I've not read up any studies or papers on this matter. I've lived around farm animals for a large part of my life so I have some anecdotal observations.

From what I've seen, they tend to align themselves into the most pleasant direction depending on the weather conditions of the moment.

- Cold but sunny: Broadside towards the sun

- Wind or rain: back-side towards the direction of origin, heads hung low. So they stand with their butts in the wind to shield their heads against the worst of it.

- Very hot: Butts toward the sun, heads hung low. Often they'll arrange themselves in lines in order to hide in one another's shade.

I've never witnessed them being aligned north-south in a way that can't be explained by the immediate weather conditions.

This was in the southern hemisphere.