An Observed Decline in the Amplitude of Recent Solar-Cycle Peaks

Chapman, G. A.; Toma, G. de; Cookson, A. M.

doi:10.1007/s11207-014-0533-7

Cited by 9 publications

(12 citation statements)

References 25 publications

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“…FA started to increase since the beginning of 1999 until the middle of 2009 and it started to increase again after the year 2010. Our results for SSCs, SG numbers, FA and Ca II K-flux support the analysis of Kilcik et al (2011), de Toma et al (2004,2013) and Chapman et al (2014).…”

Section: Facular Area and Ca II K-fluxsupporting

confidence: 92%

Temporal variations of different solar activity indices through the solar cycles 21-23

et al. 2017

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Here, we compare the sunspot counts and the number of sunspot groups (SGs) with variations of total solar irradiance (TSI), magnetic activity, Ca II K-flux, faculae and plage areas. We applied a time series method for extracting the data over the descending phases of solar activity cycles (SACs) 21, 22 and 23, and the ascending phases 22 and 23. Our results suggest that there is a strong correlation between solar activity indices and the changes in small (A, B, C and H-modified Zurich Classification) and large (D, E and F) SGs. This somewhat unexpected finding suggests that plage regions substantially decreased in spite of the higher number of large SGs in SAC 23 while the Ca II K-flux did not decrease by a large amount nor was it comparable with SAC 22 and relates with C and DEF type SGs. In addition to this, the increase of facular areas which are influenced by large SGs, caused a small percentage decrease in TSI while the decrement of plage areas triggered a higher decrease in the magnetic field flux. Our results thus reveal the potential of such a detailed comparison of the SG analysis with solar activity indices for better understanding and predicting future trends in the SACs.

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Section: Facular Area and Ca II K-fluxsupporting

confidence: 92%

Temporal variations of different solar activity indices through the solar cycles 21-23

et al. 2017

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“…Our detailed analysis of the variation of TSI fluxes in the cycles 22 -24 showed that the assumption in Svalgaard (2013) which was done on observational data of Penn and Livingston (2006), (2011) and Chapman et al . (2014) is true: at one and the same level of F 10.7 the value of TSI at the cycles 23 -24 increases, see Fig.…”

Section: Discussionmentioning

confidence: 89%

“…It increases the radiation flux from the photosphere due to the decreasing of deficit of bright photosphere's flux in dark spots. Moreover, the relative amplitudes of the total areas of spots in the cycle's maximums decrease in the cycles 23+24 compared to the cycle 22, and the ratio of total areas of faculae to total areas of spots in the cycle 24 is growing according to Chapman et al . (2014).…”

Section: Introductionmentioning

confidence: 99%

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General trends in the change in solar activity indices in the period from the late XX to early XXI century

Бруевич

Yakunina

2015

Geomagn. Aeron.

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The analysis of the observations of solar activity indexes SSN (NOAA Sunspot Numbers), the radio flux at a wavelength of 10.7 cm (F 10.7 ) and the solar constant (TSI) during the cycles 22 -24 is presented. We found a decrease of the observed values of the SSN obs which was calculated with SSN syn (using regression relationships between SSN and F 10.7 ) after 1990 year on 20 -25% instead of 35%, as was previously assumed. The changes in characteristics of the most popular index, SSN, such as decrease in the number of sunspots, the reduction of the magnetic field in small and medium-sized spots are not in full compliance with the proposed scenario of solar activity predicted by radio flux F 10.7 in the cycles 23 and 24, and cannot be fully explained by the influence on the SSN values of additional minimum of 50 -70 year cycle. We have also showed that the observed changes of SSN lead to a slight increase of the solar constant TSI during the cycles 23 -24 compared to the cycle 22.

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“…Their study provides evidence for a possible link between the spatial evolution of magnetic flux emergence and rate of solar flares, which is consistent with our results (see also Joshi et al 2006b). In particular, many irregularities in sunspot manifestations during cycle 23 have been well observed and extensively studied (Russell et al 2010;Lukianova & Mursula 2011;Lefèvre & Clette 2011;Clette & Lefèvre 2012;Livingston et al 2012;Chapman et al 2014) that finally point to the complexities of underlying solar dynamo processes. Lefèvre & Clette (2011) found that cycle 23 is quite distinguishable from the previous cycle in terms of significant deficit in small sunspot, while large-scale spots remained largely unaffected.…”

Section: Discussionmentioning

confidence: 99%

Evolutionary aspects and north-south asymmetry of soft X-ray flare index during solar cycles 21, 22, and 23

Joshi

Bhattacharyya

Pandey

et al. 2015

A&A

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Aims. In this paper, we investigate the temporal evolution and north-south (N-S) asymmetry in the occurrence of solar flares during cycle 21, 22, and 23, and compare the results with traditional solar activity indices. Methods. The flare activity is characterized by a soft X-ray (SXR) flare index, which incorporates information about flare occurrences during a selected interval along with the peak intensity of individual events. Results. The SXR flare index correlates well with other conventional parameters of solar activity. Further, it exhibits a significantly higher correlation with sunspot area over sunspot number, which suggests the variations in sunspot area to be more closely linked with the transient energy release in the solar corona. The cumulative plots of the flare index indicate a slight excess of activity in the northern hemisphere during cycle 21, while a southern excess clearly prevails for cycles 22 and 23. The study reveals a significant N-S asymmetry, which exhibits variations with the phases of solar cycle. The reliability and persistency of this asymmetry significantly increases when the data is averaged over longer periods, while an optimal level is achieved when data is binned for 13 Carrington rotations. The time evolution of the flare index further confirms evolution of dual peaks in solar cycles during the solar maxima and violation of Gnevyshev-Ohl rule for the pair of solar cycles 22 and 23. Conclusions. The SXR flare index in the northern and the southern hemispheres of the Sun exhibits significant asymmetry during the evolutionary phases of the solar cycle, which implies that N-S asymmetry of solar flares is manifested in terms of the flare counts as well as the intensity of flare events.

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An Observed Decline in the Amplitude of Recent Solar-Cycle Peaks

Cited by 9 publications

References 25 publications

Temporal variations of different solar activity indices through the solar cycles 21-23

Temporal variations of different solar activity indices through the solar cycles 21-23

General trends in the change in solar activity indices in the period from the late XX to early XXI century

Evolutionary aspects and north-south asymmetry of soft X-ray flare index during solar cycles 21, 22, and 23

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