P'K' Manoharan

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Radio Scintillation Imaging of Solar
Wind Structures from Sun to Earth
Radio Scintillation Imaging of Solar
Wind Structures from Sun to Earth
P.K. Manoharan Radio Astronomy Centre National
Centre for Radio Astrophysics Tata Institute of
Fundamental Research Ooty 643001,
India mano_at_ncra.tifr.res.in
P.K. Manoharan Radio Astronomy Centre National
Centre for Radio Astrophysics Tata Institute of
Fundamental Research Ooty 643001,
India mano_at_ncra.tifr.res.in
Low-Frequency Radio Universe December 8 12,
2008 NCRA-TIFR, Pune
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This presentation is dedicated toLate Prof.
N.V.G. Sarma
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Outline of the talk
Ooty Scintillation Studies

• Outline
• Interplanetary Scintillation
• Coronal Structures and associated solar wind
• Solar-wind Speed and Density Turbulence images
• Solar Cycle 23 Changes in 3-D Solar wind
• Propagation of CME in the inner heliosphere
• Summary

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Solar Wind

• Solar wind collisionless, magnetized plasma
• Continual, but variable, out flow from the Sun
• Composed of approximately equal numbers of ions
  and electrons
• Ions predominantly of protons (95) small
  amount of doubly ionized helium and trace amounts
  of heavier ions
• Drags coronal magnetic field
• Supersonic (and super Alfvenic)
• Hot gt 105 K
• Rarified (few particles/cm-3 at 1 AU)
• Complex (due to solar variability, solar
  rotation, in-situ processes)
• Carries waves and turbulence
• Evolution of solar wind turbulence in the
  near-Sun region is important
• Role of turbulence in accelerating the solar wind
• Origin of fluctuations themselves
• Interplanetary scintillation (IPS) technique is
  useful to probe the level of turbulence in the
  solar wind

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Interplanetary Scintillation Studies
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Interplanetary Scintillation
Radio source
L-O-S
Sun
Earth
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Intensity scintillation
Intensity, I(t)
Time (t)
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IPS Power Spectrum
Space and time correlation of Intensity
fluctuations
Transformation of the autocorrelation function
gives the power spectrum
Radial dependence of density fluctuations
Scintillation Index (m) measure of density
fluctuations (turbulence)
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Solar wind Density Turbulence

• Density Turbulence
• Scintillation index, m, is a measure of
  level of turbulence
• Normalized Scintillation index, g m(R) /
  ltm(R)gt
• g gt 1 ? enhancement in ?Ne
• g ? 1 ? ambient level of ?Ne
• g lt 1 ? rarefaction in ?Ne

Scintillation enhancement w.r.t. the ambient wind
identifies the presence of solar wind transients
along the line-of-sight to the radio source
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• Interplanetary Scintillation measurements
• Provide 3-D view of the inner heliosphere
• Level of density fluctuations (or) turbulence
• Scale-size of density irregularities
• Speed of the solar wind
• Information on angular size of radio source

• Solar wind speed and Density turbulence
• spectrum, FNe(q)
• By suitably transforming and calibrating the
  intensity scintillation time series

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Solar wind Relation to coronal Structures
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Origin of low-speed wind
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What determines the solar wind speed ?
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Spectra associated with ambient low- and
high-speed solar wind flows
Solar wind Density turbulence spectrum
Density turbulence spectrum associated with
propagating CME
cut-off (inertial) scale VA/?P
N1/2 VA Alfven speed ?P
Proton cyclotron frequency N Plasma density
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Interplanetary Scintillation at Ooty
Importance of IPS technique increases when the
day to-day monitoring of heliosphere (solar wind)
is made on a grid of large number of radio
sources.

• ORT can observe Solar wind
• 20 250 Rsun
• at all helio latitudes
• large number of sources observed (900 per day)
• provide density turbulence and speed images in
  3-D

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Distribution of IPS Sources
4500 sources
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Solar rotation and radial outward flow of the
solar wind provide the 3-d structure of the
solar wind at different view angles
Computer Assisted Tomography analysis
can remove the line-of-sight integration imposed
on the solar wind parameters also provides high
spatial resolution
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Solar Wind Density Turbulence and Speed (3 days)
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Ooty IPS measurements Density Turbulence and
Speed of the Solar Wind in the Inner heliosphere
February 25 March 25, 2005
CR2027
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Distribution of IPS Sources
(angular size of compact component)
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Solar Cycle 23 - Photospheric Magnetic Field
Latitude (deg)
1
Year
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Solar Cycle 23 Solar Wind Density Distribution
Solar Wind Density Turbulence (Ooty)
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Solar Cycle 23 Solar wind Speed Distribution
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Interaction and Shock formation

• An interaction region compresses the magnetic
  field of the ambient solar wind by an amount such
  that its pressure equals the rate of change of
  the momentum of the diver.
• In the region between the shock and driver, thus
  a strong amplification of magnetic field is
  possible.

