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William Dean Pesnell - One of the best experts on this subject based on the ideXlab platform.
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Predictions of Solar Cycle 24: How are We Doing?
Space Weather, 2016Co-Authors: William Dean PesnellAbstract:Predictions of Solar activity are an essential part of our Space Weather forecast capability. Users are requiring usable predictions of an upcoming Solar Cycle to be delivered several years before Solar minimum. A set of predictions of the amplitude of Solar Cycle 24 accumulated in 2008 ranged from zero to unprecedented levels of Solar activity. The predictions formed an almost normal distribution, centered on the average amplitude of all preceding Solar Cycles. The average of the current compilation of 105 predictions of the annual-average sunspot number is 106 +/- 31, slightly lower than earlier compilations but still with a wide distribution. Solar Cycle 24 is on track to have a below-average amplitude, peaking at an annual sunspot number of about 80. Our need for Solar activity predictions and our desire for those predictions to be made ever earlier in the preceding Solar Cycle will be discussed. Solar Cycle 24 has been a below-average sunspot Cycle. There were peaks in the daily and monthly averaged sunspot number in the Northern Hemisphere in 2011 and in the Southern Hemisphere in 2014. With the rapid increase in Solar data and capability of numerical models of the Solar convection zone we are developing the ability to forecast the level of the next sunspot Cycle. But predictions based only on the statistics of the sunspot number are not adequate for predicting the next Solar maximum. I will describe how we did in predicting the amplitude of Solar Cycle 24 and describe how Solar polar field predictions could be made more accurate in the future.
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Solar Cycle Predictions (Invited Review)
Solar Physics, 2012Co-Authors: William Dean PesnellAbstract:Solar Cycle predictions are needed to plan long-term space missions, just as weather predictions are needed to plan the launch. Fleets of satellites circle the Earth collecting many types of science data, protecting astronauts, and relaying information. All of these satellites are sensitive at some level to Solar Cycle effects. Predictions of drag on low-Earth orbit spacecraft are one of the most important. Launching a satellite with less propellant can mean a higher orbit, but unanticipated Solar activity and increased drag can make that a Pyrrhic victory as the reduced propellant load is consumed more rapidly. Energetic events at the Sun can produce crippling radiation storms that endanger all assets in space. Solar Cycle predictions also anticipate the shortwave emissions that cause degradation of Solar panels. Testing Solar dynamo theories by quantitative predictions of what will happen in 5 – 20 years is the next arena for Solar Cycle predictions. A summary and analysis of 75 predictions of the amplitude of the upcoming Solar Cycle 24 is presented. The current state of Solar Cycle predictions and some anticipations of how those predictions could be made more accurate in the future are discussed.
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Solar Cycle Predictions
2012Co-Authors: William Dean PesnellAbstract:Solar Cycle predictions are needed to plan long-term space missions; just like weather predictions are needed to plan the launch. Fleets of satellites circle the Earth collecting many types of science data, protecting astronauts, and relaying information. All of these satellites are sensitive at some level to Solar Cycle effects. Predictions of drag on LEO spacecraft are one of the most important. Launching a satellite with less propellant can mean a higher orbit, but unanticipated Solar activity and increased drag can make that a Pyrrhic victory as you consume the reduced propellant load more rapidly. Energetic events at the Sun can produce crippling radiation storms that endanger all assets in space. Solar Cycle predictions also anticipate the shortwave emissions that cause degradation of Solar panels. Testing Solar dynamo theories by quantitative predictions of what will happen in 5-20 years is the next arena for Solar Cycle predictions. A summary and analysis of 75 predictions of the amplitude of the upcoming Solar Cycle 24 is presented. The current state of Solar Cycle predictions and some anticipations how those predictions could be made more accurate in the future will be discussed.
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Solar Cycle Prediction
2011Co-Authors: William Dean PesnellAbstract:Solar Cycle predictions are needed to plan long-term space missions; just like weather predictions are needed to plan your next vacation. Fleets of satellites circle the Earth collecting many types of science data, protecting astronauts, and relaying information. All of these satellites are sensitive at some level to Solar Cycle effects. Predictions of drag on LEO spacecraft are one of the most important. Launching a satellite with less propellant can mean a higher orbit, but unanticipated Solar activity and increased drag can make that a Pyrrhic victory. Energetic events at the Sun can produce crippling radiation storms that endanger all assets in space. Testing Solar dynamo theories by quantitative predictions of what will happen in 5-20 years is the next arena for Solar Cycle predictions. I will describe the current state of Solar Cycle predictions and anticipate how those predictions could be made more accurate in the future.
