蒙德极小期（MM）是1645年至1715年间一个持续的太阳活动极小期。多项研究已经发现，现有数据库中包含的MM时期无黑子日存在大量有问题的记录。我们找到了Johann Heinrich Muller提供的一份关于确切无黑子日（1709年下半年）和有黑子日（1709年1月和8月）的清单。我们利用超几何概率分布，根据Muller的数据计算了活动日比例（ADF）的最可能值以及上下限。我们的样本并非严格随机，因为Muller在观测到太阳黑子时会连续数日记录观测结果。因此，我们的结果代表了1709年太阳活动的上限阈值。我们将该结果与为道尔顿极小期和最近几个太阳周期计算的ADF年度值进行了比较。我们得出结论：1709年的太阳活动水平低于道尔顿极小期和最近几个太阳周期中的大多数年份。因此，本研究估算的1709年太阳活动水平为MM时期太阳活动水平较低提供了有力证据。
英文摘要：
The Maunder Minimum (MM) was a period of prolonged solar activity minimum between 1645 and 1715. Several works have identified a significant number of problematic spotless days in the MM included in existing databases. We have found a list of exact spotless (in the second half of 1709) and spot days (January and August 1709) provided by Johann Heinrich Muller. We computed the most probable value and upper/lower limits of the active day fraction (ADF) from Muller's data using the hypergeometrical probability distribution. Our sample is not strictly random because Muller recorded observations in consecutive days when he observed sunspots. Therefore, our result represents an upper threshold of solar activity for 1709. We compared this result with annual values of the ADF calculated for the Dalton Minimum and the most recent solar cycles. We concluded that it was less active than most years both in the Dalton Minimum and in the most recent solar cycles. Therefore, the solar activity level estimated in this work for 1709 represents robust evidence of low solar activity levels in the MM.
We propose that the poloidal field at the end of the last sunspot cycle before the Maunder minimum fell to a very low value due to fluctuations in the Babcock--Leighton process. With this assumption, a flux transport dynamo model is able to explain various aspects of the historical records of the Maunder minimum remarkably well on choosing the parameters of the model suitably to give the correct growth time.
Maunder Minimum forms an archetype for the Grand minima, and detailed knowledge of its temporal development has important consequences for the solar dynamo theory dealing with long-term solar activity evolution. Here we reconsider the current paradigm of the Grand minimum general scenario by using newly recovered sunspot observations by G. Marcgraf and revising some earlier uncertain data for the period 1636--1642, i.e., one solar cycle before the beginning of the Maunder Minimum. The new and revised data dramatically change the magnitude of the sunspot cycle just before the Maunder Minimum, f…
We compile and analyze the sunspot observations made by John Flamsteed for the period 1672-1703, corresponding to the second part of the Maunder Minimum, which appear in the correspondence of this famous astronomer. We include in an appendix the original texts of the sunspot records kept by Flamsteed. We compute an estimate of the level of solar activity using these records, and compare the results with the latest reconstructions of solar activity during the Maunder Minimum, obtaining values characteristic of a grand solar minimum. Finally, we discuss a phenomenon observed and described by Ste…
Aims: Although the time of the Maunder minimum (1645--1715) is widely known as a period of extremely low solar activity, claims are still debated that solar activity during that period might still have been moderate, even higher than the current solar cycle #24. We have revisited all the existing pieces of 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 posi…
An analysis of the sunspot observations made by Hevelius during 1642-1645 is presented. These records are the only systematic sunspot observations just before the Maunder Minimum. We have studied different phenomena meticulously recorded by Hevelius after translating the original Latin texts. We re-evaluate the observations of sunspot groups by Hevelius during this period and obtain an average value 7% greater than that calculated from his observations given in the current group database. Furthermore, the average of the active day fraction obtained in this work from Hevelius' records previous …
Two important sources of information about sunspots in the Maunder minimum are the Spörer catalog and observations of the Paris observatory, which cover in total the last quarter of the 17th and the first two decades of the 18th century. These data, in particular, contain information about sunspot latitudes. As we showed in previous papers, dispersions of sunspot latitude distributions are tightly related to sunspot indices, so we can estimate the level of solar activity in this epoch by a method which is not based on direct calculation of sunspots and is weakly affected by loss of observation…
The Maunder Minimum (1645-1715 approximately) was a period of very low solar activity and a strong hemispheric asymmetry, with most of sunspots in the southern hemisphere. In this paper, two data sets of sunspot latitudes during the Maunder minimum have been recovered for the international scientific community. The first data set is constituted by latitudes of sunspots appearing in the catalogue published by Gustav Spörer nearly 130 years ago. The second data set is based on the sunspot latitudes displayed in the butterfly diagram for the Maunder Minimum which was published by Ribes and Nesme-…