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Radial Evolution of Coronal Mass Ejections
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Coronal Mass Ejections
Coronal Mass Ejections

• ? Largest phenomenon associated with the
  dissipation of
• magnetic flux at and above the surface of
  the Sun
• ? Travel outward at range of speeds, 10 -- 2500
  km/s
• ? Mass involved in each ejection is 1014
  1015 g
• ? Main cause of large geo-magnetic storms
• ? CMEs appear to be an important factor of
  space weather,
• which has multiple geospheric, biospheric,
  and technological
• effects.
• ? A great interest in understanding the
  propagation and arrival
• of Earth-directed CMEs, which cause major
  storms at the
• Earths magnetosphere.
• ? However, there are many open questions
  concerning CMEs
• origin, evolution, structure/extent in the
  interplanetary space

• ? Largest phenomenon associated with the
  dissipation of
• magnetic flux at and above the surface of
  the Sun
• ? Travel outward at range of speeds, 10 -- 2500
  km/s
• ? Mass involved in each ejection is 1014
  1015 g
• ? Main cause of large geo-magnetic storms
• ? CMEs appear to be an important factor of
  space weather,
• which has multiple geospheric, biospheric,
  and technological
• effects.
• ? A great interest in understanding the
  propagation and arrival
• of Earth-directed CMEs, which cause major
  storms at the
• Earths magnetosphere.
• ? However, there are many open questions
  concerning CMEs
• origin, evolution, structure/extent in the
  interplanetary space

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IPS Imaging of interplanetary disturbances (CIRs
and CMEs)
Shock
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Continuous acceleration? energy source?
IPS
Height-Time Plot
LASCO
Speed-Distance Plot
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CME Propagation Speed (from Sun to Earth)
Height Time plot
Radial Evolution of Speed
K.E. lost/dissipated within lt100Rsun 1032 erg
VCME R-0.08 at R lt 100 Rsun VCME R-0.72 at
R gt 100 Rsun
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• VCME(R) of 30 CMEs
• IPS LASCO provide sky-plane speeds
• Include constant speed, accelerating and
• decelerating events
• VCME(R) can be represented by power-law
• forms
• VCME(R) R-ß R lt 50 R?
• VCME(R) R-a R 100 - 200 R?
• 2-step effective acceleration
• Transition around 70 80 R?
• at R lt 70 R? -0.3 lt ß lt 0.06

Speed Profiles VCME(R)
deceleration
constant speed
acceleration
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CME Initial Speed vs Acceleration Slope at R gt
70 R?
deceleration zone
V 380 km/s
a 0.2-6.410-4V1.110-7V2
Aerodynamic drag force Interaction between CME
cloud and ambient solar wind plays an important
role in controlling the propagation of CME K.E.
utilized/gained times a against the drag force
imposed by the ambient solar wind (VCME
VAMB)2 shows good linear correlation (97)
acceleration zone
zero acceleration line
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59 Events CME Initial Speed (LASCO field of view)
CME at 100 R? (Ooty IPS)
ICME Speed (at 1 AU)
Shock Speed (at 1 AU)
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Geometry of magnetic flux rope IPS, cosmic ray,
and Spacecraft measurements
from Cosmic Ray data
from ACE IMF data
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Current 3D Ooty Density Reconstruction
The left movie shows an ecliptic cut through the
3D Ooty IPS density reconstruction and the right
movie show a meridional cut (from East of the
Sun-Earth line) of the same both with the Earth
on the right-hand side and its orbit shown in
each case
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Speed Comparisons with Wind in situ Data
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CME internal energy
Summary
Ooty IPS measurements can provide the 3-D view of
solar wind transients, their dynamics, and nature
of interaction at the near-earth environment.

• Near-Earth Manifestations required dynamic
  pressure and kinetic energy density depend on the
  energy exerted/deposited by the CME in the sheath
  portion of the shock
• compression energy available from the CME
  expansion
• Ooty images will be useful in understanding the
  reconnection processes associated with the
  earth-directed CMEs.
• Space Weather Forecast Ooty data will play a
  crucial role

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Thank You
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Radial Evolution of CIRs
75 solar radii
100 solar radii
expansion
150 solar radii
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Initial Speed Arrival Time at 1 AU
TCME 109 - 0.5 10-1 VCME 1.1 10-5 V2CME
hours VCME 400 km/s, TCME 90 hours
(considerable assistance by CME expansion) VCME
2000 km/s, TCME dominated by interaction
Includes energy provided by CME Expansion SW
interaction
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Bastille Day EventCoronal Mass Ejection July
14, 2000
TRACE Image of magnetic flux rope
236-MHz radio contour on Ha image
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CME in the interplanetary medium
LASCO Images lt30 Rsun
Waves Radio Spectrum
Ooty Scintillation Images 50 - 250 Rsun