Analysis of existing data When it comes to further analysis of existing data it is possible to study the spatial variation of auroral emissions during a substorm period for which there exists ALIS data from 4-6 stations with 30 to 60 s time resolution during a period of approximately half an hour. There is more work to be done regarding, e.g. the time variation of the $O(^1D)$ excitation rate of HF induced airglow.