Author name code: soon ADS astronomy entries on 2022-09-14 author:"Soon, Willie Wei-Hock" ------------------------------------------------------------------------ Title: The interplanetary origins of geomagnetic storm with Dstmin ≤ - 50 nT during solar cycle 24 (2009-2019) Authors: Qiu, Shican; Zhang, Zhiyong; Yousof, Hamad; Soon, Willie; Jia, Mingjiao; Tang, Weiwei; Dou, Xiankang Bibcode: 2022AdSpR..70.2047Q Altcode: In this study, we analyzed 149 geomagnetic storms of moderate and intensity (i.e., Dstmin ≤ - 50 nT) occurred during the solar cycle 24 from 2009 to 2019, and identified their interplanetary sources. Among them, there are 20 strong storms with - 200 nT ≤ Dst min ≤ - 100 nT , and 2 super-strong storms with Dstmin ≤ - 200 nT . We have found that corotating interaction regions (CIRs) account for 37% (55/149) of geomagnetic storms, interplanetary coronal mass ejections (ICMEs) result in 30% (45/149) of geomagnetic storms and sheath regions (SH) are responsible for 15% (23/149) of geomagnetic storms. Meanwhile, 18/20 of the strong storms are caused by the structures associated with interplanetary coronal mass ejections (ICME, SH, and SH + ICME), while the CIR constitutes only to 2/20 of the strong storms. It is found that the two super-strong geomagnetic storms are caused by the SH + ICME. Our findings also suggest that geomagnetic storms in different periods of solar activity are caused by different interplanetary structures, which is consistent with previous research. In comparison to solar cycle 23, there is no substantial geomagnetic storm induced by CIR during the dwindling and subsiding phases of solar cycle 24. In the descending stage, the proportion of moderate events caused by ICME decreases, and ICMEs cause no super-strong event. In ascending stage, neither strong nor super strong events occur. Title: The New Composite Solar Flare Index from Solar Cycle 17 to Cycle 24 (1937 - 2020) Authors: Velasco Herrera, Victor Manuel; Soon, Willie; Knoška, Štefan; Perez-Peraza, Jorge Alberto; Cionco, Rodolfo G.; Kudryavtsev, Sergey M.; Qiu, Shican; Connolly, Ronan; Connolly, Michael; Švanda, Michal; Acosta Jara, José; Gregori, Giovanni Pietro Bibcode: 2022SoPh..297..108V Altcode: The chromosphere is a highly dynamic outer plasma layer of the Sun. Its physical processes accounting for the variability are poorly understood. We reconstructed the solar chromospheric flare index (SFI) to study the solar chromospheric variability from 1937 to 2020. The new SFI database is a composite record of the Astronomical Institute Ondřejov Observatory of the Czech Academy of Sciences from 1937 - 1976 and the records of the Kandilli Observatory of Istanbul, Turkey from 1977 - 2020. The SFI records are available in daily, monthly, and yearly resolutions. We carried out the time-frequency analyses of the new 84-year long SFI records using the wavelet transform. We report the periodicities of 21.88 (Hale cycle), 10.94 (Schwabe cycle), 5.2 (quasi-quinquennial cycle), 3.5, 1.7, 1, 0.41 (or 149.7 days, Rieger cycle), 0.17 (62.1 days), 0.07 (25.9 days, solar rotational modulation) years. All these periodicities seem always present and persistent throughout the observational interval. Thus, we suggest that there is no reason to assume these solar periodicities are absent from other solar cycles. Time variations of the amplitude of each oscillation or periodicity were also studied using the inverse wavelet transform. We found that for the SFI the most active flare cycles over the record were Cycles 17, 19, and 21, while Cycles 20, 22, 23, and 24 were the weakest ones with Cycle 18 was intermediate in flare activity. This shows several differences to the equivalent relationships for solar activity implied by sunspot number records. Furthermore, this confirms that solar activity trends and variability in the chromosphere as captured by SFI are not necessarily the same as those of the Sun's photosphere, as implied by the sunspot number activity records, for instance. We have also introduced a new signal/noise wavelet coherence metric to analyze two different chromospheric indices available (i.e. the SFI and the disk-integrated chromospheric Ca II K activity indices) and to quantify the differences and similarities of the oscillations within the solar chromosphere. Our findings suggest the importance of carrying out additional co-analyses with other solar activity records to find physical inter-relations and connections between the different solar layers from the photosphere, the chromosphere to the corona. Title: Group Sunspot Numbers: A New Reconstruction of Sunspot Activity Variations from Historical Sunspot Records Using Algorithms from Machine Learning Authors: Velasco Herrera, Víctor Manuel; Soon, Willie; Hoyt, Douglas V.; Muraközy, Judit Bibcode: 2022SoPh..297....8V Altcode: Historical sunspot records and the construction of a comprehensive database are among the most sought after research activities in solar physics. Here, we revisit the issues and remaining questions on the reconstruction of the so-called group sunspot numbers (GSN) that was pioneered by D. Hoyt and colleagues. We use the modern tools of artificial intelligence (AI) by applying various algorithms based on machine learning (ML) to GSN records. The goal is to offer a new vision in the reconstruction of sunspot activity variations, i.e. a Bayesian reconstruction, in order to obtain a complete probabilistic GSN record from 1610 to 2020. This new GSN reconstruction is consistent with the historical GSN records. In addition, we perform a comparison between our new probabilistic GSN record and the most recent GSN reconstructions produced by several solar researchers under various assumptions and constraints. Our AI algorithms are able to reveal various new underlying patterns and channels of variations that can fully account for the complete GSN time variability, including intervals with extremely low or weak sunspot activity like the Maunder Minimum from 1645 - 1715. Our results show that the GSN records are not strictly represented by the 11-year cycles alone, but that other important timescales for a fuller reconstruction of GSN activity history are the 5.5-year, 22-year, 30-year, 60-year, and 120-year oscillations. The comprehensive GSN reconstruction by AI/ML is able to shed new insights on the nature and characteristics of not only the underlying 11-year-like sunspot cycles but also on the 22-year Hale's polarity cycles during the Maunder Minimum, among other results previously hidden so far. In the early 1850s, Wolf multiplied his original sunspot number reconstruction by a factor of 1.25 to arrive at the canonical Wolf sunspot numbers (WSN). Removing this multiplicative factor, we find that the GSN and WSN differ by only a few percent for the period 1700 to 1879. In a comparison to the international sunspot number (ISN) recently recommended by Clette et al. (Space Sci. Rev. 186, 35, 2014), several differences are found and discussed. More sunspot observations are still required. Our article points to observers that are not yet included in the GSN database. Title: Magnetic and Rotational Evolution of ρ CrB from Asteroseismology with TESS Authors: Metcalfe, Travis S.; van Saders, Jennifer L.; Basu, Sarbani; Buzasi, Derek; Drake, Jeremy J.; Egeland, Ricky; Huber, Daniel; Saar, Steven H.; Stassun, Keivan G.; Ball, Warrick H.; Campante, Tiago L.; Finley, Adam J.; Kochukhov, Oleg; Mathur, Savita; Reinhold, Timo; See, Victor; Baliunas, Sallie; Soon, Willie Bibcode: 2021ApJ...921..122M Altcode: 2021arXiv210801088M During the first half of main-sequence lifetimes, the evolution of rotation and magnetic activity in solar-type stars appears to be strongly coupled. Recent observations suggest that rotation rates evolve much more slowly beyond middle age, while stellar activity continues to decline. We aim to characterize this midlife transition by combining archival stellar activity data from the Mount Wilson Observatory with asteroseismology from the Transiting Exoplanet Survey Satellite (TESS). For two stars on opposite sides of the transition (88 Leo and ρ CrB), we independently assess the mean activity levels and rotation periods previously reported in the literature. For the less active star (ρ CrB), we detect solar-like oscillations from TESS photometry, and we obtain precise stellar properties from asteroseismic modeling. We derive updated X-ray luminosities for both stars to estimate their mass-loss rates, and we use previously published constraints on magnetic morphology to model the evolutionary change in magnetic braking torque. We then attempt to match the observations with rotational evolution models, assuming either standard spin-down or weakened magnetic braking. We conclude that the asteroseismic age of ρ CrB is consistent with the expected evolution of its mean activity level and that weakened braking models can more readily explain its relatively fast rotation rate. Future spectropolarimetric observations across a range of spectral types promise to further characterize the shift in magnetic morphology that apparently drives this midlife transition in solar-type stars. Title: Does Machine Learning reconstruct missing sunspots and forecast a new solar minimum? Authors: Velasco Herrera, V. M.; Soon, W.; Legates, D. R. Bibcode: 2021AdSpR..68.1485V Altcode: The retrodiction and prediction of solar activity are two closely-related problems in dynamo theory. We applied Machine Learning (ML) algorithms and analyses to the World Data Center's newly constructed annual sunspot time series (1700-2019; Version 2.0). This provides a unique model that gives insights into the various patterns of the Sun's magnetic dynamo that drives solar activity maxima and minima. We found that the variability in the ~ 11 -year Sunspot Cycle is closely connected with 120-year oscillatory magnetic activity variations. We also identified a previously under-reported 5.5 year periodicity in the sunspot record. This 5.5-year pattern is co-modulated by the 120-year oscillation and appears to influence the shape and energy/power content of individual 11-year cycles. Our ML algorithm was trained to recognize such underlying patterns and provides a convincing hindcast of the full sunspot record from 1700 to 2019. It also suggests the possibility of missing sunspots during Sunspot Cycles -1, 0, and 1 (ca. 1730s-1760s). In addition, our ML model forecasts a new phase of extended solar minima that began prior to Sunspot Cycle 24 (ca. 2008-2019) and will persist until Sunspot Cycle 27 (ca. 2050 or so). Our ML Bayesian model forecasts a peak annual sunspot number (SSN) of 95 with a probable range of 80-115 for Cycle 25 between 2023 and 2025. Title: Possible Origin of Some Periodicities Detected in Solar-Terrestrial Studies: Earth's Orbital Movements Authors: Cionco, R. G.; Kudryavtsev, S. M.; Soon, W. W. -H. Bibcode: 2021E&SS....801805C Altcode: Periodicities matching planetary cycles have been argued to be detected in key geophysical time series. In general, these periodicities were indirectly attributed to a planetary influence on solar activity. This supposes that planetary gravity affects the internal functioning of the Sun's dynamo, that is, the planetary hypothesis (PH) of the solar cycles. The Earth's heliocentric dynamics already includes the planetary gravitational effects on the Sun. Taking into account this fact, these periodicities, ultimately attributed to possible planetary modulations of the solar activity, could have a more direct origin in cyclical changes in the relative Sun-Earth geometry, but then, wrongly or partially explained invoking internal solar changes. We present an original decomposition analysis of the high-precision ephemeris DE431 from NASA/JPL in order to obtain and classify the most important planetary/lunar purely periodic changes of the Earth's orbital movement at sub-Milanković scales. A comprehensive list of cyclic changes of the Earth's orbital parameters involved in the relative Sun-Earth position and the Earth's speed around the Sun is given. We show that these particular geophysical quasi-periods are identifiable in the cyclic oscillations of these orbital parameters. Since the Earth's movement in space physically affects the manner in which the solar radiant flux reaches the planet, these oscillations provide, unlike the PH, a clear, causal, and testable link for their possible attribution. Title: How much has the Sun influenced Northern Hemisphere temperature trends? An ongoing debate Authors: Connolly, Ronan; Soon, Willie; Connolly, Michael; Baliunas, Sallie; Berglund, Johan; Butler, C. John; Cionco, Rodolfo Gustavo; Elias, Ana G.; Fedorov, Valery M.; Harde, Hermann; Henry, Gregory W.; Hoyt, Douglas V.; Humlum, Ole; Legates, David R.; Lüning, Sebastian; Scafetta, Nicola; Solheim, Jan-Erik; Szarka, László; van Loon, Harry; Velasco Herrera, Víctor M.; Willson, Richard C.; Yan, Hong; Zhang, Weijia Bibcode: 2021RAA....21..131C Altcode: 2021arXiv210512126C In order to evaluate how much Total Solar Irradiance (TSI) has influenced Northern Hemisphere surface air temperature trends, it is important to have reliable estimates of both quantities. Sixteen different estimates of the changes in TSI since at least the 19th century were compiled from the literature. Half of these estimates are "low variability" and half are "high variability". Meanwhile, five largely-independent methods for estimating Northern Hemisphere temperature trends were evaluated using: 1) only rural weather stations; 2) all available stations whether urban or rural (the standard approach); 3) only sea surface temperatures; 4) tree-ring widths