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 Kiso Sugadaira Fuji Toyokawa Data Solar Wind Speed Scintillation level (g-value) Frequency 327MHz Aperture Size = ~ 2000 or ~ 3400 ㎡

3. 41m(E-W) 106m (N-S) Solar Wind Imaging Facility (SWIFT) Frontend and signal combiners Cylindrical parabolic reflector Dipole antennas 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 408MHz Radio Sky (Haslam et al., 1982) Note: The system temperature increases at low elevation

6. Model Fitting Analysis of IPS Power Spectrum Speed=379km/s Axial Ratio=0.99 Spectral Index=3.17 Speed=499km/s Axial Ratio=0.51 Spectral Index=4.34 3C48 2009/4/63C49 2009/4/6

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

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

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

16. Toyokawa Observatory SWIFT

17. Specifications of STEL IPS Radiotelescopes Toyokawa (SWIFT) Fuji (FIT) Kiso (KIT) Sugadaira Tsys (K)146151221229 NF0.720.871.610.75 Pre-amplifierHEMTGa-As FETTransisterGa-As FET Ae ( ㎡ ) 1970 (@zenith) 150014091120 Beam Cont. N- S ElectronicalMechanical Beam Cont. E- W (Fixed)Electronical Physical Aperture 108 m NS × 40 m EW 20 m NS × 100 m EW 27 m NS × 75 m EW 20 m NS × 100 m EW

18. Comparison between New and Old IPS System Specifications NewOld A/D Resolution16 bits13 bits Sampling Period20 ms (median mean of 10kHz sampling data) 50 ms Start/End Time Resolution Every 0 secondsEvery 0 minutes Observation TimeJST (UT)Sidereal Time Duration of IPS Obs~2.7 min7.5 – 15 min 1 Block for FFT Analysis512 points1024 points Automatic Gain Cont. (H/W) NoneYes High-Pass Filtering for IPS Data (H/W) NoneYes PCWin-XP (samba/nfs)Win95/MS-DOS (nfs)

19. Large-Aperture Parabolic Reflector  88m×39m×η=3432×η ㎡  Efficiency η obs ~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 Solar Wind Imaging Facility (SWIFT)