We revisited the sunspot observations published by Johannes Hevelius in his book Machina Coelestis (1679) corresponding to the period 1653-1675 (just in the middle of the Maunder Minimum). We show detailed translations of the original Latin texts describing the sunspot records and provide the general context of these sunspot observations. From this source only, we present an estimate of the annual values of the Group Sunspot Number based only on the records that explicitly inform about the presence or absence of sunspots. Although we obtain very low values of the Group Sunspot Number, in accor…
We present five decades of chromospheric activity measurements in 59 Sun-like stars as time series. These include and extend the 35 yr of stellar chromospheric activity observations by the Mount Wilson Survey (1966--2001), and continued observations at Keck by the California Planet Search (1996--). The Mount Wilson Survey was studied closely in 1995, and revealed periodic activity cycles similar to the Sun's 11 yr cycle. The California Planet Search provides more than five decades of measurements, significantly improving our understanding of these stars' activity behavior. We have curated the …
We study the magnetic activity cycle of HD 4915 using the \ion{Ca}{2} H \& K emission line strengths measured by Keck I/HIRES spectrograph. The star has been observed as a part of California Planet Search Program from 2006 to present. We note decreasing amplitude in the magnetic activity cycle, a pattern suggesting the star's entry into a Magnetic Grand Minimum (MGM) state, reminiscent of the Sun's Maunder and Dalton Minima. We recommend further monitoring of the star to confirm the grand minimum nature of the dynamo, which would provide insight into the state of the Sun's chromosphere and the…
The sun occasionally undergoes the so-called grand minima, in which its magnetic activity, measured by the number of sunspots, is suppressed for decades. The most prominent grand minima, since the beginning of telescopic observations of sunspots, is the Maunder minimum (1645-1715), when the sunspots became rather scarce. The mechanism underlying the grand minima remains poorly understood as there is little observational information of the solar magnetic field at that time. In this study, we examine the records of one candidate aurora display in China and Japan during the Maunder minimum. The p…
Naked-eye sunspot observations (NESO, hereafter) have been recorded for last two millennia, approximately. This kind of records were made around the world, mainly in Asian civilizations, and they are compiled in several catalogues. In this work, we analyze solar activity in days of the 19th century when NESO were recorded. We found that only more than five sunspot groups were recorded in 39 % of days corresponding to these NESO events. Furthermore, regarding the largest groups observed in days when NESO were reported, we show the uncorrected areas of these groups were below 200 millionths of s…
Fluctuations in the Sun's magnetic activity, including episodes of grand minima such as the Maunder minimum have important consequences for space and planetary environments. However, the underlying dynamics of such extreme fluctuations remain ill-understood. Here we use a novel mathematical model based on stochastically forced, non-linear delay differential equations to study solar cycle fluctuations, in which, time delays capture the physics of magnetic flux transport between spatially segregated dynamo source regions in the solar interior. Using this model we explicitly demonstrate that the …
The Maunder Minimum (MM) was a prolonged period of low solar activity that occurred between 1645 and 1715. The true level of solar activity corresponding to this epoch is still a matter of debate. In order to compare solar activity during the MM with that of other epochs, we have evaluated the umbra-penumbra area ratio (U/P hereafter) during the MM. Thus, we have analyzed 196 sunspot drawings including 48 different sunspots observed during the period 1660-1709. The mode value of the ratio obtained from the occurrence frequency distribution lies between 0.15 and 0.25. Furthermore, the median an…
The Maunder Minimum corresponds to a prolonged minimum of solar activity a phenomenon that is of particular interest to many branches of natural and social sciences commonly considered to extend from 1645 until 1715. However, our knowledge of past solar activity has improved significantly in recent years and, thus, more precise dates for the onset and termination of this particularly episode of our Sun can be established. Based on the simultaneous analysis of distinct proxies we propose a redefinition of the Maunder Minimum period with the core "Deep Maunder Minimum" spanning from 1645 to 1700…
Spectropolarimetric Constraints on the Maunder Minimum Analog HD 166620: Evidence for Weakened Magnetic Braking
