ionospheric modulation & climate geo-engineering
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Ionospheric modification and ELF/VLF
wave generation by HAARP
Nikolai G. Lehtinen and Umran S. Inan
STAR Lab, Stanford University
January 7, 2006
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Generation of ELF/VLF waves
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HAARP
After upgrade in March 2006:
180 crossed dipole antennas
3.6 MW power
~2 GW effective radiated HF power (2.8-10
MHz) (lightning has ~20 GW isotropic ERP)
High Frequency Active Auroral Research Program
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HAARP and other HF heating
facilities
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Important electron-molecule interaction
concept: Dynamic friction force
Inelastic processes:
Rotational,
vibrational,electronic level
excitations
Dissociative
losses
Ionization
(E/N)br=130 Td where 1 Td = 10-21 V-m2
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Kinetic Equation Solver
(modified ELENDIF)
Time-dependent solution forf(v,t) = f0(v,t) + cos f1(v,t)
(almost isotropic)
Physical processes inluded in ELENDIF: Quasistatic electric field
Elastic scattering on neutrals and ions
Inelastic and superelastic scattering
Electron-electron collisions
Attachment and ionization
Photon-electron processes
External source of electronsNew:
Non-static (harmonic) electric field
Geomagnetic field
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Importance of these processes
The quasistatic
approximation
used by ELENDIFrequires m>>
Geomagnetic field
is also important:
H~2 x 1 MHz
H
HAARP
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Analytical solution
Margenau distribution
where l=v/ m=(N m)-1=const
Druyvesteyn distribution =0
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Calculated electron distributions
Electron distributions for various RMS E/N
(in Td). f>0 corresponds to extaordinary
wave (fH=1 MHz, h=91 km)
Effectiveelectric field issmaller than in
DC case:
+ ordinary
- extraordinary
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Breakdown field
(used for the estimate of m,eff)
Breakdown occurs
when ion> att
The point ofbreakdown (shown
with ) shifts up in
oscillating field
f(v) at ionization
energy (~15 eV) is
most important
h = 91 km, extraordinary, fH=1 MHz
2
13 1 31
2 10
br br H
DC
E E
N N N s m
+
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HF wave propagation
Power flux (1D), including losses:
HF conductivity (ordinary/extaordinary)
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Calculated HF electric field
Normalized field,
E/Ebr is shown
For comparison,we show the
dynamic friction
function
The N2 vibrational
threshold or
breakdown field arenot exceeded for
current or
upgraded HAARPpower
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Is breakdown achievable at all?
The electric fieldcan be higher in anon-steady statecase
Electric breakdownfield with altitude: Decreases due to
thinningatmosphere
But, increases due
to oscillations andmagnetization.
2
13 1 3
12 10
br br H
DC
E E
N N N s m
+
Propagation with no absorption
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Temperature modification
(daytime, x mode)
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Comparison of Maxwellian and
non-Maxwellian approaches
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DC conductivity changes
(for electrojet current)
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Conductivity tensor (DC)
Conductivity changes due to modification of
electron distribution
Approximate formulas were used previously
Pedersen (transverse)
Hall (off-diagonal)
Parallel
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Conductivity modification
Pedersenconductivity isincreased
Parallelconductivity is
decreased
C d ti it f ti f E/N
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Conductivity as a function of E/N
(x-mode, h=80 km, f=0,3,7 MHz)
Solid line shows
conductivitymodifications byDC field
Black intervalsconnect theconductivitiesmodified by
maximumHAARP heatingbefore and afterupgrade
R l ti h f d ti it
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Relative change of conductivity
(E)/ (E=0)
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Electric current calculations
In most previous works, it is
assumed that the electrojet field
Eej=const => inaccurate at lowfrequencies (no account for the
accumulation of charge) We assume static current, i.e.
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3D stationary J
Vertical B
Ambient E is along x
Ambient current ismostly along y
Models with E=0 donot consider closing
side currents max J/J0~0.3 for this
case
C l l t d J/J f i
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Calculated J/J0 for various
frequencies
Range 70-130km
Modified region
radius ~10 kmbefore upgradeand ~5 km afterupgrade
Calculatedmaximumcurrent and its
modificationoccur at~109km
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Conclusions
Our model includes both: Non-Maxwellian electron distribution
Self-absorption
Maxwellian electron distribution models,which calculate Te, cannot account forthe nonlinear T
esaturation.
The non-Maxwellian model allows tocalculate processes for which high-energy
tail of the electron distribution isimportant, such as: optical emissions
breakdown processes.
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Work in progress
Electrojet current modulation in non-static case
ELF/VLF emission
ELF/VLF wave propagation along the
geomagnetic field line
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