Grand Minima Of Solar Activity Research Articles

Динамика растительности юга Приморья при климатической ритмике малого ледникового периода

Six stages of vegetation development have been identified on the basis of a palynological study of floodplain deposits of the Tsukanovka River (southern Primorye). The first stage is transitional from the medieval warm period, the next four stages are comparable with the climatic phases of the Little Ice Age. The sixth stage in the development of vegetation reflects the modern warming in the 20th century, when modern landscapes have been formed with the participation of the anthropogenic factor. The specific development of a complex of atmospheric-hydrospheric processes, which developed under the direct influence of long-term variations in solar activity, was the reason for the emergence of the Little Ice Age. The coldest phase in the territory of southern Primorye occurred at the end of the 17th century and coincided with the Maunder Grand Minimum of solar activity (1645–1715), it is also characterized by a decrease in humidity. The development of forest vegetation in the valley of the Tsukanovka River recorded alternating warm and cold episodes during the Little Ice Age. In relatively warm phases, the proportion of oak and other broad-leaved trees increased in the forest vegetation in southern Primorye, while in cold phases the proportion of alder increased. In the first half of the XVI century on the territory of southern Primorye, an increase in humidity due to an increase in precipitation is noted. The correlation of paleoclimatic rhythms identified on the basis of spore-pollen analysis results during the Little Ice Age in southern Primorye, with dendrochronological data for the southern Sikhote-Alin and other regions of the northern hemisphere, as well as with historical evidence from neighboring China, has showed the synchronism of the onset of climatic events in the regions, which reflects their global nature and global scale.

Solar activity imprints in tree ring-data from northwestern Russia

The Sun's role in climate variability is now a subject of debates, especially in the context of understanding contribution of solar forcing to modern global warming. Besides, there are some evidences of the approaching new Grand Solar Minimum with Little Ice Age climatic conditions. This expectation is based on the occurrence of the extended solar minimum of 2006–2009. To investigate the possible Sun-climate connection the regional tree-ring chronology covering the period from 1445 to 2005 was analyzed. A total of 36 timber cores of pine Pinus sylvestris L. were sampled near the northern tree-line at Loparskaya station (68.6 N, 33.3 E), including the oldest living pine with more than 560 years of age. The data were processed using modern methods adopted in dendrochronology (cross-dating and standardization) with the help of COFECHA and ARSTAN programs. The analysis revealed significant cooling events, coinciding with the Spoerer (1400–1540), Maunder (1645–1715), Dalton (1790–1830), and Gleissberg (1880–1910) Grand Solar Minima. The application of MTM-spectrum and wavelet decomposition analysis identified the existence of the main cycles of solar activity (5.4, 11.7 and 22 years) in tree-ring width variations. As possible extraterrestrial forcings of climate change we consider here variations in solar irradiance and cosmic ray intensity modulated by the interplanetary magnetic field. As solar and cosmic ray activity indicators we used the annual sunspot number, geomagnetic aa index and Be^10 cosmogenic isotope records. To examine the relationship in time-frequency scale between tree-ring growth and solar activity, the cross wavelet transform and wavelet coherence analysis were applied to the time series. The wavelet coherence analysis identified that the 11 yr and 22 yr periodicities were clearly manifested in the all solar-tree rings connections during and around the Grand Minima of solar activity including the Maunder minimum, when, as is known, sunspots were practically absent. These results confirm the existence of solar activity effect on climate and tree growth above the Arctic Circle and are important for understanding the modern climatic processes.

