V. A. Alexeev

Russian Academy of Sciences | RAS · Vernadsky Institute of Geochemistry and Analytical Chemistry

Abstract—The paper presents data obtained on the production rates of cosmogenic radionuclides of different half-life in 42 chondrites that fell in 1959–2016. A quantitative approach is developed for using cosmogenic radionuclides as natural detectors of galactic cosmic rays (GCR) for different time periods and for different heliocentric distances....

This work was performed within the OLYMPIA experiment on the study of tracks of heavy and superheavy cosmic ray nuclei in olivine crystals from Marjalahti and Eagle Station pallasites. Depth distributions of the track formation rate for heavy cosmic ray nuclei in olivine crystals from pallasites of different pre-atmospheric sizes were obtained. The...

The results of multiyear investigations of cosmogenic radionuclide production rates along the orbits of 42 chondrites, fallen successively to the Earth in 1959-2016 are presented. They constitute a long set of homogeneous data, statistical smoothing of which demonstrates some main regularities of distribution and variation of the galactic cosmic ra...

Cosmogenic radionuclides with half-life periods T 1/2 ranging from several days to a million years, produced in the nuclear reactions of galactic cosmic rays (GCR) with meteoritic matter, provide valuable information on the GCR intensity variations on a long time scale (~1 million years) within meteorite orbits 2-4 AU from the Sun. Information on t...

The results of multiyear investigations of cosmogenic radionuclide production rates along the orbits of 42 chondrites that fell to the Earth between 1959 and 2016 are presented. They constitute a long set of homogeneous data, statistical smoothing of which demonstrates some main regularities of the distribution and variation of the galactic cosmic...

Based on the analysis of published data on exposure ages of iron meteorites determined with the ⁴⁰K/K method (TK) and ages calculated using short-lived cosmogenic radionuclides (with the half-life T1/2 < 1 Myr) in combination with stable cosmogenic isotopes of noble gases (TRS), the following results have been obtained. (1) The distribution of TRS...

The results of study of cosmogenic radionuclide production rates of 54Mn, 22Na and 26Al in 7 chondrites of known orbits, which have fallen to Earth during different years of solar cycles in 1959- 2013, are presented. Information is obtained on galactic cosmic ray (GCR) distribution and variations conditioned by temporal accumulation of a layer of t...

The aim of the OLIMPIYA experiment is to search for and identify traces of heavy and superheavy nuclei of galactic cosmic rays (GCR) in olivine crystals from stony-iron meteorites serving as nuclear track detectors. The method is based on layer-by-layer grinding and etching of particle tracks in these crystals. Unlike the techniques of other author...

The distribution of the cosmic-ray exposure ages (T) of iron meteorites was analyzed to establish the possible variations in the intensity of the galactic cosmic ray (GCR) over the last billion years. The analysis was made for the entire data set containing ~80 age values from the literature (Voshage et al., 1983) and the corrected set after the ex...

To ascertain probable variations of the intensity of galactic cosmic rays (GCR) for the recent billion years, the distribution of exposure ages T of iron meteorites has been analyzed. We considered all ~80 values of ages from the data by Voshage and Feldmann (1979), Voshage et al. (1983), and Voshage (1984), as well as a set of values obtained from...

Cosmogenic radionuclides produced by galactic cosmic rays (GCR) in meteorites during their motion in space are natural detectors of the GCR intensity and variations along the meteorite orbits. On the basis of measured and calculated contents of cosmogenic radionuclides in the freshly fallen Chelyabinsk and Košice chondrites some peculiarities of ge...

Based on the example of the measured and calculated contents of cosmogenic radionuclides in freshly fallen Chelyabinsk and Kosice chondrites, an indirect approach to studying variations in galactic cos_ mic rays is presented that uses variations in the rates of production of radionuclides with different half_lives in the meteorites that continuousl...

Measurement of radionuclide content in environment matter provides information on transport processes and on possible contamination of the environment. Why do we measure cosmogenic radionuclides in meteorites? Except for chronology, they don’t yield information on meteorites, but they contribute to better understanding of radiation conditions in sp...

The stream of micrometeorites onto Earth about 470 million years ago was within a factor of ~3-4 only, but not 2-3 orders of magnitude.

The explosive break-up of the Chelyabinsk fireball was probably facilitated by its pre-entry shock-induced structure. The Chelyabinsk event demonstrates that effective asteroid-hazard mitigation requires structural knowledge of the threatening body.

