Fourth European Space Weather Week 5-9 Nov TEC F ORECASTING D URING D ISTURBED S PACE W EATHER C ONDITIONS : A P OSSIBLE A LTERNATIVE TO THE IRI-2001 Yurdanur Tulunay 1, Erdem Turker Senalp 2, Ersin Tulunay 2 ODTU / METU Ankara, TURKEY (1)Dept. of Aerospace Eng., (2) Dept. of Electrical and Electronics Eng. ESWW4, 5-9 Nov. 2007, Brussels1

CONTENTS 1. Introduction 2. METU-NN-C 3. Data Organisation 4. Results 5. Conclusions 6. Acknowledgements 7. References ESWW4, 5-9 Nov. 2007, Brussels2

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 ESWW4, 5-9 Nov. 2007, Brussels3

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? ESWW4, 5-9 Nov. 2007, Brussels4

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 ESWW4, 5-9 Nov. 2007, Brussels5

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] ESWW4, 5-9 Nov. 2007, Brussels6

Fig. 1. Construction of the METU-NN-C Models [Senalp et al., 2007] ESWW4, 5-9 Nov. 2007, Brussels

Block 1: METU-NN model estimates the state-like variables for the METU-C ESWW4, 5-9 Nov. 2007, Brussels8 k : Discrete time index u Dp (k) : Inputs x Dq (k) : the internal variables of the METU-C

Block 2: Construction of Nonlinear Static Block of METU-C ESWW4, 5-9 Nov. 2007, Brussels9

Block 3:Construction of Linear Dynamic Block of METU-C ESWW4, 5-9 Nov. 2007, Brussels10

The Generic METU-NN-C Model ESWW4, 5-9 Nov. 2007, Brussels11

ESWW4, 5-9 Nov. 2007, Brussels12 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) SSN max. years ESWW4, 5-9 Nov. 2007, Brussels13

RESULTS

Fig. 2 Observed and one hour ahead Forecast Hailsham TEC values for April, May 2002 [Senalp et al., 2007] ESWW4, 5-9 Nov. 2007, Brussels15

Fig. 3. METU-NN-C and IRI-2001 during disturbed conditions (Hailsham) ESWW4, 5-9 Nov. 2007, Brussels16

- Fig. 4. Scatter diagrams and best-fit lines: in April 2002 at Hailsham ESWW4, 5-9 Nov. 2007, Brussels17 METU-NN-C IRI-2001

Table 1. Performance of models (18-19 April 2002; Hailsham) ESWW4, 5-9 Nov. 2007, Brussels18

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 ESWW4, 5-9 Nov. 2007, Brussels19

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 ESWW4, 5-9 Nov. 2007, Brussels20

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