Upgrade of STEL Multi-Station Interplanetary Scintillation System and Recent Observations of the Solar WindMunetoshi Tokumaru, Masayoshi Kojima, Kenichi Fujiki, Hiroaki Itoh, and Tomoya Iju(STEL, Japan).Given by Mario M. Bisi (CASS-UCSD)and Periasamy Manoharan (Ooty)

STEL 327-MHz Multi-Station IPS SystemSWIFTKiso IPS Telescope (KIT)Fuji IPS Telescope (FIT)Sugadaira antennaToyokawa antennaMeasurementsSolar wind speed Scintillation level (g-value)~Ne

41m(E-W)106m (N-S)New IPS Antenna at ToyokawaSWIFT (Solar Wind Imaging FaciliTy)Meridian Transit Obs.Beam: 1 (Steerable in NS)Frequency 327 MHzEffective Area: Ae3382cosD2()~90%D(): directivity of dipole

Receiver Housing

Variations of Scintillation Level and g-value for Source B1730-13 in 2008IPS levelIPS levelg-valueTimeTimeRadial DistanceThe g-value represents the relative variation of scintillation level; i.e. solar wind density fluctuations Ne (Gapper et al., 1982).

All-Sky g-maps2008/11/04ToyokawaKiso

Model Fitting Analysis of IPS Power SpectrumSpeed=379km/sAxial Ratio=0.99Spectral Index=3.17Speed=499km/sAxial Ratio=0.51Spectral Index=4.343C48 2009/4/63C49 2009/4/6

Further Development of Multi-Station IPS SystemUpgrade of Fuji and Kiso IPS TelescopesDipoles, Antenna Driving System, Receiver Backend, PCs (FY2009-2010)Receiver Frontend (FY2011; not funded yet)This allows us to take correlation between Toyokawa and Fuji, Kiso to derive the solar wind speedFuji IPS Telescope (FIT)Kiso IPS Telescope (KIT)

19912000Solar wind speed mapsBlue= fastRed = slow1996(Solar Minimum)

Comparison of Solar Wind Speed Maps between CR 1910 and 20702008.5.13~6.91996.6.1~6.28Fast winds exist over the poles and equator.Slow winds are in between them. i.e. Non-Dipolar Structure. The previous minimum data exhibit a Dipolar Structure.

Synoptic Carrington Solar Wind Speed Maps for 2008 (Cycle 23/24) and 1996Cycle 22/23)Equatorial fast wind Rapid evolution of the large-scale structureLarger latitude width of slow wind region

SummaryUpgrade Project of STEL Multi-Station IPS SystemDevelopment of a New IPS Antenna at Toyokawa (SWIFT), and Preliminary ObservationsImprovement of Fuji and Kiso IPS AntennasRecent STEL ObservationsPeculiar Aspect of the Current Sunspot MinimumRef. Tokumaru et al., GRL, in press, 2009 (doi:10.1029/2009GL037461). Continuous monitoring of the solar wind is needed.

Toyokawa IPS Workshop2007 October 30-31A Series of IPS workshopsSan Diego, US (2004), Pushchino, Russina (2006)TopicsIPS Observations and Space Weather StudiesCollaboration with Spacecraft MissionBasic Sciences Using Heliospheric Sounding MeasurementsIPS World Network and Common Database22 participants from US, UK, Germany, India, Russia, Mexico, and Japan IPSWLFR

This slide shows four large antennas dedicated for IPS observations.We are collecting IPS data regularly using this system between April and December. The observing frequency is 327-MHz, and this frequency allows us to observe the solar wind between 0,1 and 1 AU.We derive solar wind speeds and scintillation level, so-called g-value from IPS observations using this system.We have carried out IPS observations for long time, but IPS still serves as a useful tool for studying the solar wind. So, we started an upgrade project to enhance capability of our IPS observations.As the first step, we have constructed a new IPS antenna at Toyokawa.

This slide shows the new IPS antenna at Toyokawa.