Institute for Astronomy, University of Hawai‘i at Mānoa（夏威夷大学马诺阿分校天文研究所）；Department of Physics and Astronomy, Uppsala University（乌普萨拉大学物理与天文学系）；Center for Solar-Stellar Connections, WDRC（日恒联系中心，WDRC）
We observed 51 Peg, the first detected planet-bearing star, in a 55 ks XMM-Newton pointing and in 5 ks pointings each with Chandra HRC-I and ACIS-S. The star has a very low count rate in the XMM observation, but is clearly visible in the Chandra images due to the detectors' different sensitivity at low X-ray energies. This allows a temperature estimate for 51 Peg's corona of T<1MK; the detected ACIS-S photons can be plausibly explained by emission lines of a very cool plasma near 200eV. The constantly low X-ray surface flux and the flat-activity profile seen in optical CaII data suggest that 5…
The solar analogs of M67 let us glimpse the probable behavior of the Sun on time scales surpassing the duration of human civilization. M67 can serve as a solar proxy because its stars share a similar age and composition with the Sun. Previous surveys of M67 observed that 15% of its Sun-like stars exhibited chromospheric activity levels below solar minimum, which suggest that these stars might be in activity-minimum states analogous to the Maunder Minimum. The activity diagnostic used, the HK index (relative intensities of the Ca II H&K lines integrated over 1 Ang. bandpasses), was measured fro…
The Maunder Minimum was the period between 1645 and 1715 whose main characteristic was abnormally low and prolonged solar activity. However, some authors have doubted this low level of solar activity during that period by questioning the accuracy and objectivity of the observers. This work presents a particular case of a sunspot observed during the Maunder Minimum with an unusual shape of its umbra and penumbra: a hexagon. This sunspot was observed by Cassini in November 1676, just at the core of the Maunder Minimum. This historical observation is compared with a twin case that occurred recent…
Quiet, but not silent. The X-ray activity of the Maunder minimum star HD 166620
Eberhard Karls Universität Tübingen（蒂宾根大学）；University of California at Berkeley（加州大学伯克利分校）；Max-Planck-Institut für extraterrestrische Physik（马克斯·普朗克地外物理学研究所）
A revision is presented of the sunspot observations made by Charles Malapert from 1618 to 1626, studying several documentary sources that include those observations. The revised accounting of the group numbers recorded by Malapert for that period shows new information unavailable in the current sunspot group database. The average solar activity level calculated from these revised records of Malapert is by almost one third greater than that calculated from his records included in the current group database. Comparison of the sunspot observations made by Malapert and by other astronomers of that…
We propose that at the beginning of the Maunder minimum the poloidal field or amplitude of meridional circulation or both fell abruptly to low values. With this proposition, a flux transport dynamo model is able to reproduce various important aspects of the historical records of the Maunder minimum remarkably well.
The Maunder minimum (MM) of greatly reduced solar activity took place in 1645-1715, but the exact level of sunspot activity is uncertain as based, to a large extent, on historical generic statements of the absence of spots on the Sun. Here we aim, using a conservative approach, to assess the level and length of solar cycle during the Maunder minimum, on the basis of direct historical records by astronomers of that time. A database of the active and inactive days (days with and without recorded sunspots on the solar disc respectively) is constructed for three models of different levels of conse…
Aims: We demonstrate the universal character of the quiet-Sun chromosphere among inactive stars (solar-type and giants). By assessing the main physical processes, we shed new light on some common observational phenomena. Methods: We discuss measurements of the solar Mt. Wilson S-index, obtained by the Hamburg Robotic Telescope around the extreme minimum year 2009, and compare the established chromospheric basal Ca II K line flux to the Mt. Wilson S-index data of inactive ("flat activity") stars, including giants. Results: During the unusually deep and extended activity minimum of 2009, the Sun…
The sunspot groups have been observed since 1610 and their numbers have been used for evaluating the amplitude of solar activity. Daniel Mögling recorded his sunspot observations for more than 100 days in 1626 - 1629 and formed a significant dataset of sunspot records before the Maunder Minimum. Here, we have analysed his original manuscripts in the Universitäts- und Landesbibliothek Darmstadt (ULBD) to review Mögling's personal profile and observational instruments and derive number and positions of the sunspot groups. In his manuscript, we have identified 134 days with an exact sunspot group…
