Cosmogenic Radionuclides Research Articles

Monitoring of GCR temporal and spatial variations in the inner heliosphere according to cosmogenic radionuclides in fresh-fallen meteorites

The meteorite data on monitoring of the GCR gradient variations at 2-4 AU from the Sun in 1957-2010 testify to the influence of the character of the solar magnetic field inversions during the maximum of the solar cycles on depth of the GCR modulation in the heliosphere.

Spatial and Temporal Variations in Landscape Evolution: Historic and Longer-Term Sediment Flux through Global Catchments

AbstractSediment generation and transport through terrestrial catchments influence soil distribution, geochemical cycling of particulate and dissolved loads, and the character of the stratigraphic record of Earth history. To assess the spatiotemporal variation in landscape evolution, we compare global compilations of stream gauge–derived () and cosmogenic radionuclide (CRN)–derived (predominantly 10Be; ) denudation of catchments (mm/yr) and sediment load of rivers (Mt/yr). Stream gauges measure suspended sediment loads of rivers during several to tens of years, whereas CRNs provide catchment-integrated denudation rates at 102–105-yr time scales. Stream gauge–derived and CRN-derived sediment loads in close proximity to one another (<500 km) exhibit broad similarity ( stream gauge samples; CRN samples). Nearly two-thirds of CRN-derived sediment loads exceed historic loads measured at the same locations (). Excessive longer-term sediment loads likely are a result of longer-term recurrence of large-magnitude ...

宇宙線・地下生成起源核種と希ガス同位体を環境トレーサーとした地下水の滞留時間と地形変化プロセスの推定

宇宙線・地下生成起源核種と希ガス同位体を環境トレーサーとした地下水の滞留時間と地形変化プロセスの推定

AMS measurements of cosmogenic and supernova-ejected radionuclides in deep-sea sediment cores

Samples of two deep-sea sediment cores from the Indian Ocean are analyzed with accelerator mass spectrometry (AMS) to search for traces of recent supernova activity around 2 Myr ago. Here, long-lived radionuclides, which are synthesized in massive stars and ejected in supernova explosions, namely 26Al, 53Mn and 60Fe, are extracted from the sediment samples. The cosmogenic isotope 10Be, which is mainly produced in the Earths atmosphere, is analyzed for dating purposes of the marine sediment cores. The first AMS measurement results for 10Be and 26Al are presented, which represent for the first time a detailed study in the time period of 1.7-3.1 Myr with high time resolution. Our first results do not support a significant extraterrestrial signal of 26Al above terrestrial background. However, there is evidence that, like 10Be, 26Al might be a valuable isotope for dating of deep-sea sediment cores for the past few million years.

Reconstruction and Prediction of Variations in the Open Solar Magnetic Flux and Interplanetary Conditions

Historic geomagnetic activity observations have been used to reveal centennial variations in the open solar flux and the near-Earth heliospheric conditions (the interplanetary magnetic field and the solar wind speed). The various methods are in very good agreement for the past 135 years when there were sufficient reliable magnetic observatories in operation to eliminate problems due to site-specific errors and calibration drifts. This review underlines the physical principles that allow these reconstructions to be made, as well as the details of the various algorithms employed and the results obtained. Discussion is included of: the importance of the averaging timescale; the key differences between “range” and “interdiurnal variability” geomagnetic data; the need to distinguish source field sector structure from heliosphericallyimposed field structure; the importance of ensuring that regressions used are statistically robust; and uncertainty analysis. The reconstructions are exceedingly useful as they provide calibration between the in-situ spacecraft measurements from the past five decades and the millennial records of heliospheric behaviour deduced from measured abundances of cosmogenic radionuclides found in terrestrial reservoirs. Continuity of open solar flux, using sunspot number to quantify the emergence rate, is the basis of a number of models that have been very successful in reproducing the variation derived from geomagnetic activity. These models allow us to extend the reconstructions back to before the development of the magnetometer and to cover the Maunder minimum. Allied to the radionuclide data, the models are revealing much about how the Sun and heliosphere behaved outside of grand solar maxima and are providing a means of predicting how solar activity is likely to evolve now that the recent grand maximum (that had prevailed throughout the space age) has come to an end.

