Harrison Jones, SHINE 2006 Workshop An Observational Review of Coronal Holes and their Connection to the Heliosphere An Observational Review of Coronal

Harrison Jones, SHINE 2006 Workshop

An Observational Review of Coronal An Observational Review of Coronal Holes and their Connection to the Holes and their Connection to the

HeliosphereHeliosphere

Harrison P. JonesHarrison P. JonesNational Solar ObservatoryNational Solar Observatory

Invited Talk, SHINE 2006 WorkshopInvited Talk, SHINE 2006 Workshop02 August 200602 August 2006


WG1 Session: WG1 Session: RECONCILING OBSERVED AND RECONCILING OBSERVED AND

MODELED CORONAL HOLESMODELED CORONAL HOLES Holly Gilbert Chair, Thursday, Aug 3, 9:45Holly Gilbert Chair, Thursday, Aug 3, 9:45

how to observationally identify coronal holeshow to observationally identify coronal holes Are models correct in what they are predicting?Are models correct in what they are predicting? instrumentation (current and future)instrumentation (current and future) using models and observations to help using models and observations to help

identify/clarify sources of the solar windidentify/clarify sources of the solar wind magnetic flux balance issuesmagnetic flux balance issues Invited SpeakersInvited Speakers

Carl Henney SOLIS/VSM Coronal Hole Maps Carl Henney SOLIS/VSM Coronal Hole Maps Guiliana de Toma Multiwavelength observations and Guiliana de Toma Multiwavelength observations and

identificationidentification Roberto Lionello MHD and potential field modelsRoberto Lionello MHD and potential field models


History of Coronal Hole History of Coronal Hole ObservationsObservations

Perhaps first noticed by Waldmeir from Perhaps first noticed by Waldmeir from coronagraph data in mid 1950’s.coronagraph data in mid 1950’s.

Later seen in early EUV & XUV rocket Later seen in early EUV & XUV rocket observations.observations.

More extensive study in late 60’s from More extensive study in late 60’s from OSO 4, AS&E XUV images.OSO 4, AS&E XUV images.

First systematic studies from Skylab and First systematic studies from Skylab and ground-based He I 1083 nm ground-based He I 1083 nm spectroheliograms in 1970’s.spectroheliograms in 1970’s.


What are coronal holes?What are coronal holes?

Areas conspicuously lacking in coronal emissionAreas conspicuously lacking in coronal emission Usually seen in soft Xray/EUV spacecraft Usually seen in soft Xray/EUV spacecraft

images or He I 1083 nm ground-based imagesimages or He I 1083 nm ground-based images Occur above unipolar, but not particularly strong, Occur above unipolar, but not particularly strong,

areas in photospheric magnetogramsareas in photospheric magnetograms Chromospheric network in He I 1083 nm has Chromospheric network in He I 1083 nm has

less contrast than in quiet Sunless contrast than in quiet Sun Boundaries tend to be sharpBoundaries tend to be sharp Anybody can see them, but precise agreement Anybody can see them, but precise agreement

between two people is rarebetween two people is rare


27 August 1996

NSO 1083 nm SOHO/EIT 17.1 nm


27 August 1996

NSO Coronal Hole Map NSO Magnetogram


Coronal Hole RecognitionCoronal Hole Recognition

See tomorrow’s talks by Henney and de TomaSee tomorrow’s talks by Henney and de Toma Malanushenko and Jones (2005, Malanushenko and Jones (2005, Sol PhysSol Phys 226226, 3, 3)) Looked at scatterplots (correlative properties) of Looked at scatterplots (correlative properties) of

He I 1083 nm central intensity, half width, and He I 1083 nm central intensity, half width, and velocity.velocity.

Found that width and intensity correlate Found that width and intensity correlate differently in coronal holes and quiet sundifferently in coronal holes and quiet sun

Formed linear combination of quantities such Formed linear combination of quantities such that coronal hole is clearly separated from quiet that coronal hole is clearly separated from quiet SunSun



2000 Apr 17

Intensity

Normalized Intensity + width

Normalized Intensity - width





What’s Important about Coronal Holes?What’s Important about Coronal Holes?

