Transition of the Sunspot Number from Zurich to Brussels in 1980: A Personal Perspective

TL;DR

This paper details the smooth transition of the sunspot number record from Zurich to Brussels in 1980, ensuring continuity in this vital solar activity data series, and discusses the historical and organizational context of this change.

Contribution

It provides a detailed account of the organizational and procedural aspects involved in transferring the sunspot number record from Zurich to Brussels in 1980.

Findings

Successful transfer avoided discontinuity in sunspot data series

Historical context of Zurich's sunspot number determination

Organizational process for scientific data continuity

Abstract

The Swiss Federal Observatory, which had been founded in 1863 by Rudolf Wolf, was dissolved in connection with the retirement of Max Waldmeier in 1979. The determination of the Zurich sunpot number, which had been a cornerstone activity of the observatory, was then discontinued by ETH Zurich. A smooth transition of the responsibility for the sunspot number from Zurich to Brussels could however be achieved in 1980, through which it was possible to avoid a discontinuity in this important time series. Here we describe the circumstances that led to the termination in Zurich, how Brussels was chosen for the succession, and how the transfer was accomplished.