Is there a planetary influence on solar activity?

Context. Understanding the Sun’s magnetic activity is important because of its impact on the Earth’s environment. Direct observations of the sunspots since 1610 reveal an irregular activity cycle with an average period of about 11 years, which is modulated on longer timescales. Proxies of solar activity such as 14 C and 10 Be show consistently longer cycles with well-defined periodicities and varying amplitudes. Current models of solar activity assume that the origin and modulation of solar activity lie within the Sun itself; however, correlations between direct solar activity indices and planetary configurations have been reported on many occasions. Since no successful physical mechanism was suggested to explain these correlations, the possible link between planetary motion and solar activity has been largely ignored. Aims. While energy considerations clearly show that the planets cannot be the direct cause of the solar activity, it remains an open question whether the planets can perturb the operation of the solar dynamo. Here we use a 9400 year solar activity reconstruction derived from cosmogenic radionuclides to test this hypothesis.Methods. We developed a simple physical model for describing the time-dependent torque exerted by the planets on a non-spherical tachocline and compared the corresponding power spectrum with that of the reconstructed solar activity record. Results. We find an excellent agreement between the long-term cycles in proxies of solar activity and the periodicities in the planetary torque and also that some periodicities remain phase-locked over 9400 years.Conclusions. Based on these observations we put forward the idea that the long-term solar magnetic activity is modulated by planetary effects. If correct, our hypothesis has important implications for solar physics and the solar-terrestrial connection.

Combining amino acid racemization and cosmogenic radionuclides to construct a chronological framework for the Clyde Foreland Formation, eastern Canadian Arctic

Combining amino acid racemization and cosmogenic radionuclides to construct a chronological framework for the Clyde Foreland Formation, eastern Canadian Arctic

44Ti, 26Al and 53Mn samples for nuclear astrophysics: the needs, the possibilities and the sources

Exploration of the physics involved in the production of cosmogenic radionuclides requires experiments using the same rare, radioactive nuclei in sufficient quantities. For this work, such exotic radionuclides have been extracted from previously proton-irradiated stainless steel samples using wet chemistry separation techniques. The irradiated construction material has arisen from an extended material research programme at the Paul Scherrer Institute, called STIP (SINQ Target Irradiation Program), where several thousand samples of different materials were irradiated with protons and neutrons of energies up to 570 MeV. In total, 8 × 1017 atoms of 44Ti, ∼1016 atoms of 26Al and ∼1019 atoms of 53Mn are available from selected samples. These materials may now be used to produce targets or radioactive beams for nuclear reaction studies with protons, neutrons and α-particles. The work is part of the ERAWAST initiative (Exotic Radionuclides from Accelerator Waste for Science and Technology), aimed at facilitating new collaborations between the isotope producers and users from different scientific fields including nuclear astrophysics.

The Pingding segment of the Altyn Tagh Fault (91°E): Holocene slip‐rate determination from cosmogenic radionuclide dating of offset fluvial terraces

Morphochronologic slip‐rates on the Altyn Tagh Fault (ATF) along the southern front of the Pingding Shan at ∼90.5°E are determined by cosmogenic radionuclide (CRN) dating of seven offset terraces at two sites. The terraces are defined based upon morphology, elevation and dating, together with fieldwork and high‐resolution satellite analysis. The majority of the CRN model ages fall within narrow ranges (&lt;2 ka) on the four main terraces (T1, T2, T3 and T3′), and allow a detailed terrace chronology. Bounds on the terrace ages and offsets of 5 independent terraces yield consistent slip‐rate estimates. The long‐term slip‐rate of 13.9 ± 1.1 mm/yr is defined at the 95% confidence level, as the joint rate probability distribution of the rate derived from each independent terrace. It falls within the bounds of all the rates defined on the central Altyn Tagh Fault between the Cherchen He (86.4°E) and Akato Tagh (∼88°E) sites. This rate is ∼10 mm/yr less than the upper rate determined near Tura at ∼87°E, in keeping with the inference of an eastward decreasing rate due to progressive loss of slip to thrusts branching off the fault southwards but it is greater than the 9 ± 4 mm/yr rate determined at ∼90°E by GPS surveys and other geodetic short‐term rates defined elsewhere along the ATF. Whether such disparate rates will ultimately be reconciled by a better understanding of fault mechanics, resolved transient deformations during the seismic cycle or by more accurate measurements made with either approach remains an important issue.

