1 November, 20061 November, 2006 SHI MeetingSHI Meeting

IPS and Solar ImagingIPS and Solar Imaging

Divya OberoiDivya OberoiMIT Haystack ObservatoryMIT Haystack Observatory

OutlineOutline

The lowThe low--frequency advantagefrequency advantageInterplanetary Scintillation studiesInterplanetary Scintillation studiesSolar ImagingSolar ImagingAn example from Early Deployment An example from Early Deployment observationsobservationsPrototype arrayPrototype arrayConclusionConclusion

The low frequency advantageThe low frequency advantage

Propagation effects due to solar wind Propagation effects due to solar wind become increasingly discernible below become increasingly discernible below 1GHz1GHzIonospheric propagation effects are Ionospheric propagation effects are (hopefully) manageable down to ~100 (hopefully) manageable down to ~100 MHzMHzAvailability of useful astronomical sourcesAvailability of useful astronomical sources~100~100--300 MHz optimal300 MHz optimal

Low frequency technologyLow frequency technology

Very wide fields of viewVery wide fields of viewSimultaneous access to a large part of the skySimultaneous access to a large part of the skyAll sky imagingAll sky imaging

Essentially digital instrumentsEssentially digital instrumentsImpressive hardware capabilities at affordable prices Impressive hardware capabilities at affordable prices Large number of simultaneous independent beamsLarge number of simultaneous independent beams

Affordability of computationAffordability of computationWould not have been possible just 5 yrs agoWould not have been possible just 5 yrs ago

Interplanetary Scintillation (IPS)Interplanetary Scintillation (IPS)Plane wavefront incident from a Plane wavefront incident from a distant compact sourcedistant compact source

The density fluctuations in the The density fluctuations in the Solar Wind act like a medium Solar Wind act like a medium with fluctuating refractive index, with fluctuating refractive index, leading to corrugations in the leading to corrugations in the emerging wavefrontemerging wavefront

These phase fluctuations These phase fluctuations develop into intensity develop into intensity fluctuations by the time they fluctuations by the time they reach the observer reach the observer

The resulting interference The resulting interference pattern sweeps past the pattern sweeps past the telescope, leading to IPStelescope, leading to IPS

IPS GeometryIPS Geometry

Earth

Sun

LOS to the source

A lineA line--ofof--sight sight samples solar wind samples solar wind fromfrom

•• an extended region an extended region on the solar surface on the solar surface (linear extent of (linear extent of ~100°)~100°)

•• an extended an extended window in time (few window in time (few days)days)

Lines of sight in one solar rotationLines of sight in one solar rotation

Kojima, M., STELab

If certain If certain assumptions assumptions are satisfied, are satisfied, the IPS data the IPS data can yield a can yield a tomographic tomographic reconstruction reconstruction of the of the heliosphereheliosphere

http://http://casswww.ucsd.edu/solar/forecast/index_v_n.htmlcasswww.ucsd.edu/solar/forecast/index_v_n.html

Jackson and Hick (UCSD), Kojima (STEL)

• Velocity• Density

Limitations of existing observationsLimitations of existing observations

~40 sources/day ~1000 ~40 sources/day ~1000 obsobsnn/Carrington /Carrington rotrotnn

# of constraints/# of free parameters ~ 1# of constraints/# of free parameters ~ 1⇒⇒ reconstructions with 6.5reconstructions with 6.5°°x6.5x6.5°° pixelspixels

11°°x1x1°° resolution and 2 constraints per free parameter resolution and 2 constraints per free parameter ⇒⇒ 100 fold increase in number of observations100 fold increase in number of observations

Limits success to periods of low activity and Limits success to periods of low activity and simple solar wind structuresimple solar wind structure

Limited spatial and temporal sampling of the Limited spatial and temporal sampling of the heliosphereheliosphere

IPS with the MWAIPS with the MWA--LFDLFDWide fields of view + ~16Wide fields of view + ~16 independent beams independent beams for each polarization for each polarization ⇒⇒Vastly improved heliospheric sampling Vastly improved heliospheric sampling --

addresses the most constraining bottleneckaddresses the most constraining bottleneck~20,000 ~20,000 -- 40,000 observations per Carrington 40,000 observations per Carrington rotation, compared to ~1000 currently availablerotation, compared to ~1000 currently availableBetter sensitivity than the existing dedicated IPS Better sensitivity than the existing dedicated IPS instruments instruments ⇒⇒ a larger number of sources will a larger number of sources will be accessible be accessible Better equipped to handle time evolutionBetter equipped to handle time evolution