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predictions of Solar Cycle 24
Solar Physics, 2008Co-Authors: William Dean PesnellAbstract:A summary and analysis of more than 50 predictions of the amplitude of the upcoming Solar Cycle 24 is presented. All of the predictions were published before Solar minimum and represent our efforts to anticipate Solar maximum at ever-earlier epochs. The consistency of the predictions within their assigned categories is discussed. Estimates of the significance of the predictions, compared to the climatological average, are presented.
David H. Hathaway - One of the best experts on this subject based on the ideXlab platform.
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an updated Solar Cycle 25 prediction with aft the modern minimum
arXiv: Solar and Stellar Astrophysics, 2018Co-Authors: Lisa Upton, David H. HathawayAbstract:Over the last decade there has been mounting evidence that the strength of the Sun's polar magnetic fields during a Solar Cycle minimum is the best predictor of the amplitude of the next Solar Cycle. Surface flux transport models can be used to extend these predictions by evolving the Sun's surface magnetic field to obtain an earlier prediction for the strength of the polar fields, and thus the amplitude of the next Cycle. In 2016, our Advective Flux Transport (AFT) model was used to do this, producing an early prediction for Solar Cycle 25. At that time, AFT predicted that Cycle 25 will be similar in strength to the Cycle 24, with an uncertainty of about 15% . AFT also predicted that the polar fields in the southern hemisphere would weaken in late 2016 and into 2017 before recovering. That AFT prediction was based on the magnetic field configuration at the end of January 2016. We now have 2 more years of observations. We examine the accuracy of the 2016 AFT prediction and find that the new observations track well with AFT's predictions for the last two years. We show that the southern relapse did in fact occur, though the timing was off by several months. We propose a possible cause for the southern relapse and discuss the reason for the offset in timing. Finally, we provide an updated AFT prediction for Solar Cycle 25 which includes Solar observations through January of 2018.
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the Solar Cycle
arXiv: Solar and Stellar Astrophysics, 2015Co-Authors: David H. HathawayAbstract:The Solar Cycle is reviewed. The 11-year Cycle of Solar activity is characterized by the rise and fall in the numbers and surface area of sunspots. A number of other Solar activity indicators also vary in association with the sunspots including; the 10.7cm radio flux, the total Solar irradiance, the magnetic field, flares and coronal mass ejections, geomagnetic activity, galactic cosmic ray fluxes, and radioisotopes in tree rings and ice cores. Individual Solar Cycles are characterized by their maxima and minima, Cycle periods and amplitudes, Cycle shape, the equatorward drift of the active latitudes, hemispheric asymmetries, and active longitudes. Cycle-to-Cycle variability includes the Maunder Minimum, the Gleissberg Cycle, and the Gnevyshev-Ohl (even-odd) Rule. Short-term variability includes the 154-day periodicity, quasi-biennial variations, and double-peaked maxima. We conclude with an examination of prediction techniques for the Solar Cycle and a closer look at Cycles 23 and 24.
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The Solar Cycle
Living Reviews in Solar Physics, 2010Co-Authors: David H. HathawayAbstract:The Solar Cycle is reviewed. The 11-year Cycle of Solar activity is characterized by the rise and fall in the numbers and surface area of sunspots. We examine a number of other Solar activity indicators including the 10.7 cm radio flux, the total Solar irradiance, the magnetic field, flares and coronal mass ejections, geomagnetic activity, galactic cosmic ray fluxes, and radioisotopes in tree rings and ice cores that vary in association with the sunspots. We examine the characteristics of individual Solar Cycles including their maxima and minima, Cycle periods and amplitudes, Cycle shape, and the nature of active latitudes, hemispheres, and longitudes. We examine long-term variability including the Maunder Minimum, the Gleissberg Cycle, and the Gnevyshev-Ohl Rule. Short-term variability includes the 154-day periodicity, quasi-biennial variations, and double peaked maxima. We conclude with an examination of prediction techniques for the Solar Cycle.