as temperature proxies; 5) glacier length records as temperature proxies. The standard estimates which use urban as well as rural stations were somewhat anomalous as they implied a much greater warming in recent decades than the other estimates, suggesting that urbanization bias might still be a problem in current global temperature datasets - despite the conclusions of some earlier studies. Nonetheless, all five estimates confirm that it is currently warmer than the late 19th century, i.e., there has been some "global warming" since the 19th century. For each of the five estimates of Northern Hemisphere temperatures, the contribution from direct solar forcing for all sixteen estimates of TSI was evaluated using simple linear least-squares fitting. The role of human activity on recent warming was then calculated by fitting the residuals to the UN IPCC's recommended "anthropogenic forcings" time series. For all five Northern Hemisphere temperature series, different TSI estimates suggest everything from no role for the Sun in recent decades (implying that recent global warming is mostly human-caused) to most of the recent global warming being due to changes in solar activity (that is, that recent global warming is mostly natural). It appears that previous studies (including the most recent IPCC reports) which had prematurely concluded the former, had done so because they failed to adequately consider all the relevant estimates of TSI and/or to satisfactorily address the uncertainties still associated with Northern Hemisphere temperature trend estimates. Therefore, several recommendations on how the scientific community can more satisfactorily resolve these issues are provided. Title: Holocene Millennial-Scale Solar Variability and the Climatic Responses on Earth Authors: Zhao, Xinhua; Soon, Willie; Velasco Herrera, Victor M. Bibcode: 2021Univ....7...36Z Altcode: No abstract at ADS Title: How the astronomical aspects of climate science were settled? On the Milankovitch and Bacsák anniversaries, with lessons for today Authors: Szarka, László; Soon, Willie W. -H.; Cionco, Rodolfo G. Bibcode: 2021AdSpR..67..700S Altcode: It was 100 years ago (on August 7, 1920), that the comprehensive mathematical foundations of climate change research, written by a Serbian researcher, Milutin Milankovitch, were published. A later interpreter and developer of his results, Georg (in Hungarian: György) Bacsák (Pozsony/Pressburg/Bratislava, June 5, 1870 - Fonyód, March 4, 1970) was born 150 years ago and died at the age of one hundred, half a century ago. In this commemorative paper we look back to special circumstances in revealing the secrets of ice ages that had puzzled scientists for at least several centuries. Recently, after 100 years, the Milankovitch theory, including related short-term forcings (ranging from interannual, multidecadal to millennial timescales) has not only been confirmed, but its climate forcing mechanism has also been identified and proposed. Owing to the uniqueness of the problem, the science of the orbital forcing of climate change can be proclaimed to be essentially settled. Title: Latitudinal insolation gradients throughout the Holocene II - High frequency variations Authors: Cionco, Rodolfo G.; Soon, Willie W. -H.; Elias, Ana G.; Quaranta, Nancy E. Bibcode: 2020AdSpR..66.1992C Altcode: In a first paper, we presented an in-depth discussion and a computational method (free of the calendar problem) to reckon any kind of latitudinal insolation gradients, LIGs, throughout the Holocene and up to CE 3000. One of the main insights from this exact definition of LIGs is that, unlike what is argued in prior works, during the Holocene, a general classification of LIGs in terms of obliquity signal or climatic precession variations is much more complex, even in summertime. It is especially evident in the Southern Hemisphere, where summer half-year LIGs evolve under the relatively stronger modulation by climatic precession. In this work, the short-term periodicities (high frequency variations in time domain) of all these LIGs are studied by means of the multitaper spectral analysis. The goal is to get more insights on the competing effects between obliquity and climatic precession during the Holocene, and to know how the relative intensity of the obliquity's periodicities is when compared to the main spectral peaks produced by the climatic precession effects at short time scales (e.g., from annual to decadal bands). Our main result is the clarification of the role of the 18.63 yr periodicity originated in the well known retrograding cycle of the Moons' orbit. We found that this lunar cycle is always present at a 99 % significance level in all the analysed LIGs, even in winter with solar cycle included. The conceptual explanation of this persistence is based on the fact that all accurate short-term orbital forcing calculation must include the lunar nodal cycle even in climatic precession variations. We propose to use more specific definitions when short-term orbital variations are taken into account in describing Milanković forcing. Title: Evidence for Solar Modulation on the Millennial-Scale Climate Change of Earth Authors: Zhao, Xinhua; Soon, Willie; Velasco Herrera, Victor M. Bibcode: 2020Univ....6..153Z Altcode: No abstract at ADS Title: The Evolution of Rotation and Magnetic Activity in 94 Aqr Aa from Asteroseismology with TESS Authors: Metcalfe, Travis S.; van Saders, Jennifer L.; Basu, Sarbani; Buzasi, Derek; Chaplin, William J.; Egeland, Ricky; Garcia, Rafael A.; Gaulme, Patrick; Huber, Daniel; Reinhold, Timo; Schunker, Hannah; Stassun, Keivan G.; Appourchaux, Thierry; Ball, Warrick H.; Bedding, Timothy R.; Deheuvels, Sébastien; González-Cuesta, Lucía; Handberg, Rasmus; Jiménez, Antonio; Kjeldsen, Hans; Li, Tanda; Lund, Mikkel N.; Mathur, Savita; Mosser, Benoit; Nielsen, Martin B.; Noll, Anthony; Çelik Orhan, Zeynep; Örtel, Sibel; Santos, Ângela R. G.; Yildiz, Mutlu; Baliunas, Sallie; Soon, Willie Bibcode: 2020ApJ...900..154M Altcode: 2020arXiv200712755M Most previous efforts to calibrate how rotation and magnetic activity depend on stellar age and mass have relied on observations of clusters, where isochrones from stellar evolution models are used to determine the properties of the ensemble. Asteroseismology employs similar models to measure the properties of an individual star by matching its normal modes of oscillation, yielding the stellar age and mass with high precision. We use 27 days of photometry from the Transiting Exoplanet Survey Satellite to characterize solar-like oscillations in the G8 subgiant of the 94 Aqr triple system. The resulting stellar properties, when combined with a reanalysis of 35 yr of activity measurements from the Mount Wilson HK project, allow us to probe the evolution of rotation and magnetic activity in the system. The asteroseismic age of the subgiant agrees with a stellar isochrone fit, but the rotation period is much shorter than expected from standard models of angular momentum evolution. We conclude that weakened magnetic braking may be needed to reproduce the stellar properties, and that evolved subgiants in the hydrogen shell-burning phase can reinvigorate large-scale dynamo action and briefly sustain magnetic activity cycles before ascending the red giant branch. Title: On the calculation of latitudinal insolation gradients throughout the Holocene Authors: Cionco, Rodolfo G.; Soon, Willie W. -H.; Quaranta, Nancy E. Bibcode: 2020AdSpR..66..720C Altcode: In paleoclimatology, the concept of latitudinal insolation gradients (LIGs), reckoned in various ways, has received increasing attention regarding glacial/inter-glacial climatic transitions and oscillations. In particular, the Holocene, which permits the reconstruction of past climatic proxies with an increasingly finer spatial and temporal resolutions, has provided evidence that suggests that LIGs are a key forcing on climate at different timescales. Nevertheless, LIGs' own dynamics (chiefly their variations in relation to astronomical parameters and geographical zones) and even basic definitions, have not been properly investigated, especially during the last part of the present geological epoch. The main reason is the lack of broadly accessible, theoretical insolation data that account for short-term orbital variations (i.e., for describing sub-Milanković-orbital forcing during the Holocene). Based on our latest astronomical-orbital solutions, we present an in-depth discussion on the calculation of LIGs and their variations all through the Holocene and 1 kyr into the future. Our results show a much more complex variety and behaviour of LIGs than those that were shown previously. We report that during the studied period, daily LIGs in summer, around the solstitial days (both hemispheres), are strongly modulated by obliquity only at mid-latitude band, whereas at tropical and polar bands LIGs are modulated by "precession". Summer half-year LIGs for the Northern Hemisphere show a marked modulation in out-of-phase sense with obliquity, just for the mid-latitude and polar bands. Surprisingly, this competing effect between "precession" and obliquity also produces the fact that the southern counterpart of these LIGs are more modulated by "precession" than obliquity. In cases involving inter-band latitudes or different intra-annual lapses, they need to be examined separately and carefully and the results could be very different from traditional presumptions. Our novel results and study are based on the precise estimation of the duration of the orbital interval considered in the definition of LIGs. Our new study also avoids the difficulties of insolation calculations regarding the relationship between orbital longitudes and time. Title: Waldmeier Effect in Stellar Cycles Authors: Garg, Suyog; Karak, Bidya Binay; Egeland, Ricky; Soon, Willie; Baliunas, Sallie Bibcode: 2019ApJ...886..132G Altcode: 2019arXiv190912148G One of the most robust features of the solar magnetic cycle is that the stronger cycles rise faster than the weaker ones. This is popularly known as the Waldmeier Effect, which has been known for more than 100 yr. This fundamental feature of the solar cycle has not only practical implications, e.g., in predicting the solar cycle, but also implications in understanding the solar dynamo. Here we ask whether the Waldmeier Effect exists in other Sun-like stars. To answer this question, we analyze the Ca II H and K S-index from Mount Wilson Observatory for 21 Sun-like G-K stars. We specifically check two aspects of Waldmeier Effect, namely, (1) WE1: the anticorrelation between the rise times and the peaks and (2) WE2: the positive correlation between rise rates and amplitudes. We show that, except for HD 16160, HD 81809, HD 155886, and HD 161239, all stars considered in the analysis show WE2, while WE1 is found to be present only in some of the stars studied. Furthermore, the WE1 correlation is weaker than the WE2. Both WE1 and WE2 exist in the solar S-index as well. Similar to the solar cycles, the magnetic cycles of many stars are asymmetric about their maxima. The existence of the Waldmeier Effect and asymmetric cycles in Sun-like stars suggests that the dynamo mechanism which operates in the Sun is also operating in other stars. Title: Reply to Li & Yang's comments on "Comparing the current and early 20th century warm periods in China" Authors: Soon, Willie Wei-Hock; Connolly, Ronan; Connolly, Michael; O'Neill, Peter; Zheng, Jingyun; Ge, Quansheng; Hao, Zhixin; Yan, Hong Bibcode: 2019ESRv..19802950S Altcode: From a cursory reading of Li & Yang's comments [Li and Yang, 2019, henceforth LY2019] on our recent review article, Soon et al. (2018) [henceforth S2018], some readers might think that LY2019 is somehow disputing our analysis and conclusions. Specifically, they claim to offer "some comments on the arbitrary or deductive conclusions ofSoon et al. (2018)as [sic.] the following five aspects…" Title: Searching for solar-like interannual to bidecadal effects on temperature and precipitation over a Southern Hemisphere location Authors: Heredia, Teresita; Bazzano, Flavia M.; Cionco, Rodolfo G.; Soon, Willie; Medina, Franco D.; Elias, Ana G. Bibcode: 2019JASTP.19305094H Altcode: Precipitation and temperature over Tucuman (26.8°S, 65.2°W), a province located in the Northwestern region of Argentina, is analyzed for the interval 1889-2018 in search of any plausible statistical associations with impacts and responses from solar variability. The aim of the study was to contribute data to the controversial issue of climate variations in response to both anthropogenic and natural forcings. The long-term behavior of Tucuman climatic series involves overall warming and augmented precipitation tendencies, possibly linked to the increasing greenhouse gases concentration or even other local man-made factors like increasing urbanization. In addition, we identified sporadic ~4 and ~8-year periodicities, and a ~20-year oscillation after the 1950-1960's. Based on the physical hint that bidecadal periodicities detected in climate parameters are probably not linked to the solar 11-year-like irradiance cycles, we expand our scope of investigations to include another effect which has been recently considered in the dynamics of large rivers as "the planetary hypothesis of the solar cycles". This new hypothesis supposes that the barycentric dynamics of the Sun could be involved in modulations of the intrinsic solar magnetic and radiative output cycles and therefore Earth-bound climatic responses. Thus, we present a wide-ranging statistical analysis of correlation, cross spectrum, and coherence