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Solar System Physics Group
IPS Using EISCAT and MERLIN:IPS Using EISCAT and MERLIN:Extremely-Long Baseline Extremely-Long Baseline Observations at Multiple Observations at Multiple
FrequenciesFrequencies
R.A.Fallows, A.R.Breen, M.M.Bisi, R.A.Jones R.A.Fallows, A.R.Breen, M.M.Bisi, R.A.Jones and G.D.Dorrianand G.D.Dorrian
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Solar System Physics Group
~1350km
Tromsø
ESR (Longyearbyen)
Jodrell Bank
~1800km
The Radio Systems UsedThe Radio Systems Used
Tromsø
Kiruna
Sodankylä
~390km
Jodrell Bank
Knockin
Cambridge
~200km
EISCAT
MERLIN
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Solar System Physics Group
Technique ImprovementsTechnique Improvements
• Multi-frequency observations:-– Correlations give results consistent with single-
frequency cases.– Improved flexibility in terms of radio systems that
can be used.
• Extremely-Long Baselines:-– Greatly improved ability to resolve solar wind
streams in the line of sight.– Better sensitivity of actual flow direction.
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Solar System Physics Group
Science HighlightsScience Highlights
• Correlation at 8s time lag detected, indicating a minimum evolution time for density variations.
• Off-radial flow direction observed in fast and slow streams, and in developing interaction region.
• 2-mode fast solar wind detected.• Solar flare radio burst seen simultaneously in
two independent radio systems.• Confirmation of iCME speed converging on
solar wind speed.
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Solar System Physics Group
Dual-Frequency CorrelationsDual-Frequency Correlations
• Two test observations carried out in May 2003 after 1420MHz upgrade to Kiruna and Sodankyla antennas.
• Further trials in September 2003.• ESR trialled for IPS for the first time in May
2004.
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Solar System Physics Group
September 2003 TrialsSeptember 2003 Trials
1256-057, distance = 27Rs
928MHz
928/1420MHz
928/1420MHz
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Solar System Physics Group
September 2003 TrialsSeptember 2003 Trials
1150-003, distance = 37Rs
928MHz
928/1420MHz
928/1420MHz
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Solar System Physics Group
Using the ESRUsing the ESR
0319+415, distance = 85Rs
928/1420MHz
928/500MHz
1420/500MHz
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Solar System Physics Group
Comparison With TheoryComparison With Theory
Single stream assuming a point source used in this model.
Cross-correlations fit very well.
Poor fit to Auto-correlations, probably because source is broad.
Matlab script courtesy of Bill Coles
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Solar System Physics Group
Extremely-Long BaselinesExtremely-Long Baselines
• MERLIN in the UK used for IPS for a number of years, often in 5GHz mode for measurements in acceleration region.
• Upgrade of EISCAT to 1420MHz prompted trial of simultaneous EISCAT/MERLIN observations.
• Significant correlation found, even with baselines of 2000km.
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Solar System Physics Group
May 2002 TrialsMay 2002 Trials
0319+415, 15/05/2002Sodankylä-Jodrell Bank
High northern latitude source.
Clear fast and slow peaks.
Significant correlation observed at time-lags of up to 8s.
Baselines of Observation: Parallel: -1631 to -1911 km; Perp.: -146 to +57 km
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Solar System Physics Group
Determining Flow DirectionDetermining Flow Direction
Ecliptic plane
Beam 1Beam 2
Parallel baseline, B par Perpendicular
baseline, B perp
Sky-Plane View:
Level of cross-correlation increases and then decreases as baselines rotate through the radial direction and across the solar wind flow.
Maximum correlation occurs when the baselines lie in the direction of flow.
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Solar System Physics Group
Fast and Slow Stream DirectionsFast and Slow Stream Directions
Over-expansion in the fast wind?
Effects of stream interaction or genuine expansion (resulting in a 'convergence layer' between fast and slow streams)?
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Solar System Physics Group
Interacting StreamsInteracting Streams
0431+206, 15/05/2002Sodankylä-Jodrell Bank
Source just south of helioequator; raypath along boundary of equatorial coronal hole.
Intermediate flow.