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Solar Cycle Forecasting
Space Science Reviews, 2008Co-Authors: David H. HathawayAbstract:Predicting the behavior of a Solar Cycle after it is well underway (2–3 years after minimum) can be done with a fair degree of skill using auto-regression and curve fitting techniques that don’t require any knowledge of the physics involved. Predicting the amplitude of a Solar Cycle near, or before, the time of Solar Cycle minimum can be done using precursors such as geomagnetic activity and polar fields that do have some connection to the physics but the connections are uncertain and the precursors provide less reliable forecasts. Predictions for the amplitude of Cycle 24 using these precursor techniques give drastically different values. Recently, dynamo models have been used directly with assimilated data to predict the amplitude of sunspot Cycle 24 but have also given significantly different predictions. While others have questioned both the predictability of the Solar Cycle and the ability of current dynamo models to provide predictions, it is clear that Cycle 24 will help to discriminate between some opposing dynamo models.
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a synthesis of Solar Cycle prediction techniques
Journal of Geophysical Research, 1999Co-Authors: David H. Hathaway, Robert M Wilson, Edwin J ReichmannAbstract:A number of techniques currently in use for predicting Solar activity on a Solar Cycle timescale are tested with historical data. Some techniques, e.g., regression and curve fitting, work well as Solar activity approaches maximum and provide a month-by-month description of future activity, while others, e.g., geomagnetic precursors, work well near Solar minimum but only provide an estimate of the amplitude of the Cycle. A synthesis of different techniques is shown to provide a more accurate and useful forecast of Solar Cycle activity levels. A combination of two uncorrelated geomagnetic precursor techniques provides a more accurate prediction for the amplitude of a Solar activity Cycle at a time well before activity minimum. This combined precursor method gives a smoothed sunspot number maximum of 154 ± 21 at the 95% level of confidence for the next Cycle maximum. A mathematical function dependent on the time of Cycle initiation and the Cycle amplitude is used to describe the level of Solar activity month by month for the next Cycle. As the time of Cycle maximum approaches a better estimate of the Cycle activity is obtained by including the fit between previous activity levels and this function. This Combined Solar Cycle Activity Forecast gives, as of January 1999, a smoothed sunspot maximum of 146 ± 20 at the 95% level of confidence for the next Cycle maximum.
Kristof Petrovay - One of the best experts on this subject based on the ideXlab platform.
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Solar Cycle prediction
Living Reviews in Solar Physics, 2020Co-Authors: Kristof PetrovayAbstract:A review of Solar Cycle prediction methods and their performance is given, including early forecasts for Cycle 25. The review focuses on those aspects of the Solar Cycle prediction problem that have a bearing on dynamo theory. The scope of the review is further restricted to the issue of predicting the amplitude (and optionally the epoch) of an upcoming Solar maximum no later than right after the start of the given Cycle. Prediction methods form three main groups. Precursor methods rely on the value of some measure of Solar activity or magnetism at a specified time to predict the amplitude of the following Solar maximum. The choice of a good precursor often implies considerable physical insight: indeed, it has become increasingly clear that the transition from purely empirical precursors to model-based methods is continuous. Model-based approaches can be further divided into two groups: predictions based on surface flux transport models and on consistent dynamo models. The implicit assumption of precursor methods is that each numbered Solar Cycle is a consistent unit in itself, while Solar activity seems to consist of a series of much less tightly intercorrelated individual Cycles. Extrapolation methods, in contrast, are based on the premise that the physical process giving rise to the sunspot number record is statistically homogeneous, i.e., the mathematical regularities underlying its variations are the same at any point of time, and therefore it lends itself to analysis and forecasting by time series methods. In their overall performance during the course of the last few Solar Cycles, precursor methods have clearly been superior to extrapolation methods. One method that has yielded predictions consistently in the right range during the past few Solar Cycles is the polar field precursor. Nevertheless, some extrapolation methods may still be worth further study. Model based forecasts are quickly coming into their own, and, despite not having a long proven record, their predictions are received with increasing confidence by the community.