Analysis of pre-telescopic sunspots and auroras from 8th to 16th century

In this paper, we use non-parametric kernel approach to estimate the probability density function (pdf) of auroral-night and naked-eye-sunspot series over multi-century timescale. We selected the events observed in medieval epoch, and auroral records from low geographical latitude (<45°). These astronomical phenomena are recorded mainly in the Oriental historical sources and much less in Occidental sources. The collected events are published in many recent catalogues. The density function are calculated using the Gaussian kernel, including 95% CI obtained by bootstrapping.Results confirm the existence of strong connection between auroras and sunspot activity, especially from 11th to 16th century. Indeed, a high correlation degree r = 0.72 is obtained for the period AD 800–1500 between the two pdf of sunspots (pdfS) and auroras (pdfA) for bandwidth h = 10 years, and exceed 0.8 for h > 43 years. However, we notice a time-shift between the two density functions. To calculate it, we use the cross-correlation technique, and we find τ = −5.9 years, that is strangely close to the half of solar cycle period. It is very important to note that our results revealed that the high frequency of low latitude auroras occurs before the maximum of naked-eye sunspots activity, and not afterward, on contrary to what is expected.The pdf curves show multiple peaks occurring at quasi-periodic times and show clearly the three grand minima of solar activity: Oort, Wolf and Spörer. In auroral-night data, the mean period at 95% CI obtained is:T‾=61±7years. Using power spectrum analysis, we observe clearly a strong signal of 60 years period that is a new evidence of the existence of such cycle. More importantly, we identified a cycle of 262 years period in the sunspot data, and a new oscillation of 310 years in auroral-night data. These two cycles appear clearly in the pdf curves using optimized bandwidth obtained by the direct plug-in approach of Sheather and Jones.

Cosmic Rays and Clouds Variations Effect on the Climate is Insignificantly

It is believed that an increase in the area of the cloud cover in the lower atmosphere of the Earth caused by the influence grows of galactic cosmic rays in the period of the Grand minimum of solar activity lead to an increase the reflected part of incoming solar radiation back into space and by that to a cooling of the climate down to the Little Ice Age. We will try to estimate an inverse aspect of simultaneously influence of increase in the area of the cloud cover in to the narrowing of the transmission of the windows of atmospheric transparency, which practically compensates of this cooling by means of accumulation of energy. An increase in the reflection of the thermal radiation of the Earth surface and of the solar radiation reflected from it, as well as the significant amplification of the greenhouse effect, presents an important additional source of heating due to the increase in the area of the cloud cover in the lower atmosphere. The impact of the increase in the area of the cloud cover caused by the influence grows of cosmic rays on the climate is very small.

Sunspot Cycle Minima and Pandemics: The Case for Vigilance?

Direct records of sunspots and the solar cycle have been maintained in astronomical observatories for about 1610 AD, while indirect records derived from 14C analysis of ice cores go back to about 900 AD. Minima in the sunspot cycle present conditions conducive to the entry or activation of new pathogens and also for mutations of already circulating bacteria and viruses. Three grand minima of solar activity on record–the Sporer minimum (1450-1550 AD), Maunder minimum (1650-1700 AD) and the Dalton minimum (1800-1830) have all been marked by a preponderance of pandemics–Small Pox, English Sweats, Plague and Cholera. The sunspot numbers recorded for the present period 2002-2017 include the deepest sunspot minimum (Cycle 23-24) since records began, and a trend to declining numbers throughout the cycle. The same period has seen the resurgence of several pandemics– SARS, MERS, Zika, Ebola, Influenza A. We consider it prudent to take note of these facts whilst planning future strategies for pandemic surveillance and control.

A Revised Collection of Sunspot Group Numbers

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 greater than the level obtained using the original Hoyt and Schatten data, although it remains compatible with a grand minimum of solar activity. The new collection is available in digital format.

Polar cap magnetic field reversals during solar grand minima: could pores play a role?

We study the magnetic flux carried by pores located outside active regions with sunspots and investigate their possible contribution to the reversal of the global magnetic field of the Sun. We find that they contain a total flux of comparable amplitude to the total magnetic flux contained in polar caps. The pores located at distances of 40--100~Mm from the closest active region have systematically the correct sign to contribute to the polar cap reversal. These pores can predominantly be found in bipolar magnetic regions. We propose that during grand minima of solar activity, such a systematic polarity trend, akin to a weak magnetic (Babcock-Leighton-like) source term could still be operating but was missed by the contemporary observers due to the limited resolving power of their telescopes.

Sunspots During the Maunder Minimum from Machina Coelestis by Hevelius

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 accordance with a grand minimum of solar activity, these values are significantly higher in general than the values provided by Hoyt and Schatten (1998) for the same period.

