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Solar synoptic maps usually refer to assembled composites recorded over a full solar
rotation of about 27 days. Synoptic maps can be derived from single wavelength images
or from multi-wavelength images highlighting solar features of interest (see above).
Images for this dataset were provided by numerous solar observatories. The Boulder
H-alpha (6563 A) synoptic maps, or charts, were first developed by McIntosh as an
outgrowth of efforts to infer solar magnetic fields. These McIntosh synoptic charts
identify regions of positive and negative magnetic polarity separated by a magnetic
neutral line. Superposed on many of the maps are the locations of coronal holes observed
in X-rays and from HeI spectro-heliograms at 10830 A. Features of interest evident
at various wavelengths include; 3934 A (Calcium, Ca II K-line) ¿ used to monitor structures
in the lower chromosphere, in particular faculae which are clearly discerned in Ca
II but less so in white-light images (only near the limb) and not in H-alpha 5303
A (Iron, Fe XIV) ¿ Monitor the chromosphere 5694 A (Calcium, Ca XV) ¿ Ca XV emissions
from the sun are used to detect coronal hot spots. Also referred to as the solar yellow
line 6374 A (Iron, FE X) ¿ Monitor the chromosphere 6563 A (Hydrogen, H-alpha); chromospheric
imaging of solar flares, sunspots, plage, filaments and prominences, also chromospheric
network 10830 A (Helium, He I); preferred wavelength to image coronal holes which
are not as readily apparent in Ca II and H-alpha |