Different cosmogenic radionuclides have specific depth distributions inside isotropically irradiated cosmic bodies, in particular, in meteorites. Their combinations turn out to be sensitive to size of the meteorites. It allows us to use such combinations to elaborate several specific methods for estimation of size of meteorites.

This paper presents the results of the mineralogical, petrographic, elemental, and isotopic analysis of the Chelyabinsk meteorite and their geochemical interpretation. It was shown that the meteorite can be assigned to LL5-group ordinary chondrites and underwent moderate shock metamorphism (stage S4). The Chelyabinsk meteorite contains a significan...

The origin and evolution of the biosphere are inseparably associated with energy supplied to the Earth's surface from the Sun. Variations in solar activity, changes in the orbital parameters of the Earth, and processes in the Earth's atmosphere cause variations in the total solar irradiance and may bring about appreciable climate changes that direc...

The character of the solar magnetic field restructuring and its effect on the modulation depth of galactic cosmic rays (GCR) in the heliosphere is studied. The use of long runs of homogeneous data on GCR intensities in the stratosphere makes it possible to estimate the integral GCR gradients along the meteorite orbits. It is interesting that the GC...

Meteorite data on monitoring the variations in GCR gradients at 2–4 AU from the Sun over the period 1957–2010 demonstrate the effect of the inversion of solar magnetic fields (SMFs) during the solar maximum periods of 11- year solar cycles on the depth of GCR modulation in the heliosphere.

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.

Cosmogenic radionuclides in the successively fallen chondrites in 1959-2009 were used for the investigation of the peculiarities of the various solar cycles.

The meteorite data on monitoring of the intensity and gradient of the galactic cosmic rays (GCR) in the heliosphere during 5 solar cycles are used for the correlative analysis with the variations of the solar activity (SA), strength of the interplanetary magnetic field (IMF) and tilt angle of the heliospheric current sheet (HCS). The dependence of...

Based on the analysis of data in [1, 2] on the concentrations of noble gases and the cosmic ray exposure age (CREA) of chromite grains in fossil meteorites, it was demonstrated in [3] that the distributions of gas concentrations and cosmic ray exposure ages can be explained under the assumption of the fall of a single meteorite in the form of a met...

Cosmogenic radionuclide measurements in the fresh-fallen chondrites Tamdakht and Ash Creek are used for evaluation of the galactic cosmic ray intensity along the chondrite orbits during the transitional minimum between 23rd and 24th solar cycles.

The flux of extraterrestrial micrometeorites on all Earth after disruption of the L-chondrite parent body has increased approximately 2-3 times, but not in two orders of magnitude.

Abstract—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 ch...

The content of cosmogenic radionuclides, in particular, ^60Co and ^26Al, as well as VH-nucleus track density in the fresh-fallen Kilabo LL6-chondrite are measured. The obtained results and the available data of [5] on the content of ^26Al and noble gases in the fresh-fallen Bensour LL6-chondrite are used with earlier developed methods for determina...

From the analysis of the data acquired for the chromite grains recovered from fossil meteorites from Sweden (Heck et al., 2004, 2008), the dependence of the exposure age of meteorites on a mass of the examined samples was obtained (Alexeev, 2010). This dependence, whatever its nature, puts into question the validity of the conclusion on a long last...

The results of the track and cosmogenic radionuclide study in the fresh-fallen Ash Creek and Tamdakht chondrites are used in order to estimate the pre-atmospheric size and ablation as well as the most probable elements of orbits of the chondrites.

It is highly probable that all meteorites found in Sweden have cosmic-ray exposure ages less than 2 Ma and that all these meteorites are fragments of one meteoroid.

We present the results of the analysis of the data obtained by Heck et al. (2004; 2008) regarding the contents of 4He and 20,21,22Ne and the exposure age of chromite grains recovered from fossil meteorites (L-chondrites) found in marine limestone—mid-Ordovician sediments—in the Thorsberg and Gullhogen quarries of southern Sweden. It has been shown...

Abstract—Based on the analysis of data in [1, 2] on the concentrations of noble gases and the cosmic ray exposure age (CREA) of chromite grains in fossil meteorites, it was demonstrated in [3] that the distributions of gas concentrations and cosmic ray exposure ages can be explained under the assumption of the fall of a single meteorite in the form...

The Ash Creek L6 chondrite: Cosmogenic radionuclides, thermoluminescence, and tracks of VH nuclei data are discussed.

