We have developed a comprehensive catalog of the variable differential rotation measured near the... more We have developed a comprehensive catalog of the variable differential rotation measured near the solar photosphere. This catalog includes measurements of these flows obtained using several techniques: direct Doppler, granule tracking, magnetic pattern tracking, global helioseismology as well as both time-distance and ring-diagram methods of local helioseismology. We highlight historical differential rotation measurements to provide context and thereafter provide a detailed comparison of the MDI-HMI-GONG-Mt. Wilson overlap period (April 2010-Jan 2011) and investigate the differences between velocities obtained from different techniques and attempt to explain discrepancies. A comparison of the rotation rate obtained by magnetic pattern tracking with the rotation rates obtained using local and global helioseismic techniques shows that magnetic pattern tracking measurements correspond to helioseismic flows located at a depth of 25 to 28 Mm. In addition, we show the torsional oscillatio...
We used historical synoptic data the Mount Wilson Observatory (MWO) to study long-term changes in... more We used historical synoptic data the Mount Wilson Observatory (MWO) to study long-term changes in sunspot magnetic field strengths over the period of 1920-1959. By selecting sunspots with the strongest field strength for each observing day, we find that the average field strengths in sunspots vary with solar cycle with amplitude of a few hundred Gauss. The data show no statistically significant long-term trend over the period of about 40 years covered by these observations. We also find that the fractional distribution of sunspots changes from cycle to cycle. From Cycle 15 to Cycle 19, MWO data show a steady increase in fraction of sunspots with weaker field strengths (<1000 G), while the fraction of sunspots with strongest field strengths (>3000 G) steadily decreases. The fraction of sunspots with field strengths between 1000-3000 Gauss does not change in any systematic way. In contract, the fractional distribution of sunspots by their area (i.e., small, intermediate, and lar...
The total solar irradiance (TSI) is considered one of the main factors determining the terrestria... more The total solar irradiance (TSI) is considered one of the main factors determining the terrestrial climate, and its variations are included in many numerical models evaluating the effects of natural as compared to anthropogenic factors of climate change. For the purposes of climate change, it is important to estimate both past and future TSI variations, which are caused by variations of the solar magnetic fields. Various proxies are used for reconstructing the long term evolution of TSI, which have some inevitable limitations leading to big uncertainties. We suggest an independent proxy-geomagnetic activity records, and present a reconstruction of TSI which supports higher long term TSI variability than generally accepted, and a prediction for a decrease in TSI in the following cycles, which can be taken into account in models of the expected future climate variability.
The possible application of temperature reconstructions based on measurement of the 40Ar concentr... more The possible application of temperature reconstructions based on measurement of the 40Ar concentration in ice layers of the Greenland ice sheet to study past solar activity with radiocarbon data is considered. The rate of 14С production and the heliosphere modulation potential from the 2nd millennium B.C. to the middle of the 18th century A.D. is reconstructed with allowance for the Earth’s climate variation. The temperature reconstruction based on the 40Ar content in the annual ice layers of Greenland revealed two global minima of solar activity with duration of ~200 years during the cold Sub-Atlantic period, which lasted on the Earth from 900 B.C. to 300 B.C. This suggests that solar-activity variation can influence climate change.
Traditional indices, which we call apparent indices, describe the current state of solar activity... more Traditional indices, which we call apparent indices, describe the current state of solar activity and are very important for understanding the influence of the Sun on Earth. To study the productivity of the solar dynamo, however, we need a different index that would describe each magnetic region once – at the moment of its maximum area. We refer to such indices as generative ones. The aim of this work is to produce such a generative series improving the procedure by Nagovitsyn et al. (Geomagn. Aeron. 58, 1170, 2018). We use sunspot group data from two archives – Royal Greenwich Observatory (1875 – 1976) and Kislovodsk Mountain Astronomical Station (1955 – 2019). We produce generative indices with annual values of sunspot group areas $A$ , and counts of sunspot groups $C$ . Unified 145-year series of these indices were compiled. We study the characteristics of the indices $A$ and $C$ , and indices derived from them for two sunspot group populations – large long-living groups and small short-living groups according to Nagovitsyn and Pevtsov (Astrophys. J. 833, 94, 2016) – for the northern and southern hemispheres separately. We find a 50-year variation in several indices on the 145-year interval, and detect a similar phase variation in the north-south asymmetry taken with the opposite sign. Perhaps this indicates the existence of another secular cycle along with the Gleissberg cycle on the Sun. The obtained series of indices $A$ and $C$ can be useful for studying the long-term properties of the solar dynamo.
