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Letfus, V.

doi:10.1023/a:1005208223601

Cited by 20 publications

(4 citation statements)

References 10 publications

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“…This study supports the earlier conclusions that the group sunspot number series (Hoyt & Schatten 1998) is more consistent and homogeneous than the Wolf sunspot number series in earlier observations (e.g., Letfus 1999Letfus , 2000Hathaway et al 2002;Usoskin & Mursula 2003;Usoskin 2013). …”

Section: Discussionsupporting

confidence: 91%

Inconsistency of the Wolf sunspot number series around 1848

Leussu

Usoskin

Arlt

et al. 2013

A&A

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Aims. Sunspot numbers form a benchmark series in many studies, but may still contain inhomogeneities and inconsistencies. In particular, an essential discrepancy exists between the two main sunspot number series, Wolf and group sunspot numbers (WSN and GSN, respectively), before 1848. The source of this discrepancy has remained unresolved so far. However, the recently digitized series of solar observations in 1825-1867 by Samuel Heinrich Schwabe, who was the primary observer of the WSN before 1848, makes such an assessment possible. Methods. We construct sunspot series, similar to WSN and GSN but using only Schwabe's data. These series, called here WSN-S and GSN-S, respectively, were compared with the original WSN and GSN series for the period 1835-1867 for possible inhomogeneities.Results. This study supports the earlier conclusions that the GSN series is more consistent and homogeneous in the earlier part than the WSN series. We show that: the GSN series is homogeneous and consistent with the Schwabe data throughout the entire studied period; the WSN series decreases by roughly 20% around 1848, which is caused by the change of the primary observer from Schwabe to Wolf and an inappropriate individual correction factor used for Schwabe in the WSN; this implies a major inhomogeneity in the WSN, which needs to be corrected by reducing its values by 20% before 1848; the corrected WSN series is in good agreement with the GSN series.

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Section: Discussionsupporting

confidence: 91%

Inconsistency of the Wolf sunspot number series around 1848

Leussu

Usoskin

Arlt

et al. 2013

A&A

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“…5). This might imply that the group sunspot number values are somewhat too small during the first half of the 18th century, in general agreement with the results of Letfus (2000). We note that the two reconstructed SN series lie closer together than the GSN and WSN series in the common time interval, i.e., between 1700 and 1900.…”

Section: Reconstruction Of Sunspot Numberssupporting

confidence: 87%

Reconstruction of solar activity for the last millennium using $^\mathsf{10}$Be data

Usoskin

Мурсула

Solanki

et al. 2003

A&A

109

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Abstract. In a recent paper (Usoskin et al. 2002a), we have reconstructed the concentration of the cosmogenic 10 Be isotope in ice cores from the measured sunspot numbers by using physical models for 10 Be production in the Earth's atmosphere, cosmic ray transport in the heliosphere, and evolution of the Sun's open magnetic flux. Here we take the opposite route: starting from the 10 Be concentration measured in ice cores from Antarctica and Greenland, we invert the models in order to reconstruct the 11-year averaged sunspot numbers since 850 AD. The inversion method is validated by comparing the reconstructed sunspot numbers with the directly observed sunspot record since 1610. The reconstructed sunspot record exhibits a prominent period of about 600 years, in agreement with earlier observations based on cosmogenic isotopes. Also, there is evidence for the century scale Gleissberg cycle and a number of shorter quasi-periodicities whose periods seem to fluctuate in the millennium time scale. This invalidates the earlier extrapolation of multi-harmonic representation of sunspot activity over extended time intervals.

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“…In case of performing the earth acquisition for COMS at the selected one of the calculated time period, the algorithm and simulation result for attitude maneuver process, maneuver time and duration is verified. The actually realized earth acquisi-equation suggested by Wolf at the Zürich Observatory in 1849 (Letfus 2000, Vaquero 2007). An observed sunspot number is defined by multiplying the number of observed sunspot groups, g, by 10 and adding the number of observed, isolated sunspots, f, to the product.…”

Section: Introductionmentioning

confidence: 99%

Relative Sunspot Number Observed from 2002 to 2011 at ButterStar Observatory

Oh¹,

Chang²

2012

Journal of Astronomy and Space Sciences

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The ButterStar Observatory at the Dongducheon High School has been working for photographic observations of the Sun since October 16, 2002. In this study, we observed the Sun at the ButterStar observatory for 3,364 days from October 16, 2002 to December 31, 2011, and analyzed the photographic sunspot data obtained in 1,965 days. The correction factor K b for the entire observing period is 0.9519, which is calculated using the linear least square method to the relationship between the daily sunspot number, R B , and the daily international relative sunspot number, R i . The yearly correction factor calculated for each year varies slightly from year to year and shows a trend to change along the solar cycle. The correction factor is larger during the solar maxima and smaller during the solar minima in general. This implies that the discrepancy between a relative sunspot number, R, and the daily international relative sunspot number, R i , can be reduced by using a yearly correction factor. From 2002 to 2008 in solar cycle 23, 35.4% and 64.6% of sunspot groups and 35.1% and 64.9% of isolated sunspots in average occurred in the northern hemisphere and in the southern hemisphere, respectively, and from 2008 to 2011 in solar cycle 24, 61.3% and 38.7% of sunspot groups and 65.0% and 35.0% of isolated sunspots were observed, respectively. This result shows that the occurrence frequency for each type of sunspot group changes along the solar cycle development, which can be interpreted as the emerging and decaying process of sunspot groups is different depending on the phase of solar cycle. Therefore, it is considered that a following study would contribute to the efforts to understand the dependence of the dynamo mechanism on the phase of solar cycle.

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Cited by 20 publications

References 10 publications

Inconsistency of the Wolf sunspot number series around 1848

Inconsistency of the Wolf sunspot number series around 1848

Reconstruction of solar activity for the last millennium using $^\mathsf{10}$Be data

Relative Sunspot Number Observed from 2002 to 2011 at ButterStar Observatory

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