Miszelle

Wittmann, Reinhard

doi:10.1515/9783110949575-011

Cited by 4 publications

(4 citation statements)

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“…It is typical to believe that historical records of NES observations necessarily imply very high levels of solar activity (e.g., Ogurtsov et al 2003), assuming that observable spots must have a large area exceeding 1900 msd (millionths of the solar disc) with a reference to Wittmann (1978). However, this work does not provide any argumentation for such a value and, as shown below, is not correct.…”

Section: Do Nes Observations Imply High Activity?mentioning

confidence: 79%

The Maunder minimum (1645–1715) was indeed a grand minimum: A reassessment of multiple datasets

Usoskin

Arlt

Asvestari

et al. 2015

A&A

193

172

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Aims. Although the time of the Maunder minimum (1645-1715) is widely known as a period of extremely low solar activity, it is still being debated whether solar activity during that period might have been moderate or even higher than the current solar cycle #24. We have revisited all existing evidence and datasets, both direct and indirect, to assess the level of solar activity during the Maunder minimum. Methods. We discuss the East Asian naked-eye sunspot observations, the telescopic solar observations, the fraction of sunspot active days, the latitudinal extent of sunspot positions, auroral sightings at high latitudes, cosmogenic radionuclide data as well as solar eclipse observations for that period. We also consider peculiar features of the Sun (very strong hemispheric asymmetry of the sunspot location, unusual differential rotation and the lack of the K-corona) that imply a special mode of solar activity during the Maunder minimum.Results. The level of solar activity during the Maunder minimum is reassessed on the basis of all available datasets. Conclusions. We conclude that solar activity was indeed at an exceptionally low level during the Maunder minimum. Although the exact level is still unclear, it was definitely lower than during the Dalton minimum of around 1800 and significantly below that of the current solar cycle #24. Claims of a moderate-to-high level of solar activity during the Maunder minimum are rejected with a high confidence level.

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Section: Do Nes Observations Imply High Activity?mentioning

confidence: 79%

The Maunder minimum (1645–1715) was indeed a grand minimum: A reassessment of multiple datasets

Usoskin

Arlt

Asvestari

et al. 2015

A&A

193

172

View full text Add to dashboard Cite

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“…Even that effort may be stymied if in fact there is no quiet Sun. 4) Rutten (1973); (5) Falciani et al (1974); (6) Koutchmy et al (1977); ( 7) Wittmann (1978); (8) Kuhn et al (1985Kuhn et al ( , 1987; (9) Kuhn et al (1988); (10) Kuhn et al (1998) Note. -Observation times indicated are approximate.…”

Section: Discussionmentioning

confidence: 99%

Latitudinal Variation of the Solar Photospheric Intensity

Rast

Ortiz

Meisner

2008

ApJ

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We have examined images from the Precision Solar Photometric Telescope ( PSPT ) at the Mauna Loa Solar Observatory ( MLSO) in search of latitudinal variation in the solar photospheric intensity. Along with the expected brightening of the solar activity belts, we have found a weak enhancement of the mean continuum intensity at polar latitudes (continuum intensity enhancement $0.1%Y0.2%, corresponding to a brightness temperature enhancement of $2.5 K). This appears to be thermal in origin and not due to a polar accumulation of weak magnetic elements, with both the continuum and Ca ii K intensity distributions shifted toward higher values with little change in shape from their midlatitude distributions. Since the enhancement is of low spatial frequency and of very small amplitude, it is difficult to separate from systematic instrumental and processing errors. We provide a thorough discussion of these and conclude that the measurement captures real solar latitudinal intensity variations.

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“…Other astronomers before Eddy had also named the period after Annie and Edward Maünder. This absence of sunspots was not an error due to the lack of observations or to the quality of the telescopes at the time as there was evidence for a cycle before the minimum (Wittmann 1978). Spörer noted that during one 28-year period within the Maünder Minimum (1672-1699), observations recorded fewer than 50 sunspots, much fewer than is typically observed today.…”

Section: Introductionmentioning

confidence: 88%

Spatial-temporal forecasting the sunspot diagram

Covas¹

2017

A&A

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Aims. We attempt to forecast the Sun's sunspot butterfly diagram in both space (i.e. in latitude) and time, instead of the usual onedimensional time series forecasts prevalent in the scientific literature. Methods. We use a prediction method based on the non-linear embedding of data series in high dimensions. We use this method to forecast both in latitude (space) and in time, using a full spatial-temporal series of the sunspot diagram from 1874 to 2015.Results. The analysis of the results shows that it is indeed possible to reconstruct the overall shape and amplitude of the spatialtemporal pattern of sunspots, but that the method in its current form does not have real predictive power. We also apply a metric called structural similarity to compare the forecasted and the observed butterfly cycles, showing that this metric can be a useful addition to the usual root mean square error metric when analysing the efficiency of different prediction methods. Conclusions. We conclude that it is in principle possible to reconstruct the full sunspot butterfly diagram for at least one cycle using this approach and that this method and others should be explored since just looking at metrics such as sunspot count number or sunspot total area coverage is too reductive given the spatial-temporal dynamical complexity of the sunspot butterfly diagram. However, more data and/or an improved approach is probably necessary to have true predictive power.

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Miszelle

Cited by 4 publications

References 0 publications

The Maunder minimum (1645–1715) was indeed a grand minimum: A reassessment of multiple datasets

The Maunder minimum (1645–1715) was indeed a grand minimum: A reassessment of multiple datasets

Latitudinal Variation of the Solar Photospheric Intensity

Spatial-temporal forecasting the sunspot diagram

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