HD 166620 was recently identified as a Maunder Minimum candidate based on nearly 50 years of Ca II H & K activity data from Mount Wilson and Keck-HIRES (Baum et al. 2022). These data showed clear cyclic behavior on a 17-year timescale during the Mount Wilson survey that became flat when picked up later with Keck-HIRES planet-search observations. Unfortunately, the transition between these two data sets -- and therefore the transition into the candidate Maunder Minimum phase -- contained little to no data. Here we present additional Mount Wilson data not present in Baum et al. (2022) along with…
We explore the sensitivity of the frequencies of low-degree solar p-modes to near-surface magnetic flux on different spatial scales and strengths, specifically to active regions with strong magnetic fields and ephemeral regions with weak magnetic fields. We also use model reconstructions from the literature to calculate average frequency offsets back to the end of the Maunder minimum. We find that the p-mode frequencies are at least three times less sensitive (at 95% confidence) to the ephemeral-region field than they are to the active-region field. Frequency shifts between activity cycle mini…
Sunspot positions from various historical sets of solar drawings are analysed with respect to the tilt angles of bipolar sunspot groups. Data by Scheiner, Hevelius, Staudacher, Zucconi, Schwabe, and Spoerer deliver a series of average tilt angles spanning a period of 270 years, additional to previously found values for 20th-century data obtained by other authors. We find that the average tilt angles before the Maunder minimum were not significantly different from the modern values. However, the average tilt angles of a period 50 years after the Maunder minimum, namely for cycles 0 and 1, were …
Both direct observations and reconstructions from various datasets, suggest that conditions were radically different during the Maunder Minimum (MM) than during the space era. Using an MHD model, we develop a set of feasible solutions to infer the properties of the solar wind during this interval. Additionally, we use these results to drive a global magnetospheric model. Finally, using the 2008/2009 solar minimum as an upper limit for MM conditions, we use results from the International Reference Ionosphere (ILI) model to speculate on the state of the ionosphere. The results describe interplan…
One of the most enigmatic phenomena related to solar activity is the so-called Maunder minimum phase. It consists of the lowest sunspot's counting ever registered for the Sun, and never so far confirmed for other stars. Since the spectroscopic observations of stellar activity at the Mount Wilson Observatory, the solar analog HD43587 has shown a very low and apparently invariant activity level, which makes it a Maunder minimum candidate. We analyze the chromospheric activity evolution of HD43587 and its evolutive status, intending to unravel the reasons for this low and flat activity. We use an…
The solar activity during the Maunder Minimum (MM; 1645 -- 1715) has been considered significantly different from the one captured in modern observations, in terms of sunspot group number and sunspot positions, whereas its actual amplitudes and distributions is still under active discussions. In its core period (1650/1660 -- 1700), Martin Fogelius and Henrich Siverus have formed significant long-term series in the existing databases with numerous spotless days, as the 13th and 7th most active observers before the end of the MM. In this study, we have analysed their original archival records, r…
Meridional circulation is an important ingredient in flux transport dynamo models. We have studied its importance on the period, the amplitude of the solar cycle, and also in producing Maunder-like grand minima in these models. First, we model the periods of the last 23 sunspot cycles by varying the meridional circulation speed. If the dynamo is in a diffusion-dominated regime, then we find that most of the cycle amplitudes also get modeled up to some extent when we model the periods. Next, we propose that at the beginning of the Maunder minimum the amplitude of meridional circulation dropped …
We present reconstructed sunspot positions based on observations reported in letters between Gottfried Kirch and other contemporary astronomers from AD 1680 to 1709, i.e. in the last decades of the Maunder Minimum. The letters were compiled and edited by Herbst (2006). The letters (and observations) from Kirch are mostly by Gottfried Kirch, but some also by his 2nd wife Maria M. Kirch (married 1692) and their son Christfried Kirch (born 1694). Using excerpts from the letters, some with drawings, we found some 35 sunspot groups (often for several days in a row or with interruptions) by Kirch an…
A simple method to detect inconsistencies in low annual sunspot numbers based on the relationship between these values and the annual number of active days is described. The analysis allowed for the detection of problems in the annual sunspot number series clustered in a few specific periods and unambiguous, namely: i) before Maunder minimum, ii) the year 1652 during the Maunder minimum, iii) the year 1741 in Solar Cycle -1, and iv) the so-called "lost" solar cycle in 1790s and subsequent onset of the Dalton Minimum.
