Understanding the temporal variation of cosmic radiation and solar activity during the Holocene is essential for studies of the solar-terrestrial relationship. Cosmic-ray produced radionuclides, such ...as 10Be and 14C which are stored in polar ice cores and tree rings, offer the unique opportunity to reconstruct the history of cosmic radiation and solar activity over many millennia. Although records from different archives basically agree, they also show some deviations during certain periods. So far most reconstructions were based on only one single radionuclide record, which makes detection and correction of these deviations impossible. Here we combine different 10Be ice core records from Greenland and Antarctica with the global 14C tree ring record using principal component analysis. This approach is only possible due to a new high-resolution 10Be record from Dronning Maud Land obtained within the European Project for Ice Coring in Antarctica in Antarctica. The new cosmic radiation record enables us to derive total solar irradiance, which is then used as a proxy of solar activity to identify the solar imprint in an Asian climate record. Though generally the agreement between solar forcing and Asian climate is good, there are also periods without any coherence, pointing to other forcings like volcanoes and greenhouse gases and their corresponding feedbacks. The newly derived records have the potential to improve our understanding of the solar dynamics and to quantify the solar influence on climate.
The Sun is the main driver of Earth's climate, yet the Sun's role in forcing decadal-to-centennial climate variations has remained controversial, especially in the context of understanding ...contributions of natural climate forcings to continuing global warming. To properly address long-term fingerprints of solar forcing on climate, long-term, very high-resolution, globally distributed climate proxy records are necessary. In this study we compile and evaluate a near global collection of annually-resolved tree-ring-based climate proxies spanning the past two millennia. We statistically assess these records in both the time and frequency domains for solar forcing (i.e. Total Solar Irradiance; TSI) and climate variability with emphasis on centennial time scales. Analyses in the frequency domain indicate significant periodicities in the 208-year frequency band, corresponding to the DeVries cycle of solar activity. Additionally, results from Superposed Epoch Analysis (SEA) point toward a possible solar contribution in the temperature and precipitation series. However, solar-climate associations remain weak, with for example no clear linkage distinguishable in the southwestern United States drought records at centennial time scales. Other forcing factors, namely volcanic activity, appear to mask the solar signal in space and time. To investigate this hypothesis, we attempted to extract volcanic signals from the temperature proxies using a statistical modelling approach. Wavelet analysis of the volcanic contribution reveals significant periodicities near the DeVries frequency during the Little Ice Age (LIA). This remarkable and coincidental superposition of the signals makes it very difficult to separate volcanic and solar forcing during the LIA. Nevertheless, the "volcano free" temperature records show significant periodicities near the DeVries periodicity during the entire past 1500years, further pointing to solar mechanisms and emphasising the need for solar related studies in the absence of strong multi-decadal volcanic forcing.
Strength and structure of the Earth's magnetic field control the deflection of energetic charged particles of solar and cosmic origin. Therefore variations of the geomagnetic field occurring on ...geological timescales affect the penetration of charged particles into the atmosphere. During solar proton events (SPEs) the flux of high‐energy protons from the Sun is markedly increased. In order to investigate the impact of SPEs on the middle atmospheric ozone on longer timescales, two‐dimensional atmospheric chemistry and transport simulations have been performed using simulated time series of SPEs covering 200 years. Monte Carlo calculations were used to obtain ionization rates, which were then applied to the atmosphere under the consideration of different shielding properties of the geomagnetic field. The present‐day magnetic field configuration and four other scenarios were analyzed. For the first time, field configurations representing possible realistic situations during reversals have been investigated with respect to SPE‐caused ozone losses. With decreasing magnetic field strength the impacts on the ozone are found to significantly increase especially in the Southern Hemisphere, and subsequently, the flux of harmful ultraviolet radiation increases at the Earth's surface. The ozone destructions are most pronounced in the polar regions, and for some field configurations they exceed the values of ozone hole situations after large SPEs. In contrast to ozone holes the depletions due to SPEs are not restricted to winter and spring times but persist into polar summer.
