EISCAT Tromsø

Progress in Interplanetary Scintillation Bill Coles, University of California at San Diego A. The Solar Wind: B. Radio Scattering: C. Observations: D. Recent progress:

Eclipse in White Light - HAO - Feb. 16, India Helmet streamers Typical of Solar Maximum

Eclipse in White Light - HAO - March, Typical of Solar Minimum Coronal Hole

The Solar Wind 1.The existence of the solar wind could have been inferred from the shape of helmet streamers. 2. It could also have been inferred from measurements of the aurora. 3. It was inferred from observations of the direction of the ionic comet-tails.

Coronal hole Soft X-ray Telescope (SXT) on Yohkoh Satellite

Mauna Loa Mk3 WLC and Yohkoh SXT Polar coronal holes

The LASCO C2 Coronagraph at Solar Minimum Sun Occulting Disc Sun Grazing Comet

Closeup of Loops from Trace

Sun Solar Wind  drifting intensity pattern incident plane wave compact radio source receiving antennas baseline Plan view of an ecliptic observation drifting phase pattern angular spectrum of plane waves

Radio Scattering Velocity Measurement Raw Time Series at 2 AntennasAuto and Cross Correlations

Velocity Map typical of Solar Minimum

Velocity vs Latitude over Solar Cycle UCSDNagoya Dennison & Hewish, 1966 Hewish & Symonds, 1967 Solar Maximum

VLA Observations of Angular Scattering  s) = e -0.5 D(s)

Anisotropy vs Solar Distance Model A R (R) of plasma expected A R (R) for radio wave The vertical bars indicate variation not statistical error

Helios (equatorial)Ulysses (polar) VLBA (polar) Grall et al., VLA par (polar) Harmon and Coles (mean) Paetzold & Bird (polar) VLA perp Woo & Armstrong (mean) Scale Dependence of Anisotropy

Manoharan obs Coles and Harmon tabulation from various sources

Observed coherence scale Equatorial - no inner scale Polar - with inner scale

These characteristics of the solar wind microstructure have been known for 20 years. They lead John Harmon to propose that the micro- structure was caused by obliquely propagating Alfven waves because these waves would satisfy all four of the properties discussed: 1.They would cause radial elongation of the structure 2.The elongation would decrease with distance 3.The spectrum would be flatter than Kolmogorov 4.The waves would damp at the ion inertial scale. The problem is that these waves would also cause the intensity diffraction pattern to move outwards with respect to the flow at the group velocity of the waves V A. For quite some time we did not think this was compatible with the observations. We now believe that the velocity observations are compatible with these waves.

240 km 160 km 80 km The Resolving Power of Long Baselines

at 11 R s  V PAR alone  V PERP alone  V PERP = 80 km/s  V PAR = ( km/s)

Cross Correlation of Intensity in Fast Wind 10 R S at VLBA -solar minimum -half the baselines shown -slow and fast peaks clear -best fit model not unique

Cross Correlation of Intensity in Fast Wind 3 R S at VLBA

Measured IPS Parallel Velocity Distribution theoretical model upper envelope = V MODEL + V A

Aug 234Position of on GMRT Imaging at 600 MHz.

Implication Variations in angular scattering are not obviously correlated with variations in density. Angular scattering is  a column integral of density 2, whereas white light brightness is  a column integral of density. Apparently scattering near the Sun is dominated by small but dense structures which are invisible in white light because their contribution to integrated density is negligible, however they contribute to scattering because they contribute significantly to the integral of density 2.