Data on the content of the 14C cosmogenic isotope in tree rings, which were obtained as a result ... more Data on the content of the 14C cosmogenic isotope in tree rings, which were obtained as a result of laboratory measurements, are often used when solar activity (SA) is reconstructed for previous epochs, in which direct observations are absent. However, these data contain information not only about SA variations but also about changes in the Earth climatic parameters, such as the global temperature and the CO2 content in the Earth’s atmosphere. The effect of these variations on the 14C isotope content in different natural reservoirs after the last glacial termination to the middle of the Holocene is considered. The global temperature and the CO2 content increased on this time interval. In this case the 14C absolute content in the atmosphere increased on this time interval, even though the 14С to 12С isotope concentration ratio (as described by the Δ14С parameter) decreased. These variations in the radiocarbon absolute content can be caused by its redistribution between natural reservoirs. It has been indicated that such a redistribution is possible only when the rate of carbon exchange between the ocean and atmosphere depends on temperature. The values of the corresponding temperature coefficient for the 17–10 ka BC time interval, which make it possible to describe the carbon redistribution between the ocean and atmosphere, have been obtained.
A new series of yearly-mean relative sunspot numbers SN2 that has been extrapolated into the past... more A new series of yearly-mean relative sunspot numbers SN2 that has been extrapolated into the past (to 1610) is presented. The Kislovodsk series with the scale factor b = 1.0094 ± 0.0059 represents a reasonable continuation of the mean-monthly and mean-yearly total sunspot areas of the Greenwich series after 1976. The second maximum of the 24th solar-activity cycle was not anomalously low, and was no lower than 6 of the past 13 cycles. A series A2 of values for the total sunspot area in 1610–2015 has been constructed, and is complementary to new versions of the series of the relative number of sunspots SN2 and the number of sunspot groups GN2. When needed, this series can be reduced to yield a quantity having a clear physical meaning—the spot absolute magnetic flux ΦΣ(t)[Mx] = 2.16 × 1019A(t) [mvh]. The maximum sunspot area during the Maunder minimum is much higher in the new series compared to the previous version. This at least partially supports the validity of arguments that cast doubt on the anomalously low ampltude of the solar cycles during the Maunder minimum that has been assumed by many researchers earlier.
We briefly review the history of observations of magnetic fields on the Sun, and describe early m... more We briefly review the history of observations of magnetic fields on the Sun, and describe early magnetograps for full disk measurements. Changes in instruments and detectors, the cohort of observers, the knowledge base etc may result in non-uniformity of the long-term synoptic datasets. Still, such data are critical for detecting and understanding the long-term trends in solar activity. We demonstrate the value of historical data using studies of active region tilt (Joy’s law) and the evolution of polar field and its reversal. Using the longest dataset of sunspot field strength measurements from Mount Wilson Observatory (1917-present) supplemented by shorter datasets from Pulkovo (1956–1997) and Crimean (1956-present) observatories we demonstrate that the magnetic properties of sunspots did not change over the last hundred years. We also show that the relationship between the sunspot area and its magnetic flux can be used to extend the studies of magnetic field in sunspots to period...
We have developed a comprehensive catalog of the variable differential rotation measured near the... more We have developed a comprehensive catalog of the variable differential rotation measured near the solar photosphere. This catalog includes measurements of these flows obtained using several techniques: direct Doppler, granule tracking, magnetic pattern tracking, global helioseismology as well as both time-distance and ring-diagram methods of local helioseismology. We highlight historical differential rotation measurements to provide context and thereafter provide a detailed comparison of the MDI-HMI-GONG-Mt. Wilson overlap period (April 2010-Jan 2011) and investigate the differences between velocities obtained from different techniques and attempt to explain discrepancies. A comparison of the rotation rate obtained by magnetic pattern tracking with the rotation rates obtained using local and global helioseismic techniques shows that magnetic pattern tracking measurements correspond to helioseismic flows located at a depth of 25 to 28 Mm. In addition, we show the torsional oscillatio...
We used historical synoptic data the Mount Wilson Observatory (MWO) to study long-term changes in... more We used historical synoptic data the Mount Wilson Observatory (MWO) to study long-term changes in sunspot magnetic field strengths over the period of 1920-1959. By selecting sunspots with the strongest field strength for each observing day, we find that the average field strengths in sunspots vary with solar cycle with amplitude of a few hundred Gauss. The data show no statistically significant long-term trend over the period of about 40 years covered by these observations. We also find that the fractional distribution of sunspots changes from cycle to cycle. From Cycle 15 to Cycle 19, MWO data show a steady increase in fraction of sunspots with weaker field strengths (<1000 G), while the fraction of sunspots with strongest field strengths (>3000 G) steadily decreases. The fraction of sunspots with field strengths between 1000-3000 Gauss does not change in any systematic way. In contract, the fractional distribution of sunspots by their area (i.e., small, intermediate, and lar...
The total solar irradiance (TSI) is considered one of the main factors determining the terrestria... more The total solar irradiance (TSI) is considered one of the main factors determining the terrestrial climate, and its variations are included in many numerical models evaluating the effects of natural as compared to anthropogenic factors of climate change. For the purposes of climate change, it is important to estimate both past and future TSI variations, which are caused by variations of the solar magnetic fields. Various proxies are used for reconstructing the long term evolution of TSI, which have some inevitable limitations leading to big uncertainties. We suggest an independent proxy-geomagnetic activity records, and present a reconstruction of TSI which supports higher long term TSI variability than generally accepted, and a prediction for a decrease in TSI in the following cycles, which can be taken into account in models of the expected future climate variability.
