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Strong evidence of low levels of solar activity during the Maunder Minimum
V. M. S. Carrasco, H. Hayakawa, C. Kuroyanagi +2
The Maunder Minimum (MM) was a period of prolonged solar activity minimum between 1645 and 1715. Several works have identified a significant number of problematic spotless days in…
Soonspot: Software to Determine Areas and Sunspot Positions
P. Galaviz, V. M. S. Carrasco, F. Sánchez-Bajo +2
A new software (Soonspot) for the determination of the heliographic coordinates and areas of sunspots from solar images is presented. This program is very user-friendly and the acc…
Sunspot characteristics at the onset of the Maunder Minimum based on the observations of Hevelius
V. M. S. Carrasco, J. M. Vaquero, M. C. Gallego +8
An analysis of the sunspot observations made by Hevelius during 1642-1645 is presented. These records are the only systematic sunspot observations just before the Maunder Minimum.…
Sunspot Catalogue of the Observatory of the University of Coimbra (1929-1941)
V. M. S. Carrasco, J. M. Vaquero, M. C. Gallego +3
A sunspot catalogue was published by the Coimbra Astronomical Observatory (Portugal), now named Geophysical and Astronomical Observatory of the University of Coimbra, for the perio…
A Sunspot Catalog for the Period 1952-1986 from Observations Made at the Madrid Astronomical Observatory
A. J. P. Aparicio, L. Lefèvre, M. C. Gallego +5
Sunspot catalogs are very useful for studying the solar activity of the recent past. In this context, a catalog covering more than three solar cycles made by the astronomers of the…
The umbra-penumbra area ratio of sunspots during the Maunder Minimum
V. M. S. Carrasco, J. M. García-Romero, J. M. Vaquero +4
The Maunder Minimum (MM) was a prolonged period of low solar activity that occurred between 1645 and 1715. The true level of solar activity corresponding to this epoch is still a m…
A Curious History of Sunspot Penumbrae: An Update
V. M. S. Carrasco, J. M. Vaquero, R. M. Trigo +1
The ratio of penumbral to umbral area of sunspots is an important topic for solar and geophysical studies. Hathaway (Solar Physics, 286, 347, 2013) found a curious behaviour in thi…
Extreme value theory applied to the millennial sunspot number series
F. J. Acero, M. C. Gallego, J. A. García +2
In this work, we use two decadal sunspot number series reconstructed from cosmogenic radionuclide data (14C in tree trunks, SN-14C and 10Be in polar ice, SN-10Be) and the Extreme V…
Analysing the spotless days as predictors of the solar activity from the new sunspot number
V. M. S. Carrasco, J. M. Vaquero, M. C. Gallego
The use of the spotless days to predict the future solar activity is here revised based on the new version of the sunspot number index with a 24-month filter. Data from Solar Cycle…
A Revised Collection of Sunspot Group Numbers
J. M. Vaquero, L. Svalgaard, V. M. S. Carrasco +7
We describe a revised collection of the number of sunspot groups from 1610 to the present. This new collection is based on the work of Hoyt and Schatten (Solar Phys. 179, 189, 1998…
Revisiting the prediction of solar activity based on the relationship between the solar maximum amplitude and max-max cycle length
V. M. S. Carrasco, J. M. Vaquero, M. C. Gallego
It is very important to forecast the future solar activity due to its effect on our planet and near space. Here, we employ the new version of the sunspot number index (version 2) t…
A Normalized Sunspot-Area Series Starting in 1832: an Update
V. M. S. Carrasco, J. M. Vaquero, M. C. Gallego +1
A new normalized sunspot-area series has been reconstructed from the series obtained by the Royal Greenwich Observatory and other contemporary institutions for the period 1874 - 20…
Monitoring the Solar Radius from the Royal Observatory of the Spanish Navy during the Last Quarter-Millennium
J. M. Vaquero, M. C. Gallego, J. J. Ruiz-Lorenzo +5
The solar diameter has been monitored at the Royal Observatory of the Spanish Navy (today the Real Instituto y Observatorio de la Armada: ROA) almost continuously since its creatio…
Sunspot Observations during the Maunder Minimum from the Correspondence of John Flamsteed
V. M. S. Carrasco, J. M. Vaquero
We compile and analyze the sunspot observations made by John Flamsteed for the period 1672-1703, corresponding to the second part of the Maunder Minimum, which appear in the corres…
Level and length of cyclic solar activity during the Maunder minimum as deduced from the active day statistics
J. M. Vaquero, G. A. Kovaltsov, I. G. Usoskin +2
The Maunder minimum (MM) of greatly reduced solar activity took place in 1645-1715, but the exact level of sunspot activity is uncertain as based, to a large extent, on historical…
Sunspots during the Maunder Minimum from Machina Coelestis by Hevelius
V. M. S. Carrasco, J. Villalba Álvarez, J. M. Vaquero
We revisited the sunspot observations published by Johannes Hevelius in his book Machina Coelestis (1679) corresponding to the period 1653-1675 (just in the middle of the Maunder M…
Sunspot latitudes during the Maunder Minimum: a machine-readable catalogue from previous studies
J. M. Vaquero, J. M. Nogales, F. Sánchez-Bajo
The Maunder Minimum (1645-1715 approximately) was a period of very low solar activity and a strong hemispheric asymmetry, with most of sunspots in the southern hemisphere. In this…
A Note on the Relationship between Sunspot Numbers and Active Days
J. M. Vaquero, S. Gutiérrez-López, A. Szelecka
We have studied the relationship between three different versions of the sunspot number (Group, International and American sunspot number) and the number of active days (i.e., the…
Reconstructing Past Solar Activity using Meridian Solar Observations: the Case of the Royal Observatory of the Spanish Navy (1833-1840)
J. M. Vaquero, M. C. Gallego
Solar meridian observations have been used to evaluate the solar activity of the past. Some important examples are the solar meridian observations made at the Basilica of San Petro…
The Sunspot Catalogues of Carrington, Peters, and de la Rue: Quality Control and Machine-readable Versions
R. Casas, J. M. Vaquero
In the 19th century, several astronomers made observations of sunspots, recording their positions and sometimes their areas. These observations were published in the form of extens…