Lessons learned from predictions of Solar Cycle 24

Pesnell, W. D.

doi:10.1051/swsc/2020060

Cited by 33 publications

(14 citation statements)

References 46 publications

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“…Putting these empirical results together allows the probability of extreme geomagnetic storms to be quantified if the timing and magnitude of the coming solar cycle is known. Within plausible ranges (Pesnell, 2020;Nandy, 2021), the amplitude of the solar cycle can change the occurrence probability of an, e.g., 1-in-100-years event by about a factor of three. E.g.…”

Section: Discussionmentioning

confidence: 99%

Extreme Space-Weather Events and the Solar Cycle

et al. 2021

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Space weather has long been known to approximately follow the solar cycle, with geomagnetic storms occurring more frequently at solar maximum than solar minimum. There is much debate, however, about whether the most hazardous events follow the same pattern. Extreme events – by definition – occur infrequently, and thus establishing their occurrence behaviour is difficult even with very long space-weather records. Here we use the 150-year $aa_{H}$ a a H record of global geomagnetic activity with a number of probabilistic models of geomagnetic-storm occurrence to test a range of hypotheses. We find that storms of all magnitudes occur more frequently during an active phase, centred on solar maximum, than during the quiet phase around solar minimum. We also show that the available observations are consistent with the most extreme events occurring more frequently during large solar cycles than small cycles. Finally, we report on the difference in extreme-event occurrence during odd- and even-numbered solar cycles, with events clustering earlier in even cycles and later in odd cycles. Despite the relatively few events available for study, we demonstrate that this is inconsistent with random occurrence. We interpret this finding in terms of the overlying coronal magnetic field and enhanced magnetic-field strengths in the heliosphere, which act to increase the geoeffectiveness of sheath regions ahead of extreme coronal mass ejections. Putting the three “rules” together allows the probability of extreme event occurrence for Solar Cycle 25 to be estimated, if the magnitude and length of the coming cycle can be predicted. This highlights both the feasibility and importance of solar-cycle prediction for planning and scheduling of activities and systems that are affected by extreme space weather.

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Section: Discussionmentioning

confidence: 99%

Extreme Space-Weather Events and the Solar Cycle

et al. 2021

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“…In this study, we find that the probability of individual flare events is also correlated to the total sunspot number through the solar cycle, which closely follows the polar field strength. To put this work in context we point out that the polar field data has been used to inform solar cycle predictions with reasonable accuracy (Pesnell, 2012;Pesnell, 2020). We believe this work represents the first time the global field has been used to augment the prediction of solar flares.…”

Section: Discussionmentioning

confidence: 97%

Incorporating polar field data for improved solar flare prediction

Aktukmak

Sun

Bobra

et al. 2022

Front. Astron. Space Sci.

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In this paper, we consider incorporating data associated with the sun’s north and south polar field strengths to improve solar flare prediction performance using machine learning models. When used to supplement local data from active regions on the photospheric magnetic field of the sun, the polar field data provides global information to the predictor. While such global features have been previously proposed for predicting the next solar cycle’s intensity, in this paper we propose using them to help classify individual solar flares. We conduct experiments using HMI data employing four different machine learning algorithms that can exploit polar field information. Additionally, we propose a novel probabilistic mixture of experts model that can simply and effectively incorporate polar field data and provide on-par prediction performance with state-of-the-art solar flare prediction algorithms such as the Recurrent Neural Network (RNN). Our experimental results indicate the usefulness of the polar field data for solar flare prediction, which can improve Heidke Skill Score (HSS2) by as much as 10.1%1.

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“…From the sunspot number in the top panel it is apparent that over the period of this study, encompassing most of the space age, the strength of the solar activity cycles has been progressively declining. Much has been written regarding the possible cause(s) of this decrease and its consequences (e.g., Pesnell, 2020 and references therein), but for the purposes of this study our primary interest concerns the changes in coronal structure that have affected the ecliptic solar wind. The OMNI measurements in the second through fourth panels in Figure 1 show the previously recognized decreasing trends in the interplanetary magnetic field strength (2nd panel) and solar wind density (4th panel), with long‐term velocity changes (3rd panel) less well‐defined.…”

Section: Data and Model Resourcesmentioning

confidence: 99%

Solar Cycle Variability in Coronal Holes and Their Effects on Solar Wind Sources

Luhmann

Lee

et al. 2022

Space Weather

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Various upstream spacecraft have now observed the solar wind conditions affecting the Earth since the 1970s, covering over four solar activity cycles. These measurements provide a long term picture of the related patterns in large scale incident plasma and magnetic field parameters of interest for both interpreting cycles in geospace effects, and understanding how the Sun controls our space environment. This paper focuses on the latter, in part to provide context at the start of the new solar cycle 25, and toward establishing connections between the 1 AU ecliptic solar wind behavior and the unprecedented near‐Sun measurements of heliospheric features on Parker Solar Probe and Solar Orbiter. Magnetograph data‐based potential field source surface models provide a basic picture of how the solar wind sources, including those that give rise to corotating high speed streams in the ecliptic, have changed since the beginning of the record of regular solar wind measurements. In particular, they suggest the contributions from low to mid latitude coronal holes dominate the observed cycles (21–24), especially the weaker cycles (23 and 24), impacting upstream measurement interpretations, modeling, and forecasting considerations. For example, recurring features are affected by differential rotation of the Sun's surface field, which through its effects on the corona, can produce solar wind streams reappearing at ∼25–30 days intervals instead of at the canonical 27.3 days Carrington rotation rate. In addition, the conditions that lead to the corotating stream structure that can dominate periods of low solar activity are seen to be more complicated than suggested by the simple concepts of early studies. The overall results illustrate where in the cycles well‐defined, long‐lived large scale structures can be expected, and the advantages of synoptic displays of 1 AU solar wind parameters for anticipating timings of recurring features.

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Lessons learned from predictions of Solar Cycle 24

Cited by 33 publications

References 46 publications

Extreme Space-Weather Events and the Solar Cycle

Extreme Space-Weather Events and the Solar Cycle

Incorporating polar field data for improved solar flare prediction

Solar Cycle Variability in Coronal Holes and Their Effects on Solar Wind Sources

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