Solar Pole Research at NSO
J. Harvey & NSO Staff

Terra Incognita

18 Nov 2008

Solar-C2

Justification• Strong influence on heliosphere• Nearly permanent coronal hole
• Large scale flows are different– Small rotational effects– Convergence of meridional flow

• Help diagnose solar cycle dynamo

18 Nov 2008

Solar-C

3

What to Observe?
• Motions– Rotation– Meridional flow
– Convective flows• Magnetic field– Long-term flux budget– Properties of network and emerging fluxfeatures• Limb darkening
18 Nov 2008

Solar-C4

Observational Challenges• Severe foreshortening/complete obscuration• Nearly horizontal ray paths through features• Variation of line formation height• Need years of regular observations• Require high cadence for some studies• Global helioseismology is poor near poles Hard to get useful, definitive results
18 Nov 2008

Solar-C5

Polar Work at NSO
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Magnetic flux budget
Polar coronal hole evolution
Tracer rotation
Distribution of ephemeral regions
Latitude distribution of flux
Intranetwork Bhoriz
Chromospheric field
Comparison with coronal jets and plumes
Vector field observationsGONG helioseismology
Limb darkening at various wavelengths

18 Nov 2008

Solar-C

6

Sampling of Results(as time permits)

18 Nov 2008

Solar-C7

Large Scale Polar Flux

Harvey (1997)• Photosphere• Flux streams to poles• LOS corrected to flux

• ~Cos10 θ; asymmetric• CR averages• Cycle 23 ≈ ⅔ Cycle 22

18 Nov 2008

Solar-C

8

Flux Feature Latitude Distribution• Photosphere• LOS field• cos(ρ) division• Polar projection• Larger elements
concentrated ~70º
• Nearly unipolar• Only 1 sample• Uncertain limbeffects19960308
Harvey (1997)
18 Nov 2008

Solar-C• Need more studies
9Uniform Intranetwork Bhoriz• 7 h of 10 m LOS• σ of average• No latitude variation• Random polarities• Only 1 study• Low resolution• Expected if local?
• Need more studies
Harvey et al. (2007)18 Nov 2008

Solar-C

10

Polar Field in Chromosphere±75 G±15
• CaII λ8542 Å• Wing ~250 km• Core ~1100 km• Strong canopy• Less seething Bhor
• Better S/N• Line profile varies• Little studied yet18Novdepth2008
linewingcore

Solar-C

NSO/SOLIS20041006

11

Flux Feature Latitude Distribution• Chromospheric B║• Fall 2006 & 2007
• ρ visibility corrected• Normalized by area
• Larger features only
• Like photosphere• Needs more work

Raouafi et al.
(2007, 2008)18 Nov 2008

Solar-C12

Bipoles, Jets & Plumes• Stereo/Secchi EUV• SOLIS B║ chrom• Jets → plumes• Transient bipoles• Need much bettermag cadence
Raouafi et al. (2008)18 Nov 2008

Solar-C13

Vector Field• B║ weak @ poles• B┴ strong @ poles• Network strong• Network is ~radial• Need moresensitivitySOLIS 20080326

18 Nov 2008

Solar-C

14

Equator-Pole Limb Darkening• Single detector• ΔT < ±3.4 K• Implies T & T(z) ~uniformwith latitude• Limited by atmosphere &equipment• Need better measurements

Livingston & Milkey (2009)18 Nov 2008

Solar-C

15

Conclusion• Plan A high-latitude view of poles wouldprovide new (unique) and far better
information than we presently have abouta mysterious region. It is the bolder, moreadventurous path.
• Plan A or B for Solar-C would each bevery valuable – we can be happy witheither choice.
18 Nov 2008

Solar-C

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