  The sunspot number is analyzed by using detailed sunspot data, including
aspects of observability, sunspot sizes, and proper identification of sunspot
groups as discrete entities of the solar activity. The tests show that besides
the subjective factors there are also objective causes of the ambiguities in
the series of sunspot numbers. To introduce an alternative activity measure the
physical meaning of the sunspot number has to be reconsidered. It contains two
components whose numbers are governed by different physical mechanisms, this is
one source of the ambiguity. This article suggests an activity index, which is
the amount of emerged magnetic flux. The only long-term proxy measure is the
detailed sunspot area dataset with proper calibration to the magnetic flux
amount. The Debrecen sunspot databases provide an appropriate source for the
establishment of the suggested activity index.
