From the Wolf number to the International Sunspot Index: 25 years of SIDC

Clette, F.; Berghmans, D.; Vanlommel, Petra; Linden, R. A. M. Van der; Koeckelenbergh, A.; Wauters, L.

doi:10.1016/j.asr.2006.12.045

Cited by 115 publications

(106 citation statements)

References 45 publications

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“…At present, there are a handful of independent SN reconstructions, all differing in their assessments of the level of solar activity in the past (e.g. Hoyt & Schatten 1998;Clette et al 2007;Clette et al 2014;Lockwood, Owens & Barnard 2014b;Svalgaard & Schatten 2016;Usoskin et al 2016a;Friedli 2017). These SN series are based on a significant number of fragmentary observations by individual observers, each subject to different E-mail: ilya.usoskin@oulu.fi (IGU); m.j.owens@reading.ac.uk (MJO) processing techniques.…”

Section: Introductionmentioning

confidence: 99%

Assessment of different sunspot number series using the cosmogenic isotope ⁴⁴ Ti in meteorites

Asvestari

Usoskin

Kovaltsov

et al. 2017

Mon. Not. R. Astron. Soc.

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Many sunspot number series exist suggesting different levels of solar activity during the past centuries. Their reliability can be assessed only by comparing them with alternative indirect proxies. We test different sunspot number series against the updated record of cosmogenic radionuclide 44 Ti measured in meteorites. Two bounding scenarios of solar activity changes have been considered: the HH-scenario (based on the series by Svalgaard and Schatten), in particular, predicting moderate activity during the Maunder minimum, and the LL-scenario (based on the R G series by Lockwood et al.) predicting moderate activity for the 18th-19th centuries and the very low activity level for the Maunder minimum. For each scenario, the magnetic open solar flux, the heliospheric modulation potential and the expected production of 44 Ti were computed. The calculated production rates were compared with the corresponding measurements of 44 Ti activity in stony meteorites fallen since 1766. The analysis reveals that the LL-scenario is fully consistent with the measured 44 Ti data, in particular, recovering the observed secular trend between the 17th century and the Modern grand maximum. On the contrary, the HH-scenario appears significantly inconsistent with the data, mostly due to the moderate level of activity during the Maunder minimum. It is concluded that the HHscenario sunspot number reconstruction significantly overestimates solar activity prior to the mid-18th century, especially during the Maunder minimum. The exact level of solar activity after 1750 cannot be distinguished with this method, since both H-and L-scenarios appear statistically consistent with the data.

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Section: Introductionmentioning

confidence: 99%

Assessment of different sunspot number series using the cosmogenic isotope ⁴⁴ Ti in meteorites

Asvestari

Usoskin

Kovaltsov

et al. 2017

Mon. Not. R. Astron. Soc.

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“…In 1849, Wolf at the Zürich Observatory proposed the widely used formula: R Z = 10g + f, where f is the number of individual sunspots, and g is the number of sunspot groups (Letfus 2000, Clette et al 2007, Vaquero 2007 …”

Section: Introductionmentioning

confidence: 99%

“…The SIDC (Berghmans et al 2005) collects monthly observations from various stations worldwide in order to calculate the International Relative Sunspot Number R i (Letfus 2000, Clette et al 2007, Vaquero 2007. The center broadcasts the daily, monthly, and yearly sunspot numbers, with middle-range predictions (up to 12 months).…”

Section: Introductionmentioning

confidence: 99%

Does Correction Factor Vary with Solar Cycle?

