B-mode plots, spherical harmonics?, fundamental modes?

[Spinnor]

If the B-mode sky plots could be Fourier transformed what would be a plot of the lowest order B-mode harmonic plotted on a sphere look like?

I guess we need two functions of spherical coordinates, one function for amplitude at points on a sphere and one function for the orientation at the same points on a sphere?

Is there a hypothetical "gravitational wave" that gives rise to this lowest order harmonic?

Thanks for any help!

 

[Spinnor]

Looks like part of the answer is here,

http://background.uchicago.edu/~whu/polar/webversion/node8.html

http://background.uchicago.edu/~whu/polar/webversion/node4.html#figscalarmap

http://background.uchicago.edu/~whu/polar/webversion/node5.html#figvectormap

http://background.uchicago.edu/~whu/polar/webversion/node6.html#figtensormap

http://background.uchicago.edu/~whu/polar/webversion/node9.html