solar system physics group heliospheric physics with lofar andy breen, richard fallows solar system...

Solar System Physics Group

Heliospheric physics with LOFAR

Andy Breen, Richard Fallows Solar System Physics Group

Aberystwyth University

Mario BisiCenter for Astrophysics and Space Sciences

University of California, San Diego


Solar wind: supersonic outflow of plasma from Sun into space

Carries solar magnetic field with it

Carries solar disturbances out to planets

Carves out cavity in interstellar medium – heliosphere

Similar winds found around all Sun-like stars (& dwarf stars)

Heliospheres and stellarspheresHeliospheres and stellarspheres


Examples of heliospheric structuresExamples of heliospheric structuresMacrostructure

Background structurebasically bimodal (most clearly at solar minimum)

fast flow above open field regions, slow flow above streamersorigin of slow wind not well-understood

Stream interaction regionsCoronal mass ejections

“Mesostructure”Smaller scale features than macrostructure

Very obvious in STEREO HI imagesCME internal structure

Smaller transients (“Sheeley blobs”, “Rouillard blobs”)Other uncatagorised “stuff” - but lots of it

MicrostructureIPS scale irregularities (10s-100s km)

Turbulence


Examples of macro- and mesoscale structures in the solar

wind, April 2007(STEREO HI-1A)

How do these structures interact with each other and with the background wind?

How is the structure of the background wind influenced by interaction with these structures?

Interaction between structures and solar system objects (e.g. comets, planetary environments..)


White-light imaging and radio observationsWhite-light imaging and radio observationsor, why do we need radio observations now we've got STEREO?or, why do we need radio observations now we've got STEREO?

Temporal resolutionSTEREO HI cameras return images every 40 minutes (inner field, HI-1) or 2 hours (outer field, HI-2). Radio scintillation (IPS) measurements can give density-proxy and bulk velocity estimates on < 10 minute cadences

Different sensitivity to electron density:White light imagers observe photospheric light Thomson-scattered by solar wind electrons – linear sensitivity to N

e

IPS observes interference pattern cast by refraction (by solar wind turbulence) of signals from deep-sky sources - ~ N

e2

sensitivity

Multi-site IPS measurements can detect other solar wind properties e.g. magnetic field rotation in CMEs/transients....


3D velocity reconstruction from EISCAT IPS data (B.V. Jackson and M.M. Bisi)

To study:• Internal structure of CMEs• CME/solar wind interaction• CME/SIR interaction• Evolution of mesoscale structure• Interaction of mesoscale structure with CMEs and SIRs• Interaction of solar wind structures with comets and planetary environments• Cometary and planetary tails

Need at least as good spatial resolution (sources/day..) as Ootacamund, many more long-baseline 2-site observations/day than STELab or EISCAT


LOFARLOFAR

LOFAR should provide all these things!

Ample collecting areaPlenty of combinations of 2-site observations

Should be able to match Ootacamund’s number of source-observations/day, exceed 100 2-site observations/day (currently being verified!)

~5°angular resolution in tomographic reconstructions looks achievable with LOFAR data

MWA will match (and probably exceed) number of source-observations/day, but won’t offer 2-site measurements

Won’t be able to study physical parameters (turbulence, flow direction) that LOFAR will be able to detect


IPS requires:• Rapid sampling rate (>50 Hz, ideally >100 Hz)• Wide receiver pass-band (> 10 MHz)

Only total received power measurements are required

• Want to observe as many sources/day as possible, on as many days as possible

• Want to make many 2-site measurements

Experiment should run on “remote” (non-core) sites, ideally in background mode

Want to observe > 1 source at a time – multiple beams Need to automatically schedule, make, pipeline and 1st-

stage process observations

LOFAR – what's needed for IPSLOFAR – what's needed for IPS


First resultsFirst results

Time-series of received power from 3C273 on LOFAR LBA, Nov. 2010


3C273 on LBA, November 2010 – scintillation clearly present


Scintillation spectrum from LOFAR LBA 3C273Clear scintillation out to > 5 Hz

Form consistent with IPS (scintillation from solar wind)


What’s needed What’s needed nownow

Need to safeguard non-core observing time for solar and heliospheric experiments

IPS experiment for LOFAR needs further development•2-site measurements•Multi-beam capability•Automatic pipelining•Automated scheduling

1st IPS LOFAR observations now carried outMore development run-time needed1st long-baseline 2-site observations (Netherlands-Chilbolton?) to be trialled this winter (aim!)


Acknowledgements

EISCAT scientific association (EISCAT data)

B.V. Jackson, P. Hick (CASS, UCSD), for help - and code - for tomographic reconstructions

LOFAR staff for invaluable help with IPS experiment development

LOFAR Pulsars KSP busy group for help and co-operation with IPS experiment development

solar system physics group heliospheric physics with lofar andy breen, richard fallows solar system...

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