Skylab Solar Workshop I Skylab Solar Workshop I Coronal Holes and High Speed Wind Streams (1976, Coronal Holes and High Speed Wind Streams (1976,

J. B. Zirker, ed.)J. B. Zirker, ed.) Many excellent articles (Bohlin, Krieger, Levine, Many excellent articles (Bohlin, Krieger, Levine,

Withbroe, Kopp, Hundhausen, Gilman, Svalgaard)Withbroe, Kopp, Hundhausen, Gilman, Svalgaard)

Skylab and SHINE 06 workshop participantsSkylab and SHINE 06 workshop participants Uri FeldmanUri Feldman Bernie JacksonBernie Jackson Leif SvalgaardLeif Svalgaard S.T. WuS.T. Wu


Skylab Solar Workshop I ParadigmSkylab Solar Workshop I Paradigm

Open fields originate in coronal holes and Open fields originate in coronal holes and near active regions.near active regions.

High-speed solar wind (~700 km/s) is High-speed solar wind (~700 km/s) is associated with polar coronal holes and some associated with polar coronal holes and some equatorial coronal holes.equatorial coronal holes.

Lower speed wind occurs near heliospheric Lower speed wind occurs near heliospheric neutral lines and is associated with active neutral lines and is associated with active regions and helmet streamers.regions and helmet streamers.


What people rememberWhat people remember

Coronal hole ≡ Coronal hole ≡ Open fieldOpen field ≡ High speed wind ≡ High speed wind


What is an open magnetic What is an open magnetic region?region?

A spatial domain in which magnetic lines of A spatial domain in which magnetic lines of force extend from the solar surface far force extend from the solar surface far (hundreds of solar radii) into the heliosphere (hundreds of solar radii) into the heliosphere and cannot be traced back to the Sun.and cannot be traced back to the Sun.

Provides a direct connection for plasma flow Provides a direct connection for plasma flow to the Earth and other planetsto the Earth and other planets..

No one has ever directly observed an open No one has ever directly observed an open field line all the way from the surface into the field line all the way from the surface into the distant heliosphere.distant heliosphere.


Recognizing Open-Field Recognizing Open-Field StructuresStructures

Mapping in-situ magnetic fields back to the Mapping in-situ magnetic fields back to the solar surfacesolar surface

Extrapolation of measured surface fields into Extrapolation of measured surface fields into the heliospherethe heliosphere Common practice to map inward to and Common practice to map inward to and

extrapolate out to a “source surface” at ~ 2Rextrapolate out to a “source surface” at ~ 2R

Intensity or density patterns as tracers of field Intensity or density patterns as tracers of field lineslines

Correlation of structural patterns on the Sun Correlation of structural patterns on the Sun and in the heliosphereand in the heliosphere


McComas 2003McComas 2003


Coronal Holes as Sources of (High-Coronal Holes as Sources of (High-speed) Solar Windspeed) Solar Wind

See WG1/2See WG1/2 session on Origin and Evolution of the Solar session on Origin and Evolution of the Solar Wind following this talk.Wind following this talk.

See poster by Zhao and ZurbuchenSee poster by Zhao and Zurbuchen


Solar Wind Sources at MinimumSolar Wind Sources at Minimum Neugebauer Neugebauer et al. et al. 1998,1998, JGR 103, 14,587-14,599JGR 103, 14,587-14,599

Compared mapping techniquesCompared mapping techniques Good general agreement between SS and MHD methods Good general agreement between SS and MHD methods

(SS with current sheet not so good-but see poster by (SS with current sheet not so good-but see poster by Hughes, Arge, and Owens)Hughes, Arge, and Owens)

Predicted open field regimes matched pretty well with Predicted open field regimes matched pretty well with He 1083 nm coronal holes with notable exceptions. He 1083 nm coronal holes with notable exceptions.

Near solar min, all high-speed streams from Ulysses Near solar min, all high-speed streams from Ulysses and Wind mapped back to polar coronal holesand Wind mapped back to polar coronal holes

Lower-speed streams (300-600 km/s) mapped Lower-speed streams (300-600 km/s) mapped back to equatorial coronal holes or equatorward back to equatorial coronal holes or equatorward of polar coronal holes.of polar coronal holes.

