Cell area raster

I have large raster datasets (>80GB) that are in lat long format and that I would like not to project. However I would like to construct a raster containing the area/surface (m2) of each cell of the initial raster. Is there an efficient way of creating such a raster? I am using ArcMap 10.1 and hence using the raster map calculator with $$YMAP does not seem to work.
Thanks