Extreme space weather conditions pose significant problems for standard space weather models, which are available for some limited realistic parameter ranges. As a good example, anomalous spikes of ...cosmic ray induced 10Be have been found during the Maunder Minimum (AD1645–1715) at the qA negative solar minima, which cannot be quantitatively explained by standard drift theories of cosmic ray transport alone. Such an extreme amplification of solar cycle modulation of cosmic rays is presumably related to the altered condition of heliospheric environment at the prolonged sunspot disappearance, providing a clue for comprehensive understandings of long‐term changes in heliospheric environment, solar cycle modulation of cosmic rays, and the maximal range of incident cosmic ray flux that is very important for our practical space activities. Model sophistication to achieve precise forecast of such extreme condition of the heliosphere and the incoming cosmic ray flux is also of urgent need as the Sun is currently showing a tendency toward lower activity. Here we show that the cosmic ray spikes found at the Maunder Minimum may be explained by the contribution from the cross‐sector transport mechanism working in the heliosheath where cosmic ray particles effectively drift across stacked magnetic sectors due to the larger cyclotron radius than the distance between the sectors. Based on the new interpretation of the 10Be record, we clarify potentially important problems for space weather modelers to help with more realistic modeling of the heliosphere during periods of extremely weak solar activity, such as the Maunder Minimum.
Key Points
Anomalous spikes of 10Be are found during the Maunder Minimum
The spikes cannot be explained by drift theories of cosmic ray transport alone
The spikes are explained by cross‐sector mechanism working in the heliosheath
Recently, a new low‐noise record of solar activity has been reconstructed for the past 9400 years by combining two 10Be records from Greenland and Antarctica with 14C from tree rings Steinhilber et ...al., . This record confirms earlier results, namely, that the Sun has varied with distinct periodicities in the past. We present a prediction of mean solar magnetic activity averaged over 22 years for the next 500 years mainly based on the spectral information derived from the solar activity record of the past. Assuming that the Sun will continue to vary with the same periodicities for the next centuries, we extract the spectral information from the past and apply it to two different methods to predict the future of solar magnetic activity. First, the two methods are tested by predicting past changes. Our methods are able to predict periods of high and low solar activities for a few centuries in the past. However, they are less successful in predicting the correct amplitude. Then, the methods were used to predict the period 2000–2500. Both methods predict a period of low activity around 2100 A.D. Between 2100 and 2350 A.D., the results are inconsistent regarding the duration of the low‐activity state in 2100 A.D. and the level of activity until 2250 A.D. Around 2250 A.D., both methods predict a period of moderate activity. After 2350 A.D., both methods point to a period of high activity. The period of high activity will end around 2400 A.D. and will be followed by a period of moderate activity.
Key PointsSuccessful predication of solar ‐activity in the pastPrediction of solar activity until 2500ADTwo models give similar results
The Heliosphere in Time McCracken, Ken; Beer, Juerg; Steinhilber, Friedhelm ...
Space science reviews,
06/2013, Letnik:
176, Številka:
1-4
Journal Article
Recenzirano
The paleo-cosmic ray records are used to study the properties of the heliosphere and solar processes over the past 9300 years. They show that both varied greatly over that time, ranging from ∼26 ...“Grand Minima” of duration 50–100 yr when the Sun was inactive, to periods similar to the past 50 years of strong solar activity. This shows that the detailed information regarding the heliosphere gained during the “space era” represents an extreme case, and is not representative of the majority of the past 9300 yr. The data confirm that the 11 and 22-year cycles of solar activity continued through the Spoerer and Maunder Grand Minima. Throughout the 9300 yr interval, “Grand Minima” usually occurred in groups of 2 to 4, similar to the group of four that occurred in the interval 1000–1800 AD. The groups are separated by ∼1000 yr intervals without Grand Minima. Frequency spectra of the full 9300 yr record show that the heliospheric and solar phenomena exhibit >10 well-defined and persistent periodicities. We speculate that the solar dynamo exhibits a 2300 yr periodicity, wherein it alternates between two different states of activity. In the first (∼800 yr duration) solar activity weakens greatly every 100–200 yr resulting in a sequence of Grand Minima, while in the other, the solar dynamo suffers smaller changes; the centenary scale solar and heliospheric changes are smaller, being similar to those that occurred in the interval 1890–1910. The paleo-cosmic ray evidence suggests that the Sun has now entered this more uniform period of activity, following the sequence of Grand Minima (Wolf, Spoerer, Maunder, and Dalton) that occurred between 1000 and 1800 AD.