Level and length of cyclic solar activity during the Maunder minimum as deduced from the active-day statistics

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 conservatism (loose ML, optimum MO and strict MS models) regarding generic no-spot records. We have used the active day fraction to estimate the group sunspot number during the MM. A clear cyclic variability is found throughout the MM with peaks at around 1655--1657, 1675, 1684 and 1705, and possibly 1666, with the active day fraction not exceeding 0.2, 0.3 or 0.4 during the core MM, for the three models. Estimated sunspot numbers are found very low in accordance with a grand minimum of solar activity. We have found, for the core MM (1650-1700), that: (1) A large fraction of no-spot records, corresponding to the solar meridian observations, may be unreliable in the conventional database. (2) The active day fraction remained low (below 0.3-0.4) throughout the MM, indicating the low level of sunspot activity. (3) The solar cycle appears clearly during the core MM. (4) The length of the solar cycle during the core MM appears $9\pm 1$ years, but there is an uncertainty in that. (5) The magnitude of the sunspot cycle during MM is assessed to be below 5-10 in sunspot numbers; A hypothesis of the high solar cycles during the MM is not confirmed.

Cosmogenic Isotope Variability During the Maunder Minimum: Normal 11-year Cycles Are Expected

The amplitude of the 11-year cycle measured in the cosmogenic isotope 10Be during the Maunder Minimum is comparable to that during the recent epoch of high solar activity. Because of the virtual absence of the cyclic variability of sunspot activity during the Maunder Minimum this seemingly contradicts an intuitive expectation that lower activity would result in smaller solar-cycle variations in cosmogenic radio-isotope data, or in none, leading to confusing and misleading conclusions. It is shown here that large 11-year solar cycles in cosmogenic data observed during periods of suppressed sunspot activity do not necessarily imply strong heliospheric fields. Normal-amplitude cycles in the cosmogenic radio-isotopes observed during the Maunder Minimum are consistent with theoretical expectations because of the nonlinear relation between solar activity and isotope production. Thus, cosmogenic-isotope data provide a good tool to study solar-cycle variability even during grand minima of solar activity.

Variation of Solar, Interplanetary and Geomagnetic Parameters during Solar Cycles 21-24

The length of solar cycle 23 has been prolonged up to about 13 years. Many studies have speculated that the solar cycle 23/24 minimum will indicate the onset of a grand minimum of solar activity, such as the Maunder Minimum. We check the trends of solar (sunspot number, solar magnetic fields, total solar irradiance, solar radio flux, and frequency of solar X-ray flare), interplanetary (interplanetary magnetic field, solar wind and galactic cosmic ray intensity), and geomagnetic (Ap index) parameters (SIG parameters) during solar cycles 21-24. Most SIG parameters during the period of the solar cycle 23/24 minimum have remarkably low values. Since the 1970s, the space environment has been monitored by ground observatories and satellites. Such prevalently low values of SIG parameters have never been seen. We suggest that these unprecedented conditions of SIG parameters originate from the weakened solar magnetic fields. Meanwhile, the deep 23/24 solar cycle minimum might be the portent of a grand minimum in which the global mean temperature of the lower atmosphere is as low as in the period of Dalton or Maunder minimum.

Grand minima of solar activity and sociodynamics of culture

Indices of creative productivity introduced by C. Murrey were used to verify S. Ertel’s conclusion about a global increase in creative productivity during the prolonged minimum of solar activity in 1640–1710. It was found that these indices for mathematicians, philosophers, and scientists increase in the Maunder era by factor of 1.6 in comparison with intervals of the same length before and after the minimum. A similar effect was obtained for mathematicians and philosophers for five earlier equitype minima in total (an increase by a factor of 1.9). The regularity that is revealed is confirmed by the fact that the most important achievements of high-ranking mathematicians and philosophers during the whole time period (2300 years) considered in this study fall on epochs of reduced levels of solar activity. The rise in the probability of the generation of rational ideas during grand minima is reflected also in the fact that they precede the appearance of written language and farming. Ultra-low-frequency electromagnetic fields appear to serve as a physical agent stimulating the activity of the brain’s left hemisphere during the epochs of minima.