This antenna has a large aperture area, which enables to observe more sources than other antennas. Since resolution of deconvolved IPS data depends on no. of lines-of-sight used in a day, we expect to improve our IPS observations by using this antenna.

In October 2007 we had a small workshop at Toyokawa. At that time, this antenna was under construction.

This is one of pictures taken when workshop participants visited the antenna site. This is another picture taken on the upper deck of the antenna.The low-noise receivers are installed in this box.

We completed development of this antenna in last summer, and have performed preliminary IPS observations to examine the system performance.This slide shows scintillation level measurements for a good IPS source made using the Toyokawa new antenna in 2008. The scintillation level was estimated from power spectra of IPS.

This plots shows radial variation of scintillation level, and this is time variation of scintillation level. As the line-of-sight of this source approached to the sun, the scintillation level systematically increased owing to enhanced density fluctuations near the sun. We fit such a power law function to observed scintillation data, and derived the g-value by normalizing the data with this function. Lower two plots show g-value data. These g-value data represent the relative variation of density fluctuations delta Ne. We observe many sources in a day, and derive the g-value by fitting this function to IPS data for each source.

This slide shows sky projection maps of g-value derived from Toyokawa new antenna and Kiso antenna for this day. The solar wind was mostly calm, so most of the g-value data were nearly equal to unity, and there was no enhancement. An important point to note is that no. of lines-of-sight of Toyokawa antenna is much greater than that of Kiso. IPS power spectra contain a various kind of information of the solar wind plasma. We can determine some of them by fitting the theoretical model to observed spectra. This slide show examples of the spectral fitting analysis of Toyokawa IPS observations.In these cases, the solar wind speed, the axial ratio and spectral index of density turbulence were determined from the fitting analysis.We also estimate the solar wind speed from cross correlation analysis of three-station IPS data.We will compare the speed data derived by spectral fit with three-station measurements.

At present, Toyokawa antenna cannot take correlation with other antennas, since the data format is different.

So, we are working to upgrade Fuji and Kiso systems. It will take one or two years to complete this project. This upgrade allow us to derive the solar wind speed from Toyokawa, Fuji, and Kiso IPS data.This slide shows the solar wind speed maps derived from our IPS observations between 1991 and 2000; corresponding to cycle 22 and 23 maxima. Red color represents the slow speed wind, and blue is the fast wind. As shown here, the solar wind structure systematically evolves during the sunspot cycle.Now the solar activity is very low, and we have a lot of spotless days, thus this solar minimum is a bit strange.Our IPS data taken in this minimum show unusual features of the solar wind. This slide shows synoptic Carrington maps of the solar wind speed obtained from IPS observations in 2008 and 1996; current and previous minima.The solar wind during the previous minimum exhibited a dipolar structure which consists of slow wind at the equator and fast winds over both poles. On the other hand, the solar wind structure in the current minimum greatly differed from this structure. Fast winds exist at the equator as well as at the poles, and slow wind exist in between. Thus, the structure is significantly non-dipolar. Another important point to note is that the solar wind during the current minimum shows a high degree of variability.This slide show synoptic annual maps of the solar wind speed for 2008 and 1996. The equatorial slow wind observed in 1996 was very stable, and show little change over several rotations. In contrast, the slow wind observed in last year showed a rapid variation, and this is greatly different from the previous minimum.In addition, there is a big difference in latitude width of the slow wind between 1996 and 2008.Now I summarize may talk.Recently we have developed the new IPS antenna at Toyokawa, and observations, and started preliminary IPS observations using it.We are working on upgrade of existing two IPS antennas at Fuji and Kiso.

I also reported peculiar features of the solar wind revealed from our IPS observations during this minimum.I think that we need to carefully monitor how the solar wind evolves in the cycle 24.

Thank you. In 2007, we had a small workshop at Toyokawa, Japan.This meeting was third one to discuss remote sensing observations of the heliosphere, and 22 participants from various countries joined this meeting. The following topics were addressed in this meeting.