EISCAT Troms

1
EISCAT Tromsø
2
Progress in Interplanetary Scintillation Bill
Coles, University of California at San Diego A.
The Solar Wind B. Radio Scattering C.
Observations D. Recent progress
3
Helmet streamers
Eclipse in White Light - HAO - Feb. 16, 1980 -
India
Typical of Solar Maximum
4
Coronal Hole
Eclipse in White Light - HAO - March, 18 1988
Typical of Solar Minimum
5
The Solar Wind

• 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.

6
Coronal hole
Soft X-ray Telescope (SXT) on Yohkoh Satellite
7
Mauna Loa Mk3 WLC and Yohkoh SXT
Polar coronal holes
8
The LASCO C2 Coronagraph at Solar Minimum
Occulting Disc
Sun
Sun Grazing Comet
9
(No Transcript)
10
Closeup of Loops from Trace
11
(No Transcript)
12
Plan view of an ecliptic observation
drifting intensity pattern
drifting phase pattern
incident plane wave
receiving antennas
Solar Wind
?
compact radio source
baseline
Sun
angular spectrum of plane waves
13
Radio Scattering Velocity Measurement
Raw Time Series at 2 Antennas
Auto and Cross Correlations
14
(No Transcript)
15
Velocity Map typical of Solar Minimum
16
1990
1994
1991
1995
1992
1996
1993
1997
17
Velocity vs Latitude over Solar Cycle
UCSD
Nagoya
Dennison Hewish, 1966
Hewish Symonds, 1967
Solar Maximum
18
VLA Observations of Angular Scattering
r(s) e-0.5 D(s)
19
Anisotropy vs Solar Distance
The vertical bars indicate variation not
statistical error
Model AR(R) of plasma
expected AR(R) for radio wave
20
Scale Dependence of Anisotropy
Helios (equatorial)
Ulysses (polar)
Woo Armstrong (mean)
Paetzold Bird (polar)
VLA perp
VLBA (polar)
Harmon and Coles (mean)
Grall et al., VLA par (polar)
21
Manoharan obs
Coles and Harmon tabulation from various sources
22
Equatorial - no inner scale
Polar - with inner scale
Observed coherence scale
23

• 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
• They would cause radial elongation of the
  structure
• The elongation would decrease with distance
• The spectrum would be flatter than Kolmogorov
• 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 VA. 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.

24
(No Transcript)
25
(No Transcript)
26
(No Transcript)
27
The Resolving Power of Long Baselines
80 km
160 km
240 km
28
?VPAR (520 - 1200 km/s)
?VPERP 80 km/s
951021 at 11 Rs
?VPERP alone
?VPAR alone
29
Cross Correlation of Intensity in Fast Wind 10
RS at VLBA
-solar minimum -half the baselines shown -slow
and fast peaks clear -best fit model not unique
30
Cross Correlation of Intensity in Fast Wind 3
RS at VLBA
31
Measured IPS Parallel Velocity Distribution
upper envelope VMODEL VA
theoretical model
32
(No Transcript)
33
(No Transcript)
34
GMRT Imaging at 600 MHz.
Aug 2
3
4
Position of 0854201 on
35
(No Transcript)
36
Implication Variations in angular scattering are
not obviously correlated with variations in
density. Angular scattering is ? a column
integral of density2, 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
density2.
37
(No Transcript)