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Fourth European Space Weather Week5-9 Nov. 2007

TEC FORECASTING DURING DISTURBED

SPACE WEATHER CONDITIONS:

A POSSIBLE ALTERNATIVE TO THE IRI-2001

Yurdanur Tulunay1, Erdem Turker Senalp2, Ersin Tulunay2

ODTU / METU Ankara, TURKEY

(1) Dept. of Aerospace Eng., ytulunay@metu.edu.tr

(2) Dept. of Electrical and Electronics Eng.

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CONTENTS

1. Introduction

2. METU-NN-C

3. Data Organisation

4. Results

5. Conclusions

6. Acknowledgements

7. References

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INTRODUCTION

Ionospheric processes: highly nonlinear and dynamic

TEC: key parameter in navigation and telecommunication

METU Group: specialized on data driven modelling since 1990’s

Recently developped: NN and Cascade Model based on the Hammerstein system modelling

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Objective:

• to forecast TEC with higher accuracy under the influence of the extreme solar events.

A case study: Solar Events of April 2002

• A possible alternative to IRI-2001?

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Why and How?

• Mathematical models of the ionospheric parameters (i.e. TEC) DIFFICULT

• Data-driven approaches (i.e. NN modelling) employed in parallel with the mathematical models

• Therefore, METU-NN-C using Bezier curves to represent nonlinearities

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METU-NN-C

• TEC map over Europe constructed by METU-NN in 2004 and 2006 (Tulunay et al. [2004a, 2006] )

• to increase the performance, a new technique,METU-NN-C developped [Senalp, 2007]

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Fig. 1. Construction of the METU-NN-C Models[Senalp et al., 2007]

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1

2

3

Block 1: METU-NN model estimates the state-like variables for the METU-C

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k : Discrete time index

uDp(k) : Inputs

xDq(k) : the internal variables of the METU-C

Block 2: Construction of Nonlinear Static Block of METU-C

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Block 3: Construction of Linear Dynamic Block of METU-C

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The Generic METU-NN-C Model

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Phases of Application of METU-NN-C:

• ‘Training’ • ‘Test’

Inputs: • Present value of TEC: TEC(k)• Temporal parameters: Trigonometric comp. of time

Bezier curves to represent NONLINEARITIES

METU-NN: State-like variable estimator

Output:• Forecast TEC values one hour in advance

DATA ORGANIZATION

• 10-min GPS-TEC data of

Chilbolton (51.8˚N; 1.26˚W) Hailsham (50.9˚N; 0.3˚E)

• Development Step:Training: Chilbolton TEC (April; May 2000, 2001)

Validation: Chilbolton TEC (April-May 2000, 2001)

• Operation Step:Validation: Hailsham TEC (April; May 2002)

• 2000-2002 SSN max. years

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RESULTS

Fig. 2 Observed and one hour ahead Forecast Hailsham TEC values for April, May 2002 [Senalp et al., 2007]

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Fig. 3. METU-NN-C and IRI-2001 during disturbed conditions (Hailsham)

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- Fig. 4. Scatter diagrams and best-fit lines: in 18-19 April 2002 at Hailsham

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METU-NN-C IRI-2001

Table 1. Performance of models

(18-19 April 2002; Hailsham)

METU-NN-C IRI-2001Normalized Error (%) 20.04 204.1

Cross Correlation Coefficient (x10-2) 98.7 83.8

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CONCLUSIONS

• During disturbed SW conditions, METU-NN-C seems to show better performance over IRI-2001

• METU-NN-C Model - more versatile and has got advantages provided that the representative data are available

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Acknowledgements

This work is partially supported by

• EU action of COST 296 (Mitigation of Ionospheric Effects on Radio Systems)

• TUBITAK-ÇAYDAG (105Y003)

• GPS-TEC data are kindly provided by Dr. Lj. R. Cander

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