SURA-WIND experiments: intensity fluctuations due to Faraday effect

1. Yu. Tokarev,Yu.Belov, G. Boiko, G. Komrakov SURA-WIND experiments: intensity fluctuations due to Faraday effect Radiophysical Research Institute, N.Novgorod, Russia Authors are grateful to J.-L. Bougeret (LESIA, Meudon, France) and M.Kaiser (NASA/GSFC, Greenbelt, USA) for fruitful collaboration

2. SURA radar facility Vasil’sursk, Russia (56.07 N, 46 E) Operating frequency 4.3 – 9.5 MHz Antenna array sizes 300 m x 300 m Zenith angle range –45o - +45o Circular polarization modes (O or X) Three transmitter submodules Effective power radiation 17–160 MW

3. WIND spacecraft Sunward WIND orbits Ecliptic plane localization Revolving axis is pointed to South ecliptic pole Apogee 80 – 250 Re Perigee 10 – 15 Re RAD2 WAVES receiver Operating frequency range 1.075 –13.835 MHz Two orthogonal dipole antennas X(11m) and Y(15m) Spinning vehicle (3 sec per turn) Sensitivity 7 nV/ Hz0.5 Freq. width 20 kHzSampling rate 63 ms

4. Development of high frequency pecularity duringthe s/c moving away the Earth magnetosphere WIND trajectory Fluctuation spectra of received SURA signals

5. Example of spectrum decomposition to ionospheric and IPS components

6. Example of time record with pronounced Faraday effect

7. Total intensityItot and Iz / ItotratioDecember 27, 1999

8. Example ofsession with regular Iz / ItotvariationsNovember 23, 1999

9. Example ofsession with quasi-regular Iz / ItotvariationsAug 18-19, 1999

10. Izand Itot fluctuation spectra of Faraday fringesAug 18-19, 1999

11. Iz dynamic spectrum of Faraday fluctuationsAug 18-19, 1999

12. Degree of linear polarization and total intensityAug 18-19,1999

13. Degree of linear polarization and total intensityNovember 23, 1999

14. Degree of linear polarizationof SURA radiation: Basic equations Z– zenith angle, A – azimuth of line of sight Faraday rotation angle =33 m Rotation measure Ionosphere: Characteristic frequency of Faraday fluctuations: Magnetotail:

15. CONCLUSIONS • A method to study the polarization state of radio signals of ground-based transmitters using RAD2 WAVES observations for SEP-mode is proposed. • It was found that degree of linear polarization of SURA emission out the earth ionosphere is close to expected value only for angular range near center of the radar beam. • Obtained results could be used for calibration of space radio instrumentation particularly of the STEREO radio receivers at first stage of the mission.

16. References C.G.M.van't Klooster, Yu.Belov, Yu.Tokarev, J.L.Bougeret, B.Manning, M.Kaiser. Experimental 9 MHz Transmission from Vasil'sursk in Russia to the WIND Spacecraft of NASA. Preparing for the FUTURE. 1995. V.5. N.4. P.1-3. Yu.V.Tokarev, M.Kaiser , Yu.I.Belov, G.N Boiko, N.V.Muravieva. Small-scale turbulence of solar wind around the near-Earth bow shock. Astronomicheskii Vestnik. 2000. V.34. N.2. Pp.1-4 (in Russian). N. A. Barkhatov, N. S. Belliustin, J.-L. Bougeret, S. Yu. Sakharov and Yu.V. Tokarev. Influence of solar wind magnetic field on small-scale near-earth turbulence. Izvestya VUZov, Radiophysica. 2001. V.44. N 12. Pp.993-1002 (in Russian). N.Muravieva and Yu.V.Tokarev. Decametric sounding of near Earth plasma: correlation and fractal analysis of scintillation data. Astrophysics and Space Science. 2001. V.277. P.331-334. Yu.V.Tokarev. Turbulence of geo-disturbed region of solar wind (SURA-WIND experiments). Proc. of FSU Conference “Actual problems of solar physics and star activity”. N.Novgorod, June 2-7, 207, 2003. V I. Pp. 191-196 (in Russian).