Formation of Artificial Ionospheric Ducts

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Formation of Artificial Ionospheric Ducts

• Gennady Milikh, Dennis Papadopoulos
• University of Maryland,
• Joe Huba, Glenn Joyce
• Naval Research Laboratory
• Umran Inan, Dennys Piddyachiy,
• Stanford University
• Chia-Lee Chang, BAE systems
• Michel Parrot, LPCE/CNRS, France
• Evgenii Mishin, Boston College

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• Introduction
• Naturally induced field aligned irregularities
  of the plasma density exhibit enhanced refractive
  indices and act as ducts that guide waves in the
  whistler range between the two hemispheres.
• HF heating of the ionosphere creates density
  perturbations that may propagate into the
  plasmasphere, thus produce artificial ducts.

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• Objectives
• To present the results of a theoretical study
  that addresses generation of artificial ducts by
  strong HF heating of the F-region of the
  ionosphere.
• To check the model against observations of the
  density perturbations caused by the HAARP while
  detected by the Demeter satellite.

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• The SAMI2 model of the ionosphere
• Huba,Joyce,Fedder, JGR, 105A,2000
• SAMI2 models the plasma along the Earths dipole
  field from one hemisphere to another.
• The model solves ion continuity equations for
  seven ion species along with momentum and
  temperature equations for ions and electrons.
• It includes models of neutral atmosphere,
  horizontal winds, and photo-deposition into the
  atmosphere, along with model for the ion
  chemistry.

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• The SAMI2 model has been modified
• Perrine,Milikh,Papadopoulos,Huba,Joyce, Rad
  Sci,41,2006
• A flexible source of electron heating was added.
  
• The source is characterized by the heating rate
  per electron (Q, in K/s), its altitude z0,
  vertical extent of the heated region, and its
  geographic coordinates.

• - is the absorption coefficient, W radiated
  HF - power,
• V the HF - heated volume.
• For the current HAARP q could reach 5,000 K/s.

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Output of the Model

• A thermal wave is generated near the F2 peak as a
  result of strong electron HF-heating.
• Such a wave propagates through the
  ionosphere/magnetosphere, and can reach the
  conjugate point.
• Amplitude of the perturbations (in ion and
  electron temperature and density) have a
  non-linear saturation relationship to the
  strength of the heating source.

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Ion Temperature
At 400 km from the source along the field line
Ion temperature with ambient conditions shown
by dashed lines. Heating parameters for these
data Q 5000 K/s, z0 380 km.
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Ion fraction
At 400 km from the source along the field line
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Analysis of the Demeter Observations

• We focus on the ion temperature and density of
  O, H, He measured by Demeter flying at 670 km
  height.
• Altogether 6 observations were available
• In 2 cases the ionosphere was transparent for
  the HAARP radio beam

• no perturbations were detected
• In the rest 4 cases the increase of the ion
  temperature was detected along with the ion
  outflows.

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f3.2 MHz O-mode 0.1 Hz Magn. Zen. No electrojet
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The outflows of oxygen ions pushes upward the
hydrogen ions, thus reducing their density at the
Demeters altitude. Demeter measures
Ey250-300 mV/m thus VD4-5 km/s

• Since HF-heating starts 5-10 min before Demeter
  over-flies HAARP, the outflows spread by
  1,500-2,000 km.

• The ExB drift is directed Southward leading to
  the observed asymmetry in the ion outflows.

• The shift between the ion temperature and
  density peaks is due to two different generation
  mechanisms
• 1. Local electron heating generates thermal
  wave.
• 2. Plasma density perturbed at the heated spot
  creates pressure imbalance driving plasma along
  B.

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f3.3 MHz O-mode 0.2 HZ Magn. Zen
The shortest distance to HAARP 137 km
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F2.85MHz O-mode 0.7 Hz Mag. Zen.
Shortest distance to HAARP 94 km
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f4.4 MHz X-mode 0.2 Hz Magn. Zen. Shortest
distance to HAARP 110 km
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Conclusions

• Ion outflows due to the ionospheric heating by
  HAARP were detected by Demeter.
• The best conditions for the outflows generation
  occurred when matching F2 peak in the absence of
  the electrojet.
• Modified SAMI2 model provides qualitative
  predictions of the outflows amplitude.
• In order to improve our predictions a version of
  SAMI2 developed for studies of the high latitude
  ionosphere will be used.

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Additional slides
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Comments increase in O density was masked by
the ionospheric disturbances occurred at 630.
It is 1 min shift between Ti and ni peaks.
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Comments the electrojet is heated by the HF beam
of X-mode, and relatively low intensity, however
a weaker outflows occur. The hydrogen and helium
ions are pushed upward by the outflows of the
oxygen ions. It is no shift between Ti and ni
peaks.