AN ELECTRON DENSITY PROFILE MODEL FOR THE SOUTH AFRICAN IONOSPHERE Lee-Anne McKinnell Physics...
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Transcript of AN ELECTRON DENSITY PROFILE MODEL FOR THE SOUTH AFRICAN IONOSPHERE Lee-Anne McKinnell Physics...
AN ELECTRON DENSITY PROFILE AN ELECTRON DENSITY PROFILE MODEL FOR THE SOUTH AFRICAN MODEL FOR THE SOUTH AFRICAN
IONOSPHEREIONOSPHERE
Lee-Anne McKinnell
Physics Department, Rhodes University, Grahamstown, South Africa
Space Physics Group, Hermanus Magnetic Observatory (HMO), Hermanus, South Africa
South African Ionosonde Network
Grahamstown(33.3ºS, 26.5ºE)
Louisvale(28.5ºS,21.2ºE)
(22.4ºS, 30.9ºE )Madimbo
Hermanus(34.4ºS, 19.2ºE)
1973 – 2008N(h) profiles from 1996
2000 – 2008
2000 – 2008
Installed June 2008
Neural Networks
Training a computer to learn the relationship between a given set of inputs and a corresponding output
highly suitable for non-linear relationships
Main requirement -- an archived database describing the history of the relationship
South African region Grahamstown, n(h) profile data from 1996, characteristics from 1973 Louisvale & Madimbo, n(h) profile data from 2000
SABIM Model
• South African region
• Bottomside ionospheric model
• Electron density profile
• Several NNs combined
Special Features
• F1 Probability Network
• Smoothing technique
Criterion for optimisation
• rms error on individual parameters
• Ability to reproduce realistic profiles
0
20
40
60
80
100
120
140
160
180
200
220
1973 1977 1981 1985 1989 1993 1997 2001 2005
Year
R2
Grahamstown 3 ionosondes
Solar Activity
SABIMSouth African
Bottomside Ionospheric Model
Day Number
Solar Activity
Hour
Magnetic Activity
ElectronDensityProfile
Model
Geomagneticposition info
Neural Network basedempirical ionospheric model
for theSouth African region
E layer Profile
Is E layer predictable?E limits NN
Predict E layerfoE, hmE,
E profile NNs
Determining the probability of an F1 layer
F1 Probability NNOutput determines 1) or 2) or 3)
1) No F1 layerF2NN
2) F1 layer definiteF1F2NN
3) F1 layer in L conditionL Algorithm
Smoothing Technique
The Model
F layer Profile
F2 Layer NetworkIncluded
Peak parameters – foF2, hmF2Chebyshev coefficients
Profile constructedfoF2 – global foF2 network used
F1 Layer NetworkIncluded
Peak parameters – foF1, hmF1Chebyshev coefficients
Profile constructedL-algorithm,
weighted avg btn F1 and No F1
0
1
2
3
4
5
6
7
8
0 5 10 15 20 25
hour, [ut]
fof2
, [M
Hz]
Summer
Winter
Louisvale -- Low Solar
0
1
2
3
4
5
6
7
8
0 5 10 15 20 25
hour, [ut]
fof2
, [M
Hz]
Summer
Winter
Grahamstown -- Low Solar
0
1
2
3
4
5
6
7
8
9
0 5 10 15 20 25
hour, [ut]
fof2
, [M
Hz]
Summer
Winter
Madimbo -- Low Solar
0
1
2
3
4
5
6
7
8
0 5 10 15 20 25
hour, [ut]
fof2
, [M
Hz]
Summer
Winter
mid point -- Low Solar
Diurnal foF2 variations
3.5
3.7
3.9
4.1
4.3
4.5
4.7
4.9
5.1
5.3
5.5
0 50 100 150 200 250 300 350
Day Number
foF
1, [
MH
z]
measured
predicted
Madimbo
3.5
3.7
3.9
4.1
4.3
4.5
4.7
4.9
5.1
5.3
5.5
0 50 100 150 200 250 300 350
Day Number
foF
1, [
MH
z]
measured
predictedLouisvale
3.5
3.7
3.9
4.1
4.3
4.5
4.7
4.9
5.1
5.3
5.5
0 50 100 150 200 250 300 350
Day Number
foF
1, [
MH
z]
measured
predictedGrahamstown
foF1 variations
2007
10h00 UT
foF1
2.4
2.6
2.8
3
3.2
3.4
3.6
3.8
4
0 50 100 150 200 250 300 350
Day Number
foE
, [M
Hz]
measured
predicted
Madimbo
2.4
2.6
2.8
3
3.2
3.4
3.6
3.8
4
0 50 100 150 200 250 300 350
Day Number
foE
, [M
Hz]
measured
predicted
Louisvale
2.4
2.6
2.8
3
3.2
3.4
3.6
3.8
4
0 50 100 150 200 250 300 350
Day Number
foE
, [M
Hz]
measured
predictedGrahamstown
2007
10h00 UT
foE
foE variations
80
130
180
230
280
330
2 4 6 8 10 12 14frequency, [MHz]
hei
gh
t, [
km]
Actual
SABIM
IRI2001
Louisvale
DN=90, R=113
80
130
180
230
280
330
2 4 6 8 10frequency, [MHz]
hei
gh
t, [
km]
Actual
SABIM
IRI2001
Madimbo
DN=340, R=105
80
100
120
140
160
180
200
220
240
260
280
2 3 4 5 6 7 8frequency, [MHz]
hei
gh
t, [
km]
Actual
SABIM
IRI2001
Grahamstown
DN=93, R=17
Predicted profiles
80
130
180
230
280
2 4 6 8 10frequency, [MHz]
hei
gh
t, [
km]
Actual
SABIM
IRI2001
Grahamstown
DN=186, R=120
foE
hmE
foF1
hmF1
Summer
10h00 UT Contour Plots
foE
hmE
foF1
hmF1
Winter
10h00 UT Contour Plots
10h00 UT Contour Plots
foF2
foF2
hmF2
hmF2
Winter
Summer
F1 Probability
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
3.5 4 4.5 5 5.5 6 6.5 7 7.5
Hour, UT
Pro
bab
ilit
y
P(N)
P(L)
P(F)
Summer, High R
No F1 F1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
13.5 14 14.5 15 15.5 16 16.5 17 17.5
Hour, UT
Pro
bab
ilit
y P(N)
P(L)
P(F)
Summer, High R
No F1 F1
-0.1
0.1
0.3
0.5
0.7
0.9
1.1
3.5 5.5 7.5 9.5 11.5 13.5 15.5 17.5
Hour, UT
Pro
bab
ilit
y
P(N)
P(L)
P(F)
Autumn, High R
No F1No F1
80
130
180
230
280
330
2 3 4 5 6 7 8 9 10
frequency, MHz
hei
gh
t, k
m
Max
Min
DN = 27, HR = 10h00, R = 83, A = 3.81
Grahamstown
Uncertainty
Future Plans
• extend SABIM to include Hermanus data
• update every 2 years
• use manually obtained F1 information for F1 probability network
• expand uncertainty network