The possible application of temperature reconstructions based on measurement of the 40Ar concentr... more The possible application of temperature reconstructions based on measurement of the 40Ar concentration in ice layers of the Greenland ice sheet to study past solar activity with radiocarbon data is considered. The rate of 14С production and the heliosphere modulation potential from the 2nd millennium B.C. to the middle of the 18th century A.D. is reconstructed with allowance for the Earth’s climate variation. The temperature reconstruction based on the 40Ar content in the annual ice layers of Greenland revealed two global minima of solar activity with duration of ~200 years during the cold Sub-Atlantic period, which lasted on the Earth from 900 B.C. to 300 B.C. This suggests that solar-activity variation can influence climate change.
Traditional indices, which we call apparent indices, describe the current state of solar activity... more Traditional indices, which we call apparent indices, describe the current state of solar activity and are very important for understanding the influence of the Sun on Earth. To study the productivity of the solar dynamo, however, we need a different index that would describe each magnetic region once – at the moment of its maximum area. We refer to such indices as generative ones. The aim of this work is to produce such a generative series improving the procedure by Nagovitsyn et al. (Geomagn. Aeron. 58, 1170, 2018). We use sunspot group data from two archives – Royal Greenwich Observatory (1875 – 1976) and Kislovodsk Mountain Astronomical Station (1955 – 2019). We produce generative indices with annual values of sunspot group areas $A$ , and counts of sunspot groups $C$ . Unified 145-year series of these indices were compiled. We study the characteristics of the indices $A$ and $C$ , and indices derived from them for two sunspot group populations – large long-living groups and small short-living groups according to Nagovitsyn and Pevtsov (Astrophys. J. 833, 94, 2016) – for the northern and southern hemispheres separately. We find a 50-year variation in several indices on the 145-year interval, and detect a similar phase variation in the north-south asymmetry taken with the opposite sign. Perhaps this indicates the existence of another secular cycle along with the Gleissberg cycle on the Sun. The obtained series of indices $A$ and $C$ can be useful for studying the long-term properties of the solar dynamo.
Data on the content of the 14C cosmogenic isotope in tree rings, which were obtained as a result ... more Data on the content of the 14C cosmogenic isotope in tree rings, which were obtained as a result of laboratory measurements, are often used when solar activity (SA) is reconstructed for previous epochs, in which direct observations are absent. However, these data contain information not only about SA variations but also about changes in the Earth climatic parameters, such as the global temperature and the CO2 content in the Earth’s atmosphere. The effect of these variations on the 14C isotope content in different natural reservoirs after the last glacial termination to the middle of the Holocene is considered. The global temperature and the CO2 content increased on this time interval. In this case the 14C absolute content in the atmosphere increased on this time interval, even though the 14С to 12С isotope concentration ratio (as described by the Δ14С parameter) decreased. These variations in the radiocarbon absolute content can be caused by its redistribution between natural reservoirs. It has been indicated that such a redistribution is possible only when the rate of carbon exchange between the ocean and atmosphere depends on temperature. The values of the corresponding temperature coefficient for the 17–10 ka BC time interval, which make it possible to describe the carbon redistribution between the ocean and atmosphere, have been obtained.
A new series of yearly-mean relative sunspot numbers SN2 that has been extrapolated into the past... more A new series of yearly-mean relative sunspot numbers SN2 that has been extrapolated into the past (to 1610) is presented. The Kislovodsk series with the scale factor b = 1.0094 ± 0.0059 represents a reasonable continuation of the mean-monthly and mean-yearly total sunspot areas of the Greenwich series after 1976. The second maximum of the 24th solar-activity cycle was not anomalously low, and was no lower than 6 of the past 13 cycles. A series A2 of values for the total sunspot area in 1610–2015 has been constructed, and is complementary to new versions of the series of the relative number of sunspots SN2 and the number of sunspot groups GN2. When needed, this series can be reduced to yield a quantity having a clear physical meaning—the spot absolute magnetic flux ΦΣ(t)[Mx] = 2.16 × 1019A(t) [mvh]. The maximum sunspot area during the Maunder minimum is much higher in the new series compared to the previous version. This at least partially supports the validity of arguments that cast doubt on the anomalously low ampltude of the solar cycles during the Maunder minimum that has been assumed by many researchers earlier.
We briefly review the history of observations of magnetic fields on the Sun, and describe early m... more We briefly review the history of observations of magnetic fields on the Sun, and describe early magnetograps for full disk measurements. Changes in instruments and detectors, the cohort of observers, the knowledge base etc may result in non-uniformity of the long-term synoptic datasets. Still, such data are critical for detecting and understanding the long-term trends in solar activity. We demonstrate the value of historical data using studies of active region tilt (Joy’s law) and the evolution of polar field and its reversal. Using the longest dataset of sunspot field strength measurements from Mount Wilson Observatory (1917-present) supplemented by shorter datasets from Pulkovo (1956–1997) and Crimean (1956-present) observatories we demonstrate that the magnetic properties of sunspots did not change over the last hundred years. We also show that the relationship between the sunspot area and its magnetic flux can be used to extend the studies of magnetic field in sunspots to period...
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Papers by Yury Nagovitsyn