Modelling grand minima of solar activity using a flux transport dynamo model

AbstractThe occurrence of grand minima like the Maunder minimum is an intriguing aspect of the sunspot cycle. We use the flux transport dynamo model to explain the grand minima, showing that they arise when either the poloidal field or the meridional circulation falls to a sufficiently low value due to fluctuations. Assuming these fluctuations to be Gaussian and determining the various parameters from the data of the last 28 cycles, we carry on a dynamo simulation with both these fluctuations. The results are remarkably close to the observational data.

Grand minima of solar activity during the last millennia

AbstractIn this review we discuss the occurrence and statistical properties of Grand minima based on the available data covering the last millennia. In particular, we consider the historical record of sunspot numbers covering the last 400 years as well as records of cosmogenic isotopes in natural terrestrial archives, used to reconstruct solar activity for up to the last 11.5 millennia, i.e. throughout the Holocene. Using a reconstruction of solar activity from cosmogenic isotope data, we analyze statistics of the occurrence of Grand minima. We find that: the Sun spends about most of the time at moderate activity, 1/6 in a Grand minimum and some time also in a Grand maximum state; Occurrence of Grand minima is not a result of long-term cyclic variations but is defined by stochastic/chaotic processes; There is a tendency for Grand minima to cluster with the recurrence rate of roughly 2000-3000 years, with a weak ≈210-yr periodicity existing within the clusters. Grand minima occur of two different types: shorter than 100 years (Maunder-type) and long ≈150 years (Spörer-type). It is also discussed that solar cycles (most possibly not sunspots cycle) could exist during the Grand minima, perhaps with stretched length and asymmetric sunspot latitudinal distribution.These results set new observational constraints on long-term solar and stellar dynamo models.

Dynamo hysteresis and grand minima of solar activity

A nonlinear dynamo model that allows for the dependence of the turbulent diffusivity on the magnetic field shows the phenomenon of a hysteresis. In a certain range of dynamo numbers, two types of solutions are possible: decaying oscillations of weak fields and magnetic cycles with a constant and large amplitude, which are settled depending on the initial conditions. Fluctuations in α-parameter cause transitions between these two regimes and calculations show the intermittency of magnetic cycles with a relatively large amplitude and epochs of weak magnetic fields. This behavior can serve as a model of grand minima of solar activity like the well-known Maunder minimum.

On the effect of a new grand minimum of solar activity on the future climate on Earth

The current exceptionally long minimum of solar activity has led to the suggestion that the Sun might experience a new grand minimum in the next decades, a prolonged period of low activity similar to the Maunder minimum in the late 17th century. The Maunder minimum is connected to the Little Ice Age, a time of markedly lower temperatures, in particular in the Northern hemisphere. Here we use a coupled climate model to explore the effect of a 21st‐century grand minimum on future global temperatures, finding a moderate temperature offset of no more than −0.3°C in the year 2100 relative to a scenario with solar activity similar to recent decades. This temperature decrease is much smaller than the warming expected from anthropogenic greenhouse gas emissions by the end of the century.

On the common solar signal in different cosmogenic isotope data sets

In this article, we aim to determine frequency ranges and intervals of time in which the solar signal dominates in different cosmogenic isotope data. From a 14C‐based reconstruction of cosmic ray intensity over the last millennia, we computed expected 10Be variations in two Antarctic sites (Dom Fuji and South Pole) and two Greenland sites (Dye‐3 and GISP‐2) and compared them with the actually measured 10Be abundance at the sites. By applying different methods of analysis, such as bivariate correlation, conventional FFT coherence, and wavelet coherence, we found the following: (1) The modeled series, on the basis of 14C data, are in good agreement with the measured 10Be data sets, on different timescales and at different locations, confirming the existence of a common solar signal in both isotope data. (2) The 10Be data are driven by the solar signal on timescales from about 100 years up to 1000 years or even to multimillennial scales (at the longer scales, paleomagnetism plays an increasingly important role). (3) The local climate dominates the 10Be data mostly on short (&lt;100 years) timescales, but the solar signal becomes important even at short scales during periods of Grand minima of solar activity. (4) There is an indication of a possible systematic uncertainty in the early Holocene, likely due to a not‐perfectly‐stable thermohaline circulation, which requires additional studies. We have shown that both 14C‐ and 10Be‐based records are consistent with each other over a wide range of timescales and time intervals. They form a robust basis for quantitative reconstructions of solar activity variations in the past.