Chang¹,

Oh²

2012

Journal of Astronomy and Space Sciences

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Monitoring sunspots consistently is the most basic step required to study various aspects of solar activity. To achieve this goal, the observers must regularly calculate their own correction factor k and keep it stable. Relatively recently, two observing teams in South Korea have presented interesting papers which claim that revisions that take the yearly-basis k into account lead to a better agreement with the international relative sunspot number R i , and that yearly k apparently varies with the solar cycle. In this paper, using artificial data sets we have modeled the sunspot numbers as a superposition of random noise and a slowly varying background function, and attempted to investigate whether the variation in the correction factor is coupled with the solar cycle. Regardless of the statistical distributions of the random noise, we have found the correction factor increases as sunspot numbers increase, as claimed in the reports mentioned above. The degree of dependence of correction factor k on the sunspot number is subject to the signal-to-noise ratio. Therefore, we conclude that apparent dependence of the value of the correction factor k on the phase of the solar cycle is not due to a physical property, but a statistical property of the data.

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“…This last equation has been used to determine the International Sunspot Number over the past four centuries (Waldmeier, 1961;McKinnon, 1987;Clette et al, 2007). Further background information on the determination of R I and its various limitations can be found in the articles by Clette et al (2007Clette et al ( , 2014, and Cliver, Clette, and Svalgaard (2013).…”

Section: The International Sunspot Number (R I )mentioning

confidence: 99%

“…Further background information on the determination of R I and its various limitations can be found in the articles by Clette et al (2007Clette et al ( , 2014, and Cliver, Clette, and Svalgaard (2013).…”

Section: The International Sunspot Number (R I )mentioning

confidence: 99%

Re-examination of the Daily Number of Sunspot Groups for the Royal Observatory, Greenwich (1874 – 1885)

2016

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The daily number of sunspot groups on the solar disk, as recorded by the programme of sunspot observations performed under the aegis of the Royal Observatory, Greenwich, UK, and subsequently the Royal Greenwich Observatory (RGO), is re-examined for the interval 1874 -1885. The motivation for this re-examination is the key role that the RGO number of sunspot groups plays in the calculation of Group Sunspot Numbers (Hoyt and Schatten in Solar Phys. 179, 189, 1998a; Solar Phys. 181, 491, 1998b). A new dataset has been derived for the RGO daily number of sunspot groups in the interval 1874 -1885. This new dataset attempts to achieve complete consistency between the sunspot data presented in the three main sections of the RGO publications and also incorporates all known errata and additions. It is argued that days for which no RGO solar photograph was acquired originally should be regarded, without exception, as being days without meaningful sunspot data. The daily number of sunspot groups that Hoyt and Schatten assign to days without RGO photographs is frequently just a lower limit. Moreover, in the absence of a solar photograph, the daily number of sunspot groups is inevitably uncertain because of the known frequent occurrence of sunspot groups that exist for just a single day. The elimination of days without photographs changes the list of inter-comparison days on which both the primary RGO observer and a specified secondary comparison observer saw at least one sunspot group. The resulting changes in the personal correction factors of secondary observers then change the personal correction factors of overlapping tertiary observers, etc. In this way, numerical changes in the personal correction factors of secondary observers propagate away from Sunspot Number Recalibration

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From the Wolf number to the International Sunspot Index: 25 years of SIDC

Cited by 115 publications

References 45 publications

Assessment of different sunspot number series using the cosmogenic isotope ⁴⁴ Ti in meteorites

Assessment of different sunspot number series using the cosmogenic isotope ⁴⁴ Ti in meteorites

Does Correction Factor Vary with Solar Cycle?

Re-examination of the Daily Number of Sunspot Groups for the Royal Observatory, Greenwich (1874 – 1885)

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From the Wolf number to the International Sunspot Index: 25 years of SIDC

Cited by 115 publications

References 45 publications

Assessment of different sunspot number series using the cosmogenic isotope 44 Ti in meteorites

Assessment of different sunspot number series using the cosmogenic isotope 44 Ti in meteorites

Does Correction Factor Vary with Solar Cycle?

Re-examination of the Daily Number of Sunspot Groups for the Royal Observatory, Greenwich (1874 – 1885)

Contact Info

Product

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Assessment of different sunspot number series using the cosmogenic isotope ⁴⁴ Ti in meteorites

Assessment of different sunspot number series using the cosmogenic isotope ⁴⁴ Ti in meteorites