Solar System Physics Group IPS Using EISCAT and MERLIN: Extremely-Long Baseline Observations at Multiple Frequencies R.A.Fallows, A.R.Breen, M.M.Bisi,

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


~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


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.


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.


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.


September 2003 TrialsSeptember 2003 Trials

1256-057, distance = 27Rs

928MHz

928/1420MHz

928/1420MHz


September 2003 TrialsSeptember 2003 Trials

1150-003, distance = 37Rs

928MHz

928/1420MHz

928/1420MHz


Using the ESRUsing the ESR

0319+415, distance = 85Rs

928/1420MHz

928/500MHz

1420/500MHz


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


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.


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


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.


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)?


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


Interacting StreamsInteracting Streams

Results indicate significant off-radial flow

Ulysses observations of CIRs from 1992 and 1996 indicate similar degree of off-radial flow.


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


June 2006 ObservationsJune 2006 Observations

0521+166Distance: 24RsLatitude: 81°S

20060610

20060611

Twin-peak (multi-peak???) fast stream seen.


Interplanetary Magnetic Cloud?Interplanetary Magnetic Cloud?

0319+415 on 20050514

Probable 2 fast streams with varying flow direction.Interplanetary magnetic cloud passing through?


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.


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).


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.


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?


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.



Signal variation appeared to correspond with solar flare and radio burst seen by GOES and Phoenix-2.



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.


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?


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?


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

Documents

Solar System Physics Group IPS Using EISCAT and MERLIN: Extremely-Long Baseline Observations at Multiple Frequencies R.A.Fallows, A.R.Breen, M.M.Bisi,