Geomagnetic hourly average and minute values from digital data

The production of geomagnetic hourly average values from discrete one minute values, and the production of the one minute values themselves from more rapidly sampled data, are investigated. It is shown that hourly average values obtained from an average of one minute values within the hour should form a homogenous set with those previously obtained by handscaling of analogue records. Generation of the one minute values by digital filtering of more rapidly sampled data is recommended. A simple cosine weighting applied to 5 or 10 second sampled data (13 or 7 point filter respectively) is suggested.