that is not uncommon. Another part of this is the type A & B disruptions which may be better left for another day. Thanks for the detailed replies Geoff, I'll have a think about those after work today. Just a point to make about the overall way it comes across. While it's fine for us who are into this stuff, and sympathetic to the difficulties, someone like Svalgaard is going to dismiss it as 'armwaving' or 'special pleading' unless you can find a way to tabulate, analyse and summarise the results from all the 'AM disturbances' within the range of interest. I appreciate your comment that " there are so many permutations that no cycle (trident) would prob look the same." and understand the reasons for it, but nonetheless, some generally applicable heuristic statements have to be laid out which are not contradicted by more than, say, one event in twenty (95% significance), otherwise it carries no weight for reviewers. To be honest Greg, I've not had time to think it through. But my good lady assures me I'm of the hook for the rest of this afternoon, so lets discuss it a bit further. Any thoughts on how this could be tested in a spreadsheet with monthly position data? I think you are a bit quicker on the draw with the equations than I am. Presumably its solving a vector addition and translating that back to spherical co-ordinates? It seems more a case of getting the right data. As