
Polarization Stream Electric Field)

• Duskside Region-2 FACs close poleward across
  low-conductance gap
• SAPS Strong poleward Electric Fields are set up
  across the sub-auroral ionosphere
• SAPS erodes the outer plasmasphere

AURORAL OVAL
LOW SSAPS E FIELD
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Millstone Hill Radar Scans Span Auroral and
Polarization Stream Convection 20-Year Database
used to Determine Statistical Features
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Average Latitude of SAPS
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Geo-effective Convection PatternTwo-Cell
Auroral Convection SAPS
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March 31, 2001DMSP F13
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Where does the SED Plasma Come From?Inner
Magnetosphere Low Latitude View
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Low-Latitude Ionosphere PlasmasphereEffects
of Sub-AuroralDisturbance Electric Fields

• Undershielded eastward electric field Strong
  uplift at equator redistributes plasma to higher
  latitudes
• Mid-Latitude TEC Spread EA BulgeDownwelling
  poleward/sunward plasma transport increase TEC
  at low mid latitudes
• SED/TEC plumes plasma tailsSAPS overlaps
  outer plasmasphere (PBL) carrying thermal plasma
  sunward

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References Greenspan et al. (March 1989 storm)
Basu et al. (July 2000 storm)
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Spread F (Bubbles) in Enhanced TEC
RegionFoster Rich, 1998
(Courtesy J. Makela)
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Equatorial Anomalies Spread Poleward
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October 30, 2003 Plasma Redistribution
TEC hole
Similar Structure
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Another Example - Similar Structure
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Watch for formation of Bulge at 1930 UT(6
hours later Bulge remains at 285 E longitude)
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Space-Based View of May 2003 Event
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Bulge seen from Ground by GPS TEC
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March 31, 2001 1908 UT
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Ionosphere / Storm Effects

• Ionospheric Conductivity (E F Region) Affects
  Magnetospheric Currents
• Cold Plasma Redistribution Alters I-T Flywheel
  Coupling and Current Dissipation
• Cold Plasma Alters W-P Interactions
• Plasmaspheric Material Injected into Tail and
  Plasma Sheet as Erosion Plumes Enter Cusp
• I-M Coupling in SAPS Affects Ring Current
  Development

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Mid-Latitude SED forms a source for thePolar
TOI(as Dst Falls)
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October 29/30, 2003 StormGlobal Thermal
PlasmaRedistribution
Northern Hemisphere
Global TEC (Noon in center)
Southern Hemisphere
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Points to Remember

• Electric Fields Map between Altitude Regimes
  Independent of their Source (This is especially
  true in the Inner Magnetosphere where parallel
  electric fields usually can be ignored)
• The Bulk of Thermal Plasma is of Ionospheric
  Origin (Solar production at low
  altitude/latitude)
• Thermal Plasma Dynamics is Controlled by the
  Electric Field (ExB)
• Ionospheric effects Map into the Magnetosphere

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Ionospheric Storm Fronts

• During strong geomagnetic disturbances,
  greatly-enhanced ionospheric total electron
  content (TEC) develops at mid latitudes in the
  post-noon sector
• Plumes of storm-enhanced density (SED) are swept
  toward the cusp ionosphere by the sub-auroral
  (SAPS) electric field
• Plasma Redistribution Spans Equatorial Mid -
  Auroral and Polar Latitudes

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Why the Big Effect in the Atlantic
Sector?Polarization E Field at Conductivity
Gradient(Sunset Terminator 21 UT)
18LT 00LT 06LT
S
Pre-reversal enhancement
Vz E/B
East West E Field
B 30 smaller near SAA