Hi Carebear
11-1am and pm are the best times because our front and back energy channels connect automatically which makes our practice easier.

While those times are the best for me, I also practice between 5 - 7am and pm because I find them to be really good as well.

For me 11-1am and pm is best, 5-7am and pm better, and any other time good.

I don't know wbout the magnetic pull of the earth at those times but I do know that the 24 hours of a day are connected 2 hourly, with each of the twelve major meridians.

11am-1pm - heart (baby yin time)
11pm-1am - gallbladder (baby yang time)
5am-7am - large intestine
5pm-7pm - kidney

Hope this helps
with love
Jetay