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Solar Cycle prediction
Living reviews in solar physics, 2010Co-Authors: Kristof PetrovayAbstract:A review of Solar Cycle prediction methods and their performance is given, including forecasts for Cycle 24. The review focuses on those aspects of the Solar Cycle prediction problem that have a bearing on dynamo theory. The scope of the review is further restricted to the issue of predicting the amplitude (and optionally the epoch) of an upcoming Solar maximum no later than right after the start of the given Cycle. Prediction methods form three main groups. Precursor methods rely on the value of some measure of Solar activity or magnetism at a specified time to predict the amplitude of the following Solar maximum. Their implicit assumption is that each numbered Solar Cycle is a consistent unit in itself, while Solar activity seems to consist of a series of much less tightly intercorrelated individual Cycles. Extrapolation methods, in contrast, are based on the premise that the physical process giving rise to the sunspot number record is statistically homogeneous, i.e., the mathematical regularities underlying its variations are the same at any point of time and, therefore, it lends itself to analysis and forecasting by time series methods. Finally, instead of an analysis of observational data alone, model based predictions use physically (more or less) consistent dynamo models in their attempts to predict Solar activity. In their overall performance during the course of the last few Solar Cycles, precursor methods have clearly been superior to extrapolation methods. Nevertheless, most precursor methods overpredicted Cycle 23, while some extrapolation methods may still be worth further study. Model based forecasts have not yet had a chance to prove their skills. One method that has yielded predictions consistently in the right range during the past few Solar Cycles is that of K. Schatten et al., whose approach is mainly based on the polar field precursor. The incipient Cycle 24 will probably mark the end of the Modern Maximum, with the Sun switching to a state of less strong activity. It will therefore be an important testbed for Cycle prediction methods and, by inference, for our understanding of the Solar dynamo.
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Solar Cycle prediction
arXiv: Solar and Stellar Astrophysics, 2010Co-Authors: Kristof PetrovayAbstract:A review of Solar Cycle prediction methods and their performance is given, including forecasts for Cycle 24 and focusing on aspects of the Solar Cycle prediction problem that have a bearing on dynamo theory. The scope of the review is further restricted to the issue of predicting the amplitude (and optionally the epoch) of an upcoming Solar maximum no later than right after the start of the given Cycle. Prediction methods form three main groups. Precursor methods rely on the value of some measure of Solar activity or magnetism at a specified time to predict the amplitude of the following Solar maximum. Their implicit assumption is that each numbered Solar Cycle is a consistent unit in itself, while Solar activity seems to consist of a series of much less tightly intercorrelated individual Cycles. Extrapolation methods, in contrast, are based on the premise that the physical process giving rise to the sunspot number record is statistically homogeneous, i.e., the mathematical regularities underlying its variations are the same at any point of time, and therefore it lends itself to analysis and forecasting by time series methods. Finally, instead of an analysis of observational data alone, model based predictions use physically (more or less) consistent dynamo models in their attempts to predict Solar activity. In their overall performance precursor methods have clearly been superior to extrapolation methods. Nevertheless, some extrapolation methods may still be worth further study. Model based forecasts have not yet have had a chance to prove their skills. One method that has yielded predictions consistently in the right range during the past few Solar Cycles is that of K. Schatten et al., whose approach is mainly based on the polar field precursor. The incipient Cycle 24 will probably mark the end of the Modern Maximum, with the Sun switching to a state of less strong activity.
W. Dean Pesnell - One of the best experts on this subject based on the ideXlab platform.
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An Early Prediction of the Amplitude of Solar Cycle 25
Solar Physics, 2018Co-Authors: W. Dean Pesnell, Kenneth H. SchattenAbstract:A “Solar Dynamo” (SODA) Index prediction of the amplitude of Solar Cycle 25 is described. The SODA Index combines values of the Solar polar magnetic field and the Solar spectral irradiance at 10.7 cm to create a precursor of future Solar activity. The result is an envelope of Solar activity that minimizes the 11-year period of the sunspot Cycle. We show that the variation in time of the SODA Index is similar to several wavelet transforms of the Solar spectral irradiance at 10.7 cm. Polar field predictions for Solar Cycles 21 – 24 are used to show the success of the polar field precursor in previous sunspot Cycles. Using the present value of the SODA index, we estimate that the next Cycle’s smoothed peak activity will be about $140 \pm30$ Solar flux units for the 10.7 cm radio flux and a Version 2 sunspot number of $135 \pm25$ . This suggests that Solar Cycle 25 will be comparable to Solar Cycle 24. The estimated peak is expected to occur near $2025.2 \pm1.5$ year. Because the current approach uses data prior to Solar minimum, these estimates may improve as the upcoming Solar minimum draws closer.