The larger pictureThe larger pictureWe will haveWe will have

IPS (MWAIPS (MWA--LFD) LFD) -- ∫∫F(V, F(V, δδnnee22, , αα) ) dsds

FR (MWAFR (MWA--LFD) LFD) -- ∫∫nnee BB.d.dssHI (SMEI/STEREO) HI (SMEI/STEREO) -- ∫∫nnee dsds

Integral measures of different physical Integral measures of different physical properties of the same medium properties of the same medium –– truly truly complementary informationcomplementary informationAll these data should be used to simultaneously All these data should be used to simultaneously constraint a single selfconstraint a single self--consistent modelconsistent modelThe models are getting thereThe models are getting there……

Solar ImagingSolar Imaging

The Sun…The Sun…is a highly time and frequency variable sourceis a highly time and frequency variable sourcehas a complex source structurehas a complex source structureneeds reliable imaging of faint features in needs reliable imaging of faint features in presence of bright features (high dynamic range presence of bright features (high dynamic range imaging)imaging)

500 tiles, compact configuration 500 tiles, compact configuration ⇒⇒ ExcellentExcellentinstantaneous monochromatic Point Spread Functioninstantaneous monochromatic Point Spread Function

has emission at angular scales of up to ~degreehas emission at angular scales of up to ~degreeMany small baselines Many small baselines ⇒⇒ Sensitivity to large angular Sensitivity to large angular scalesscales

MWAMWA--LFD is very well suited for solar imagingLFD is very well suited for solar imagingAngular resolution is bit smaller than the expected Angular resolution is bit smaller than the expected scatter broadening sizescatter broadening size

Type II burstsType II burstsComplex and controversial relationship with CMEs and Complex and controversial relationship with CMEs and flares, large space weather impactflares, large space weather impact100% association with flares and CMEs, though converse 100% association with flares and CMEs, though converse is not trueis not trueTheoretical modelsTheoretical models

Shocks produced by the fast moving Shocks produced by the fast moving ejectaejecta leads to the type II leads to the type II emissionemissionFlare blast waves Flare blast waves –– sudden heating of coronal loopssudden heating of coronal loops

55--15min, 5015min, 50--150 MHz, 150 MHz, --0.2 MHz/s, 1/month (Sol max)0.2 MHz/s, 1/month (Sol max)160 MHz: T160 MHz: TBB ~10~101111K, S ~10K, S ~1088 JyJyPlasma emission at plasma frequency and its harmonicPlasma emission at plasma frequency and its harmonicExtensively studied in frequencyExtensively studied in frequency--time plane, but very time plane, but very few imagesfew images

Let’s get a pictureLet’s get a picture

Imaging spectroscopy Imaging spectroscopy -- spatially resolved radio images, spatially resolved radio images, with sufficient time cadence, trace out the evolution and with sufficient time cadence, trace out the evolution and location of the type II emission regionlocation of the type II emission region

Comparison with Coronagraph imagesComparison with Coronagraph images

This is emission at This is emission at ννPP, propagation effects should be , propagation effects should be significant. Simultaneous imaging at significant. Simultaneous imaging at ννPP and 2and 2ννPP will give will give us a good handle on thatus a good handle on thatCould any fine spectral and temporal structures still Could any fine spectral and temporal structures still remain to be discovered in solar burst emission?remain to be discovered in solar burst emission?

Type III burstsType III bursts

30 kHz 30 kHz –– 1 GHz, 11 GHz, 1--few sfew s170 MHz: T170 MHz: TBB ~10~108 8 K, S ~10K, S ~1055 Jy, Jy, --130 MHz/s130 MHz/sFF--H pairs are often seenH pairs are often seenCommon whenever a moderately active region is Common whenever a moderately active region is visiblevisible

Plasma emission at fundamental and harmonicPlasma emission at fundamental and harmonicElectron beams moving along open field lines Electron beams moving along open field lines (0.2c < v < 0.6c)(0.2c < v < 0.6c)

Early Deployment ExperimentsEarly Deployment Experiments

• 4 campaigns, April - September 2005

• Mileura, Western Australia

• 80 – 327 MHz

• 3 Tiles

• Bandwidth – 4 MHz

15 September 200504:53 04:56 04:59 05:03 05:06 05:10 05:13 UT

TIME

Each panel= 60 seconds

Res: 50msec

FREQUENCY98.5-102.5 MHz

Color: signal amplitude in dB, spanning a range of ~12 dB.

