HF PROPAGATION Results : Metal
Oxide Space Cloud (MOSC)
Experiment
Dev Joshi
Research Assistant
Department of Physics, Boston College(BC)
Institute For Scientific Research(ISR), BC
ISR SEMINAR
1
Ionospheric Modification
Experiments
Ionosphere
Rocket
Metal Vapor
Release
HF Tx
ALTAIR Incoherent
Scatter RADAR
HF Rx
Two types of Ionospheric modification experiments :
• Ionization Depletion
• Ionization Enhancement
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HF PROPAGATION Results : Metal
Oxide Space Cloud Experiment
Outline :
• Introduction
• Ionosphere Modification
Experiment
• HF propagation in ionosphere
• Observations
• Modeling Results
• Conclusions
3
Ionospheric Modification
Experiments
 Ionospheric Modification Experiments: Various materials have been injected
into the high atmosphere creating perturbations to the ambient medium.
• To detect plasma drift velocities and electric fields.
• To create artificial comets.
• To exploit the ionosphere and magnetosphere as a plasma
laboratory without walls.
• To increase or decrease the plasma density in the
ionosphere to trigger large scale phenomenon.
• Payload for each rocket included
‒ Two canisters of samarium
(5 kg yield)
‒ Dual Frequency RF Beacon
(NRL CERTO)
• Ground diagnostics from 5 sites included:
‒ Incoherent Scatter Radar ,GPS/VHF
Scintillation Rxs, All-Sky Cameras,
Optical Spectrograph, Ionosondes,
Beacon Rx, HF Tx/RX
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Ionization Depletion and
Enhancement
 Ionization Depletion Chemistry
• H2O, H2, SF6
• An example with water and hydrogen molecules
These panels show pre-event conditions (a) and the resultant
perturbations at 14 minutes (b), 40 minutes (c), and 107 minutes (d)
after the Shuttle thruster firing in Space Lab 2 mission.
 Ionization Enhancement
• Barium, Strontium, Xenon, Lithium, or Cesium: Photoionization
• Lanthanides: Photoionization and Chemi- ionization
An image of
enhanced
plasma in
MOSC
experiment 5
RF propagation : Appleton formula
The Appleton formula:
𝑛2
= µ −𝑖χ
where,
𝑋=
2=
1 −
𝑁𝑒2
, 𝑌𝐿
є0𝑚ω2
𝑋
𝑌𝑇2
1 −𝑖𝑍 − 2 1 −𝑋 −𝑖𝑍
±
𝑌𝑇 4
4 1 −𝑋 −𝑖𝑍
2
+𝑌𝐿2
1 2
= 𝑒𝐵𝐿/𝑚ω , YT = e𝐵𝑇/mω 𝑎𝑛𝑑 𝑍 = υ/ω
A magnetoplasma is birefringent and
anisotropic.
Reflection Condition:
The positive sign : 𝑋 = 1
Two characteristic modes Possible:
+ Ordinary mode
- Extraordinary mode
And the negative sign gives
𝑋 = 1 − 𝑌, 𝑋 = 1 + 𝑌
Ordinary Wave
Extra-ordinary Wave
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RF propagation : Appleton formula
When collisions are negligible :
𝑛2 = µ2 = 1 −
2𝑋(1 − 𝑋)
2(1 − 𝑋) − 𝑌𝑇2 ± 𝑌𝑇2 + 4 1 − 𝑋 2𝑌𝐿2
1
2
When the magnetic field is negligible :
𝑋
𝑛2 = µ − 𝑖 χ 2 = 1 −
1 − 𝑖𝑍
When both collisions and magnetic field effects are negligible :
𝑛2 = µ2 = 1 − X = 1 −
𝑓𝑁 = 9 𝑁
𝜔
= 2π𝑝 =
𝑓𝑁 2
𝑓
; 𝑓𝑁 = plasma frequency
α′
; N is in electrons per cubic meter
Higher Electron Density
Lower Refractive Index
Lower Electron Density
Higher Refractive Index
2
𝑛𝑜𝑒
ϵ0𝑚
• Cold Plasma
• No collisions
• No magnetic field
α′ > α
α
Refraction of radio waves by the ionosphere due to the changes in
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the electron density
Determination of Electron Densities
A’
T = Transmitter
R = Receiver
Real Path
Virtual Path
A
B
B’
Ionosphere
Vertical
T’ R’
Oblique
Earth
C
T
Virtual Height :
ℎ′
=𝑐
ℎ𝑟 𝑑ℎ
0 𝑢
=
ℎ𝑟
𝜇′𝑑ℎ
0
R
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Determination of Electron Densities
Ionosonde
Measures electron density profile up to the
peak density height only (f ≤ fpeak)
Incoherent Scatter Radar
Measures direct scatter from
electrons providing full height
density profile (f >> fpeak)
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ALTAIR Radar
Advanced Research Project Agency (ARPA)
Long-range Tracking and Identification
Radar (ALTAIR)
• Dual Frequency:
150 MHz/422 MHz
• Max Bandwidth:
7 MHz/18 MHz
• 46 m dish
• Peak Power
VHF: 6.0 MW
UHF: 6.4 MW
• Incoherent Scatter: Direct scatter from
electrons in the ionosphere (10-4 m2;
equivalent to a ~dime!)
