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Interpreting the CHARM Page:

For a detailed description of CHARM algorigthm, please see the methods paper: Krista and Gallagher (2009)

The EIT 195 Å disk images are shown as cylindrical Lambert equal-area projection maps. The projection is limited to 80 degrees due to limb-extrapolation effects. The white corners shift over the year due to the change in the B angle, for which the projection is corrected for. After the detection of low intensity regions in the EIT 195 Å images, corresponding MDI magnetograms are used to determine the flux imbalance in the detected regions. Depending on the flux-imbalance, low intensity regions are classed as coronal holes (CH). This is based on the knowledge that CHs are dominated by a single polartity.

Please note that the error in the MDI magnetic field measurements increases considerable towards the solar limb and hence the flux imbalance might not be detected in certain polar CHs. For this reason polar holes are occasionally unidentified in the observations. We are currently working on a reliable resolution to this issue.

The identified CHs are grouped based on neighbouring distances. Members of a CH group appear contoured with the same colour and numbered with the same group number.

Group ID: the overall CH group number.

Location: the location of the CH group centroid (or geometric center).

E/W-most points: the east-most and west-most points of a CH group boundary.

Area: overall area of a CH group in Mm2.

Bz: the average magnetic field of a CH group in Gauss units.

Phi: the average magnetic flux of a CH group in Maxwell units.

If you would like to use CHARM meta data for any publications, please contact the author:

Larisza D. Krista
: larisza.krista<at>noaa<dot>gov
NOAA/SWPC, University of Colorado
and cite teh methods paper:
Krista and Gallagher, 2009, Solar Physics, 256, 87-100