Extreme Value Theory and the New Sunspot Number Series

Acero, Francisco Javier; Carrasco, V. M. S.; Gallego, M. C.; García, José Álvarez; Vaquero, J. M.

doi:10.3847/1538-4357/aa69bc

Cited by 18 publications

(20 citation statements)

References 47 publications

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“…Moreover, the return levels are reaching a plateau, and it will be unlikely that the sunspot numbers will attain values greater than the already observed ones in the future. This generally agrees with a similar analysis carried out using the sunspot number based in telescopic data for the last four centuries (Acero et al 2017). …”

Section: Discussionsupporting

confidence: 91%

Extreme Value Theory Applied to the Millennial Sunspot Number Series

Acero

Gallego

García

et al. 2018

ApJ

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In this work, we use two decadal sunspot number series reconstructed from cosmogenic radionuclide data ( 14 C in tree trunks, Be in polar ice, SN-10Be) and the Extreme Value Theory to study variability of solar activity during the last 9 millennia.The peaks-over-threshold technique was used to compute, in particular, the shape parameter of the generalized Pareto distribution for different thresholds. Its negative value implies an upper bound of the extreme SN-10Be and SN-14C time series. The return level for 1000 and 10000 years were estimated leading to values lower than the maximum observed values, expected for the 1000-year, but not for the 10000-year return levels, for both series. A comparison of these results with those obtained using the observed sunspot numbers from telescopic observations during the last four centuries suggest that the main characteristics of solar activity have already been recorded in the telescopic period (from 1610 to nowadays) which covers the full range of solar variability from a Grand minimum to a Grand maximum.

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Section: Discussionsupporting

confidence: 91%

Extreme Value Theory Applied to the Millennial Sunspot Number Series

Acero

Gallego

García

et al. 2018

ApJ

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“…However, it should be pointed out that the extreme value theory can be used to study the solar extreme events. For example, Acero et al (2017Acero et al ( , 2018Acero et al ( , 2019 employed this technique to study the temporal variability of the sunspot number and the solar radio flux, and found that there is an upper bound for the distribution of the peak values of the photospheric and coronal indicators. Therefore, the coronal magnetic activity exhibits the similar kind of behavior as the sunspot activity, implying that the features that cause the coronal modulation are rooted in surface magnetic structures.…”

Section: Comparison With the Sunspot Number Datamentioning

confidence: 99%

Systematic regularity of solar coronal rotation during the time interval 1939–2019

Deng

Zhang

Deng

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Temporal variation of the solar coronal rotation appears to be very complex and its relevances to the eleven-year solar activity cycle are still unclear. Using the modified coronal index for the time interval from 1939 January 1 to 2019 May 31, the systematic regularities of the solar coronal rotation are investigated. Our main findings are as follows: (1) from a global point of view, the synodic coronal rotation period with a value of 27.5 days is the only significant period at the periodic scales shorter than 64 days; (2) the coronal rotation period exhibit an obviously decreasing trend during the considered time interval, implying the solar corona accelerates its global rotation rate in the long run; (3) there exist significant periods of 3.25, 6.13, 9.53, and 11.13 years in the period length of the coronal rotation, providing an evidence that the coronal rotation should be connected with the quasi-biennial oscillation, the eleven-year solar cycle, and the 22-year Hale cycle (or the magnetic activity reversal); and (4) the phase relationship between the coronal rotation period and the solar magnetic activity is not only time-dependent but also frequency-dependent. For a small range around the 11-year cycle band, there is a systematic trend in the phase, and the small mismatch in this band brings out the phase to drift. The possible mechanism for the above analysis results is discussed.

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“…For this purpose, we use a set of statistical techniques commonly called extreme value theory (EVT). These techniques are beginning to be used to better characterize the extreme values of different indices related to space storms (Acero et al, 2017(Acero et al, , 2018Elvidge & Angling, 2018).…”

Section: Introductionmentioning

confidence: 99%

A Limit for the Values of the Dst Geomagnetic Index

Acero

Vaquero

Gallego

et al. 2018

Geophysical Research Letters

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The study of the extreme weather space events is important for a technological-dependent society. Extreme value theory could be decisive to characterize those extreme events in order to have the knowledge to make decisions in technological, economic, and social matters, in all fields with possible impacts. In this work, the hourly values of the Dst geomagnetic index have been studied for the period 1957-2014 using the peaks-over-threshold technique. The shape parameter obtained from the fit of the generalized Pareto distribution to the extreme values of the |Dst| index leads to a negative value implying an upper bound for this time series. This result is relevant because the estimation of this limit for the extreme values leads to 850 nT as the highest expected value for this geomagnetic index. Thus, from the previous characterization of the Carrington geomagnetic storm and our results, it could be considered the worst-case scenario.

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Extreme Value Theory and the New Sunspot Number Series

Cited by 18 publications

References 47 publications

Extreme Value Theory Applied to the Millennial Sunspot Number Series

Extreme Value Theory Applied to the Millennial Sunspot Number Series

Systematic regularity of solar coronal rotation during the time interval 1939–2019

A Limit for the Values of the Dst Geomagnetic Index

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