Recently active contractile deformation in the forearc of southern Peru

Geomorphic and structural features of southern Peru (14–18°S) provide strong evidence for distributed crustal deformation along range-sub-parallel contractile structures. We use in situ produced cosmogenic radionuclides, in conjunction with field and remote mapping, to determine the ages of geomorphic features and find (1) ancient surfaces (>1Ma) preserved as a result of very low surface erosion rates, (2) young (∼30ka) low-relief pediment surfaces developed during recent landscape modifications, (3) active tectonic structures accommodating compressional stresses, and (4) Pleistocene river incision rates of ∼0.3mm/yr consistent with longer-term rates. In this region of southern Peru, the steep western wedge (trench to arc area) of the Andean margin presently maintains the high topography of the Altiplano through a combination of uplift and contractile deformation along steep east-dipping faults and isostatic responses to the focused removal of large amounts of crustal material through canyon incision.

State of geoscientific research within the lorandite experiment (LOREX)

The LORandite EXperiment (acronym LOREX) is the only geochemical solar neutrino experiment still actively persued. The Tl-mineral lorandite, TlAsS2, occurs in the ore deposit Allchar, Macedonia, close to the border of Greece. The polychronous and polygenetic Sb-As-Tl-Au Allchar deposit was formed by complex physico-chemical processes occurring in a heterogeneous geological environment and by interaction of polyphase hydrothermal fluids with the surrounding magmatic, sedimentary and metamorphic rocks. The genesis of ore mineralization is related to the products of polyphase magmatic activity of Pliocene age (~6.5 to ~1.8 Ma) and its spatial location was controlled by magmatic, structural and lithological factors. The Allchar deposit comprises several orebodies of various shapes, textural-structural characteristics and element associations. Thallium mineralization, which is of significance for the LOREX project, has been proved in two locations: (i) ore body Crven Dol in the northern part and (ii) ore body Centralni Deo in the central part of the Allchar deposit. The age of Tl-mineralization is 4.22 Ma at the Crven Dol locality and 4.31 Ma at Rudina near to the Centralni Deo locality. The present depth of ore mineralization from the present soil surface is about 30 m to 140 m, whereas the paleodepth of its formation is considerably bigger. Using the method of quantitative geomorphological analysis, and AMS- and MS-measurements of cosmogenic radionuclides 26Al, 21Ne, and 3He, the erosion rate has been established to be ~70 m/Ma in the broader area of the Crven Dol locality and ~130 m/Ma in the Centrani Deo of the Allchar deposit. On the basis of these erosion rates and ages of Tl-mineralization, we have calculated the paleo-depth of Lorandite to be ca 180 m ± 35 m to 420 m ± 80 m. Geochemical and mineralogical investigations on lorandite in particular its trace elements (Pb, U, and Th), the quantity of lorandite in the two ore bodies, the geological age and the paleo depth of Tl-mineralization have provided encouraging results and indicate the feasibility of the LOREX project.

A chronological framework for the Clyde Foreland Formation, Eastern Canadian Arctic, derived from amino acid racemization and cosmogenic radionuclides