between Tucuman's climatic series and solar orbital parameters, including also the analysis of hemispheric mean temperatures. Our results show significant coherence at the ~20-year cycle, which is clearly present in the Sun's barycentric dynamic that could in turn be linked to some features of the quasi-decadal solar activity variations. Title: Covariations of chromospheric and photometric variability of the young Sun analogue HD 30495: evidence for and interpretation of mid-term periodicities Authors: Soon, W.; Velasco Herrera, V. M.; Cionco, R. G.; Qiu, S.; Baliunas, S.; Egeland, R.; Henry, G. W.; Charvátová, I. Bibcode: 2019MNRAS.483.2748S Altcode: 2018MNRAS.tmp.3133S This study reports the synchronization between the chromospheric and photometric variability at time-scale of about 1.6-1.8 yr as observed for the young, rapidly rotating solar analogue HD 30495. In addition, HD 30495 may be presenting evidence of surface differential rotation at time-scales of about 11 d and 21 d, as well as the sunspot-like decadal cycles at 11-12 yr or so. We apply a new gapped wavelet method of time-frequency analysis for studying the variability in a new composite of the chromospheric S-index (1967-2018) and the longest photometric Δ(b + y)/2 index (1993-2018). We discuss and interpret our results in relation to other observed mid-term periodicities roughly of the same time-scales that had been found recently from not only chromospheric and photospheric activity indices but also from coronal X-ray emissions as observed in a considerably large set of stellar samples including those young Sun analogues from the Kepler satellite project. Thus, there is an apparent universality of such mid-term activity modulation time-scales as this solar-stellar magnetic phenomenon is well observed directly for a host of solar activity related indices covering the photopsheric, chromospheric, coronal, and even the heliospheric (utilizing the measures of incoming galactic cosmic rays as a probe of activity variations) activity records. This is why we made a further attempt to interpret the results in search of a realistic generation mechanism as well as spatio-temporal persistency of the phenomenon under a wide scenario of dynamo simulations. Title: Comparing the current and early 20th century warm periods in China Authors: Soon, Willie Wei-Hock; Connolly, Ronan; Connolly, Michael; O'Neill, Peter; Zheng, Jingyun; Ge, Quansheng; Hao, Zhixin; Yan, Hong Bibcode: 2018ESRv..185...80S Altcode: Most estimates of Chinese regional Surface Air Temperatures since the late-19th century have identified two relatively warm periods - 1920s-40s and 1990s-present. However, there is considerable debate over how the two periods compare to each other. Some argue the current warm period is much warmer than the earlier warm period. Others argue the earlier warm period was comparable to the present. In this collaborative paper, including authors from both camps, the reasons for this ongoing debate are discussed. Several different estimates of Chinese temperature trends, both new and previously published, are considered. A study of the effects of urbanization bias on Chinese temperature trends was carried out using the new updated version of the Global Historical Climatology Network (GHCN) - version 4 (currently in beta production). It is shown that there are relatively few rural stations with long records, but urbanization bias artificially makes the early warm period seem colder and the recent warm period seem warmer. However, current homogenization approaches (which attempt to reduce non-climatic biases) also tend to have similar effects, making it unclear whether reducing or increasing the relative warmth of each period is most appropriate. A sample of 17 Chinese temperature proxy series (12 regional and 5 national) is compared and contrasted specifically for the period since the 19th century. Most proxy series imply a warm early-20th century period and a warm recent period, but the relative warmth of these two periods differs between proxies. Also, with some proxies, one or other of the warm periods is absent. Title: Sudden Sodium Layers: Their Appearance and Disappearance Authors: Qiu, Shican; Soon, Willie; Xue, Xianghui; Li, Tao; Wang, Wanyin; Jia, Mingjiao; Ban, Chao; Fang, Xin; Tang, Yihuan; Dou, Xiankang Bibcode: 2018JGRA..123.5102Q Altcode: Temperature variation has been proposed to play an important role in the formation of the sporadic sodium layers (SSLs or NaS) in subtropic area, based on the observed significant correlation between SSLs and high temperatures. The icy-dust particle, which could form in the extremely cold conditions and act as absorbers of sodium species, was proposed to be a possible candidate for the sodium reservoir of the SSLs. In this study, the University of Science and Technology of China temperature/wind lidar and the sodium fluorescence lidar at a subtropic station Hefei (31°N, 117°E), China, were used to observe sodium density, temperature, and wind profiles simultaneously throughout the SSL events. Based on the observations of two SSLs occurring on 12 and 13 May 2013, the possibility of an icy-dust layer existing and acting as the sodium reservoir is tested for the first time in details. Both events experienced an extremely cold temperature (<150 K) several hours before the onset of SSLs, followed by a subsequently fast production of sodium atoms during a large temperature enhancement (>40 K). An empirical model including two main steps is then proposed: first, sodium species are collected by an icy-dust reservoir and stored during the extremely cold phase; second, free sodium atoms could be released from the reservoir by a possible trigger. As a result, this kind of SSLs could possibly be regarded as a quasi-continuous phenomenon caused and modulated by temperature variations with an icy-dust model that can exhibit intermittent time variations related to the water vapor concentration. Title: The quasi-biennial oscillation of 1.7 years in ground level enhancement events Authors: Velasco Herrera, V. M.; Pérez-Peraza, J.; Soon, W.; Márquez-Adame, J. C. Bibcode: 2018NewA...60....7V Altcode: The so-called Ground Level Enhancement events are sporadic relativistic solar particles measured at ground level by a network of cosmic ray detectors worldwide. These sporadic events are typically assumed to occur by random chance. However, we find that by studying the last 56 ground level enhancement events reported from 1966 through 2014, these events occur preferentially in the positive phase of the quasi-biennial oscillation of 1.7 year periodicity. These discrete ground level enhancement events show that there is another type of solar emission (i.e., wavelike packets) that occurs only in a specific phase of a very particular oscillation. We interpret this empirical result to support that ground level enhancement events are not a result of purely stochastic processes. We used the Morlet wavelet to analyze the phase of each of the periodicities found by the wavelet analyses and local variations of power spectral density in these sporadic events. We found quasi-regular periodicities of 10.4, 6.55, 4.12, 2.9, 1.73, 0.86, 0.61, 0.4 and 0.24 years in ground level enhancements. Although some of these quasi-biennial oscillation periodicities (i.e., oscillations operating between 0.6 and 4 years) may be interpreted as simply harmonics and overtones of the fundamental solar cycle from the underlying sun-spot magnetism phenomenon. The sources of these periodicities are still unclear. Also there is no clear mechanism for the variability of the quasi-biennial oscillation periodicities itself. The quasi-biennial oscillation periodicities are broadly considered to be a variation of solar activity, associated with the solar dynamo process. Also, the intensity of these periodicities is more important around the years of maximum solar activity because the quasi-biennial oscillation periodicities are modulated by the solar cycle where the Sun is more energetically enhanced during activity maxima. To identify the relationships among ground level enhancement, solar, and cosmic rays indices in time-frequency framework, we apply the wavelet coherence analysis. The fingerprints of solar activity and galactic cosmic rays on these phenomena can also be discerned in terms of the prominent quasi-biennial oscillation of about 1.7 years. Title: Lunar fingerprints in the modulated incoming solar radiation: In situ insolation and latitudinal insolation gradients as two important interpretative metrics for paleoclimatic data records and theoretical climate modeling Authors: Cionco, Rodolfo Gustavo; Valentini, José Ernesto; Quaranta, Nancy Esther; Soon, Willie W. -H. Bibcode: 2018NewA...58...96C Altcode: We present a new set of solar radiation forcing that now incorporated not only the gravitational perturbation of the Sun-Earth-Moon geometrical orbits but also the intrinsic solar magnetic modulation of the total solar irradiance (TSI). This new dataset, covering the past 2000 years as well as a forward projection for about 100 years based on recent result by Velasco-Herrera et al. (2015), should provide a realistic basis to examine and evaluate the role of external solar forcing on Earth climate on decadal, multidecadal to multicentennial timescales. A second goal of this paper is to propose both in situ insolation forcing variable and the latitudinal insolation gradients (LIG) as two key metrics that are subjected to a deterministic modulation by lunar nodal cycle which are often confused with tidal forcing impacts as assumed and interpreted in previous studies of instrumental and paleoclimatic records. Our new results and datasets are made publicly available for all at PANGAEA site. Title: Evolution of Long Term Variability in Solar Analogs Authors: Egeland, Ricky; Soon, Willie; Baliunas, Sallie; Hall, Jeffrey C.; Henry, Gregory W. Bibcode: 2017IAUS..328..329E Altcode: 2017arXiv170402388E Earth is the only planet known to harbor life, therefore we may speculate on how the nature of the Sun-Earth interaction is relevant to life on Earth, and how the behavior of other stars may influence the development of life on their planetary systems. We study the long-term variability of a sample of five solar analog stars using composite chromospheric activity records up to 50 years in length and synoptic visible-band photometry about 20 years long. This sample covers a large range of stellar ages which we use to represent the evolution in activity for solar mass stars. We find that young, fast rotators have an amplitude of variability many times that of the solar cycle, while old, slow rotators have very little variability. We discuss the possible impacts of this variability on young Earth and exoplanet climates. Title: Generalization of the cross-wavelet function Authors: Velasco Herrera, V. M.; Soon, W.; Velasco Herrera, G.; Traversi, R.; Horiuchi, K. Bibcode: 2017NewA...56...86V Altcode: We introduce the method of multiple cross-wavelet algorithm, hereafter also as Einstein's cross functions, for the time-frequency study of solar activity records or any astronomical and geophysical time series in general. The main purpose of this algorithm is to allow the simultaneous examination of the time-frequency information contents in n > 2 time series available. Previous cross-wavelet algorithm only permit the study of two time series at a time and was not extended to the generalized n > 2 problems until now. Furthermore, our new work lifted the restriction from the original formulation that are valid only for stationary processes. We applied our new algorithm to several of the solar activity proxies available in order to demonstrate the broad and powerful utility of this technique. We have used solar activity proxy records that are obtained under different geophysical archives and time periods which are, in turn, suitable for studying both the statistical and physical properties for solar variations valid on timescales of multi-century, millennium to several millennia. We focus on documenting the methodology in this paper rather than any elaborate interpretation of the results. Title: VizieR Online Data Catalog: Calibrated solar S-index time series (Egeland+, 2017) Authors: Egeland, R.; Soon, W.; Baliunas, S.; Hall, J. C.; Pevtsov, A. A.; Bertello, L. Bibcode: 2017yCat..18350025E Altcode: The Mount Wilson HK Program observed the Moon with both the HKP-1 and HKP-2 instruments. After removing 11 obvious outliers, there are 162 HKP-1 observations taken from 1966 September 2 to 1977 June 4 with the Mount Wilson 100 inch reflector, covering the maximum of cycle 20 and the cycle 20-21 minimum. As mentioned in Baliunas+ (1995ApJ...438..269B), observations of the Moon resumed in 1993 with the HKP-2 instrument. After removing 10 obvious outliers, there are 75 HKP-2 observations taken from 1994 March 27 to 2002 November 23 with the Mount Wilson 60 inch reflector, covering the end of cycle 22 and the cycle 23 minimum, extending just past the cycle 23 maximum. The end of observations coincides with the unfortunate termination of the HK Project in 2003.

We seek to extend our time series of solar variability beyond cycle 23 by establishing a proxy to the NSO Sacramento Peak (NSO/SP) observations taken from 1976 to 2016, covering cycles 21 to 24. The spectral intensity scale is set by integrating a 0.53Å band centered at 3934.869Å in the K-line wing and setting it to the fixed value of 0.162.

We extend the S-index record back to cycle 20 using the composite K time series of Bertello+ (2016SoPh..291.2967B). See section 3 for further explanations.

