A synoptic map shows data of the entire solar surface.
Synoptic maps can be presented in a variety of projections.
- One typical format is longitude and sine latitude.
- Another is longitude, latitude
There are at least two kinds of solar synoptic maps.
- Traditional synoptic maps, such as the traditional and non-traditional Carrington Charts, are diachronic maps assembled from measurements collected over a long period, typically a solar rotation. Strips of data observed near central meridian are combined to form a global map. Each longitude shows the surface as it was observed at a different time. There is no effective way to account for differential rotation or field evolution in a diachronic synoptic map.
Synchronic maps, such as the Synchronic Chart or the Synchronic Frame, shows the entire solar surface observed at a particular instant of time. This is more like a traditional terrestrial weather synoptic map. Inevitably such maps of the Sun are approximations that combine observations taken at different times that have been evolved in some way according to a model.
A synchronic chart can be constructed from a diachronic synoptic map by stretching each longitude appropriately to account for differential rotation. Such a synchronic chart is valid only at a single instant of time.
- A model synchronic chart can also be constructed by applying some form of surface transport model to observed magnetic fields.
A synchronic frame is a special kind of synchronic chart that incorporates a Heliographic Frame. The heliographic frame is effectively treated a partial synoptic map that is inserted into a synchronic chart. A heliographic frame can be constructed from a single magnetogram or set of magnetograms. Merging a heliographic frame that measures the magnetic field over an extended area on the solar surface with a synchronic chart provides perhaps the best approximation of the global field at a particular instant.