Recovery of the Solar Cycle from Maunder-like Grand Minima Episodes: A Quantification of the Necessary Polar Flux Threshold through Solar Dynamo Simulations
The Sun occasionally goes through Maunder-like extended grand minima when its magnetic activity drops considerably from the normal activity level for several decades. Many possible theories have been proposed to explain the origin of these minima. However, how the Sun managed to recover from such inactive phases every time is even more enigmatic. The Babcock--Leighton type dynamos, which are successful in explaining many features of the solar cycle remarkably well, are not expected to operate during grand minima due to the lack of a sufficient number of sunspots. In this Letter, we explore the…
Using a summary curve of two eigen vectors of solar magnetic field oscillations derived with Principal Components Analysis (PCA) from synoptic maps for solar cycles 21-24 as a proxy of solar activity, we extrapolate this curve backwards three millennia revealing 9 grand cycles lasting 350-400 years each. The summary curve shows a remarkable resemblance to the past sunspot and terrestrial activity: grand minima - Maunder Minimum (1645-1715 AD), Wolf minimum (1280-1350 AD), Oort minimum (1010-1050 AD) and Homer minimum (800-900 BC); grand maxima - modern warm period (1990-2015), medieval warm pe…
The Maunder Minimum (1645-1715) is currently considered the only grand minimum within telescopic sunspot observations since 1610. During this epoch, the Sun was extremely quiet and unusually free from sunspots. However, despite reduced frequency, candidate aurorae were reported in the mid-European sector during this period and have been associated with occurrences of interplanetary coronal mass ejections (ICMEs), whereas some of them have been identified as misinterpretations. Here, we have analysed reports of candidate aurorae on 1 June 1680 with simultaneous observations in mid-Europe, and c…
Visible coronal structure, in particular the spatial evolution of coronal streamers, provides indirect information about solar magnetic activity and the underlying solar dynamo. Their apparent absence of structure observed during the total eclipses of throughout the Maunder Minimum has been interpreted as evidence of a significant change in the solar magnetic field from that during modern cycles. Eclipse observations available from the more recent Dalton Minimum may be able to provide further information, sunspot activity being between the levels seen during recent cycles and in the Maunder Mi…
Reconstructions of total solar irradiance (TSI) rely mainly on linear relations between TSI variation and indices of facular area. When these are extrapolated to the prolonged 15th - 17th century Spörer and Maunder solar activity minima, the estimated solar dimming is insufficient to explain the mid- millennial climate cooling of the Little Ice Age. We draw attention here to evidence that the relation departs from linearity at the lowest activity levels. Imaging photometry and radiometry indicate an increased TSI contribution per unit area from small network faculae by a factor of 2-4 compared…
The solar cycle periodically reshapes the magnetic structure and radiative output of the Sun and determines its impact on the heliosphere roughly every 11 years. Besides this main periodicity, it shows century-long variations (including periods of abnormally low solar activity called grand minima). The Maunder Minimum (1645-1715) has generated significant interest as the archetype of a grand minimum in magnetic activity for the Sun and other stars, suggesting a potential link between the Sun and changes in terrestrial climate. Recent reanalyses of sunspot observations have yielded a conflicted…
A solar-type dynamo model in a spherical shell is developed with allowance for random dependence of the poloidal field generation mechanism on time and latitude. The model shows repeatable epochs of strongly decreased amplitude of magnetic cycles similar to the Maunder minimum of solar activity. Random dependence of dynamo-parameters on latitude brakes the equatorial symmetry of generated fields. The model shows the correlation of the occurrence of grand minima with deviations in the dynamo-field from dipolar parity. An increased north-south asymmetry of magnetic activity can, therefore, be an…
In this study we overview recent advances with prediction of solar activity using as a proxy solar background magnetic field and detection of grand solar cycles of about 400 years separated by grand solar minima (GSMs).The previous GSM known as the Maunder minimum was recorded from 1645 to 1715. The terrestrial temperature during Maunder Minimum was reduced by up to 1.0C that led to freezing rivers, cold winters and summers. The modern GSM started in 2020 and will last for three solar cycles until 2053. During this GSM two processes will affect the input of solar radiation: a decrease of solar…