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Predicting Solar Cycle 24 Using a Geomagnetic Precursor Pair
Solar Physics, 2014Co-Authors: W. Dean PesnellAbstract:We describe using Ap and F10.7 as a geomagnetic-precursor pair to predict the amplitude of Solar Cycle 24. The precursor is created by using F10.7 to remove the direct Solar-activity component of Ap. Four peaks are seen in the precursor function during the decline of Solar Cycle 23. A recurrence index that is generated by a local correlation of Ap is then used to determine which peak is the correct precursor. The earliest peak is the most prominent but coincides with high levels of non-recurrent Solar activity associated with the intense Solar activity of October and November 2003. The second and third peaks coincide with some recurrent activity on the Sun and show that a weak Cycle precursor closely following a period of strong Solar activity may be difficult to resolve. A fourth peak, which appears in early 2008 and has recurrent activity similar to precursors of earlier Solar Cycles, appears to be the "true" precursor peak for Solar Cycle 24 and predicts the smallest amplitude for Solar Cycle 24. To determine the timing of peak activity it is noted that the average time between the precursor peak and the following maximum is ≈ 6.4 years. Hence, Solar Cycle 24 would peak during 2014. Several effects contribute to the smaller prediction when compared with other geomagnetic-precursor predictions. During Solar Cycle 23 the correlation between sunspot number and F10.7 shows that F10.7 is higher than the equivalent sunspot number over most of the Cycle, implying that the sunspot number underestimates the Solar-activity component described by F10.7. During 2003 the correlation between aa and Ap shows that aa is 10 % higher than the value predicted from Ap, leading to an overestimate of the aa precursor for that year. However, the most important difference is the lack of recurrent activity in the first three peaks and the presence of significant recurrent activity in the fourth. While the prediction is for an amplitude of Solar Cycle 24 of 65 ± 20 in smoothed sunspot number, a below-average amplitude for Solar Cycle 24, with maximum at 2014.5 ± 0.5, we conclude that Solar Cycle 24 will be no stronger than average and could be much weaker than average.
Kenneth H. Schatten - One of the best experts on this subject based on the ideXlab platform.
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An Early Prediction of the Amplitude of Solar Cycle 25
Solar Physics, 2018Co-Authors: W. Dean Pesnell, Kenneth H. SchattenAbstract:A “Solar Dynamo” (SODA) Index prediction of the amplitude of Solar Cycle 25 is described. The SODA Index combines values of the Solar polar magnetic field and the Solar spectral irradiance at 10.7 cm to create a precursor of future Solar activity. The result is an envelope of Solar activity that minimizes the 11-year period of the sunspot Cycle. We show that the variation in time of the SODA Index is similar to several wavelet transforms of the Solar spectral irradiance at 10.7 cm. Polar field predictions for Solar Cycles 21 – 24 are used to show the success of the polar field precursor in previous sunspot Cycles. Using the present value of the SODA index, we estimate that the next Cycle’s smoothed peak activity will be about $140 \pm30$ Solar flux units for the 10.7 cm radio flux and a Version 2 sunspot number of $135 \pm25$ . This suggests that Solar Cycle 25 will be comparable to Solar Cycle 24. The estimated peak is expected to occur near $2025.2 \pm1.5$ year. Because the current approach uses data prior to Solar minimum, these estimates may improve as the upcoming Solar minimum draws closer.
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Solar activity forecast for Solar Cycle 23
Geophysical Research Letters, 1996Co-Authors: Kenneth H. Schatten, Daniel J. Myers, Sabatino SofiaAbstract:In this paper, we predict the next Cycle's activity and improve the timing of Solar Cycle predictions. Dynamobased Solar activity prediction techniques rely upon two properties inherent in the Solar Cycle: that Solar magnetism oscillates between poloidal and toroidal components; and that there is a degree of “magnetic persistence” in dynamos, which in the case of the Sun, results in the dependence of many magnetic related quantities (activity related quantities) upon the amount of magnetism embedded below the Sun's surface. Using the SODA (Solar Dynamo Amplitude) index as a measure of magnetic persistence, we predict that Solar Cycle #23 will reach a mean smoothed F10.7 peak of 182±30 Solar flux units (sfu) and a mean sunspot number Rz of 138±30. This is particularly intriguing because the “folklore” is that odd Cycles are larger than the preceding even Cycle. Additionally, by tracking the equatorward march of Solar activity, the timing of the Cycle can be better estimated. From this, we estimate that the next Solar maximum will occur near May, 2000 ±9 months.
