Variations in the geomagnetic dipole moment during the Holocene and the past 50 kyr

Knudsen, Mads Faurschou; Riisager, Peter; Donadini, F.; Snowball, Ian; Muscheler, Raimund; Korhonen, Kimmo; Pesonen, L. J.

doi:10.1016/j.epsl.2008.04.048

Cited by 132 publications

(151 citation statements)

References 48 publications

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“…5. The first 4500 years are covered by the reconstructions based on the VADM values published by Knudsen et al (2008) and partially by the one based on the VADM presented by Genevey et al (2008). VADM and VDM reconstructions are jointly available from approximately 5000 BC to 1700 AD, which is the period covered by the Korte & Constable (2005) reconstruction.…”

Section: Reconstructions For the Holocenementioning

confidence: 99%

“…Note that we have employed the global reconstructions from Genevey et al (2008). Figure 4 displays the reconstructions of the geomagnetic field intensity, including VADM reconstructions by Knudsen et al (2008) and Genevey et al (2008), and the VDM reconstructions by Genevey et al (2008) and Korte & Constable (2005). Here, we consider this set of reconstructions to estimate the uncertainty of the TSI reconstruction caused by uncertainties in the geomagnetic field.…”

Section: Reconstructions Of the Solar Irradiancementioning

confidence: 99%

“…Panel (a) presents the reconstructions of the TSI. The reconstructions based on the VADM models by Knudsen et al (2008) and Genevey et al (2008) are presented as blue and thin red lines, respectively. The reconstructions based on the VDM models by Korte & Constable (2005) and Genevey et al (2008) are displayed as the gray and cyan lines, respectively.…”

Section: Reconstructions For the Last 3000 Yearsmentioning

confidence: 99%

“…The statistical properties of the TSI reconstructions for the whole Holocene based on the paleomagnetic reconstructions by Knudsen et al (2008), Genevey et al (2008), and Korte & Constable (2005) are presented in panels (a)−(c) of Fig. A.2, respectively.…”

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confidence: 99%

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Evolution of the solar irradiance during the Holocene

Vieira

Solanki

Krivova

et al. 2011

A&A

324

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Context. Long-term records of solar radiative output are vital for understanding solar variability and past climate change. Measurements of solar irradiance are available for only the last three decades, which calls for reconstructions of this quantity over longer time scales using suitable models. Aims. We present a physically consistent reconstruction of the total solar irradiance for the Holocene. Methods. We extend the SATIRE (Spectral And Total Irradiance REconstruction) models to estimate the evolution of the total (and partly spectral) solar irradiance over the Holocene. The basic assumption is that the variations of the solar irradiance are due to the evolution of the dark and bright magnetic features on the solar surface. The evolution of the decadally averaged magnetic flux is computed from decadal values of cosmogenic isotope concentrations recorded in natural archives employing a series of physics-based models connecting the processes from the modulation of the cosmic ray flux in the heliosphere to their record in natural archives. We then compute the total solar irradiance (TSI) as a linear combination of the jth and jth + 1 decadal values of the open magnetic flux. In order to evaluate the uncertainties due to the evolution of the Earth's magnetic dipole moment, we employ four reconstructions of the open flux which are based on conceptually different paleomagnetic models. Results. Reconstructions of the TSI over the Holocene, each valid for a different paleomagnetic time series, are presented. Our analysis suggests that major sources of uncertainty in the TSI in this model are the heritage of the uncertainty of the TSI since 1610 reconstructed from sunspot data and the uncertainty of the evolution of the Earth's magnetic dipole moment. The analysis of the distribution functions of the reconstructed irradiance for the last 3000 years, which is the period that the reconstructions overlap, indicates that the estimates based on the virtual axial dipole moment are significantly lower at earlier times than the reconstructions based on the virtual dipole moment. We also present a combined reconstruction, which represents our best estimate of total solar irradiance for any given time during the Holocene. Conclusions. We present the first physics-based reconstruction of the total solar irradiance over the Holocene, which will be of interest for studies of climate change over the last 11 500 years. The reconstruction indicates that the decadally averaged total solar irradiance ranges over approximately 1.5 W/m 2 from grand maxima to grand minima.

