Carrington Coordinates and Solar Maps

Abstract

Solar synoptic charts are normally displayed using Carrington Coordinates with each Carrington rotation being centered at a Carrington longitude of 180^∘ and with a full 360^∘ of solar surface properties included. For the case of reproducing solar magnetic fields in the corona and heliosphere, these maps are wrapped onto the solar surface to provide the boundary conditions for a solution to a set of modeling equations such as the potential field theory equations. Due to differential rotation, the full solar surface cannot be reproduced in this fashion since different parts of the solar surface are observed at different times. We describe here the proper technique for combining observations of the solar magnetic or velocity fields made at different times into a representation of the whole solar surface at a particular specified time that we refer to as a “snapshot heliographic map“.