1. NATIONAL INSTITUTE FOR SPACE RESEARCH – INPE/MCT SOUTHERN REGIONAL SPACE RESEARCH CENTER – CRS/CCR/INPE – MCT FEDERAL UNIVERSITY OF SANTA MARIA - UFSM SPACE SCIENCE LABORATORY OF SANTA MARIA - LACESM/CT – UFSM ANALYSIS OF THE IONOSPHERIC IRREGULARITIES MEASUREMENTS USING GPS RECEIVERS FOR THE SOUTH ATLANTIC MAGNETIC ANOMALY REGION Cláudio M. Paulo, Nelson J. Schuch, E. R. de Paula, Luiz Felipe C. de Rezende, Dimas I. Alves. PASI: Pan-American Advanced Studies Institute School and Workshop on the Dynamics and Chemistry of the Upper Atmosphere October 4 - 9, 2010 - San Juan, Argentina

2. Objectives To present some Sudden Ionospheric Disturbances (SID) To present SID effects in GPS signal. It was analyzed and calculated the zonal drift velocity for the Plasma Bubbles during a quiet and a disturbed period. PASI: Pan-American Advanced Studies Institute School and Workshop on the Dynamics and Chemistry of the Upper Atmosphere October 4 - 9, 2010 - San Juan, Argentina

3. The Ionosphere PASI: Pan-American Advanced Studies Institute School and Workshop on the Dynamics and Chemistry of the Upper Atmosphere October 4 - 9, 2010 - San Juan, Argentina

4. Ionospheric Bubbles PASI: Pan-American Advanced Studies Institute School and Workshop on the Dynamics and Chemistry of the Upper Atmosphere October 4 - 9, 2010 - San Juan, Argentina The Ionospheric plasma Bubbles are affected by: The solar cycle Local time Season Magnetic disturbances Latitude and longitude  In Brazil, the bubbles occur from September to March, between 6 p.m. up to 12 p.m. local time and in the post midnight sector during some magnetic storms (de Paula et al., 2006). Disturbed Period: bubbles drift to west Quiet Period: bubbles drift to east

5. Triggering of Ionospheric Bubbles PASI: Pan-American Advanced Studies Institute School and Workshop on the Dynamics and Chemistry of the Upper Atmosphere October 4 - 9, 2010 - San Juan, Argentina The quick increase of density gradients creates an instability in the plasma which is based on Hydrodynamic Rayleigh-Taylor Instability. (Kelley, 1989)

6. GPS – Global Positioning System The network consist in more than 29 satellites Transmitting in: L1 = 1.575 GHz L2 = 1.227 GHz  Precision in the calculation of position in real time. PASI: Pan-American Advanced Studies Institute School and Workshop on the Dynamics and Chemistry of the Upper Atmosphere October 4 - 9, 2010 - San Juan, Argentina

7. Changes in the satellite signal Loss of lock occurs when a receiver is stressed by two factors: The rapid phase variations causing a Doppler shift in the GPS signal which may exceed the bandwidth of phase lock loop (PLL), resulting in a loss of phase lock (Leick, 1995; Skone et al, 2001). The rapid amplitude fluctuations in which the signal amplitude becomes too small to be sensed by the loop discriminator (Humphreys et al., 2005; Kintner et al., 2005). PASI: Pan-American Advanced Studies Institute School and Workshop on the Dynamics and Chemistry of the Upper Atmosphere October 4 - 9, 2010 - San Juan, Argentina Scintillation in the signal amplitude and phase contribute to the loss of lock of the GPS receivers.

8. GPS Receiver PASI: Pan-American Advanced Studies Institute School and Workshop on the Dynamics and Chemistry of the Upper Atmosphere October 4 - 9, 2010 - San Juan, Argentina GEC-Plessey GPS card Cornell University (Beach and Kintner, 2001) Acquiring data at 50 Hz sampling rate in a single frequency L1 ( 1,575.42 MHz ) signal amplitude. This system is able to track up to 12 satellites simultaneously with one channel reserved for the instrumental noise. There are two kinds of scintillation monitor: SCINTMON and CASCADE. Connected in the Computer

9. GPS Receiver PASI: Pan-American Advanced Studies Institute School and Workshop on the Dynamics and Chemistry of the Upper Atmosphere October 4 - 9, 2010 - San Juan, Argentina Receivers antennas installed on the east-west magnetic direction at the top of the build of the Southern Regional Space Research Center – CRS/CCR/INPE – MCT in collaboration with the Space Science Laboratory of Santa Maria – LACESM/CT – UFSM, Santa Maria-RS, Brazil

10. Scintillation Monitor ( Beach, 1998; Rodrigues, 2003 ) PASI: Pan-American Advanced Studies Institute School and Workshop on the Dynamics and Chemistry of the Upper Atmosphere October 4 - 9, 2010 - San Juan, Argentina SCINTEC is a software system created to monitor and generate real time maps of Ionospheric Scintillation and total electron content (TEC). http://www.inpe.br/scintec/realtime.php The scintillation S4 index Standard deviation relative to the average:

11. PASI: Pan-American Advanced Studies Institute School and Workshop on the Dynamics and Chemistry of the Upper Atmosphere October 4 - 9, 2010 - San Juan, Argentina Characterization of Disturbed and Quiet Days

12. Scintillations of GPS signal PASI: Pan-American Advanced Studies Institute School and Workshop on the Dynamics and Chemistry of the Upper Atmosphere October 4 - 9, 2010 - San Juan, Argentina Ionospheric irregularities, as Plasma Bubbles, are determinant factors to cause scintillation. Scintillation occurs when a radio wave cross the Ionosphere and it suffers a distortion of phase and amplitude. Scintillation

13. PASI: Pan-American Advanced Studies Institute School and Workshop on the Dynamics and Chemistry of the Upper Atmosphere October 4 - 9, 2010 - San Juan, Argentina Irregularity Zonal Velocity East West

14. Conclusions The study of Ionospheric Bubbles characteristics is important for understanding their effects over the satellite communication. Suggestions to improve the GPS performance due to the Ionospheric Scintillations: -To use dual frequency receivers (expensive solution) -To increase the number of available satellites (Galileo) -To build more robust receivers, decreasing the bandwidth of GPS card (however this procedure may cause increase of loss of lock). PASI: Pan-American Advanced Studies Institute School and Workshop on the Dynamics and Chemistry of the Upper Atmosphere October 4 - 9, 2010 - San Juan, Argentina

15. Thank You Muchas Gracias Contact: E-mail : cmpaulo@lacesm.ufsm.br Southern Regional Space Research Center – CRS/INPE – MCT in collaboration with the Space Science Laboratory of Santa Maria – LACESM/CT – UFSM, Santa Maria, Brazil PASI: Pan-American Advanced Studies Institute School and Workshop on the Dynamics and Chemistry of the Upper Atmosphere October 4 - 9, 2010 - San Juan, Argentina