MURI Review

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MURI Review
Stanford MURI Efforts, LEP Enhancements, and
New Insights about NWC Umran S Inan Space,
Telecommunications and Radioscience Laboratory
Electrical Engineering Department Stanford
University, Stanford, California
94305 http//www-star.stanford.edu/vlf/
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Inner Belt VLF Wave-injection Experiment
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Stanford AIP (Antenna in Plasma) Code

• Current AIP code provides a self consistent fluid
  representation of the plasma dynamics in each of
  three regions.
• Developed for simulation in magnetized
  collisionless environments.

• SHEATH MODEL
• Time-domain
• Solves Poisson-fluid system
• 4-moments (including heat flux tensor)

• WARM PLASMA MODEL
• Time-domain
• Solves Maxwell-fluid system
• 3-moments (including pressure tensor)

• COLD PLASMA MODEL
• Time and frequency domain methods
• Solves linearized Maxwell-fluid system

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Comparison of VLF Transmitters
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DEMETER View of ELF/VLF Activity
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NWC Signal on DEMETER
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DEMETER Energetic Electron Detector

• Energetic Electron Detector
• Pattern after successful DEMETER mission
• French m-sat
• High geometric factor
• High-time resolution

Detector Implanted Si S 490 mm2 (? 25 mm)
External shielding 2 mm Al
Foil for p and h? rejection 6 ?m
Mass 525 g
Power 895 mW
Energy range 0.07-0.7(2.5) MeV 256 channels
Maximum geometrical factor 1.2 cm2.ster
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NWC-Induced Precipitation on DEMETER

• NWC-induced precipitation of gt60 keV electrons
  clearly visible in both hemispheres
• The narrow energy peak varies with latitude
  consistently with cyclotron resonance interaction
  at the geomagnetic equator
• NWC-induced precipitation clearly competes well
  with the natural background
• Precipitation region located poleward of NWC,
  consistent with theory

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Irregularities LH Waves over NWC
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Parrot et al., 2007
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Irregularities are overhead while precipitation
is poleward
Oct 23, 2005
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NWC on DEMETER
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NWC on DEMETER
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NWC on DEMETER
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Lightning Induced Electron Precipitation (LEP)
(a)
(c)
(d)
(b)
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LEP Events on DEMETER
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Enhanced Precipitation Region Maintained by a
Thunderstorm
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Comparison with Model Predictions
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Possible Events overNorth America
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Possible LEP Bursts over CONUS
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VLF Streaks on DEMETER
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Enhanced LEP Regions
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Enhanced LEP Regions
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Enhanced LEP Regions
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Enhanced LEP Regions
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LEP Time Profile Energy Spectra Inan et
al.,1989

• Represents best LEP case measured in orbit before
  DEMETER
• Whistler intensity was taken to be Bw200 pT
• Geometric factor was 0.17 cm2-sr
• 700 counts/s for 0.2 s is only 140 counts
• Typical geometric factors of 0.001 cm2-sr give
  lt1 counts even in this best case scenario
• DEMETER IDP has geometric factor of 1.0
  cm2-sr

Theory
Data
Data
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LEP Pitch Angle Distribution Inan et al.,1989

• Even in the best LEP cases, electrons just enter
  the very edge of the loss cone
• Very small addition of new electrons into the
  loss cone must be detectable

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Inan et al., 1982 1988
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LEP as Benchmark for RBR Assessments

• Lightning-induced precipitation is a significant
  contributor to radiation belt loss in the
  inner-belt and slot regions
• Individual LEP bursts have been detected on
  satellites and on the ground
• Quantification of wave-induced precipitation
  requires that individual LEP bursts be measured
  together with whistler-mode waves
• Powerful lightning discharges illuminate the
  radiation belts with waves of intensities of 10
  to 200 pT
• Waves generated for RBR must compete well with
  lightning in order to significantly affect
  electron lifetimes

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Lightning-induced Electron Precipitation
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Lightning-induced Electron Precipitation
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Subionospheric VLF Remote Sensing
Many VLF transmitters operate worldwide,
providing a range of coherent laser-like signals
with which to probe the ionospheric regions
through which they propagate
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Holographic Imaging of Lower Ionosphere
VLF receivers at 13 high schools Provides
excellent opportunities for outreach
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Non-ducted LEP Events
(a)
(c)
In general whistler waves propagate in non-ducted
mode, illuminating large regions of the
radiation In each event, onset delay (Dt)an
onset duration (td) are measurable, corresponding
to wave/particle travel times and duration of LEP
pulse
(d)
(b)
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Spatial Extent of LEP Events
VLF Amplitude Data for 24 March 2001
Dashed line VLF paths perturbed solid line ones
are not theoretical precipitation region
superposed

• Full extent of the ionospheric disturbance
  produced by an LEP burst (due to a single flash)
  is captured
• Corresponding region of the inner radiation belt
  is affected by whistler waves from a single
  lightning flash

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Theoretical Modeling
Peter and Inan 2006
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VLF Sensing of Ionospheric Disturbances in Europe

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AWESOME North Africa Existing Planned
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Global Detection of LEP via VLF Paths
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NLK-Walsenburg
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NAA-Crete
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NWC-Adelaide
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NPM-Palmer
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Dt 1.28 sec DA 0.9 dB td 1.95 sec tr 162
sec
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Dt 1.33 sec DA 1.0 dB td 1.88 sec tr 185
sec
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Dt 1.95 sec DA 0.9 dB td 9 sec tr 223 sec
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The End
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VLF Wave-Injection with HAARP