Baselines: Parallel: -1330 to -1562 km, Perp.: -143 to -318 km
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Solar System Physics Group
Interacting StreamsInteracting Streams
Results indicate significant off-radial flow
Ulysses observations of CIRs from 1992 and 1996 indicate similar degree of off-radial flow.
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Solar System Physics Group
Fast and Faster FlowFast and Faster Flow
0319+415, 2004/05/12Tromsø -Jodrell Bank
Two-component fast wind detected, probably corresponding to polar crown and equatorial extension of coronal hole.
Flow direction off-radial by 1-2° equatorwards.
Suggestion that fast wind is more off-radial than faster wind???
Baselines: Parallel: -1760 to -1907 km; Perp.: -152 to 119 km
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Solar System Physics Group
June 2006 ObservationsJune 2006 Observations
0521+166Distance: 24RsLatitude: 81°S
20060610
20060611
Twin-peak (multi-peak???) fast stream seen.
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Solar System Physics Group
Interplanetary Magnetic Cloud?Interplanetary Magnetic Cloud?
0319+415 on 20050514
Probable 2 fast streams with varying flow direction.Interplanetary magnetic cloud passing through?
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Solar System Physics Group
Identifying CMEsIdentifying CMEs
• There are a number of indications of the presence of a CME in IPS measurements:-– A significant negative lobe in the cross-correlation
function at or near zero time lag.– Variation of features seen in the cross-correlation
function over a few hours.– Modelled axial ratio of density variations < 1.– Enhanced level of scintillation.
• CME candidates identified by calculating flight time of LASCO CMEs to potential IPS observations to see if there is a possible match.
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Solar System Physics Group
IPS Observation of 1229+020IPS Observation of 1229+020Earth-directed CME observed in LASCO on 20030914. IPS measurements of 1229+020 on 20030916 indicate presence of a CME.
Comparison with LASCO and ACE indicates CME tending towards background flow speed (as determined by previous day's IPS measurements).
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Solar System Physics Group
CME Case Study: 19970929CME Case Study: 19970929CME seen in LASCO on 19970928.
Indications seen in IPS observation of 1150-003 on 19970929.
Calculations of possible flight times based on LASCO speeds indicate that head of CME had already passed IPS line of sight.
Internal arcades identified as possible candidates.
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Solar System Physics Group
Interaction Between CME Features?Interaction Between CME Features?
Calculated radial speeds for the arcade structures indicate a declining speed leaving C3 field of view.
IPS speed shows a subsequent acceleration.
'Last front' interacting with the arcades to boost speed between C3 and IPS?
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Solar System Physics Group
Solar Flare Radio BurstSolar Flare Radio Burst
EISCAT/MERLIN observation of 0319+415 on 20050513:
Sudden intense variation in signal power received simultaneously at all EISCAT and MERLIN sites.
Seen before at EISCAT, but this is first confirmation from an independent radio system.
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Solar System Physics Group
Solar Flare Radio BurstSolar Flare Radio Burst
Signal variation appeared to correspond with solar flare and radio burst seen by GOES and Phoenix-2.
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Solar System Physics Group
Solar Flare Radio BurstSolar Flare Radio Burst
Plotting appropriate frequencies of Phoenix-2 Data and EISCAT/MERLIN data indicate an exact correlation in time. Peak of 928MHz data (right) resolved by Tromso when Phoenix-2 is saturated.
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Solar System Physics Group
Future WorkFuture Work• The Fast stream(s):-
– What are the coronal origins of the fast stream(s)?– What is the origin of the equatorward expansion seen?
• Direction of flow:-– How does this evolve with distance?– Is the slow stream really expanding polewards?
• CMEs:-– Can we measure an improved velocity profile?
• Density variations and turbulence:-– Can multi-frequency power spectra provide new
information on the power spectrum of density variations in the solar wind?
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Solar System Physics Group
Future WorkFuture Work
• New measurements of radio sources crossing the paths of the inner planets to be trialled:-– Can we detect any change in flow around the
planets Mercury and Venus?– Can we infer anything about Mercury's magnetic
field from such measurements?
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Solar System Physics Group
Remote Sensing of the Inner Remote Sensing of the Inner HeliosphereHeliosphere
A meeting bringing together the remote sensing communities studying the inner heliosphere,
including IPS and white light.
Aberystwyth, Summer 2007