(1 data file). Title: Short-term orbital forcing: A quasi-review and a reappraisal of realistic boundary conditions for climate modeling Authors: Cionco, Rodolfo G.; Soon, Willie W. -H. Bibcode: 2017ESRv..166..206C Altcode: 2016arXiv161208380C The aim of this paper is to provide geoscientists with the most accurate set of the Earth's astro-climatic parameters and daily insolation quantities, able to describe the Short-Term Orbital Forcing (STOF) as represented by the ever-changing incoming solar radiation. We provide an updated review and a pragmatic tool/database using the latest astronomical models and orbital ephemeris, for the entire Holocene and 1 kyr into the future. Our results are compared with the most important database produced for studying long-term orbital forcing showing no systematic discrepancies over the full thirteen thousand years period studied. Our detailed analysis of the periods present in STOF, as perturbed by Solar System bodies, yields a very rich dynamical modulation on annual-to-decadal timescales when compared to previous results. In addition, we addressed, for the first time, the error committed considering daily insolation as a continuous function of orbital longitudes with respect to the nominal values, i.e., calculating the corresponding daily insolation with orbital longitudes tabulated at noon. We found important relative differences up to ± 5%, which correspond to errors of 2.5 W m-2 in the daily mean insolation, for exactly the same calendar day and set of astro-climatic parameters. This previously unrecognized error could have a significant impact in both the initial and boundary conditions for any climate modeling experiment. Title: The Mount Wilson Observatory S-index of the Sun Authors: Egeland, Ricky; Soon, Willie; Baliunas, Sallie; Hall, Jeffrey C.; Pevtsov, Alexei A.; Bertello, Luca Bibcode: 2017ApJ...835...25E Altcode: 2016arXiv161104540E The most commonly used index of stellar magnetic activity is the instrumental flux scale of singly ionized calcium H & K line core emission, S, developed by the Mount Wilson Observatory (MWO) HK Project, or the derivative index {R}{HK}\prime . Accurately placing the Sun on the S scale is important for comparing solar activity to that of the Sun-like stars. We present previously unpublished measurements of the reflected sunlight from the Moon using the second-generation MWO HK photometer during solar cycle 23 and determine cycle minimum {S}23,\min =0.1634+/- 0.0008, amplitude {{Δ }}{S}23=0.0143+/- 0.0012, and mean < {S}23> =0.1701+/- 0.0005. By establishing a proxy relationship with the closely related National Solar Observatory Sacramento Peak calcium K emission index, itself well correlated with the Kodaikanal Observatory plage index, we extend the MWO S time series to cover cycles 15-24 and find on average < {S}\min > =0.1621+/- 0.0008, < {{Δ }}{S}{cyc}> =0.0145+/- 0.0012, < {S}{cyc}> =0.1694+/- 0.0005. Our measurements represent an improvement over previous estimates that relied on stellar measurements or solar proxies with non-overlapping time series. We find good agreement from these results with measurements by the Solar-Stellar Spectrograph at Lowell Observatory, an independently calibrated instrument, which gives us additional confidence that we have accurately placed the Sun on the S-index flux scale. Title: Dynamo Sensitivity In Solar Analogs With 50 Years Of Ca II H & K Activity Authors: Egeland, Ricky; Soon, Willie; Baliunas, Sallie; Hall, Jeffrey C.; Pevtsov, Alexei A.; Henry, Gregory W. Bibcode: 2016csss.confE...6E Altcode: 2016csss.confE..73E; 2016arXiv160904756E The Sun has a steady 11-year cycle in magnetic activity most well-known by the rising and falling in the occurrence of dark sunspots on the solar disk in visible bandpasses. The 11-year cycle is also manifest in the variations of emission in the Ca II H & K line cores, due to non-thermal (i.e. magnetic) heating in the lower chromosphere. The large variation in Ca II H & K emission allows for study of the patterns of long-term variability in other stars thanks to synoptic monitoring with the Mount Wilson Observatory HK photometers (1966-2003) and Lowell Observatory Solar-Stellar Spectrograph (1994-present). Overlapping measurements for a set of 27 nearby solar-analog (spectral types G0-G5) stars were used to calibrate the two instruments and construct time series of magnetic activity up to 50 years in length. Precise properties of fundamental importance to the dynamo are available from Hipparcos, the Geneva-Copenhagen Survey, and CHARA interferometry. Using these long time series and measurements of fundamental properties, we do a comparative study of stellar "twins" to explore the sensitivity of the stellar dynamo to small changes to structure, rotation, and composition. We also compare this sample to the Sun and find hints that the regular periodic variability of the solar cycle may be rare among its nearest neighbors in parameter space. Title: Corrigendum to 'A review of Holocene solar-linked climatic variation on centennial to millennial timescales: Physical processes, interpretative frameworks and a new multiple cross-wavelet transform algorithm' Earth Sci. Rev. 134 [1-15] Authors: Soon, Willie; Velasco Herrera, Victor M.; Selvaraj, Kandasamy; Traversi, Rita; Usoskin, Ilya; Arthur Chen, Chen-Tung; Lou, Jiann-Yuh; Kao, Shuh-Ji; Carter, Robert M.; Pipin, Valery; Severi, Mirko; Becagli, Silvia Bibcode: 2016ESRv..159..462S Altcode: In the article "A review of Holocene solar-linked climatic variation on centennial to millennial timescales: Physical processes, interpretative frameworks and a new multiple cross-wavelet transform algorithm", published in Earth-Science Reviews 134 (2014) 1, it was omitted to state that at the time this article was submitted the corresponding author Dr. Soon received funding from the Southern Company Services and Donors Trust. We have no indication that this funding has influenced the results presented in the article. Title: The Solar Dynamo Zoo Authors: Egeland, Ricky; Soon, Willie; Baliunas, Sallie; Hall, Jeffrey C.; Pevtsov, Alexei A.; Henry, Gregory W. Bibcode: 2016csss.confE..72E Altcode: We present composite time series of Ca II H & K line core emission indices of up to 50 years in length for a set of 27 solar-analog stars (spectral types G0-G5; within 10% of the solar mass) and the Sun. These unique data are available thanks to the long-term dedicated efforts of the Mount Wilson Observatory HK project, the Lowell Observatory Solar-Stellar Spectrograph, and the National Solar Observatory/Air Force Research Laboratory/Sacramento Peak K-line monitoring program. The Ca II H & K emission originates in the lower chromosphere and is strongly correlated with the presence of magnetic plage regions in the Sun. These synoptic observations allow us to trace the patterns long-term magnetic variability and explore dynamo behavior over a wide range of rotation regimes and stellar evolution timescales.In this poster, the Ca HK observations are expressed using the Mount Wilson S-index. Each time series is accompanied by a Lomb-Scargle periodogram, fundemental stellar parameters derived from the Geneva-Copenhagen Survey, and statistics derived from the time series including the median S-index value and seasonal and long-term amplitudes. Statistically significant periodogram peaks are ranked according to a new cycle quality metric. We find that clear, simple, Sun-like cycles are the minority in this sample. Title: Magnetic cycles at different ages of stars Authors: Oláh, K.; Kővári, Zs.; Petrovay, K.; Soon, W.; Baliunas, S.; Kolláth, Z.; Vida, K. Bibcode: 2016A&A...590A.133O Altcode: 2016arXiv160406701O
Aims: We study the different patterns of interannual magnetic variability in stars on or near the lower main sequence, approximately solar-type (G-K dwarf) stars in time series of 36 yr from the Mount Wilson Observatory Ca II H&K survey. Our main aim is to search for correlations between cycles, activity measures, and ages.
Methods: Time-frequency analysis has been used to discern and reveal patterns and morphology of stellar activity cycles, including multiple and changing cycles, in the datasets. Both the results from short-term Fourier transform and its refinement using the Choi-Williams distribution, with better frequency resolution, are presented in this study. Rotational periods of the stars were derived using multifrequency Fourier analysis.
Results: We found at least one activity cycle on 28 of the 29 stars we studied. Twelve stars, with longer rotational periods (39.7 ± 6.0 days), have simple smooth cycles, and the remaining stars, with much faster rotation (18.1 ± 12.2 days) on average, show complex and sometimes vigorously changing multiple cycles. The cycles are longer and quite uniform in the first group (9.7 ± 1.9 yr), while they are generally shorter and vary more strongly in the second group (7.6 ± 4.9). The clear age division between stars with smooth and complex cycles follows the known separation between the older and younger stars at around 2 to 3 Gyr of age. Title: Re-evaluating the role of solar variability on Northern Hemisphere temperature trends since the 19th century Authors: Soon, Willie; Connolly, Ronan; Connolly, Michael Bibcode: 2015ESRv..150..409S Altcode: Debate over what influence (if any) solar variability has had on surface air temperature trends since the 19th century has been controversial. In this paper, we consider two factors which may have contributed to this controversy:

Several different solar variability datasets exist. While each of these datasets is constructed on plausible grounds, they often imply contradictory estimates for the trends in solar activity since the 19th century.

Although attempts have been made to account for non-climatic biases in previous estimates of surface air temperature trends, recent research by two of the authors has shown that current estimates are likely still affected by non-climatic biases, particularly urbanization bias.

With these points in mind, we first review the debate over solar variability. We summarise the points of general agreement between most groups and the aspects which still remain controversial. We discuss possible future research which may help resolve the controversy of these aspects. Then, in order to account for the problem of urbanization bias, we compile a new estimate of Northern Hemisphere surface air temperature trends since 1881, using records from predominantly rural stations in the monthly Global Historical Climatology Network dataset. Like previous weather station-based estimates, our new estimate suggests that surface air temperatures warmed during the 1880s-1940s and 1980s-2000s. However, this new estimate suggests these two warming periods were separated by a pronounced cooling period during the 1950s-1970s and that the relative warmth of the mid-20th century warm period was comparable to the recent warm period.

We then compare our weather station-based temperature trend estimate to several other independent estimates. This new record is found to be consistent with estimates of Northern Hemisphere Sea Surface Temperature (SST) trends, as well as temperature proxy-based estimates derived from glacier length records and from tree ring widths. However, the multi-model means of the recent Coupled Model Intercomparison Project Phase 5 (CMIP5) climate model hindcasts were unable to adequately reproduce the new estimate - although the modelling of certain volcanic eruptions did seem to be reasonably well reproduced.

Finally, we compare our new composite to one of the solar variability datasets not considered by the CMIP5 climate models, i.e., Scafetta and Willson, 2014's update to the Hoyt and Schatten, 1993 dataset. A strong correlation is found between these two datasets, implying that solar variability has been the dominant influence on Northern Hemisphere temperature trends since at least 1881. We discuss the significance of this apparent correlation, and its implications for previous studies which have instead suggested that increasing atmospheric carbon dioxide has been the dominant influence. Title: The Maunder minimum (1645-1715) was indeed a grand minimum: A reassessment of multiple datasets Authors: Usoskin, Ilya G.; Arlt, Rainer; Asvestari, Eleanna; Hawkins, Ed; Käpylä, Maarit; Kovaltsov, Gennady A.; Krivova, Natalie; Lockwood, Michael; Mursula, Kalevi; O'Reilly, Jezebel; Owens, Matthew; Scott, Chris J.; Sokoloff, Dmitry D.; Solanki, Sami K.; Soon, Willie; Vaquero, José M. Bibcode: 2015A&A...581A..95U Altcode: 2015arXiv150705191U
Aims: Although the time of the Maunder minimum (1645-1715) is widely known as a period of extremely low solar activity, it is still being debated whether solar activity during that period might have been moderate or even higher than the current solar cycle #24. We have revisited all existing 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 positions, auroral sightings at high latitudes, cosmogenic radionuclide data as well as solar eclipse observations for that period. We also consider peculiar features of the Sun (very strong hemispheric asymmetry of the sunspot location, unusual differential rotation and the lack of the K-corona) that imply a special mode of solar activity during the Maunder minimum.
Results: The level of solar activity during the Maunder minimum is reassessed on the basis of all available datasets.
Conclusions: We conclude that solar activity was indeed at an exceptionally low level during the Maunder minimum. Although the exact level is still unclear, it was definitely lower than during the Dalton minimum of around 1800 and significantly below that of the current solar cycle #24. Claims of a moderate-to-high level of solar activity during the Maunder minimum are rejected with a high confidence level. Title: The Maunder minimum: A reassessment from multiple dataset Authors: Usoskin, Ilya; Arlt, Rainer; Asvestari, Eleanna; Kovaltsov, Gennady; Krivova, Natalie; Lockwood, Michael; Käpylä, Maarit; Owens, Matthew; Sokoloff, Dmitry D.; Solanki, Sami; Soon, Willie; Vaquero, Jose; Scott, Chris Bibcode: 2015IAUGA..2253036U Altcode: The Maunder minimum (MM) in 1645-1715 was a period of the lowest ever known solar activity recorded via sunspot numbers since 1610. Since it is the only Grand minimum of solar activity directly observed, it forms a benchmark for the solar variability studies. Therefore, it is crucially important to assess the level and other features of temporal and spatial solar magnetic variability during that time. However, because of uncertainties related mostly to ambiguity of some historical sunspot observation records, the exact level of solar activity during the MM is somewhat unclear, leaving room for continuous discussions and speculations. Many of these issues have been addressed by Jack Eddy in his cornerstone papers of 1976 and 1983, but since then numerous new pieces of evidence and datasets have appeared, making it possible to verify the paradigm of the Maunder minimum with far greater certainty than before.Here we provide a full reassessment of the Maunder minimum using all the available datasets: augmented sunspot counts and drawings; revisited historical archives; both well-known and newly revealed records of auroral observations; cosmic ray variability via cosmogenic isotope records of 14C in tree trunks, 10Be in ice cores and 44Ti in fallen meteorites. We show that, while the exact level of the activity is not easy to determine, the Sun indeed exhibited exceptionally low magnetic activity during the MM, in comparison to other periods of moderate or decreased activity, such as the Dalton minimum (ca. 1800), the Gleissberg minimum (ca. 1900) and the present weak solar cycle # 24. We show that a scenario of moderate or strong activity during the MM contradicts all the available datasets.Thus, we confirm, using all the presently available datasets of different nature, that the period of the Maunder minimum in 1645-1715 was indeed a Grand minimum, with very low solar surface magnetic activity, low intensity of the interplanetary magnetic field, as well as lower frequency and higher geographical latitude of auroral occurrence. Meanwhile some indications of the continuation, but at a very low level, of the 11-year solar cycle can be found in the data. Title: Response to the comment on: “Soon, W., and Legates, D.R., solar irradiance modulation of equator-to-pole (Arctic) temperature gradients: empirical evidence for climate variation on multi-decadal timescales. Journal of Atmospheric and solar-terrestrial physics, 93, (2013) 45-56” by F. Meunier and A. H. Reis Authors: Soon, Willie; Legates, David R. Bibcode: 2015JASTP.128...92S Altcode: We thank Meunier and Reis (hereafter as MR) for their comments on our paper. We, however, do not see the relevance of their alternative interpretation to our original results and believe this reflects their confusion regarding our conclusions rather than a discussion on physical mechanisms.