The most extensive terrestrial outcrops of glacial and glaciomarine deposits in the Eastern Canadian Arctic are exposed in sea cliffs along the Clyde Foreland and Qivitu Peninsula of Baffin Island. Collectively known as the Clyde Foreland Formation (CFF), these stacked deposits record at least seven glacial advances. Despite having been the focus of numerous investigations spanning nearly 50 years, no numerical chronological framework for the age of the deposits has been established. Previous studies relied on biostratigraphy and amino acid racemization (AAR) geochronology and postulated that the oldest units were Late Pliocene to Mid-Pleistocene in age. In this paper, we use a cosmogenic radionuclide isochron approach to determine a minimum age for the burial of a paleosol preserved within the CFF. Abundant palynomorphs in the paleosol are dominated by cool-climate taxa. Combining the paleosol burial age with a compilation of published and new CFF AAR data for marine bivalves Hiatella arctica and Mya truncata, we statistically define seven CFF aminozones and develop a piecewise isoleucine AAR calibration model for Baffin Island. From this, we estimate the minimum age of each aminozone, although the propagation of errors through all calculations produces large uncertainties for each age estimate. The youngest three CFF units, known as the Kogalu, Kuvinilk, and Cape Christian members, were most likely deposited during glaciations in the Mid- to Late-Pleistocene. The paleosol formed prior to 1.15 ± 0.20 Ma, and the underlying aminozones represent sedimentation during Early Pleistocene or latest Pliocene glaciations and record early advances of Laurentide ice across Baffin Island.

A noble gas and cosmogenic radionuclide analysis of two ordinary chondrites from Almahata Sitta

Abstract– We present the results of a noble gas (He, Ne, Ar) and cosmogenic radionuclide (10Be, 26Al, 36Cl) analysis of two chondritic fragments (#A100, L4 and #25, H5) found in the Almahata Sitta strewn field in Sudan. We confirm their earlier attribution to the same fall as the ureilites dominating the strewn field, based on the following findings: (1) both chondrite samples indicate a preatmospheric radius of approximately 300 g cm−2, consistent with the preatmospheric size of asteroid 2008 TC3 that produced the Almahata Sitta strewn field; (2) both have, within error, a 21Ne/26Al‐based cosmic ray exposure age of approximately 20 Ma, identical to the reported ages of Almahata Sitta ureilites; (3) both exhibit hints of ureilitic Ar in the trapped component. We discuss a possible earlier irradiation phase for the two fragments of approximately 10–20 Ma, visible only in cosmogenic 38Ar. We also discuss the approximately 3.8 Ga (4He) and approximately 4.6 Ga (40Ar) gas retention ages, measured in both chondritic fragments. These imply that the two chondrite fragments were incorporated into the ureilite host early in solar system evolution, and that the parent asteroid from which 2008 TC3 is derived has not experienced a large break‐up event in the last 3.8 Ga.

A Note on Solar Cycle Length During the Medieval Climate Anomaly

The growing interest in the "Medieval Climate Anomaly" (MCA) and its possible link to anomalous solar activity has prompted new reconstructions of solar activity based on cosmogenic radionuclides. These proxies however do not sufficiently constrain the Total Solar Irradiance (TSI) range, and are often defined at low temporal resolution, inadequate to infer the solar cycle length (SCL). We have reconstructed the SCL (average duration of 10.72 \pm 0.20 years) during the MCA using observations of naked-eye sunspot and aurora sightings. Thus, solar activity was most probably not exceptionally intense, supporting the view that internal variability of the coupled ocean-atmosphere system was the main driver of MCA.

Determination of the mean aerosol residence times in the atmosphere and additional 210Po input on the base of simultaneous determination of 7Be, 22Na, 210Pb, 210Bi and 210Po in urban air.

The significant differences in the activities of 210Pb, 210Bi, 210Po and cosmogenic 7Be and 22Na radionuclides in the urban aerosol samples collected in the summers 2010 and 2011 in the Lodz city of Poland were observed. Simultaneous measurement of these radionuclides, after a simple modification of the one compartment model, allows us to calculate both: the corrected aerosol residence times in the troposphere (1 ÷ 25 days) and in the lower stratosphere (103 ÷ 205 days). The relative input of the additional sources (beside of the 222Rn decay in the air) to the total activity concentrations of 210Pb, 210Bi and 210Po radionuclides in the urban air, plays a substantial role (up to 97% of the total activity) only in the case of 210Po.

