AN ELECTRON DENSITY PROFILE MODEL FOR THE SOUTH AFRICAN IONOSPHERE

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