We have reconstructed the interplanetary magnetic field (IMF), its radial component, and the open solar magnetic flux using the solar modulation potential derived from cosmogenic 10Be radionuclide ...data for a period covering the past 9300 years. Reconstructions using the assumption of both constant and variable solar wind speeds yielded closely similar results. During the Maunder Minimum, the strength of the IMF was approximately 2 nT compared to a mean value of 6.6 nT for the past 40 years, corresponding to an increase of the open solar magnetic flux of about 350%. We examine four cycles of the Hallstatt periodicity in the IMF with a mean period of ∼2250 years and an amplitude of ∼0.75 nT. Grand solar minima have largely occurred in clusters during the Hallstatt cycle minima around the years −5300, −3400, −1100, and +1500 A.D. The last cluster includes the Dalton, Maunder, and Spörer minima. We predict that the next such cluster will occur in about 1500 years. The long‐term IMF has varied between ∼2 nT and ∼8 nT and does not confirm a proposed floor (lower limit). There is a slowly changing long‐term trend of amplitude 1.5 nT, with a minimum around the year −4600 and a maximum around 0 A.D. that may be of solar origin but which also may be due to unknown long‐term changes in the atmospheric effects or geomagnetic field intensity.
The Sun is the main driver of Earth's climate, yet the Sun's role in forcing decadal-to-centennial climate variations has remained controversial, especially in the context of understanding ...contributions of natural climate forcings to continuing global warming. To properly address long-term fingerprints of solar forcing on climate, long-term, very high-resolution, globally distributed climate proxy records are necessary. In this study we compile and evaluate a near global collection of annually-resolved tree-ring-based climate proxies spanning the past two millennia. We statistically assess these records in both the time and frequency domains for solar forcing (i.e. Total Solar Irradiance; TSI) and climate variability with emphasis on centennial time scales. Analyses in the frequency domain indicate significant periodicities in the 208-year frequency band, corresponding to the DeVries cycle of solar activity. Additionally, results from Superposed Epoch Analysis (SEA) point toward a possible solar contribution in the temperature and precipitation series. However, solar-climate associations remain weak, with for example no clear linkage distinguishable in the southwestern United States drought records at centennial time scales. Other forcing factors, namely volcanic activity, appear to mask the solar signal in space and time. To investigate this hypothesis, we attempted to extract volcanic signals from the temperature proxies using a statistical modelling approach. Wavelet analysis of the volcanic contribution reveals significant periodicities near the DeVries frequency during the Little Ice Age (LIA). This remarkable and coincidental superposition of the signals makes it very difficult to separate volcanic and solar forcing during the LIA. Nevertheless, the “volcano free” temperature records show significant periodicities near the DeVries periodicity during the entire past 1500
years, further pointing to solar mechanisms and emphasising the need for solar related studies in the absence of strong multi-decadal volcanic forcing.
► Solar and volcanic fingerprints in worldwide distributed tree-ring chronologies. ► Volcanic and solar forcing are important during the Little Ice Age (LIA). ► Separation of a solar and volcanic forcing signals is difficult during the LIA. ► Solar signal detectable at the DeVries frequency during the past 2000
years. ► Need for solar related studies in the absence of multi-decadal volcanic forcing.
Extreme space weather conditions pose significant problems for standard space weather models, which are available for some limited realistic parameter ranges. As a good example, anomalous spikes of ...cosmic ray induced
10
Be have been found during the Maunder Minimum (AD1645–1715) at the qA negative solar minima, which cannot be quantitatively explained by standard drift theories of cosmic ray transport alone. Such an extreme amplification of solar cycle modulation of cosmic rays is presumably related to the altered condition of heliospheric environment at the prolonged sunspot disappearance, providing a clue for comprehensive understandings of long‐term changes in heliospheric environment, solar cycle modulation of cosmic rays, and the maximal range of incident cosmic ray flux that is very important for our practical space activities. Model sophistication to achieve precise forecast of such extreme condition of the heliosphere and the incoming cosmic ray flux is also of urgent need as the Sun is currently showing a tendency toward lower activity. Here we show that the cosmic ray spikes found at the Maunder Minimum may be explained by the contribution from the cross‐sector transport mechanism working in the heliosheath where cosmic ray particles effectively drift across stacked magnetic sectors due to the larger cyclotron radius than the distance between the sectors. Based on the new interpretation of the
10
Be record, we clarify potentially important problems for space weather modelers to help with more realistic modeling of the heliosphere during periods of extremely weak solar activity, such as the Maunder Minimum.
Key Points
Anomalous spikes of 10Be are found during the Maunder Minimum
The spikes cannot be explained by drift theories of cosmic ray transport alone
The spikes are explained by cross‐sector mechanism working in the heliosheath
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