Heliospheric and solar polarities did not match Heliospheric and solar polarities did not match for 4 of 38 identified streamsfor 4 of 38 identified streams..


Solar Wind Sources at MaximumSolar Wind Sources at Maximum NeugebauerNeugebauer et al., et al., 20022002 JGR 107, 1488JGR 107, 1488

Liewer & Neugebauer, 2004, Solar Phys 223, 209Liewer & Neugebauer, 2004, Solar Phys 223, 209

Used Ulysses and ACE dataUsed Ulysses and ACE data Good agreement with observed and mapped Good agreement with observed and mapped

source region polarities for spacecraft latitudes < source region polarities for spacecraft latitudes < 6060oo

Solar wind slower than at min, mapped to both Solar wind slower than at min, mapped to both coronal holes and active regions.coronal holes and active regions.

OO7+7+/O/O6+6+ lower from coronal holes lower from coronal holes



Solar Wind Sources at MaximumSolar Wind Sources at MaximumWang and Sheeley, 2003, ApJ 587, 818.Wang and Sheeley, 2003, ApJ 587, 818.

Used ACE measurementsUsed ACE measurements Mostly low proton speeds, high oxygen charge Mostly low proton speeds, high oxygen charge

state ratiosstate ratios Originates from small, sheared open-field regions Originates from small, sheared open-field regions

near active regions with large expansion factorsnear active regions with large expansion factors Occasional high-speed streams have small Occasional high-speed streams have small

expansion factors and low charge state ratiosexpansion factors and low charge state ratios


MHD SimulationsMHD Simulations

Many papers at this meeting regarding MAS and Many papers at this meeting regarding MAS and related algorithmsrelated algorithms

Riley, Linker, Mikic, & Zurbuchen (2003), Solar Riley, Linker, Mikic, & Zurbuchen (2003), Solar Wind 10, 79.Wind 10, 79.

Used MHD model based on NSO synoptic charts to map Used MHD model based on NSO synoptic charts to map the field to 30 Rthe field to 30 R, ballistic mapping inward from ACE and , ballistic mapping inward from ACE and

UlyssesUlysses Compared mapping to computed coronal holesCompared mapping to computed coronal holes At solar min, inferred a supergranule-sized boundary At solar min, inferred a supergranule-sized boundary

layer giving rise to slower wind speeds, and increasing layer giving rise to slower wind speeds, and increasing wind speed away from boundary layer.wind speed away from boundary layer.



Contrarian ViewpointContrarian ViewpointWoo, Habbal, Feldman, others; various publicationsWoo, Habbal, Feldman, others; various publications

Cite evidence from Mauna Loa K-Coronameter Cite evidence from Mauna Loa K-Coronameter and radio scintillations as well as coronagraph and radio scintillations as well as coronagraph and eclipse images that point to radial density and eclipse images that point to radial density structures.structures.

Suggest that open flux and fast solar wind Suggest that open flux and fast solar wind emerges from quiet Sun as well as coronal holes; emerges from quiet Sun as well as coronal holes; later papers suggest that this is ubiquitous.later papers suggest that this is ubiquitous.

Provide simulations which suggest that this idea Provide simulations which suggest that this idea is consistent with observations.is consistent with observations.

Anticipated by Hundhausen (1977) ; reduces Anticipated by Hundhausen (1977) ; reduces disagreement between magnetograph disagreement between magnetograph observations and photospheric fields inferred observations and photospheric fields inferred from spacecraft data.from spacecraft data.




Chromosphere/Transition RegionChromosphere/Transition Region

Look for preferential outflows in coronal holes in Look for preferential outflows in coronal holes in comparison with the quiet Sun; assumption is comparison with the quiet Sun; assumption is that these are related to high-speed solar wind—that these are related to high-speed solar wind—guilt by associationguilt by association

He I 1083 nm asymmetry (Dupree, Penn, Jones, He I 1083 nm asymmetry (Dupree, Penn, Jones, 1996, ApJ 467, L121)1996, ApJ 467, L121)

Looked for excess blue absorption at suggestion Looked for excess blue absorption at suggestion of Dupree and found it in two polar coronal holes.of Dupree and found it in two polar coronal holes.