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Transmitter/Receiver Geometry
N
E
Rongelap
MOSC Release Location &
Likiep-Wotho Mid-Point
Wotho
Likiep
ALTAIR
• Rongelap-Wotho link geometry is predominantly N-S and great-circle path is far
from release region
• Likiep-Wotho path is nearly E-W and release point lies nearly on mid-point of
the link—should be ideal for observing SmO+ layer
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Kwajalein Atoll
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Roi Namur
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THE RELEASE : MOVIE
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CLOUD
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Two Releases :
01 May and 09 May 2013
• Ionosphere during first release was disturbed, rising rapidly and Spread F formed within
minutes after release
• Ionosphere during second release is canonical quiescent
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Mission 41102
Pre-Release Sweep
09 May 2013
Wotho Receiver
Likiep TX
Rongelap TX
F –region second hop
F -region
Ground Wave
• Sweeps from 2-30 MHz were completed every five (5) minutes - Plots show data from only
2-14 MHz since no signatures were observed at higher frequencies
• Slightly higher peak frequencies on Wotho Likiep path relative to Rongelap-Wotho links
probably due to longer path length, lower elevation angle propagation .
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Mission 41102
1st Post-Release Sweep
Rongelap TX
09 May 2013
Wotho Receiver
Likiep TX
F-layer Secondary Echo
MOSC layer
MOSC layer
• On the Wotho geometry the layer extends up to 10 MHz peak frequency
• There is also a prominent secondary F region echo; the time delays will allow us to calculate
the range offsets
• The discrete nature of the echo suggests a localized perturbation that extends up to the Fregion peak
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Mission 41102
09 May 2013
Post-Release Sweep Wotho Receiver
2nd
Likiep TX
Rongelap TX
F-layer Secondary Echo
F-layer Secondary Echo
MOSC layer
MOSC layer
• The layer has now decreased to about 6 MHz peak density
• The F-region perturbation extends only mid-way up the density profile
• The delay is much greater on the Rongelap link geometry compared to the Wotho
geometry providing valuable information on the nature of the perturbation
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Mission 41100
3rd Post-Release Sweep
01 May 2013
Wotho Receiver
Rongelap TX
Likiep TX
F region perturbation
MOSC layer?
• No clear signatures on Rongelap link
• A bottomside F-region perturbation remains on the Wotho-Likiep link, as well as
a possible MOSC layer signature around 4 MHz
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Second Release: 09 May 2013
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Ionospheric Models
Goal : Model the Background Ionosphere and the Cloud
Background Ionosphere :
 International Reference Ionosphere (IRI)
• Standard model of the empirical ionospheric
climatology
• Developed by joint working group of Committee on
Space Research (COSPAR) and International Union
of Radio Science (URSI)
• ‘Input variables’ : R12 , iono_layer_parms =
[foF2,hmF2,foF1,hmF1,foE,hmE]
 Parametrized Ionospheric Model (PIM)
• Global model of theoretical ionospheric
climatology
• Combination of four physics-based numerical
ionospheric models
• ‘Input Variables’: F10.7 index, SSN, Kp index
Plots courtesy of William McNeil
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IRI and ALTAIR Profiles
BEFORE
30 SEC AFTER
Approximately 30 seconds after release the MOSC
cloud has a peak density of about 106 e-/cc, slightly less
than the background ionosphere (Ne = 106 corresponds
to a plasma frequency of 9 MHz).
The layer is about 30 km in diameter by this time.