</ce:displayed-quote></ce:para>In the context of this quote, note that even Pallé et al. (2009:3)admitted that “while the deseasonalized CERES data has a small year to year variability (Fig. 2 of Pallé et al., 2009), the Earthshine data seem to present overly large interannual anomalies, along with a large size of the error bars associated to the yearly means [which] is mostly due to sampling issues, as Earthshine measurements are taken from a single station.”</ce:para>To put this in a different way, the relatively short duration of Earthshine or satellite-borne measurements of global albedo is unable to provide the necessary information on how this important quantity may vary on multi-decadal timescales as studies by Soon and Legates (2013). We note that efforts to 'reconstruct' Earth albedo over a 120-to-130 year period have been discussed by Zavalishin (2014) but we stress that such research requires non-independent information regarding surface temperatures and some unproven assumptions about the thermal inertia of the hydrosphere.</ce:para></ce:sections></ja:body><ja:simple-tail view="all"><ce:bibliography Title: Indian summer monsoon rainfall: Dancing with the tunes of the sun Authors: Hiremath, K. M.; Manjunath, Hegde; Soon, Willie Bibcode: 2015NewA...35....8H Altcode: There is strong statistical evidence that solar activity influences the Indian summer monsoon rainfall. To search for a physical link between the two, we consider the coupled cloud hydrodynamic equations, and derive an equation for the rate of precipitation that is similar to the equation of a forced harmonic oscillator, with cloud and rain water mixing ratios as forcing variables. Those internal forcing variables are parameterized in terms of the combined effect of external forcing as measured by sunspot and coronal hole activities with several well known solar periods (9, 13 and 27 days; 1.3, 5, 11 and 22 years). The equation is then numerically solved and the results show that the variability of the simulated rate of precipitation captures very well the actual variability of the Indian monsoon rainfall, yielding vital clues for a physical understanding that has so far eluded analyses based on statistical correlations alone. We also solved the precipitation equation by allowing for the effects of long-term variation of aerosols. We tentatively conclude that the net effects of aerosols variation are small, when compared to the solar factors, in terms of explaining the observed rainfall variability covering the full Indian monsoonal geographical domains. Title: A composite sea surface temperature record of the northern South China Sea for the past 2500 years: A unique look into seasonality and seasonal climate changes during warm and cold periods Authors: Yan, Hong; Soon, Willie; Wang, Yuhong Bibcode: 2015ESRv..141..122Y Altcode: High-resolution late Holocene climate records that can resolve seasonality are essential for confirming past climatic dynamics, understanding the late 20th century global warming and predicting future climate. Here a new composite record of the sea surface temperature, SST, variation in the northern South China Sea (SCS) during the late Holocene is constructed by combining seven seasonally-resolved coral and Tridacna gigas Sr/Ca-based SST time-windows with the instrumental SST record from modern interval between 1990 and 2000. This composite multi-proxy marine record, together with the reconstructions from mainland China and tropical Western Pacific, indicates that the late Holocene warm periods, the Roman Warm Period (RWP) and Medieval Warm Period (MWP), were prominently imprinted and documented in the climatic and environmental history of the East Asia-Western Pacific region. Meanwhile, substantial and significant SST seasonality variations during the late Holocene were observed in the composite record. The observed increase in seasonality (or amplitude of seasonal cycles) during the cold periods around our study area was probably caused by the different amplitudes between winter versus summer SST variations in northern SCS, with much larger SST variation during winters than during summers for the late Holocene. In addition, the distinctive warm, cold and neutral climatic episodes identified in our northern SCS composite SST record correspond well with other paleo reconstructions from mainland China and especially well with the Northern Hemisphere-wide composites by Moberg et al. (2005) and Ljungqvist (2010). The overall agreement however also calls for more information and insights on how seasonal temperatures and their ranges vary on decadal-centennial timescales. Title: A phenomenological study of the timing of solar activity minima of the last millennium through a physical modeling of the Sun-Planets Interaction Authors: Cionco, Rodolfo Gustavo; Soon, Willie Bibcode: 2015NewA...34..164C Altcode: We numerically integrate the Sun’s orbital movement around the barycenter of the solar system under the persistent perturbation of the planets from the epoch J2000.0, backward for about one millennium, and forward for another millennium to 3000 AD. Under the Sun-Planets Interaction (SPI) framework and interpretation of Wolff and Patrone (2010), we calculated the corresponding variations of the most important storage of the specific potential energy (PE) within the Sun that could be released by the exchanges between two rotating, fluid-mass elements that conserve its angular momentum. This energy comes about as a result of the roto-translational dynamics of the cell around the solar system barycenter. We find that the maximum variations of this PE storage correspond remarkably well with the occurrences of well-documented Grand Minima (GM) solar events throughout the available proxy solar magnetic activity records for the past 1000 yr. It is also clear that the maximum changes in PE precede the GM events in that we can identify precursor warnings to the imminent weakening of solar activity for an extended period. The dynamical explanation of these PE minima is connected to the minima of the Sun’s position relative to the barycenter as well as the significant amount of time the Sun’s inertial motion revolving near and close to the barycenter. We presented our calculation of PE forward by another 1000 yr until 3000 AD. If the assumption of the solar activity minima corresponding to PE minima is correct, then we can identify quite a few significant future solar activity GM events with a clustering of PE minima pulses starting at around 2150 AD, 2310 AD, 2500 AD, 2700 AD and 2850 AD. Title: A review of Holocene solar-linked climatic variation on centennial to millennial timescales: Physical processes, interpretative frameworks and a new multiple cross-wavelet transform algorithm Authors: Soon, Willie; Velasco Herrera, Victor M.; Selvaraj, Kandasamy; Traversi, Rita; Usoskin, Ilya; Chen, Chen-Tung Arthur; Lou, Jiann-Yuh; Kao, Shuh-Ji; Carter, Robert M.; Pipin, Valery; Severi, Mirko; Becagli, Silvia Bibcode: 2014ESRv..134....1S Altcode: We report on the existence and nature of Holocene solar and climatic variations on centennial to millennial timescales. We introduce a new solar activity proxy, based on nitrate (NO3-) concentration from the Talos Dome ice core, East Antarctica. We also use a new algorithm for computing multiple-cross wavelet spectra in time-frequency space that is generalized for multiple time series (beyond two). Our results provide a new interpretive framework for relating Holocene solar activity variations on centennial to millennial timescales to co-varying climate proxies drawn from a widespread area around the globe. Climatic proxies used represent variation in the North Atlantic Ocean, Western Pacific Warm Pool, Southern Ocean and the East Asian monsoon regions. Our wavelet analysis identifies fundamental solar modes at 2300-yr (Hallstattzeit), 1000-yr (Eddy), and 500-yr (unnamed) periodicities, leaves open the possibility that the 1500-1800-yr cycle may either be fundamental or derived, and identifies intermediary derived cycles at 700-yr and 300-yr that may mark rectified responses of the Atlantic thermohaline circulation to external solar modulation and pacing. Dating uncertainties suggest that the 1500-yr and 1800-yr cycles described in the literature may represent either the same or two separate cycles, but in either case, and irrespective too of whether it is a fundamental or derived mode in the sense of Dima and Lohmann (2009), the 1500-1800-yr periodicity is widely represented in a large number of paleoclimate proxy records. It is obviously premature to reject possible links between changing solar activity at these multiple scales and the variations that are commonly observed in paleoclimatic records. Title: Arctic albedo changes are small compared with changes in cloud cover in the tropics Authors: Legates, David R.; Eschenbach, Willis; Soon, Willie Bibcode: 2014PNAS..111E2157L Altcode: No abstract at ADS Title: Solar irradiance modulation of Equator-to-Pole (Arctic) temperature gradients: Empirical evidence for climate variation on multi-decadal timescales Authors: Soon, Willie; Legates, David R. Bibcode: 2013JASTP..93...45S Altcode: Using thermometer-based air temperature records for the period 1850-2010, we present empirical evidence for a direct relationship between total solar irradiance (TSI) and the Equator-to-Pole (Arctic) surface temperature gradient (EPTG). Modulation of the EPTG by TSI is also shown to exist, in variable ways, for each of the four seasons. Interpretation of the positive relationship between the TSI and EPTG indices suggests that solar-forced changes in the EPTG may represent a hemispheric-scale relaxation response of the system to a reduced Equator-to-Pole temperature gradient, which occurs in response to an increasing gradient of incoming solar insolation. Physical bases for the TSI-EPTG relationship are discussed with respect to their connections with large-scale climate dynamics, especially a critical relationship with the total meridional poleward energy transport. Overall, evidence suggests that a net increase in the TSI, or in the projected solar insolation gradient which reflects any net increase in solar radiation, has caused an increase in both oceanic and atmospheric heat transport to the Arctic in the warm period since the 1970s, resulting in a reduced temperature gradient between the Equator and the Arctic. We suggest that this new interpretative framework, which involves the extrinsic modulation of the total meridional energy flux beyond the implicit assumptions of the Bjerknes Compensation rule, may lead to a better understanding of how global and regional climate has varied through the Holocene and even the Quaternary (the most recent 2.6 million years of Earth's history). Similarly, a reassessment is now required of the underlying mechanisms that may have governed the equable climate dynamics of the Eocene (35-55 million years ago) and late Cretaceous (65-100 million years ago), both of which were warm geological epochs. This newly discovered relationship between TSI and the EPTG represents the "missing link" that was implicit in the empirical relationship that Soon (2009) recently demonstrated to exist between multi-decadal TSI and Arctic and North Atlantic climatic change. Title: Variation in surface air temperature of China during the 20th century Authors: Soon, Willie; Dutta, Koushik; Legates, David R.; Velasco, Victor; Zhang, Weijia Bibcode: 2011JASTP..73.2331S Altcode: The 20th century surface air temperature (SAT) records of China from various sources are analyzed using data which include the recently released Twentieth Century Reanalysis Project dataset. Two key features of the Chinese records are confirmed: (1) significant 1920s and 1940s warming in the temperature records, and (2) evidence for a persistent multidecadal modulation of the Chinese surface temperature records in co-variations with both incoming solar radiation at the top of the atmosphere as well as the modulated solar radiation reaching ground surface. New evidence is presented for this Sun-climate link for the instrumental record from 1880 to 2002. Additionally, two non-local physical aspects of solar radiation-induced modulation of the Chinese SAT record are documented and discussed.Teleconnections that provide a persistent and systematic modulation of the temperature response of the Tibetan Plateau and/or the tropospheric air column above the Eurasian continent (e.g., 30°N-70°N; 0°-120°E) are described. These teleconnections may originate from the solar irradiance-Arctic-North Atlantic overturning circulation mechanism proposed by Soon (2009). Also considered is the modulation of large-scale land-sea thermal contrasts both in terms of meridional and zonal gradients between the subtropical western Pacific and mid-latitude North Pacific and the continental landmass of China. The Circum-global teleconnection (CGT) pattern of summer circulation of Ding and Wang (2005) provides a physical framework for study of the Sun-climate connection over East Asia. Our results highlight the importance of solar radiation reaching the ground and the concomitant importance of changes in atmospheric transparency or cloudiness or both in motivating a true physical explanation of any Sun-climate connection. We conclude that ground surface solar radiation is an important modulating factor for Chinese SAT changes on multidecadal to centennial timescales. Therefore, a comprehensive view of local and remote factors of climate change in China must take account of this as well as other natural and anthropogenic forcings. Title: Temporal derivative of Total Solar Irradiance and anomalous Indian summer monsoon: An empirical evidence for a Sun-climate connection Authors: Agnihotri, Rajesh; Dutta, Koushik; Soon, Willie Bibcode: 2011JASTP..73.1980A Altcode: Identifying the pattern of natural climate variability is of immense importance to delineate the effects of anthropogenic climate changes. Global and regional climates are suspected to vary, in unison or with delays, with the Total Solar Irradiance (TSI) at decadal to centennial timescales. Here we show that the Indian summer monsoon rainfall correlates well with the temporal derivative of TSI on multi-decadal timescales. This linkage between the temporal derivative of TSI and the Indian summer monsoon is tested and corroborated both for the instrumental period (1871-2006) and for the last ∼300 years using a speleothem δ18O record representing rainfall in southwestern India. Our analyses indicate that anomalous dry periods of the Indian monsoon are mostly coincident with negative TSI derivative. This study thus demonstrates the potential of ‘TSI derivative’ as an important indicator of natural monsoon variability on an interdecadal timescale. Title: Differential rotation of some HK-Project stars and the butterfly diagrams Authors: Katsova, M. M.; Livshits, M. A.; Soon, W.; Baliunas, S. L.; Sokoloff, D. D. Bibcode: 2010NewA...15..274K Altcode: We analyze the long-term variability of the chromospheric radiation of 20 stars monitored in the course of the HK-Project at the Mount Wilson Observatory. We apply the modified wavelet algorithm for this set of gapped time series. Besides the mean rotational periods for all these stars, we find reliable changes of the rotational periods from year to year for a few stars. Epochs of slower rotation occur when the activity level of the star is high, and the relationship repeats again during the next maximum of an activity cycle. Such an effect is traced in two stars with activity cycles that are not perfectly regular (but labeled "Good" under the classification in [Baliunas, S.L., Donahue, R.A., Soon, W.H., Horne, J.H., Frazer, J., Woodard-Eklund, L., Bradford, M., Rao, L.M., Wilson, O.C., Zhang, Q. et al., 1995. ApJ 438, 269.]) but the two stars have mean activity levels exceed that of the Sun. The averaged rotational period of HD 115404 is 18.5 days but sometimes the period increases up to 21.5 days. The sign of the differential rotation is the same as the Sun's, and the value ΔΩ / < Ω > = - 0.14. For the star HD 149661, this ratio is -0.074. Characteristic changes of rotational periods occur over around three years when the amplitude of the rotational modulation is large. These changes can be transformed into latitude-time butterfly diagrams with minimal a priori assumptions. We compare these results with those for the Sun as a star and conclude that epochs when surface inhomogeneities rotate slower are synchronous with the reversal of the global magnetic dipole. Title: The Sun-Climate Connection: A journey from solar-stellar-galactic astrophysics, to weather-climate continuum and paleoclimatic-geological insights (Invited) Authors: Soon, W. Bibcode: 2009AGUFMGC11A0681S Altcode: I will take a brief tour through some of the latest developments in solar-stellar-glactic astronomy which include understanding of the intrinsic variability of the Sun's magnetism, the weather-climate continuum, and paleoproxies of climate variability and change from the geological archives. Insights from the orbital theory for the transition between ice ages and warm interglacial climate will also be discussed and applied in terms of the framework of the latitudinal insolation gradient that has been recently proposed by Davis and Brewer (2009). Empirical evidence and interpretation for solar climatic responses on a wide range of spatial and temporal scales will be presented. Related challenges and implications will be discussed. Title: Multiple and changing cycles of active stars. II. Results Authors: Oláh, K.; Kolláth, Z.; Granzer, T.; Strassmeier, K. G.; Lanza, A. F.; Järvinen, S.; Korhonen, H.; Baliunas, S. L.; Soon, W.; Messina, S.; Cutispoto, G. Bibcode: 2009A&A...501..703O Altcode: 2009arXiv0904.1747O Aims: We study the time variations in the cycles of 20 active stars based on decade-long photometric or spectroscopic observations.