The found features in distributions of noble gas contents and of exposure ages in the fossil meteorites of Sweden imply the falling single meteorite shower instead of the intensive flux of meteorites to Earth during ~1-2 Ma about 470 Ma ago.

Abstract— An analysis of the distribution of 3He and 4He in L and H chondrites has shown that the parent body of L chondrites underwent a catastrophic collision in space 340 ± 50 Ma ago. This age differs considerably from the collision age of 520 ± 60 Ma given previously (Heymann, 1967). The parent body of H chondrites may also have undergone local...

There is no necessity to set up a hypothesis of intensive flux of meteorites to Earth during ~1-2 Ma about 480 Ma ago.

Abstract—Thermoluminescence, tracks of VH-nuclei, and cosmogenic radionuclides with various half-lives were studied of the recently fallen Bukhara CV3 and Kilabo LL6 chondrites. The obtained experimental information and theoretical modeling were utilized to examine the thermal impact and exposure histories of these chondrites, estimate the sizes an...

Thermoluminescence, tracks of VH nuclei, and cosmogenic radionuclides with various half-lives were studied of the recently fallen Bukhara CV3 and Kilabo LL6 chondrites. The obtained experimental information and theoretical modeling were utilized to examine the thermal impact and exposure histories of these chondrites, estimate the sizes and masses...

By using the previously developed methods and the measured data on cosmogenic radionuclides and tracks in the Kilabo and Bensour LL6 chondrites, their preatmospheric sizes, locations of the investigated samples, and ablation are estimated.

By using the previously developed approach and the measured contents of 26Al in the Kilabo and Bensour LL6 chondrites, their orbits are estimated, which allows us to consider the main belt asteroid 3628 Boznemcova as the source of the LL6 chondrites.

By using the previously developed methods and the measured data on cosmogenic radionuclides and tracks in the Bukhara CV3-chondrite, its preatmospheric size (R ~ 24 cm), ablation (96.9%), and orbit (q' = 2.0 +/- 0.2 AU) are estimated.

The peculiarities of global warming on the Earth during the last century are discussed.

The collision processes obviously played a leading role in the formation of meteorites. Shock and thermal metamorphism accompanying the collisions is considered therefore as the most fundamental process in the evolution of the primordial matter.

The global warming on Earth during the last century has been discussed in many studies. The most significant factors of climate change are the increase in the atmospheric concentration of greenhouse gases, catastrophic eruptions of volcanoes, and variations in the solar activity. In this paper, we consider the character of climate change and its po...

The changes of the solar activivity and terrestrial climate for last 125 years are compared.

The contents of cosmogenic Mn-54, Na-22, Al-26, and natural potassium in chondrites Bukhara CV3 and Kilabo LL6 are submitted.

Cosmogenic radionuclides with distinctive half-lives from chondritic falls were used as natural detectors of galactic cosmic rays (GCR). A unique series of uniform data was obtained for variations in the integral gradients of GCR with a rigidity of R > 0.5 GV in 1955–2000 on heliocentric distances of 1.5–3.3 AU and heliographic latitudes between 23...

Estimation of the meteorite orbits by the thermoluminescence method is considered.

The existence of a scaling range in the power of fluctuations of the interplanetary magnetic field (IMF) necessitates the separation of stochastic effects in the modulation of galactic cosmic rays (GCR) and effects caused by solar activity. In this connection, correlation analyses of processes in the three-dimensional heliosphere become of paramoun...

Meteorite data on the galactic cosmic rays, the solar activity, and temperature variations in the earth's atmosphere lead to the conclusion that the solar activity may be important factor exerting the influence upon the climate of the Earth.

At present the natural detectors of GCRs - cosmogenic radionuclides with different half-lives (especially Mn-54 and Na-22) in the chondrites fallen to Earth in 1959-2000 - provide the data on the GCR intensity (R>0.5 GV) at ~2-4 AU over ≥4 solar cycles. The correlative analysis of these data with the different indexes of solar activity (the sunspot...

The results of studying the distributions of stable radiogenic and cosmogenic isotopes of noble gases in ordinary chondrites are reviewed here: the distributions of gas-retention and exposure ages are analyzed, the chronology and consequences of catastrophic destruction of the parent bodies of H and L chondrites are discussed, the fallen and preatm...

The fresh-fallen Kunya–Urgench H5 chondrite was studied in various aspects including natural and induced (X-ray and γ-ray) thermoluminescence, tracks of VH nuclei, and cosmogenic radionuclides with different half-lives. The experimental data, comparative analysis, and theoretical modelling were used to reconstruct the shock-thermal and radiation hi...