MWA-LFD Solar Burst Observations

Res: 16 kHz

The state of the SunThe state of the Sun• Region 808 – complex active region• 53 C-class, 10 X-class and 3 M-class flares - more major flares than any other region in Solar Cycle 23 (12-18 Sep 2005)• Significant decay evident in white light images since 14 Sep 2005• C-class flare began at 0149 UT, data presented spans ~0200-0300 UT, September 16, 2005

Spatial distribution of burst Spatial distribution of burst emissionemission

a b c

-100

100

arcs

ec

J. Kasper, MKI

A high time and frequency A high time and frequency resolution surpriseresolution surprise

1420 MHz, 4 1420 MHz, 4 MHzMHz∆∆νν = 31 kHz= 31 kHz∆∆ττ = 0.5 ms= 0.5 ms∆∆θθ = 0.5= 0.5’’TTBB = 10= 1011 11 KK1944 UT13 1944 UT13 Sep, 05, 25min Sep, 05, 25min after a X1.5 after a X1.5 FlareFlareNot easy to Not easy to explain in terms explain in terms of conventional of conventional modelsmodels

Direct Imaging of CMEsDirect Imaging of CMEs

Image thermal Image thermal bremsstrahlungbremsstrahlung and/or and/or synchrotron from CMEssynchrotron from CMEsOptically thin synchrotron Optically thin synchrotron from 0.5from 0.5--5.0 5.0 MevMev e e interacting with B ~0.1 interacting with B ~0.1 to few gaussto few gaussMultiMulti--freq. observations freq. observations provide independent provide independent constraints on electron constraints on electron density and magnetic density and magnetic field in the CME loopsfield in the CME loops

Bastian et al., ApJ, 558, L65, 2001

Prototype ArrayPrototype Array

GoalsGoalsTestTest--bed for the end to end bed for the end to end systemsystemTraining set for calibration and Training set for calibration and algorithm developmentalgorithm developmentInitial solar observationsInitial solar observations

At the LFD siteAt the LFD site32 Tiles (4 nodes)32 Tiles (4 nodes)~350m max baseline~350m max baselineBandwidth, spectral and time Bandwidth, spectral and time resolution resolution –– TBD (4 MHz, 64 TBD (4 MHz, 64 kHz, 50 ms)kHz, 50 ms)Timeline Timeline –– mid to end 2007mid to end 2007

Summary of capabilitiesSummary of capabilities

22

11

00

VerVer

Type II, III, Type II, III, CMEsCMEs

YesYesYesYesYesYes??

Type II bursts, Type II bursts, CMEsCMEs

YesYesNoNo(8 s)(8 s)

YesYesEnd End 0808

Type III burstsType III burstsNoNo(20’ @200 (20’ @200

MHz)MHz)

YesYesYesYesEnd End 0707

Science goalsScience goals∆∆θθ(2(2’’ @200 MHz)@200 MHz)

∆∆ττ(50 ms)(50 ms)

∆∆νν(64 kHz)(64 kHz)

TimeTime

ConclusionConclusion

Over the next few years the MWAOver the next few years the MWA--LFD will grow in LFD will grow in its capabilities and scopeits capabilities and scopeIt will be a scientifically interesting instrument at It will be a scientifically interesting instrument at every step along the wayevery step along the wayWe are currently focused on the ‘core’ instrumentWe are currently focused on the ‘core’ instrumentThe instrument design is intrinsically flexible, can The instrument design is intrinsically flexible, can potentially serve other science objectives in the potentially serve other science objectives in the longer termlonger termEncourage the community to think about how can Encourage the community to think about how can MWAMWA--LFD contribute to their researchLFD contribute to their researchCollaboration to contribute to the core instrument, Collaboration to contribute to the core instrument, at least initiallyat least initially

IPS Source densityIPS Source densityCambridge IPS survey (81.5 MHz) Cambridge IPS survey (81.5 MHz)

Purvis et al., 1987, MNRAS, 229, 589Purvis et al., 1987, MNRAS, 229, 589--619619

1789 sources (Dec range 1789 sources (Dec range --1010°° to 83to 83°°, 58% of sky), 58% of sky)Sensitivity Sensitivity –– 5 Jy total flux, ~0.3 Jy scintillating flux at 5 Jy total flux, ~0.3 Jy scintillating flux at 9090°° elongationelongationSource size 0.2Source size 0.2”” –– 22””