Methods: A method of time-frequency analysis, as discussed in a companion paper, is applied to the data.
Results: Fifteen stars definitely show multiple cycles, but the records of the rest are too short to verify a timescale for a second cycle. The cycles typically show systematic changes. For three stars, we found two cycles in each of them that are not harmonics and vary in parallel, indicating a common physical mechanism arising from a dynamo construct. The positive relation between the rotational and cycle periods is confirmed for the inhomogeneous set of active stars.
Conclusions: Stellar activity cycles are generally multiple and variable. Title: Differential rotation of some HK Project stars and the butterfly diagrams Authors: Katsova, M. M.; Livshits, M. A.; Soon, W.; Sokoloff, D. D. Bibcode: 2009AIPC.1094..672K Altcode: 2009csss...15..672K We analyze the long-term variability of the chromospheric radiation of 20 stars monitored in the course of HK Project. We apply the modified wavelet algorithm for this set of gapped data. Besides the rotational periods for all these stars, we find reliable changes of the periods from year to year for a few stars. Epochs of the slower rotation occur when the activity level of the star is high, and they come again during the next maximum of a cycle. Such an effect is traced in two ``Good'' stars, whose cycles are not quite regular, but they are more active than the Sun. So, the mean period of rotation of the star HD 115404 is 18.5 days, and sometimes it does increase up to 21.5 days. The sign of the differential rotation is the same as one for the Sun, and ΔΩ/<Ω> = -0.14. For the star HD 149661, this ratio is -0.074. Characteristic changes of rotational periods occur over around three years when the amplitude of the rotational modulation is large. These changes can be transformed into the butterfly diagrams without a priori assumptions. We compare these results with those for the Sun as a star and conclude that epochs when surface inhomogeneities rotate slower are synchronous with reversal of the global magnetic dipole. Title: Changing stellar activity cycles Authors: Oláh, K.; Strassmeier, K. G.; Granzer, T.; Soon, W.; Baliunas, S. L. Bibcode: 2007AN....328.1072O Altcode: We investigated continuous long-term photometric datasets of thirteen active stars, Ca II variability of one single main-sequence star, and 10.7cm radio data of the Sun, with simple Fourier- and time-frequency analysis. The data reflect the strength of the activity manifested in magnetic spots. All studied stars show multiple (2 to 4) cycles of different lengths. The time-frequency analysis reveals, that in several cases of the sample one or two of the cycles exhibit continuous changes (increase or decrease). For four stars (V711 Tau, IL Hya, HK Lac, HD 100180) and for the Sun we find that the cycle length changes are strong, amounting to 10-50% during the observed time intervals. The cycle lengths are generally longer for stars with longer rotational periods. Title: Some Issues of Solar Irradiance Variability and Climatic Responses: A Brief Review Authors: Soon, W. Bibcode: 2007AGUFMGC42A..05S Altcode: In this paper, I will overview the difficulties surrounding a physical understanding of solar irradiance variability to contrast the superficial results from parametric fitting procedures. Related problems and consequences will be discussed. I will also offer some thoughts and empirical evidence for solar climatic responses on a range of spatial and temporal scales. Title: Patterns of Photometric and Chromospheric Variation among Sun-like Stars: A 20 Year Perspective Authors: Lockwood, G. W.; Skiff, B. A.; Henry, Gregory W.; Henry, Stephen; Radick, R. R.; Baliunas, S. L.; Donahue, R. A.; Soon, W. Bibcode: 2007ApJS..171..260L Altcode: 2007astro.ph..3408L We examine patterns of variation of 32 primarily main-sequence Sun-like stars [selected at project onset as stars on or near the main sequence and color index 0.42<=(B-V)<=1.4], extending our previous 7-12 yr time series to 13-20 yr by combining Strömgren b, y photometry from Lowell Observatory with similar data from Fairborn Observatory. Parallel chromospheric Ca II H and K emission data from the Mount Wilson Observatory span the entire interval. The extended data strengthen the relationship between chromospheric and brightness variability at visible wavelengths derived previously. We show that the full range of photometric variation has probably now been observed for a majority of the program stars. Twenty-seven stars are deemed variable according to an objective statistical criterion. On a year-to-year timescale, young active stars become fainter when their Ca II emission increases, while older less active stars such as the Sun become brighter when their Ca II emission increases. The Sun's total irradiance variation, scaled to the b and y stellar filter photometry, still appears to be somewhat smaller than stars in our limited sample with similar mean chromospheric activity, but we now regard this discrepancy as probably due mainly to our limited stellar sample. Title: Anharmonic and standing dynamo waves: theory and observation of stellar magnetic activity Authors: Baliunas, S.; Frick, P.; Moss, D.; Popova, E.; Sokoloff, D.; Soon, W. Bibcode: 2006MNRAS.365..181B Altcode: 2005MNRAS.tmp.1044B The familiar decadal cycle of solar activity is one expression of interannual variability of surface magnetism observed in stars on or near the lower main sequence. From studies of time-series of CaII H and K emission fluxes that go back more than 35 yr and have been accumulated for such stars at the Mount Wilson Observatory by the HK Project, we define a quantitative measure, called anharmonicity, of the cyclic component of interannual magnetic variability. Anharmonicity provides a connection between observed variations in magnetic activity and the two-dimensional description of a Parker dynamo model. We explore the parameter space of the Parker dynamo model and find an excellent counterpart in the records of several of the lowest-mass (late K-type to early M-type) active stars in the HK Project sample to the solutions containing highly anharmonic, standing dynamo waves. We interpret anharmonicity apparent in the records as resulting from non-propagating or standing dynamo waves, which operate in a regime that is substantially supercriticial. There, for the majority of a cycle, or pulse of decadal-to-interdecadal variability, the large-scale magnetic fields are generated and maintained by winding of field by differential rotation rather than by the joint action of differential rotation and helical convection. Among the less active stars (the Sun is considered such a star in the HK Project sample) we find a correspondence between anharmonicity and Parker dynamo model solutions that include simple harmonic, migratory and/or intermediate-type dynamo wave patterns over a broad range of dynamo parameters. Title: Variable solar irradiance as a plausible agent for multidecadal variations in the Arctic-wide surface air temperature record of the past 130 years Authors: Soon, Willie W. -H. Bibcode: 2005GeoRL..3216712S Altcode: This letter offers new evidence motivating a more serious consideration of the potential Arctic temperature responses as a consequence of the decadal, multidecadal and longer-term persistent forcing by the ever-changing solar irradiance both in terms of total solar irradiance (TSI, i.e., integrated over all wavelengths) and the related UV irradiance. The support for such a solar modulator can be minimally derived from the large (>75%) explained variance for the decadally-smoothed Arctic surface air temperatures (SATs) by TSI and from the time-frequency structures of the TSI and Arctic SAT variability as examined by wavelet analyses. The reconstructed Arctic SAT time series based on the inverse wavelet transform, which includes decadal (5-15 years) and multidecadal (40-80 years) variations and a longer-term trend, contains nonstationary but persistent features that are highly correlated with the Sun's intrinsic magnetic variability especially on multidecadal time scales. Title: Anharmonicity of Stellar Cycles: A Wavelet Quantification Authors: Baliunas, S.; Frick, P.; Moss, D.; Popova, E.; Sokoloff, D.; Soon, W. Bibcode: 2004SoPh..224..179B Altcode: 2005SoPh..224..179B Two quantitative measures for the anharmonicity of stellar cycles, as recorded in the Ca II H and K chromospheric activity data as well as in simple dynamo models, are presented and discussed. Title: Time-spectra of chromospheric activity of old solar-type stars: detection of rotational signals from double wavelet analysis Authors: Frick, Peter; Soon, Willie; Popova, Elena; Baliunas, Sallie Bibcode: 2004NewA....9..599F Altcode: We introduce a novel technique, called the double wavelet analysis (DWA), for the determination of stellar rotation periods from time serial data. This first paper aims narrowly at the discussion, introduction and application of the DWA technique to records of surface magnetism in solar-type (relatively old) lower main sequence stars that are obtained by the Mount Wilson Observatory (MWO) HK Project. The technique takes a series of careful steps that seek to optimize wavelet parameters and normalization schemes, ultimately allowing fine-tuned, arguably more accurate, estimates of rotation-modulated signals (with, e.g., periods of days to months) in records that contain longer periodicities such as stellar magnetic activity cycles (with, e.g., period of years). The apparent rotation periods estimated from the DWA technique are generally consistent with results from both ;first-pass; (i.e., ordinary) global wavelet spectrum and earlier classical periodogram analyses. But there are surprises as well. For example, the rotation period of the ancient subdwarf Goombridge 1830 (HD 103095), previously identified as ≈31 days, suggests under the DWA technique a significantly slower period of 60 days. DWA spectra also generally reveal a shift in the cycle period toward high frequencies (hence shorter periods) compared to the first-pass wavelet spectrum. For solar-type stars analyzed here, the character of the DWA spectrum and slope of the first-pass global wavelet spectrum produce a classification scheme that allows a star's record to be placed into one of three categories. Title: Evolution of morphological features of CMEs deduced from catastrophe model of solar eruptions Authors: Lin, J.; Soon, W. Bibcode: 2004NewA....9..611L Altcode: We describe the evolution of morphological features of the magnetic configuration of CME according to the catastrophe model developed previously. For the parameters chosen for the present work, roughly half of the total mass is nominally contained in the initial flux rope, while the remaining plasma is brought by magnetic reconnection from the corona into the current sheet and from there into the CME bubble. The physical attributes of the difference in the observable features between CME bubble and flare loop system were studied. We tentatively identified distinguishable evolutionary features like the outer shell, the expanding bubble and the flux rope with the leading edge, void and core of the 3-component CME structure. The role of magnetic reconnection is discussed as a possible mechanism for the heating of the prominence material during eruptions. Several aspects of this explanation that need improvement are outlined. Title: Stellar Magnetic Activity, the Earth and Exoplanets: How Future Space Missions Can Contribute to Understanding Solar Activity and Solar-terrestrial Influences Authors: Baliunas, S. L.; Soon, W. W. -H. Bibcode: 2004AAS...204.0809B Altcode: 2004BAAS...36..790B The solar spectral and particle output varies over time scales of minutes to eons; some of those variations are documented or claimed to have influenced the terrestrial environment. The origins of solar variability include the progress of fusion through time and the complex interaction of the interior gas and magnetic fields. The Mount Wilson HK Project has yielded information on stellar magnetic activity on more than 2,000 stars going as far back as 38 years in order to put solar magnetic activity in a physical perspective unavailable from theory and models alone. We discuss how future space missions like Space Interferometry Mission (SIM) and Stellar Imager (SI) would contribute to understanding solar variability that has influenced -- and should continue to influence -- life and the environment on earth.

