359 citations
- University of LisbonPT47 papers
- Instituto Superior TécnicoPT12 papers
- Universidade Lusófona de Humanidades e TecnologiasPT12 papers
- Institute of Astrophysics and Space SciencesPT10 papers
- Universidade do PortoPT8 papers
- University of AveiroPT8 papers
- Grupo de Física MatemáticaPT7 papers
- Universidad de ExtremaduraES6 papers
- Instituto de Engenharia de Sistemas e Computadores Investigação e DesenvolvimentoPT4 papers
- Instituto Politécnico de LisboaPT4 papers
- UninovaPT4 papers
- Institute of Physics BelgradeRS3 papers
6 papers · 1 filter
Redefining the limit dates for the Maunder Minimum
J. M. Vaquero, R. M. Trigo
The Maunder Minimum corresponds to a prolonged minimum of solar activity a phenomenon that is of particular interest to many branches of natural and social sciences commonly consid…
Revised Group Sunspot Number for 1640, 1652, and 1741
J. M. Vaquero, R. M. Trigo
Some studies have shown that our knowledge on solar activity in the years 1640, 1652, and 1741 can be improved. In this contribution, we revise the annual group sunspot numbers for…
Forty two years counting spots: solar observations by D. E. Hadden during 1890-1931 revisited
V. M. S. Carrasco, J. M. Vaquero, M. C. Gallego +1
We have recovered the sunspot observations made by David E. Hadden during 1890-1931 from Alta, Iowa. We have digitized the available data published by Hadden in different astronomi…
A Note on Solar Cycle Length during the Medieval Climate Anomaly
J. M. Vaquero, R. M. Trigo
The growing interest in the "Medieval Climate Anomaly" (MCA) and its possible link to anomalous solar activity has prompted new reconstructions of solar activity based on cosmogeni…
A Simple Method to Check the Reliability of Annual Sunspot Number in the Historical Period 1610-1847
J. M. Vaquero, R. M. Trigo, M. C. Gallego
A simple method to detect inconsistencies in low annual sunspot numbers based on the relationship between these values and the annual number of active days is described. The analys…
155-day Periodicity in Solar Cycles 3 and 4
J. M. Vaquero, R. M. Trigo, M. Vazquez +1
The near 155 days solar periodicity, so called Rieger periodicity, was first detected in solar flares data and later confirmed with other important solar indices. Unfortunately, a…