Consistent with part of line-forming region Consistent with part of line-forming region moving outward at several km/smoving outward at several km/s

Asymmetry appeared highest in cell centersAsymmetry appeared highest in cell centers


1083 nm Asymmetry1083 nm Asymmetry

Have frequently (but not always) observed effect Have frequently (but not always) observed effect in coronal holes, including disk centerin coronal holes, including disk center

Some evidence that asymmetry highest near but Some evidence that asymmetry highest near but not on network boundariesnot on network boundaries

Determination of asymmetry is at limits of Determination of asymmetry is at limits of analysis capability and is marginally stableanalysis capability and is marginally stable

Have found some agreement with 58.4 nm Have found some agreement with 58.4 nm measurements with SOHO/CDS (with Andretta)measurements with SOHO/CDS (with Andretta)

Have been working to improve analysis Have been working to improve analysis techniquestechniques



SOHO/SUMERSOHO/SUMER

Warren, Mariska, & Wilhelm (1997, ApJ 490, L187Warren, Mariska, & Wilhelm (1997, ApJ 490, L187)) No evidence for preferential outflow in cool TR No evidence for preferential outflow in cool TR

lines (CII, OVI)lines (CII, OVI) Blueshift observed in NeVIIIBlueshift observed in NeVIII

Peter (1999, ApJ 522, L77)Peter (1999, ApJ 522, L77) Full-disk scan in He I 58.4 nmFull-disk scan in He I 58.4 nm Showed blue shift in coronal holes at both Showed blue shift in coronal holes at both

polespoles Attributed to optical depth effects, not Doppler Attributed to optical depth effects, not Doppler

shiftsshifts



NeVIIINeVIII

Hassler, Dammash, Lemaire, Brekke, Curdt, Hassler, Dammash, Lemaire, Brekke, Curdt, Mason, Vial, Wilhelm (Science 283, 810)Mason, Vial, Wilhelm (Science 283, 810)

SUMER scans NeVIII 77.0 nm and Si II 153.3 nmSUMER scans NeVIII 77.0 nm and Si II 153.3 nm Used zero point from limb, also laboratory Used zero point from limb, also laboratory

referencereference Found preferential blue shifts of several km/s at Found preferential blue shifts of several km/s at

network boundaries, particularly at network network boundaries, particularly at network verticesvertices


Mid Latitude Near N pole

Ne VIII Intensity

Ne VIII Velocity

Limb zero

Lab zero


Other TR Doppler ObservationsOther TR Doppler Observations

Wilhelm, Dammasch, Marsch, and Hassler (2000, Wilhelm, Dammasch, Marsch, and Hassler (2000, AA 353, 749) observed outflows of ~3km/s AA 353, 749) observed outflows of ~3km/s observed in polar coronal holes (but not polar observed in polar coronal holes (but not polar plumes) in He I 58.4 nm, Ne VIII 77.0 nmplumes) in He I 58.4 nm, Ne VIII 77.0 nm

Madjarska, Doyle, and van Driel-Gezsztelyi (2004, Madjarska, Doyle, and van Driel-Gezsztelyi (2004, ApJ 603, L57) observed bidirectional jets near ApJ 603, L57) observed bidirectional jets near coronal hole boundaries in N IV and Ne VIII.coronal hole boundaries in N IV and Ne VIII.


Coronal hole properties in the CoronaCoronal hole properties in the Corona

Most recent work based on LASCO, UVCS, EIT, Most recent work based on LASCO, UVCS, EIT, and SUMER data from SOHO.and SUMER data from SOHO.

Wealth of information regarding density, Wealth of information regarding density, temperature, ionization structure, and velocity.temperature, ionization structure, and velocity.

Lack of direct magnetic field measurements Lack of direct magnetic field measurements (most that do exist are from radio observations).(most that do exist are from radio observations).

Comparatively sparse information close to the Comparatively sparse information close to the Sun.Sun.