This research funded in part by MIT-MSG 5710001241, JPL 1236821, AF 49620-02-1-0194, a grant from NASA HQ and GSFC to SAO for the SI Vision Mission Study, NASA NAG5-7635, NRC COBASE, CRDF 322, Richard Lounsberry Foundation, Langley-Abbot, Rollins, Scholarly Studies and James Arthur Funds (Smithsonian Institution) and several generous individuals. Title: Estimation and representation of long-term (>40 year) trends of Northern-Hemisphere-gridded surface temperature: A note of caution Authors: Soon, Willie W. -H.; Legates, David R.; Baliunas, Sallie L. Bibcode: 2004GeoRL..31.3209S Altcode: 2004GeoRL..3103209S Several quantitative estimates of surface instrumental temperature trends in the late 20th century are compared by using published results and our independent analyses. These estimates highlight a significant sensitivity to the method of analysis, the treatment of data, and the choice of data presentation (i.e., size of the smoothing filter window). Providing an accurate description of both quantitative uncertainties and sensitivity to the treatment of data is recommended as well as avoiding subjective data-padding procedures. Title: Year Without a Summer Authors: Soon, Willie; Yaskell, Steven Bibcode: 2003Mercu..32c..13S Altcode: A weak solar maximum, a major volcanic eruption, and possibly even the wobbling of the Sun conspired to make the summer of 1816 one of the most miserable ever recorded. Title: Theories of solar eruptions: a review Authors: Lin, J.; Soon, W.; Baliunas, S. L. Bibcode: 2003NewAR..47...53L Altcode: This review highlights current theoretical research on eruptive phenomena in the solar atmosphere. We start by looking back upon the early theories and their development. Any theory and model of solar eruptions must explain two key aspects of eruption physics. The first aspect concerns the original cause of the eruption and the second pertains to the nature of the morphological features that form during its evolution. Those features include rapid ejection of large-scale magnetic flux and plasma into interplanetary space, and the separating of ribbons of H α emission on the solar disk joined by a rising arcade of soft X-ray and H α loops, with hard X-ray emission at their summits and feet. We intercompare relevant theories and models by discussing their advantages as well as by pointing out important aspects that need improvement. Title: Proxy climatic and environmental changes of the past 1000 years Authors: Soon, W.; Baliunas, S. L. Bibcode: 2003ClRe...23...89S Altcode: No abstract at ADS Title: Reconstructing climatic and environmental changes of the past 1000 years: A reappraisal Authors: Soon, W.; Baliunas, S. L.; Idso, C.; Idso, S.; Legates, D. Bibcode: 2003En&En..14..233S Altcode: No abstract at ADS Title: The Maunder Minimum and the Variable Sun-Earth Connection Authors: Soon, Willie Wei-Hock; Yaskell, Steven H. Bibcode: 2003mmvs.book.....S Altcode: No abstract at ADS Title: Global warming Authors: Soon, W.; Baliunas, S. L. Bibcode: 2003PrPhG..27..448S Altcode: No abstract at ADS Title: Gauging the Sun: Comparative photometric and magnetic activity measurements of sunlike stars, 1984-2001 Authors: Lockwood, G. W.; Hall, J. C.; Skiff, B. A.; Henry, G. W.; Radick, R. R.; Baliunas, S. L.; Soon, W.; Donahue, R. A. Bibcode: 2002AAS...200.0709L Altcode: 2002BAAS...34..651L Visible light photometric observations of a small sample of sunlike stars with mean chromospheric activity levels similar to or slightly lower than the Sun's suggest that total solar irradiance variations on activity cycle timescales may be comparatively small (Lockwood et al. 1992, Nature 360, 653; Radick et al. 1998, ApJS 118, 239). The Sun's irradiance variation over the past two cycles is 0.04% rms compared with 0.1% rms for the stellar sample measured at Lowell from 1984 to 1995. This assertion can now be tested using new photometric measurements from Fairborn Observatory automated telescopes (1993-2001) that extend the duration of stellar observations to 17 years. Chromospheric activity measurements for these stars come from the Mount Wilson HK program (1966-2001) and the Lowell Observatory Solar Stellar Spectrograph program (1993-2001). In this presentation we will describe efforts to merge the overlapping Lowell and Fairborn photometry and the Mt. Wilson and Lowell HK measurements with the goal of reducing the uncertainties in previous efforts to characterize stellar photometric variations near the limit of detection. Title: Sources of solar variability responsibile for global warming of the upper ocean on decadal period scales Authors: White, W.; Dettinger, M.; Soon, W.; Baliunas, S. Bibcode: 2002cosp...34E1318W Altcode: 2002cosp.meetE1318W Global-average warming and cooling of upper ocean temperature on decadal period scales of ~0.1 K are aligned with decadal changes in the SunSs irradiance of ~0.5 W m-2 throughout the 20th Century at lags ranging from 0 to 18 months. This apparent upper ocean temperature response to solar forcing is ~3 times that expected from the Stefan-Boltzmann radiation balance for the EarthSs surface. Yet, this global-average temperature change is a small residual in the spatial integration of relatively large temperature changes of O(1.0 K) associated with a global pattern of variability that is similar to that of the El Nino-Southern Oscillation (Tourre et al., 2001). Since the latter exhibits global-average warming and cooling of 0.2 K in the absence of solar forcing (White et al., 2001), the SunSs decadal signal needs simply to excite this particular decadal mode in the EarthSs ocean-atmosphere-terrestrial system in order to produce the observed global-average temperature change. The question is, by what mechanism does it do this? Here we examine the global-average diabatic heat storage budget for the upper ocean on decadal period scales using the NCEP/NCAR atmospheric reanalysis and the SIO oceanic reanalysis. First, we find the global-average variability dominated by the tropical global-average. Second, we find the peak tropical warm phase associated with higher troposphere moisture content and cloud fraction, driven by an increase in outgoing sensible-plus-latent heat flux and outgoing longwave-minusshortwave radiative heat flux of comparable magnitudes. The sources of the anomalous warming tendency during the onset phase is the reduction in the net poleward Ekman heat flux out of the tropics and the reduction in outgoing sensible-plus-latent heat flux of similar magnitude, both in response to reduced trade wind intensity. Thus, the increase in cloud fraction during the peak tropical warm phase does not heat the underlying ocean, as assumed by Marsh and Svensmark (2000). Rather, the reduction in trade wind intensity during the onset phase is consistent with that simulated by Haigh (1996) in response to heating of the lower stratosphere by the UV portion of the total solar irradiance spectrum. Here we find a slow downward propagation of zonal wind anomalies from the lower stratosphere to the lower troposphere contributing to this reduction in trade wind intensity. Title: Reply to Comments on "Modeling climatic effects of anthropogenic CO2 emissions: Unknowns and uncertainties Authors: Risbey, James; Soon, W.; Baliunas, S.; Idso, S. B.; Kondratyev, K. Ya.; Posmentier, E. S. Bibcode: 2002ClRe...22..187R Altcode: No abstract at ADS Title: Modeling climatic effects of anthropogenic CO2 emissions: Unknows and uncerta inties Authors: Soon, W.; Baliunas, S.; Demirchan, K. S.; Idso, S. B.; Kondratyev, K. Ya.; Posmentier, E. S. Bibcode: 2001ClRe...18..259S Altcode: No abstract at ADS Title: Global Climate Change: Conceptual Aspects, 2001 Authors: Kondratyev, K. Ya.; Adamenko, V. N.; Demirchian, K. S.; Baliunas, S.; Boehmer-Christiansen, S.; Idso, S. B.; Kukla, G.; Posmentier, E. S.; Soon, W. Bibcode: 2001rass.rept.....K Altcode: No abstract at ADS Title: The impact of anthropogenic CO2 emissions: Unknows and uncertainties Authors: Soon, W.; Baliunas, S.; Demirchan, K. S.; Idso, S. B.; Kondratyev, K. Ya.; Posmentier, E. S. Bibcode: 2001PRGS..133....1S Altcode: No abstract at ADS Title: Solar and Space Weather (or SOLSPA) EuroConference: The Solar and Terrestrial Climate Authors: Soon, W. Bibcode: 2001sefp.conf...91S Altcode: No abstract at ADS Title: The Curious case of the carbon forest source Authors: Baliunas, S.; Soon, W. Bibcode: 2000WCRp....6f...3B Altcode: No abstract at ADS Title: Millennial climate Authors: Baliunas, S.; Soon, W. Bibcode: 2000WCRp....6b...3B Altcode: No abstract at ADS Title: 100000110011 (Computer Year 2099) Authors: Baliunas, S.; Soon, W. Bibcode: 2000WCRp....5v...3B Altcode: No abstract at ADS Title: Man vs. Milky Way revisited Authors: Baliunas, S.; Soon, W. Bibcode: 2000WCRp....5s...3B Altcode: No abstract at ADS Title: Climate hypersensitivity to solar forcing? Authors: Soon, W.; Posmentier, E.; Baliunas, S. Bibcode: 2000AnGeo..18..583S Altcode: We compare the equilibrium climate responses of a quasi-dynamical energy balance model to radiative forcing by equivalent changes in CO2, solar total irradiance (Stot) and solar UV (SUV). The response is largest in the SUV case, in which the imposed UV radiative forcing is preferentially absorbed in the layer above 250 mb, in contrast to the weak response from global-columnar radiative loading by increases in CO2 or Stot. The hypersensitive response of the climate system to solar UV forcing is caused by strongly coupled feedback involving vertical static stability, tropical thick cirrus ice clouds and stratospheric ozone. This mechanism offers a plausible explanation of the apparent hypersensitivity of climate to solar forcing, as suggested by analyses of recent climatic records. The model hypersensitivity strongly depends on climate parameters, especially cloud radiative properties, but is effective for arguably realistic values of these parameters. The proposed solar forcing mechanism should be further confirmed using other models (e.g., general circulation models) that may better capture radiative and dynamical couplings of the troposphere and stratosphere. Title: The Trouble with Ozone Authors: Baliunas, S.; Soon, W. Bibcode: 2000WCRp....5o...3B Altcode: No abstract at ADS Title: Photometric and Ca II H and K Spectroscopic Variations in Nearby Sun-like Stars with Planets. III. Authors: Henry, Gregory W.; Baliunas, Sallie L.; Donahue, Robert A.; Fekel, Francis C.; Soon, Willie Bibcode: 2000ApJ...531..415H Altcode: We present the results of an analysis of time-series photometry, Ca II H and K spectrophotometry, and high-dispersion visible spectra of nine nearby Sun-like stars recently identified as having planets. For the six stars whose presumed planets have orbital periods of less than 4 months (τ Boo, 51 Peg, υ And, ρ1 Cnc, ρ CrB, and 70 Vir), sine-curve fits to the photometric data show no variations with semiamplitude greater than 1 or 2 parts in 104. Photometric variations in 47 UMa are similarly small, although our photometric data of this star are slightly affected by variability of the comparison star. Nonvariability at this level of precision is sufficient to rule out surface magnetic activity as the cause of the observed radial-velocity variations in these seven stars and makes nonradial pulsations unlikely as well. Thus, our photometry provides indirect but strong support for true reflex motions-planets-in these seven stars, but cannot yet so support the planetary hypothesis for the two additional stars, 16 Cyg B and Gl 411. Continued photometric monitoring of the short-period systems may soon result in the direct detection of these planets in reflected light. We have used our photometric fluxes to search for possible transits of the extrasolar planets. Transits definitely do not occur in τ Boo, 51 Peg, υ And, and ρ1 Cnc, and probably do not occur in ρ CrB and 70 Vir. Our transit-search results are inconclusive for 47 UMa, and we cannot address the issue for 16 Cyg B and Gl 411. The precision of our photometry is sufficient to detect transits of planets even if they are not gas giants, as currently assumed, but much smaller objects with rocky compositions. The chance of finding at least one transit in the six stars is ~40%. We find significant year-to-year photometric variability only in τ Boo, which is not only the youngest star in the sample but also the star with the shallowest convective zone. The interseasonal range in its yearly mean photometric flux is ~0.002 mag, roughly twice the 0.0008 mag decadal variation in the Sun's total irradiance. Monitoring of the relative Ca II H and K fluxes began between 1966 and 1968 for 51 Peg, τ Boo, ρ CrB, and Gl 411, between 1990 and 1993 for 47 UMa, 70 Vir, 16 Cyg B, and ρ1 Cnc, and in 1996 for υ And. The data have been newly recalibrated for improved long-term instrumental stability, resulting in better precision of the Ca II records. Five of the nine stars in this study have little or no detectable year-to-year variation in Ca II flux. The remaining four show moderate or pronounced variability: τ Boo, whose radial-velocity and photometric variations have comparatively high amplitudes; Gl 411, whose planetary companion was inferred astrometrically, not spectroscopically; ρ1 Cnc, which may undergo decadal cyclic activity; and υ And, which shows moderate year-to-year variability. Except for 47 UMa, intraseasonal variability consistent with rotation was detected in the Ca II records of all stars. However, the rotation periods determined for υ And, 70 Vir, and 16 Cyg B are of low confidence. An examination of the recalibrated Ca II records for 51 Peg finds a rotation period of 22 days, in contrast to our previous result of 37 days. Ages have been estimated from the mean Ca II flux and, where possible, the rotation period. We find general consistency with the ages determined by others comparing properties determined from high-resolution spectroscopy to evolutionary models, although the uncertainties are, in general, large. Based on observations made at Mount Wilson Observatory, operated by the Mount Wilson Institute, under an agreement with the Carnegie Institution of Washington and the automatic photoelectric telescope at Fairborn Observatory in the Patagonia Mountains of southern Arizona. Title: Calculating the Climatic Impacts of Increased CO2: the Issue of Model Validation Authors: Soon, W.; Baliunas, S.; Idso, S. B.; Kondratyev, K. Ya.; Posmentier, E. S. Bibcode: 2000ESASP.463..243S Altcode: 2000sctc.proc..243S No abstract at ADS Title: The rains of Ranchipur Authors: Baliunas, S.; Soon, W. Bibcode: 2000WCRp....5j...3B Altcode: No abstract at ADS Title: The sun also warms Authors: Baliunas, S.; Soon, W. Bibcode: 2000stcl.rept...21B Altcode: No abstract at ADS Title: Variations of solar coronal hole area and terrestrial lower tropospheric air temperature from 1979 to mid-1998: astronomical forcings of change in earth's climate? Authors: Soon, W.; Baliunas, S.; Posmentier, E. S.; Okeke, P. Bibcode: 2000NewA....4..563S Altcode: The temperature anomaly of the terrestrial lower