Non-destructive gamma-spectrometry analysis of cosmogenic radionuclides in fragments of the Košice meteorite

Results of analysis of cosmogenic radionuclides (57,58,60Co, 54Mn, 46Sc, 22Na, 48V and 26Al) in fragments of the Kosice meteorite are presented and discussed. Analyses were carried out using a low-level HPGe-spectrometer placed in a lead-iron-copper shield. Twelve meteorite fragments were available for the analysis with masses from 27 to 2,163 g. The lowest massic activities were observed for 46Sc (down to 0.1 mBq/g), and the highest for 22Na (up to 2 mBq/g). The measured radionuclide activities showed differences between fragments, as indicated mainly by the 60Co data, which were caused by different positions of meteorite fragments from the center of the meteorite body.

Integrated study of the thermoluminescence, noble gases, tracks, and radionuclides in the fresh-fallen Ash Creek L6 and Tamdakht H5 chondrites

Thermoluminescence, noble gases, and the tracks of iron-group elements and cosmogenic radionuclides of various half-lives were examined in the fresh-fallen Ash Creek (L6) and Tamdakht (H5) chondrites. The experimental information thus obtained and theoretical simulations were used to study the shock-thermal and exposure histories of the chondrites, to evaluate their preatmospheric sizes and masses, values of ablation, the sizes of their orbits, and to monitor the distribution and variations in cosmic radiation in the heliosphere during the transitional period of minimum between solar cycles 23 and 24.

10Be in Ice Cores and 14C in Tree Rings: Separation of Production and Climate Effects

Cosmogenic radionuclides are more and more used in solar activity reconstructions. However, the cosmogenic radionuclide signal also contains a climate component. It is therefore crucial to eliminate the climate information to allow a better interpretation of the reconstructed solar activity indices. In this paper the method of principal components is applied to 10Be data from two ice cores from opposite hemispheres as well as to 14C data from tree rings. The analysis shows that these records are dominated by a common signal which explains about 80% of the variance on multi decadal to multi millennial time scales, reflecting their common production rate. The second and third components are significantly different for 14C and 10Be. They are interpreted as system effects introduced by the transport of 10Be and 14C from the atmosphere where they are produced to the respective natural archives where they are stored. Principal component analysis improves significantly extraction of the production signal from the cosmogenic isotope data series, which is more appropriate for astrophysical and terrestrial studies.

Centennial to millennial geomagnetic field variations

Reconstructions of the geomagnetic field in the past represent a useful tool not only to investigate the geodynamo process, but also to estimate the effect of geomagnetic shielding for any studies on cosmogenic radionuclides and galactic cosmic rays. A number of new millennial-scale geomagnetic field reconstructions have been published over the last years, based on improved global archeo- and paleomagnetic data compilations. Here we review several spherical harmonic models and compare their dipole field predictions to reconstructions based on virtual axial dipole moments and virtual geomagnetic poles. Dipole intensity estimates from cosmogenic radionuclide production records, with suitable filtering to minimise the solar influence, have also been included in the comparison to provide independent information about variations in the strength of the geomagnetic field. However, due to differences among geomagnetic models and between 14C and 10Be production records this comparison is fairly inconclusive with respect to multi-centennial variations. Different geomagnetic dipole tilt reconstructions agree well for much of the Holocene, but dipole moment estimates still differ substantially. Recent spherical harmonic models for the past 3 and 10 kyrs have improved considerably compared to earlier versions. Nevertheless at present we recommend to test if any interpretation depends on the choice of model.

Nuclear Data from AMS &amp; Nuclear Data for AMS – some examples

We summarize some recent cross-section measurements using accelerator mass spectrometry (AMS). AMS represents an ultra-sensitive technique for measuring a limited, but steadily increasing number of longer-lived radionuclides. This method implies a two-step procedure with sample activation and subsequent AMS measurement. Applications include nuclear astrophysics, nuclear technology (nuclear fusion, nuclear fission and advanced reactor concepts and radiation dose estimations). A series of additional applications involves cosmogenic radionuclides in environmental, geological and extraterrestrial studies. There is a lack of information for a list of nuclides, as pointed out by nuclear data requests. An overview of some recent measurements is given and the method is illustrated for some specific neutron-induced reactions.