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Global Observations of the Solar Wind with STEL IPS Array

2011-Aug-11/AOGS 2011. Global Observations of the Solar Wind with STEL IPS Array. M. Tokumaru , K. Fujiki, T. Iju, M. Hirota, M. Noda, and M. Kojima (STEL, Nagoya University). STEL Radiotelescope Array dedicated for IPS Observations. Sugadaira. Kiso. Data Solar Wind Speed

sebastien-romano
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Global Observations of the Solar Wind with STEL IPS Array

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  1. 2011-Aug-11/AOGS 2011 Global Observations of the Solar Wind with STEL IPS Array M. Tokumaru, K. Fujiki, T. Iju, M. Hirota, M. Noda, and M. Kojima (STEL, Nagoya University)

  2. STEL Radiotelescope Array dedicated for IPS Observations Sugadaira Kiso • Data • Solar Wind Speed • Scintillation level (g-value) Aperture Size = ~ 2000or ~ 3400㎡ Frequency 327MHz Toyokawa Fuji

  3. Solar Wind Imaging Facility (SWIFT) 41m(E-W) Cylindrical parabolic reflector Dipole antennas 106m (N-S) Frontend and signal combiners 7.2m

  4. Solar Wind Speed Synoptic Maps for 1996 (upper) and 2008 (lower) • In the previous minimum (1996), the structure was stable. • In the current minimum (2008), the structure shows rapid variability. 11 Carrington Rotations versus Heliographic Latitude (Note that the Carrington rotation number increases from right left)

  5. 327-MHz Radio Sky Observed by SWIFT Note: The system temperature increases at low elevation 408MHz Radio Sky (Haslam et al., 1982)

  6. Model Fitting Analysis of IPS Power Spectrum 3C48 2009/4/6 3C49 2009/4/6 Speed=499km/s Axial Ratio=0.51 Spectral Index=4.34 Speed=379km/s Axial Ratio=0.99 Spectral Index=3.17

  7. Upgrade of Fuji and Kiso IPS Systems • A new IPS system was developed for Fuji and Kiso stations. • The new system enables to determine the solar wind speed from the cross correlation analysis of 3-station data. • The new system also improves quality and reliability of IPS data. Fuji IPS Telescope (FIT) Kiso IPS Telescope (KIT)

  8. Cross Correlation Analysis with Upgraded STEL IPS System Solid lines: Cross Correlation Dashed/Dotted lines: Auto Correlation Taking account of the baseline geometry, we determine the solar wind speed. For this case, we obtain V=522+/-3 km/s. Here, we assume the radial flow and the anisotropy.

  9. 1996(Cycle 22/23 Minimum) 2000 1991 (Cycle 23 Maximum) (Cyclel 22 Maximum) Blue=Fast wind Red=Slow wind

  10. Solar Cycle Change in Source Surface Area of Different Speed Components during 1985-2009 from STEL IPS observations All Lat. Dominance of fast winds at high latitudes except for the solar maxima High Lat. Low Lat. Prevalence of slow winds at low latitudes (Tokumaru et al., 2010)

  11. Solar Wind Speed Synoptic Maps for 1996 (upper) and 2008 (lower) • In the previous minimum (1996), the structure was stable. • In the current minimum (2008), the structure shows rapid variability. 11 Carrington Rotations versus Heliographic Latitude (Note that the Carrington rotation number increases from right left)

  12. Solar Wind Speed Maps for 2009 and 2011

  13. Summary and Future Subjects • The STEL IPS system has been upgraded recently. Three-station measurements of the solar wind speed have been conducted with the upgraded system. • Some interesting aspects of the solar wind in the cycle 24 are revealed from our IPS observations. • We need to elucidate evolution of the solar wind during the cycle 24 in detail. • Further improvement of the IPS system is needed.

  14. STEL IPS Antennas as Viewed in Google Earth Fuji IPS Telescope (FIT) Kiso IPS Telescope (KIT)

  15. Toyokawa Observatory SWIFT

  16. Specifications of STEL IPS Radiotelescopes

  17. Comparison between New and Old IPS System Specifications

  18. Solar Wind Imaging Facility (SWIFT) • Large-Aperture Parabolic Reflector • 88m×39m×η=3432×η㎡ • Efficiency ηobs~0.65 • 192-Elements Phased Array in N-S Direction • Single Beam with a Steerable Range of 60 deg S-30 deg N • 1 Element = Combination of East and West λ/2-dipoles • Delay Correction ・Low-Noise Receiver • 327MHz ±5MHz max • Front-end: NF <1dB、VSWR <1.5 • Loop-Method Calibration System • RFI Reduction • Small Height of Focal Points • Shielding Fence at North and South Ends North South

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