Are you confusing them with the aurora borealis? Fwiw I lived in Glossop for around 15 years, rode Longdendale a lot and never saw a thing beyond the odd night rider and some bright floods somewhere above the worm farm. I don’t know if they exist or not, but I’m not sure you can plan to see them any road.
If you do end up that way, the Northern Horse Track is a pleasant amble on a mountain bike. Starts from Crowden and goes round, across the Holme Moss road low down and on up to meet the Longdendale trail above the tunnels.