Solar and Heliospheric Modulation of Galactic Cosmic Rays

The significance of external influences on the environment of Earth and its atmosphere has become evident during recent years. Especially, on time scales of several hundred years, the cosmogenic isotope concentration during the Wolf-, Spoerer-, Maunder- and Dalton-Minimum indicates an increased cosmic ray flux. Because these grand minima of solar activity coincide with cold periods, a correlation of the Earth climate with the cosmic ray intensities is plausible. Any quantitative study of the effects of energetic particles on the atmosphere and environment of the Earth must address their transport to Earth and their interactions with the Earth’s atmosphere including their filtering by the terrestrial magnetosphere. The first problem is one of the fundamental problems in modern cosmic ray astrophysics, and corresponding studies began in the 1960s based on Parker’s cosmic ray modulation theory taking into account diffusion, convection, adiabatic deceleration, and (later) the drift of energetic particles in the global heliospheric magnetic field. It is well established that all of these processes determining the modulation of cosmic rays are depending on parameters that are varying with the solar magnetic cycle. Therefore, the galactic cosmic ray intensities close to Earth is the result of a complex modulation of the interstellar galactic spectrum within the heliosphere. The modern view of this cosmic ray modulation is summarized in our contribution.

The heliospheric magnetic field from 850 to 2000 AD inferred from 10Be records

10Be found in ice cores is an indicator of cosmic ray intensity in the past. We use this isotope to study cosmic ray transport and the heliospheric magnetic field before the advent of instrumental cosmic‐ray measurements in the modern space era. The galactic cosmic ray intensity is governed by scattering, convection, and drift of the charged particles in the heliospheric magnetic field, which leads to a modulation in their intensity. We model these cosmic ray intensity changes observed at Earth during the space era with solutions of the cosmic ray transport equation. This gives a set of diffusion mean free paths during the past few solar activity cycles. A relationship is then determined between these diffusion mean free paths and satellite observations of the heliospheric magnetic field during the same period, yielding a relationship between the observed cosmic ray intensity and the heliospheric magnetic field. We then calculate the diffusion mean free paths that explain the variations in the 10Be concentration during the last millennium and use the space‐era calibration to infer heliospheric magnetic field since 850 AD. It is shown how this inversion of the 10Be data depends on the strength of the heliospheric magnetic field and variations in its turbulence, both of which are quite uncertain. Nevertheless, the results show that for a wide range of parameters, there was a significant heliospheric magnetic field with a strength of 2 to 5 nT at Earth during the so‐called Grand Minima of solar activity. It is also shown that the strength of this field has attained six maxima in the past 1150 years, all approximating the present‐day field strength, and we speculate that a limiting mechanism may be in operation. On several occasions the strength of the field has switched rapidly from ≈2 nT to ≈6 nT within 40 years. During the Grand Minima the total field derived from the 10Be data differs significantly from the open solar magnetic field calculated from the models of Solanki et al. [2002] and Schrijver et al. [2002].

Reconstruction of grand minima of solar activity from Δ14C data: Linear and nonlinear signal analysis

Using a special technique of data analysis, we have found 34 grand minima of solar activity in a 7700‐year‐long Δ14C record. The method used rests on a proper filtering of the Δ14C record and the extrapolation of verifiable results for the later history back in time. Additionally, we have applied a method of nonlinear dynamics, the recurrence rate, to back up the results. Our findings are not contradictory to the record of grand minima by Eddy [1977] but constitute a considerable extension. Hence it has become possible to look closer at the validity of models. This way, we have tested the model of Barnes et al. [1980]. There are hints for that the grand minima might solely be driven by the 209‐year period found in the Δ14C record.