troposphere, inferred from the Microwave Sounding Unit (MSU) radiometers, is found to be inversely correlated with the area of the Sun covered by coronal holes. The correlation between the monthly time series of global tropospheric temperature anomaly and total coronal hole area from January 1979 to April 1998 has a Pearson coefficient of -0.46, which is different from zero at a 95% confidence level. Physical reasonings for the explained and unexplained parts of the correlation are discussed. The coronal hole area is a physical proxy for both the global-scale, 22-yr geometrical and shorter-term, dynamical components of the cosmic ray modulation, as well as the corpuscular emission of the Sun. Other solar parameters that may indicate a solar radiative effect on climate are also evaluated. It is concluded that variable fluxes either of solar charged particles or cosmic rays modulated by the solar wind, or both, may influence the terrestrial tropospheric temperature on timescale of months to years. Title: Generations of Hurricanes Authors: Baliunas, S.; Soon, W. Bibcode: 1999WCRp....5f...3B Altcode: No abstract at ADS Title: Almighty Chance and the Dance of El Nino Authors: Baliunas, S.; Soon, W. Bibcode: 1999WCRp....5d...3B Altcode: No abstract at ADS Title: Pioneers in the Greenhouse Effect Authors: Baliunas, S.; Soon, W. Bibcode: 1999WCRp....4s....B Altcode: No abstract at ADS Title: Pioneers in the Greenhouse Effect Authors: Baliunas, S.; Soon, W. Bibcode: 1999WCRp....4S...6B Altcode: No abstract at ADS Title: The Mysteries of Carbon Dioxide Authors: Baliunas, S.; Soon, W. Bibcode: 1999WCRp....4R...6B Altcode: No abstract at ADS Title: Aerosols are Cool Authors: Baliunas, S.; Soon, W. Bibcode: 1999WCRp....4k...6B Altcode: No abstract at ADS Title: Aerosols are Cool Authors: Baliunas, S.; Soon, W. Bibcode: 1999WCRp....4Q...6B Altcode: No abstract at ADS Title: Lifetime of Surface Features and Stellar Rotation: A Wavelet Time-Frequency Approach Authors: Soon, Willie; Frick, Peter; Baliunas, Sallie Bibcode: 1999ApJ...510L.135S Altcode: 1998astro.ph.11114S We explore subtle variations in disk-integrated measurements spanning <~18 yr of stellar surface magnetism by using a newly developed time-frequency gapped wavelet algorithm. We present results based on analysis of the Mount Wilson Ca II H and K emission fluxes in four, magnetically active stars (HD 1835 [G2 V], HD 82885 [G8 IV-V], HD 149661 [K0 V], and HD 190007 [K4 V]) and sensitivity tests using artificial data. When the wavelet basis is appropriately modified (i.e., when the time-frequency resolution is optimized), the results are consistent with the existence of spatially localized and long-lived Ca II features (assumed here as activity regions that tend to recur in narrowly confined latitude bands), especially in HD 1835 and HD 82885. This interpretation is based on the observed persistence of relatively localized Ca II wavelet power at a narrow range of rotational timescales, enduring as long as >~10 yr. Title: Silvery-blue Cloudlets of the Night Authors: Baliunas, S.; Soon, W. Bibcode: 1999WCRp....4....5B Altcode: No abstract at ADS Title: Environmental effects of increased atmospheric carbon dioxide Authors: Soon, W.; Baliunas, S.; Robinson, A.; Robinson, Z. W. Bibcode: 1999ClRe...13..149S Altcode: No abstract at ADS Title: Cold World: Model Analysis shows icy trend Authors: Baliunas, S.; Soon, W. Bibcode: 1998WCRp....4g...6B Altcode: No abstract at ADS Title: Cycles of the Sun. Authors: Soon, W.; Yaskell, S. H. Bibcode: 1998AsNow..12S..15S Altcode: 1998AstNw..12S..15S Edward Maunder noted that the Sun has times of very low sunspot activity. Is the Earth's climate affected by this? Title: The Miner's Canary is Still Singing Authors: Baliunas, S.; Soon, W. Bibcode: 1998WCRp....4c...6B Altcode: No abstract at ADS Title: The summer of our discontent Authors: Baliunas, S.; Soon, W. Bibcode: 1998WCRp....3c..10B Altcode: No abstract at ADS Title: The life and times of Alfonso Nino and family Authors: Baliunas, S.; Soon, W. Bibcode: 1998WCRp....3s..10B Altcode: No abstract at ADS Title: The Milky Way and the clouds of Earth Authors: Baliunas, S.; Soon, W. Bibcode: 1998WCRp....3o..10B Altcode: No abstract at ADS Title: Nature speaks of many things, Of missing flux and butterfly wings Authors: Baliunas, S.; Soon, W. Bibcode: 1998WCRp....3k...6B Altcode: No abstract at ADS Title: Environmental effects of increased atmospheric carbon dioxide Authors: Robinson, A.; Baliunas, S. L.; Soon, W.; Robinson, Z. W. Bibcode: 1998MeSen...3..171R Altcode: No abstract at ADS Title: Activity Cycles in Lower Main Sequence and POST Main Sequence Stars: The HK Project Authors: Baliunas, Sallie L.; Donahue, Robert A.; Soon, Willie; Henry, Gregory W. Bibcode: 1998ASPC..154..153B Altcode: 1998csss...10..153B In 1966, Olin Wilson began making monthly measurements at Mount Wilson Observatory of the relative fluxes in the Ca II H (396.8 nm) and K (393.3 nm) emission cores of approximately 100 stars on or near the lower main sequence. In the late 1970's the Ca II fluxes of nearly 1,000 lower main-sequence stars were sampled, and by 1980 the program had expanded to include near-nightly observations of the stars in Wilson's sample. In 1984 the project was again extended to include the measurement of post-main sequence stars. Today, the project monitors the Ca II fluxes of 400 dwarf and giant stars, with great emphasis on stars close in mass and age to the Sun. The relative Ca II fluxes are thought to closely correspond to the strength and coverage of surface magnetism on such stars. Three general classes of long-term variations of surface magnetism have been seen in lower main sequence and post main sequence stars: 1. substantial fluctuations on time scales of a few years, with little observed repitition of periodicity; 2. nearly-periodic variations with time scales of a decade or more, with some variability in the amplitude, length and shape of each successive cycle; 3. either low-amplitude modulation on time scales of several decades or more, or essentially no long-term variability. In the lower main-sequence stars both the class of long-term variability and the time-averaged level of Ca II fluxes are influenced primarily by a star's angular momentum. In a related matter, most of the detected extra-solar planets (with orbital periods ranging from 3 to 1200 days) orbit sun-like stars with long-term Ca II flux records that are virtually flat (Class 3, above). The lack of variability is an observational bias that enhances detection of extra-solar planets orbiting sun-like stars. Title: Maunder's Minimum: Cycles of the Sun Authors: Soon, W.; Yaskell, S. H. Bibcode: 1998AsNow..12...15S Altcode: 1998AstN...12...15S; 1998AstNw..12...15S No abstract at ADS Title: Wavelet Analysis of Stellar Chromospheric Activity Variations Authors: Frick, P.; Baliunas, S. L.; Galyagin, D.; Sokoloff, D.; Soon, W. Bibcode: 1997ApJ...483..426F Altcode: Observations of chromospheric activity variations for some lower main-sequence stars from the Mount Wilson Observatory's HK project reveal a cyclic behavior comparable to the sunspot cycle. Even in the relatively short interval that they have been observed, those stars show stellar cycles and other features, like grand minima. The quasi-periodic nature of such variations is not completely compatible with the standard Fourier analysis, so we applied a wavelet analysis to study the nature of regularities in the data. We computed wavelet transforms and energy spectra for the 25 yr records of surface magnetic activity in four stars: HD 3651, HD 10700, HD 10476, and HD 201091. We present a modified wavelet technique that is suitable for analysis of data with gaps and find that the common aliasing problems due to the finite length of the observations and irregularly spaced gaps between data can be reduced on both large and small scales by applying this algorithm. Title: Time scales and trends in the central England temperature data (1659-1990): A wavelet analysis Authors: Baliunas, Sallie; Frick, Peter; Sokoloff, Dmitry; Soon, Willie Bibcode: 1997GeoRL..24.1351B Altcode: We have applied the standard wavelet and the adaptive wavelet transform algorithms to the record of the Central England Temperature (CET) from 1659-1990. Peaks in the CET spectra include 7.5±1.0 yr, 14.4±1.0 yr, 23.5±2.0 yr, as well as a previously unreported variation at 102±15 yr. Our wavelet analysis of CET agrees with previous results from Singular Spectrum Analysis (SSA) by Plaut et al. [1995] and gives additional results of variability on longer timescales. The interdecadal and century-scale variability in CET is strongly dependent on the interval of analysis. Estimates of a data trend are also shown to be sensitive to the cutoff timescale of the filter. A cooling of ≈ 0.3°C during 1659-1720 is found relative to the temperatures during the 1800s. The complex time dependence of the actual data cautions against using model-derived representations of natural variability on such long timescales. Title: Magnetic Field and Rotation in Lower Main-Sequence Stars: an Empirical Time-dependent Magnetic Bode's Relation? Authors: Baliunas, Sallie; Sokoloff, Dmitry; Soon, Willie Bibcode: 1996ApJ...457L..99B Altcode: We find a significant correlation between the magnetic and rotational moments for a sample of 112 lower main-sequence stars. The rotational moment is calculated from measurements of the rotation period in most of the stars (not from the projected rotational velocity inferred from Doppler broadening). The magnetic moment is computed from a database of homogeneous measurements of the mean level of Ca II H and K emission fluxes sampled for most of the stars over an interval of 25 yr. The slope connecting the logarithm of the magnetic moment and the logarithm of the rotational moment is about +0.5--0.6, with a Pearson correlation coefficient of about +0.9. The scatter of points from the mean relation has a component that is natural and caused by decade-long surface variability. Title: The Sun-Climate Connection Authors: Baliunas, Sallie; Soon, Willie Bibcode: 1996S&T....92...38B Altcode: No abstract at ADS Title: Interpretation of stellar Ca II activity cycles. Authors: Baliunas, S. L.; Nesme-Ribes, E.; Sokoloff, D.; Soon, W. Bibcode: 1996sube.conf...57B Altcode: Twenty-five year records of Ca II H and K chromospheric emission fluxes measured in lower main-sequence stars reveal surface magnetic activity cycles which are comparable to that of the Sun's. The observed variations can be interpreted in terms of stellar dynamo theory. The authors find the ratio of the period of stellar cycle to the period of stellar axial rotation, Pcyc/Prot, to be representative of a stellar dynamo number, D. Title: Chaos in the Sun: Is Solar Cycle Understandable? How Can Watching Stars Help? Authors: Soon, W. Bibcode: 1996cfas.book..110S Altcode: No abstract at ADS Title: Are Variations in the Length of the Activity Cycle Related to Changes in Brightness in Solar-Type Stars? Authors: Baliunas, Sallie; Soon, Willie Bibcode: 1995ApJ...450..896B Altcode: We compare the average level of chromospheric activity and cycle length for solar-type stars as determined from 25 yr records of Ca II fluxes and from the sunspot record from 1750 to 1990. Both sets of data show an inverse relation between the cycle length and average activity level, with only a minor difference in the slopes. In turn, the amplitude of Ca II variability is positively correlated with the photometric brightness change during an activity cycle. The relationship between those observables provides a physical basis for the close correlation between the length of the sunspot cycle and mean terrestrial temperature over the last few centuries as shown by Friis-Christensen & Lassen.

Solar brightness variations over the last several centuries can be estimated from this relationship by including stars with low Ca II fluxes which, we assume, are in states resembling the phase of solar activity known as the Maunder minimum (circa 1645-1715). Although the value of the slope connecting the mean level of Ca II activity and the cycle length is sensitive to the statistical treatment of the data, a lower limit to the slope can be determined reliably. This lower limit yields an increase of 0.4% of solar brightness from the solar Maunder minimum to the cyclic phase of sunspot activity which immediately followed the Maunder minimum. Title: A Study of Variability in a Sample of G and K Giants Authors: Choi, Hyung-Jin; Soon, Willie; Donahue, Robert A.; Baliunas, Sallie L.; Henry, Gregory W. Bibcode: 1995PASP..107..744C Altcode: Eight years of Ca II surface activity records from Mount Wilson Observatory measured for 12 bright G-K III stars have been analyzed in order to detect periodic variations attributable to rotation. We also present photometric V-band data for these stars from the Fairborn 0.25m Automatic Photometric Telescope (APT) that yielded a photometric period in one case and rms deviations from apparently constant brightness levels for the remaining 11 stars. The Ca II data yielded rotation periods for 10 out of 12 giant stars. We demonstrate that the photometric variability and non-variability of these stars can be predicted from their Rossby numbers calculated from our observed rotation periods and convective turnover times scaled up from the main sequence. (SECTION: Stars) Title: Chromospheric Activity and Age of Solar-Type Stars Authors: Baliunas, S. L.; Donahue, R. A.; Soon, W.; Gilliland, R.; Soderblom, D. R. Bibcode: 1995AAS...186.2109B Altcode: 1995BAAS...27..839B Main-sequence stars near one solar mass show an average level of Ca II H and K emission and rotation that decrease with age. Although the mechanism governing surface magnetism and rotation is not theoretically well-understood, the measurement of rotation or average activity level can yield an estimate of the age of a solar-mass star. Several empirically-determined functions of the decay of rotation and activity have been developed over the last several decades, but more have concentrated on stars much younger than the Sun, whose Ca II activity and rotation have been relatively easy to measure. Observations of the Ca II H and K emission were obtained of solar-mass stars in the old open clusters NGC 752 and M 67 with the KPNO 4-m telescope and HYDRA spectrograph. Those spectra yield a large (>50) smaple of stars close to one solar mass and close to the age of the Sun. Those spectra have been calibrated to the system of measurement of Ca II H and K emission fluxes of nearly 1000 lower main sequence stars obtained at Mount Wilson Observatory. The combined sample of Ca II fluxes yield: (1) a refined calibration of age as a function of activity, using rotation as an indicator of age; (2) the range of Ca II activity at a given age, caused by variations of surface magnetic activity over time scales of decades to centuries; and (3) an estimate of the uncertainty of age inferred from a measurement of the instantaneous activity level.