Solar Physics

, Volume 145, Issue 1, pp 205–206 | Cite as

Detection of a significant change in the solar diameter

  • Axel D. Wittmann
  • Edoardo Alge
  • Michele Bianda
Solar physics letters


Drift-time measurements of the solar diameter made at Izaña and Locarno in 1990–1992 show a significant increase of the observed angular semidiameter when compared to results obtained at the same two sites in 1981. The observed increase of ≈0.4″ is not due to a systematic (or long-term) variation, but seems to reflect a more complicated behaviour with time: As both series of measurements were made around a maximum of the 11-year cycle, it seems that a variation in phase with solar activity (in the sense of the Secchi-Rosa law) can be ruled out.


Solar Activity Complicated Behaviour Solar Diameter 
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Copyright information

© Kluwer Academic Publishers 1993

Authors and Affiliations

  • Axel D. Wittmann
    • 1
  • Edoardo Alge
    • 2
  • Michele Bianda
    • 2
  1. 1.Universitäts-SternwarteGöttingenGermany
  2. 2.Istituto Ricerche Solari LocarnoLocarno-MontiSwitzerland

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