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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,

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Presentation on theme: "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,"— Presentation transcript:

1 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, R.A.Jones and G.D.Dorrian

2 Solar System Physics Group ~1350km Tromsø ESR (Longyearbyen) Jodrell Bank ~1800km The Radio Systems Used Tromsø Kiruna Sodankylä ~390km Jodrell Bank Knockin Cambridge ~200km EISCAT MERLIN

3 Solar System Physics Group Technique 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.

4 Solar System Physics Group Science 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.

5 Solar System Physics Group Dual-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.

6 Solar System Physics Group September 2003 Trials 1256-057, distance = 27Rs 928MHz 928/1420MHz

7 Solar System Physics Group September 2003 Trials 1150-003, distance = 37Rs 928MHz 928/1420MHz

8 Solar System Physics Group Using the ESR 0319+415, distance = 85Rs 928/1420MHz 928/500MHz 1420/500MHz

9 Solar System Physics Group Comparison 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

10 Solar System Physics Group Extremely-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.

11 Solar System Physics Group May 2002 Trials 0319+415, 15/05/2002 Sodankylä-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

12 Solar System Physics Group Determining Flow Direction Ecliptic plane Beam 1 Beam 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.

13 Solar System Physics Group Fast 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)?

14 Solar System Physics Group Interacting Streams 0431+206, 15/05/2002 Sodankylä-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

15 Solar System Physics Group Interacting Streams Results indicate significant off-radial flow Ulysses observations of CIRs from 1992 and 1996 indicate similar degree of off-radial flow.

16 Solar System Physics Group Fast and Faster Flow 0319+415, 2004/05/12 Tromsø -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

17 Solar System Physics Group June 2006 Observations 0521+166 Distance: 24Rs Latitude: 81°S 20060610 20060611 Twin-peak (multi-peak???) fast stream seen.

18 Solar System Physics Group Interplanetary Magnetic Cloud? 0319+415 on 20050514 Probable 2 fast streams with varying flow direction. Interplanetary magnetic cloud passing through?

19 Solar System Physics Group Identifying 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.

20 Solar System Physics Group IPS Observation of 1229+020 Earth-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).

21 Solar System Physics Group CME Case Study: 19970929 CME 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.

22 Solar System Physics Group 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?

23 Solar System Physics Group Solar 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.

24 Solar System Physics Group Solar Flare Radio Burst Signal variation appeared to correspond with solar flare and radio burst seen by GOES and Phoenix-2.

25 Solar System Physics Group Solar 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.

26 Solar System Physics Group Future 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?

27 Solar System Physics Group Future 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?

28 Solar System Physics Group Remote Sensing of the Inner Heliosphere A meeting bringing together the remote sensing communities studying the inner heliosphere, including IPS and white light. Aberystwyth, Summer 2007

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