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Section: Reconstructions For the Holocenementioning

confidence: 99%

Section: Reconstructions Of the Solar Irradiancementioning

confidence: 99%

Section: Reconstructions For the Last 3000 Yearsmentioning

confidence: 99%

mentioning

confidence: 99%

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Evolution of the solar irradiance during the Holocene

Vieira

Solanki

Krivova

et al. 2011

A&A

324

279

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“…To be valid, this "paleomagnetic" approach requires a dual averaging of the data, both in time and space, to best smooth out non-dipole field components (for a discussion, see, e.g., Korte & Constable 2005;Genevey et al 2008). Here we consider the two most recent mean VADM curves built in this way, one by Genevey et al (2008), which encompasses the past 3000 years, and a second one by Knudsen et al (2008), which covers the entire Holocene. In addition, and because quite a large number of additional intensity data have recently been collected, an updated mean VADM curve was also produced for the purpose of the present study.…”

Section: Axial Dipole Evolution Over the Past 9000 Yearsmentioning

confidence: 99%

Solar activity during the Holocene: the Hallstatt cycle and its consequence for grand minima and maxima

Usoskin

Gallet

Lopes

et al. 2016

A&A

136

183

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Aims. Cosmogenic isotopes provide the only quantitative proxy for analyzing the long-term solar variability over a centennial timescale. While essential progress has been achieved in both measurements and modeling of the cosmogenic proxy, uncertainties still remain in the determination of the geomagnetic dipole moment evolution. Here we aim at improving the reconstruction of solar activity over the past nine millennia using a multi-proxy approach. Methods. We used records of the 14 C and 10 Be cosmogenic isotopes, current numerical models of the isotope production and transport in Earth's atmosphere, and available geomagnetic field reconstructions, including a new reconstruction relying on an updated archeo-and paleointensity database. The obtained series were analyzed using the singular spectrum analysis (SSA) method to study the millennial-scale trends. Results. A new reconstruction of the geomagnetic dipole field moment, referred to as GMAG.9k, is built for the last nine millennia. New reconstructions of solar activity covering the last nine millennia, quantified in terms of sunspot numbers, are presented and analyzed. A conservative list of grand minima and maxima is also provided. Conclusions. The primary components of the reconstructed solar activity, as determined using the SSA method, are different for the series that are based on 14 C and 10 Be. This shows that these primary components can only be ascribed to long-term changes in the terrestrial system and not to the Sun. These components have therefore been removed from the reconstructed series. In contrast, the secondary SSA components of the reconstructed solar activity are found to be dominated by a common ≈2400-year quasi-periodicity, the so-called Hallstatt cycle, in both the 14 C and 10 Be based series. This Hallstatt cycle thus appears to be related to solar activity. Finally, we show that the grand minima and maxima occurred intermittently over the studied period, with clustering near lows and highs of the Hallstatt cycle, respectively.

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Variations of ¹⁴C around AD 775 and AD 1795 – due to solar activity

Neuhäuser

Neuhäuser²

2015

Astron Nachr

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The motivation for our study is the disputed cause for the strong variation of 14 C around AD 775. Our method is to compare the 14 C variation around AD 775 with other periods of strong variability. Our results are: (a) We see three periods, where 14 C varied over 200 yr in a special way showing a certain pattern of strong secular variation: after a Grand Minimum with strongly increasing 14 C, there is a series of strong short-term drop(s), rise(s), and again drop(s) within 60 yr, ending up to 200 yr after the start of the Grand Minimum. These three periods include the strong rises around BC 671, AD 775, and AD 1795. (b) We show with several solar activity proxies (radioisotopes, sunspots, and aurorae) for the AD 770s and 1790s that such intense rapid 14 C increases can be explained by strong rapid decreases in solar activity and, hence, wind, so that the decrease in solar modulation potential leads to an increase in radioisotope production. (c) The strong rises around AD 775 and 1795 are due to three effects, (i) very strong activity in the previous cycles (i.e. very low 14 C level), (ii) the declining phase of a very strong Schwabe cycle, and (iii) a phase of very weak activity after the strong 14 C rise -very short and/or weak cycle(s) like the suddenly starting Dalton minimum. (d) Furthermore, we can show that the strong change at AD 1795 happened after a pair of two packages of four Schwabe cycles with certain hemispheric leadership (each package consists of two Gnevyshev-Ohl pairs, respectively two Hale-Babcock pairs). We show with several additional arguments that the rise around AD 775 was not that special. We conclude that such large, short-term rises in 14 C (around BC 671, AD 775, and 1795) do not need to be explained by highly unlikely solar super-flares nor other rare events, but by extra-solar cosmic rays modulated due to solar activity variations.

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Variations in the geomagnetic dipole moment during the Holocene and the past 50 kyr

Cited by 132 publications

References 48 publications

Evolution of the solar irradiance during the Holocene

Evolution of the solar irradiance during the Holocene

Solar activity during the Holocene: the Hallstatt cycle and its consequence for grand minima and maxima

Variations of ¹⁴C around AD 775 and AD 1795 – due to solar activity

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Variations in the geomagnetic dipole moment during the Holocene and the past 50 kyr

Cited by 132 publications

References 48 publications

Evolution of the solar irradiance during the Holocene

Evolution of the solar irradiance during the Holocene

Solar activity during the Holocene: the Hallstatt cycle and its consequence for grand minima and maxima

Variations of 14C around AD 775 and AD 1795 – due to solar activity

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Product

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Variations of ¹⁴C around AD 775 and AD 1795 – due to solar activity