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MOSC Launch 2: May 9, 2013
Modeling the Cloud
Time Period for
Modeling Cloud
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MOSC Launch 2: May 9, 2013
Modeling the Cloud
The averaged and
symmetrized cloud
profile is used to
model the cloud in
MATLAB with
latitude/longitude
increment at
0.0141degree and
height increment at
1.5510 km . The
central pixel
corresponds to
7.4369 MHz
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Ray Tracing
Haselgrove Equations:
• Fermat’s principle - δ 𝑚𝑑𝑠 = 0 , m is ray refractive index and ds the element of path length
𝑑𝑥
𝜕𝐺
𝑑𝑢
𝜕𝐺
• Variational method – ray path equations 𝑖 =
, 𝑖=;𝐺 = 𝑢 μ
𝑑𝑡
𝜕𝑢𝑖 𝑑𝑡
𝜕𝑥𝑖
• Numerical Integration of ray path equations : Runge Kutta method
Coleman Method :
• Point to point ray tracing
• Variational principle is discretized and resulting discretized equations solved
PHaRLAP:
• HF radio wave ray tracing toolbox developed by DSTO, Australia
• 2D raytracing is an implementation of the 2-D equations developed by Coleman
• 3-D engine is based upon the equations of Haselgrove
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Ray Tracing : Example
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3D Ray Trace Analysis
Rongelap To Wotho
Rongelap
Wotho
MOSC
Release
Point
•
•
•
HF signals received well off the great
circle path to the receiver
The artificial cloud bends the HF
energy through large angles
Excellent agreement between model
and observations
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3D Ray Trace Analysis
Likiep To Wotho
Wotho
MOSC Release Point
Likiep
MOSC
•
•
Likiep
Great circle path to the receiver passes
through the MOSC volume
Multiple paths between ionosphere, cloud
and receiver expected
Wotho
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Mission 41100
Pre-Release Sweep
01 May 2013
Wotho Receiver
Rongelap TX
Likiep TX
F-region – Second hop
F -region
E - layer
Ground Wave
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Mission 41100
Post-Release Sweep
1st
Rongelap TX
01 May 2013
Wotho Receiver
Likiep TX
F-layer Secondary Echo
MOSC layer
MOSC layer
• Note that the Likiep signature is only evident in high end of frequency range, showing up near f = 8 MHz
(~07:42 UT); one might conclude this is results from the temporal evolution of the cloud, yet the
Rongelap link shows the signature beginning at less than 4 MHz at least 40 seconds earlier.
• One possibility is that the lower frequency components on the direct Likiep-Wotho link were actually
blocked, refracted or ducted by the presence of the MOSC cloud.
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Mission 41100
2nd Post-Release Sweep
Rongelap TX
MOSC layer
01 May 2013
Wotho Receiver
Likiep TX
MOSC layer
• Peak density has decreased significantly over 5 minute time scale, primarily due to
expansion of the cloud
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Mission 41100
3rd Post-Release Sweep
Rongelap TX
MOSC layer
01 May 2013
Wotho Receiver
Likiep TX
F region perturbation
• The Rongelap path shows a low density residual signature of the cloud
• The Likiep path shows an emerging perturbation in the F-region
• By 07:56 and beyond MOSC has disappeared and Spread F dominates
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First Release: 01 May 2013
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MOSC Launch 1: May 1, 2013
Modeling the Ionosphere
The ‘ALTAIR’ is modelled by applying the same relative differences as in PIM in lat-lon
plane at an altitude. The technique is applied at all altitudes. As is seen, modeled ‘ALTAIR’
fails to capture the shape of the high frequency tilt in PIM.
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MOSC Launch 1: May 1, 2013
Modeling the Ionosphere
The change in height of the peak density across longitudes in PIM isn’t seen
in the modeled ‘ALTAIR’ ionosphere.
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MOSC Launch 1: May 1, 2013
Modeling the Ionosphere
An averaged shape function is chosen to apply to the change in the height of the
peak density across longitudes.
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MOSC Launch 1: May 1, 2013
Modeling the Ionosphere
The applied shape function produced delay in good agreement except 9 MHz.
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MOSC Launch 1: May 1, 2013
Modeling the Ionosphere
• The anchor profile is taken to be the
average of three ALTAIR radar profiles.
• This gives delay to a good agreement
with the observations.
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MOSC Launch 1: May 1, 2013
Modeling the Ionosphere
The ‘modeled’ bottomside is in good agreement while the top side is above the observations.
The removal of tilt due to the shape function shows further disagreement as it raises the upside.40
Modeling : Optimization Method
Optimization : Nalder Mead Down Hill Simplex Method ( Amoeba)*
• Nelder, J. and R. Mead ,1965
• Direct Method : No derivatives, only function values
• Idea : Move from high function (hot) areas to low function
(cold) areas by reflections, expansions and contractions
• “Amoeba Crawls Downhill with no assumption about function”
• Built-in function in MATLAB : fminsearch
*Minimization Technique suggested by Dr. Charles Carrano, ISR
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Optimization : Model Ionosphere
PIM doesn’t have enough degrees of freedom to fit the ALTAIR radar profile while
optimization of foF2 and hoF2 in IRI closely matches the observed ALTAIR radar
profile.
Scale Vector = [ a b c …. e]
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Optimization : Delay results
The IRI model, scaled and unscaled, doesn’t match the observed delay.
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Optimization : Delay results
• Optimization of the scaling vector matches only the upside
• Frequency specific optimization of the scale vector exactly reproduces the observed delay.
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Conclusions
• Ray tracing confirms sounder observations to high degree of fidelity
• The change in ambient natural propagation environment due to small
artificial modification can be successfully modeled
• Effects from arbitrary artificial plasma environments can be predicted
with accuracy
• Optimization technique represents a new method of assimilating
oblique ionosonde data to generate the background ionosphere
(numerous applications for HF systems)
• Future Work : Modeling of natural disturbances in the low latitude
propagation environment to understand the effects of Traveling
Ionospheric Disturbances (TIDs) and Spread F on perpendicular and
quasi-parallel (to B) paths.
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Thank You.
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