Simultaneous Determination of Simultaneous Determination of Electron Density and Flow VelocityElectron Density and Flow Velocity

Antonucci, Dodero, Giordano, Krishnakumar, & Noci, 2003 AA Antonucci, Dodero, Giordano, Krishnakumar, & Noci, 2003 AA 416, 749.416, 749.

Requires analysis of a pair of coronal lines of the Requires analysis of a pair of coronal lines of the same ion emitted by collisional and radiative same ion emitted by collisional and radiative excitationexcitation

Assumes a rapidly diverging magnetic geometry Assumes a rapidly diverging magnetic geometry and conserved electron fluxand conserved electron flux

Primary uncertainty is anisotropy of ion Primary uncertainty is anisotropy of ion temperature.temperature.

Obtain electron density results consistent with Obtain electron density results consistent with white-light determination of Guhathakurta et al white-light determination of Guhathakurta et al (1999)(1999)

Outflow velocities show rapid acceleration in the Outflow velocities show rapid acceleration in the 1.5-3R1.5-3R height range but depend strongly on height range but depend strongly on anisotropy.anisotropy.


LASCO Observations of Coronal LASCO Observations of Coronal OutflowsOutflows

Sheeley Sheeley et alet al. 1997, ApJ 484, 472. 1997, ApJ 484, 472

Observed in white light above helmut streamers.Observed in white light above helmut streamers. Originate at 3-4 ROriginate at 3-4 R . .

Constant acceleration out to ~ 30 RConstant acceleration out to ~ 30 R. .

Reach speeds of ~300 km/s.Reach speeds of ~300 km/s. Concluded that they were passive tracers of the slow Concluded that they were passive tracers of the slow

solar wind.solar wind.


Coronal Hole DynamicsCoronal Hole Dynamics

Coronal holes tend to rotate rigidlyCoronal holes tend to rotate rigidly Known at Skylab workshop (e.g. Levine) and since remarked on Known at Skylab workshop (e.g. Levine) and since remarked on

by many authors (e.g. Sheeley); see talk by Lionello in by many authors (e.g. Sheeley); see talk by Lionello in tomorrow’s WG1 session.tomorrow’s WG1 session.

Basis for interchange reconnection (Fisk, many others) Basis for interchange reconnection (Fisk, many others) Recent model (Fisk, 2005) for transport of open field lines Recent model (Fisk, 2005) for transport of open field lines

through interaction with coronal loops and relation to emerging through interaction with coronal loops and relation to emerging flux—see posters by J. Gilbert et al and Abramenko et al.flux—see posters by J. Gilbert et al and Abramenko et al.

Polar holes are long-lived (~8 yrs; Harvey and Recely, 2002)Polar holes are long-lived (~8 yrs; Harvey and Recely, 2002) Evolve from high-latitude isolated holes near polar reversalEvolve from high-latitude isolated holes near polar reversal Spread rapidly, fade away near first appearance of high latitude Spread rapidly, fade away near first appearance of high latitude

active regions.active regions. Magnetic field tends to be organized in large “cells” as shown by H-Magnetic field tends to be organized in large “cells” as shown by H-αα

synoptic chartssynoptic charts Coronal holes tend to recur in cells successively eastward of Coronal holes tend to recur in cells successively eastward of

predecessor, perhaps leading to observed synodic period of M-predecessor, perhaps leading to observed synodic period of M-regions.regions.


Some Unresolved IssuesSome Unresolved Issues

Still lack a clear observational and theoretical definitions Still lack a clear observational and theoretical definitions of coronal holes. of coronal holes.

How important is the observed fine structure?How important is the observed fine structure? How much of the Sun’s open flux originates in coronal How much of the Sun’s open flux originates in coronal

holes?holes? How are equatorial holes related to the solar wind?How are equatorial holes related to the solar wind? Why (how) does the Sun make coronal holes?Why (how) does the Sun make coronal holes? How do we observe coronal holes in new and better How do we observe coronal holes in new and better

ways?ways? Direct observations of coronal magnetic fieldsDirect observations of coronal magnetic fields Better and more extensive imaging spectroscopyBetter and more extensive imaging spectroscopy

Documents

Harrison Jones, SHINE 2006 Workshop An Observational Review of Coronal Holes and their Connection to the Heliosphere An Observational Review of Coronal