PuschinoPuschino IPS survey (102 MHz)IPS survey (102 MHz)ArtyukhArtyukh and and TyulTyul’’bashevbashev, 1996, Astronomy Reports, 42, 601, 1996, Astronomy Reports, 42, 601

414 sources in 0.144 414 sources in 0.144 srsr (1 source/1.14 deg(1 source/1.14 deg22))Sensitivity Sensitivity –– 0.1 Jy0.1 Jy50% of sources < 350% of sources < 3””

OotyOoty Radio Telescope (327 MHz)Radio Telescope (327 MHz)ManoharanManoharan, 2006, Solar Physics, 235, 345, 2006, Solar Physics, 235, 345--368368

Observe ~700 sources per dayObserve ~700 sources per daySensitivity Sensitivity –– 0.04 Jy (1 sec, 4 MHz)0.04 Jy (1 sec, 4 MHz)

IPS Survey parametersIPS Survey parametersCambridge Survey (81.5 MHz)Cambridge Survey (81.5 MHz)

4096 full4096 full--wave dipoles wave dipoles Beam Beam –– 26.8’ x 165’ 26.8’ x 165’ Sec(zSec(z))Bandwidth Bandwidth –– 10.7 MHz10.7 MHz

PuschinoPuschino Survey (102 MHz)Survey (102 MHz)Physical collecting area Physical collecting area –– 70,000 m70,000 m22

Beam Beam –– 49’ x 26’ 49’ x 26’ Sec(zSec(z))Bandwidth Bandwidth –– 160 kHz160 kHz

OotyOoty Radio Telescope (327 MHz)Radio Telescope (327 MHz)Effective collecting area Effective collecting area –– ~8,000 m~8,000 m22

Beam Beam –– 105’ x 3.5’ Sec(105’ x 3.5’ Sec(δδ))Bandwidth Bandwidth –– 4 MHz4 MHz

Bk(ν,t) = Σi {wi Vi(ν,t)

x Ginst(ν,t-τ1,i,pol,θk,φk)

x φiono(ν,t-τ2,θk,φk)}

Detection and averaging in time

and frequencyPulsar interface

BIPS, k (ν’,t’) = Σ∆t Σ∆ν Bk(ν,t) Bk*(ν,t)

2G samples/s

IPS tomographyIPS tomography

Tomographic IPS Tomographic IPS studies have been studies have been attemptedattempted

Results Results ––encouraging, but encouraging, but fall short of fall short of expectations and expectations and requirementsrequirements

Geometric projections of ~800 lines-of-sight observed during Carrington rotation 1923.

IPS TomographyIPS Tomography

Good S/N observationsGood S/N observations

~15 min on source/~15 min on source/obsobsnn

D. Oberoi, Ph.D. Thesis, 2000D. Oberoi, Ph.D. Thesis, 2000

• Minima of Cycle 23 (MayMinima of Cycle 23 (May--Aug 97)Aug 97)

•• Spanned 4 Carrington rotationsSpanned 4 Carrington rotations

•• ~1,500 hours of observation~1,500 hours of observation

•• ~700 observations per Carr. ~700 observations per Carr. RotRotnn

MWAMWA--LFD Design GoalsLFD Design Goals

Full StokesFull StokesPolarizationPolarization

8 sec8 secTemporal resolutionTemporal resolution

10001000# Spectral channels# Spectral channels

124,750 (VLA has 435)124,750 (VLA has 435)Number of baselinesNumber of baselines

16, per polarization16, per polarizationMultiMulti--beam capabilitybeam capability

20mJy in 1 sec (32 MHz, 200 MHz)20mJy in 1 sec (32 MHz, 200 MHz)Point source sensitivityPoint source sensitivity

220 MHz (Sampled); 32 MHz (Processed)220 MHz (Sampled); 32 MHz (Processed)BandwidthBandwidth

Core array ~1.5 km diameter (95%) +Core array ~1.5 km diameter (95%) +extended array ~3 km diameter (5%)extended array ~3 km diameter (5%)

ConfigurationConfiguration

1515°°--5050°°Field of ViewField of View

8000 m8000 m2 2 (at 200 MHz)(at 200 MHz)Collecting areaCollecting area

500 (8000)500 (8000)# Tiles (receptors)# Tiles (receptors)

8080--300 MHz300 MHzFrequency rangeFrequency range