SOLIS/VSM Coronal Hole Estimation Maps

SHINE August, 2006SHINE August, 2006 C.J. Henney (NSO/SOLIS)C.J. Henney (NSO/SOLIS)

SOLIS/VSM Coronal Hole SOLIS/VSM Coronal Hole Estimation MapsEstimation Maps

Carl J. HenneyCarl J. Henney(NSO/SOLIS)(NSO/SOLIS)


KPVT Coronal Hole MapsKPVT Coronal Hole Maps

Daily “hand drawn” Coronal Daily “hand drawn” Coronal Hole images by K. Harvey and Hole images by K. Harvey and F. Recely span: 1992 to 2003F. Recely span: 1992 to 2003

In addition, coronal hole In addition, coronal hole synoptic maps by K. Harvey synoptic maps by K. Harvey and F. Recely span: 1987 to and F. Recely span: 1987 to 2002 (2002 (see Harvey and Recely see Harvey and Recely 20022002).).

Non-scanned hand drawn Non-scanned hand drawn daily and synoptic maps back daily and synoptic maps back to 1974.to 1974.

The “hand drawn” maps The “hand drawn” maps stopped with the beginning of stopped with the beginning of SOLIS in September 2003. SOLIS in September 2003.


VSM Automated CH MapsVSM Automated CH Maps

SOLIS-VSM began He I SOLIS-VSM began He I 1083 nm measurements in 1083 nm measurements in August 2003.August 2003.

Daily He I 1083 nm images Daily He I 1083 nm images are publicly available (fits are publicly available (fits files will be available in fall files will be available in fall 2006), along with 2006), along with automated coronal hole automated coronal hole images and synoptic maps images and synoptic maps at: at: http://solis.nso.eduhttp://solis.nso.edu


Coronal Hole Detection RecipeCoronal Hole Detection RecipeFollowing Henney & Harvey (2005):Following Henney & Harvey (2005): Start with an average 1083 nm and an average magnetogram Start with an average 1083 nm and an average magnetogram

created with two consecutive observations respectively in created with two consecutive observations respectively in heliographic coordinates (sine-latitude and longitude). The heliographic coordinates (sine-latitude and longitude). The following images are from July 14, 2003.following images are from July 14, 2003.


Coronal Hole Detection RecipeCoronal Hole Detection Recipe

Step 1:Step 1: trim the East-West trim the East-West limb data and retain only limb data and retain only values above values above 1/101/10 the median the median of positive values.of positive values.







Step 2: Step 2: spatially smoothspatially smooth





Step 3: Step 3: set all values above set all values above zero to a fixed value.zero to a fixed value.





Step 3: Step 3: set all values above set all values above zero to a fixed value.zero to a fixed value.

Step 4:Step 4: smooth with the smooth with the morphological image analysis morphological image analysis function Close (function Close (e.g. e.g. Michielsen Michielsen and Raedt, 2001and Raedt, 2001))



Step 5:Step 5: remove regions that remove regions that are too small to be a coronal are too small to be a coronal hole. hole.

Step 6:Step 6: use the indexes of use the indexes of non-zero spatial points to fill non-zero spatial points to fill the smoothed image in step 2 the smoothed image in step 2 with a large value (e.g. 10with a large value (e.g. 1044).).




Step 6:Step 6: use the indexes of use the indexes of non-zero spatial points to fill non-zero spatial points to fill the smoothed image in step 2 the smoothed image in step 2 with a large value (e.g. 10with a large value (e.g. 1044).).




Step 6:Step 6: use the indexes of use the indexes of non-zero spatial points to fill non-zero spatial points to fill the smoothed image in step the smoothed image in step 2 with a large value (e.g. 2 with a large value (e.g. 101044).).

Step 7:Step 7: smooth with the smooth with the morphological image analysis morphological image analysis function Open.function Open.


Mean Percent UnipolarityMean Percent Unipolarity The cut-off levels for the The cut-off levels for the

percent unipolarity relative percent unipolarity relative to latitude were to latitude were determined using the determined using the “hand drawn” maps for the “hand drawn” maps for the period 1992 to 2003.period 1992 to 2003.

The area of every coronal The area of every coronal hole was projected into the hole was projected into the corresponding daily corresponding daily average magnetic image average magnetic image (in heliographic (in heliographic coordinates). coordinates).

2,781 image pairs, with 11,241 coronal holes, were used in total. Figures from Henney & Harvey (2005)



Step 8:Step 8: remove regions that remove regions that are too small to be a coronal are too small to be a coronal hole.hole.

Step 9:Step 9: remove regions that remove regions that have a low percentage of have a low percentage of unipolarity.unipolarity.

Step 10:Step 10: number the coronal number the coronal holes and apply sign of holes and apply sign of polarity.polarity.


Coronal HoleCoronal Hole Detection Comparison Detection Comparison

The auto-detection coronal hole map The auto-detection coronal hole map projected into heliocentric coordinates of projected into heliocentric coordinates of the hand-drawn.the hand-drawn.



from Malanushenko & Jones (2004)from Malanushenko & Jones (2004)

An example when the two maps differed:An example when the two maps differed:

from Henney & Harvey (2005)from Henney & Harvey (2005)



from Malanushenko & Jones (2004)from Malanushenko & Jones (2004) from Henney & Harvey (2005)from Henney & Harvey (2005)


Solar Wind ForecastingSolar Wind Forecasting

The estimated area and The estimated area and location of coronal hole location of coronal hole regions can be used to regions can be used to forecast solar wind forecast solar wind velocities (velocities (up to 8.5 days up to 8.5 days in advancein advance) using a simple ) using a simple empirical model with only empirical model with only a single full-disk a single full-disk observation (Robbins, observation (Robbins, Henney, and Harvey Henney, and Harvey 2005).2005).

From Robbins, Henney, and Harvey (2005)


Acknowledgements Acknowledgements The coronal hole data used here was compiled by K. Harvey and F. The coronal hole data used here was compiled by K. Harvey and F.

Recely using NSO KPVT observations under a grant from the NSF.Recely using NSO KPVT observations under a grant from the NSF.

SOLIS VSM data used here are produced cooperatively by NSF/NSO SOLIS VSM data used here are produced cooperatively by NSF/NSO and NASA/GSFC. and NASA/GSFC.

Part of this research was supported in part by the Office of Naval Part of this research was supported in part by the Office of Naval Research Grant N00014-91-J-1040. The National Solar Observatory Research Grant N00014-91-J-1040. The National Solar Observatory is operated by the Association of Universities for Research in is operated by the Association of Universities for Research in Astronomy, Inc. under cooperative agreement with the National Astronomy, Inc. under cooperative agreement with the National Science Foundation.Science Foundation.

ReferencesReferencesHenney, C.J., & Harvey, J.W. 2005, Henney, C.J., & Harvey, J.W. 2005, ASP conf. Series, VolASP conf. Series, Vol. 346, 261.. 346, 261.Malanushenko, O.V., & Jones, H.P. 2004, Malanushenko, O.V., & Jones, H.P. 2004, Solar Physics, Vol.Solar Physics, Vol. 222, 43. 222, 43.Robbins, S. , Henney, C.J., & Harvey, J.W. 2006, Robbins, S. , Henney, C.J., & Harvey, J.W. 2006, Solar PhysicsSolar Physics, , Vol.Vol. 233, 265. 233, 265.

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SOLIS/VSM Coronal Hole Estimation Maps