Recently discovered long-term oscillations of the solar background magnetic field associated with double dynamo waves generated in inner and outer layers of the Sun indicate that the solar activity is heading in the next three decades (2019-2055) to a Modern grand minimum similar to Maunder one. On the other hand, a reconstruction of solar total irradiance suggests that since the Maunder minimum there is an increase in the cycle-averaged total solar irradiance (TSI) by a value of about $1-1.5$ $Wm^{-2}$ closely correlated with an increase of the baseline (average) terrestrial temperature. In o…
Context. There is no consensus on the amplitude of the historical solar forcing. The estimated magnitude of the total solar irradiance difference between Maunder minimum and present time ranges from 0.1 to 6 W/m2 making uncertain the simulation of the past and future climate. One reason for this disagreement is the applied evolution of the quiet Sun brightness in the solar irradiance reconstruction models. This work addresses the role of the quiet Sun model choice and updated solar magnetic activity proxies on the solar forcing reconstruction. Aims. We aim to establish a plausible range of the…
Our knowledge of the long-term evolution of solar activity and of its primary modulation, the 11-year cycle, largely depends on a single direct observational record: the visual sunspot counts that retrace the last 4 centuries, since the invention of the astronomical telescope. Currently, this activity index is available in two main forms: the International Sunspot Number initiated by R. Wolf in 1849 and the Group Number constructed more recently by Hoyt and Schatten (1998a,b). Unfortunately, those two series do not match by various aspects, inducing confusions and contradictions when used in c…
The "Other" Centuries-Long Record of Solar Magnetic Activity Cycles: Lessons From the Stars
Penn State（宾夕法尼亚州立大学）；Center for Solar-Stellar Connections, WDRC（太阳-恒星联系中心，WDRC）；ELTE Eötvös Loránd University（罗兰大学）；Nagoya University（名古屋大学）；Institute for Space-Earth Environmental Research, Nagoya University（地球环境研究所，名古屋大学）；Institute for Advanced Research, Nagoya University（先进研究院，名古屋大学）；RAL Space, Science and Technology Facilities Council（拉尔夫空间部，英国科学与技术设施委员会）；Riken Nishina Centre（理化学研究所仁科中心）
Based on the extended Greenwich-NOAA/USAF catalogue of sunspot groups it is demonstrated that the parameters describing the latitudinal width of the sunspot generating zone (SGZ) are closely related to the current level of solar activity, and the growth of the activity leads to the expansion of SGZ. The ratio of the sunspot number to the width of SGZ shows saturation at a certain level of the sunspot number, and above this level the increase of the activity takes place mostly due to the expansion of SGZ. It is shown that the mean latitudes of sunspots can be reconstructed from the amplitudes o…
We summarize the fifty-year concerted effort to place the "activity" of the Sun in the context of the stars. As a working definition of solar activity in the context of stars, we adopt those globally-observable variations on time scales below thermal time scales, of ~ 100,000 yr for the convection zone. So defined, activity is dominated by magnetic-field evolution, including the 22-year Hale cycle, the typical time it takes for the quasi-periodic reversal in which the global magnetic-field takes place. This is accompanied by sunspot variations with 11 year periods, known since the time of Schw…
The total solar irradiance (TSI) varies on timescales of minute to centuries. On short timescales it varies due to the superposition of intensity fluctuations produced by turbulent convection and acoustic oscillations. On longer scale times, it changes due to photospheric magnetic activity, mainly because of the facular brightenings and dimmings caused by sunspots. While modern TSI variations have been monitored from space since 1970s, TSI variations over much longer periods can only be estimated using either historical observations of magnetic features, possibly supported by flux transport mo…
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 la…
We describe a revised collection of the number of sunspot groups from 1610 to the present. This new collection is based on the work of Hoyt and Schatten (Solar Phys. 179, 189, 1998). The main changes are the elimination of a considerable number of observations during the Maunder Minimum (hereafter, MM) and the inclusion of several long series of observations. Numerous minor changes are also described. Moreover, we have calculated the active-day percentage during the MM from this new collection as a reliable index of the solar activity. Thus, the level of solar activity obtained in this work is…
The Sun's activity cycle governs the radiation, particle and magnetic flux in the heliosphere creating hazardous space weather. Decadal-scale variations define space climate and force the Earth's atmosphere. However, predicting the solar cycle is challenging. Current understanding indicates a short window for prediction best achieved at previous cycle minima. Utilizing magnetic field evolution models for the Sun's surface and interior we perform the first century-scale, data-driven simulations of solar activity and present a scheme for extending the prediction window to a decade. Our ensemble …