We determined the form of the functional dependence of the rate of formation of tracks of galactic cosmic rays in meteorites (/t) on the shielding degree for ordinary chondrites with preatmospheric radius R > 5 cm based on published semiempirical data on /t. The resulting dependence was used to construct a nomogram which allowed us to estimate the...

We considered the possibility of revealing the cosmic nature of an object by determining the content of cosmogenic and natural radionuclides in it by a low-background gamma-spectrometric complex. The results of studies of the Lost City and Kaidun meteorites and for lunar soil are presented. Three samples of unclear genesis were analyzed and their t...

A nomogram for estimation of the ablation of ordinary chondrites according to the averaged production rates of cosmic ray nuclear tracks and the found mass of the meteorite are constructed.

Considered is the method of using meteorites with different inclinations and orbit lengths as sounds of galactic cosmic rays (GCR) variations in heliosphere. The obtained data on GCR radial gradients along the orbits of some chondrites are presented. The meteorite (chondrite) data imply that GCR radial gradients increase especially strongly before...

The developed methods of modeling, based on the regularities of depth distributions of cosmogenic radionuclides in cosmic bodies of different sizes and compositions, are used to estimate the pre-atmospheric sizes and the extent of orbits of 12 chondrites.

The type of the functional dependence of the ratio of the production rates of the cosmogenic isotopes 22Ne/21Nec on their location depth d (cm) in ordinary chondrites with a radius R 60 cm was determined on the basis of experimental data on the elemental production rates of cosmogenic Ne isotopes in chondrites (Leya et al., 2000a). The dependence f...

Statistical analysis of cosmogenic neon isotopic ratios in ordinary chondrites allows us to derive some regularities for estimating ablation degree of the chondrites.

Radionuclides Mn-54 and Na-22 in five chondrites fallen in 1996-2000 are used to estimate the galactic cosmic ray gradients in the heliosphere over the minimum of the 22nd solar cycle.

Cosmic-ray exposure ages and gas-retention ages have been calculated for more than 1000 ordinary chondrites. The distributions of meteorites according to ages, local times of fall, and fragment numbers and shapes have been analyzed. The H5-chondrites have been found to differ from H3-, H4-, and H6-chondrites in a number of characteristics: the H5-c...

The recently fallen Kunya-Urgench H5 chondrite was studied in various aspects including natural and induced (X-ray and gamma-ray) thermoluminescence, tracks of VH nuclei, and cosmogenic radionuclides with different half-lives. The experimental data, comparative analysis, and theoretical modeling were used to reconstruct the shock–thermal and radiat...

Data on the isotopic abundances and ratios of light rare gases (He and Ne) in 600 ordinary chondrites are analyzed. The ratio of cosmogenic isotopes (3He/21Ne)c in ∼ 20% of the ordinary chondrites has been found to lie well below the correlation line that represents the dependence of (3He/21Ne)c on (22Ne/21Ne)c . This effect shows up most clearly i...

A set of radionuclide measurements in the fresh-fallen chondrites is carried out nondestructively, as a part of our research program to study the radiation history of the chondrites, as well as the radiation conditions in the contemporary heliosphere.

High fragmentation of H5 chondrites in the Earth atmosphere and significant losses of their cosmogenic and radiogenic gases may be caused by a feature of the catastrophic event on the H chondrite parent body about 200 Ma ago.

The data on the concentration of cosmogenic neon isotopes and the density of cosmic-ray tracks in about 600 ordinary chondrites were analyzed. For ordinary chondrites of all chemical classes, the dispersion of the ratios between cosmogenic isotopes of neon, (22Ne/21Ne) c , and a fraction of meteorites with high rates of cosmic-ray-track formation w...

The recently fallen Kunya-Urgench H5 chondrite was studied in various aspects including natural and induced (X-ray and gamma-ray) thermoluminescence, tracks of VH nuclei, and cosmogenic radionuclides with different half-lives. The experimental data, comparative analysis, and theoretical modeling were used to reconstruct the shock–thermal and radiat...

Gas-retention and radiation ages of all H- and L-chondrites, for which data on the content of radiogenic and cosmogenic inert gases are available, were calculated by the same methods. Statistic distributions of the obtained ages allow to recognize peculiarities of mechanisms of the formation and evolution of ordinary chondrites. In particular, it i...

A picture of variation of the galactic cosmic ray integral gradients in 1955-1992 along the orbits of 14 freshfallen chondrites is presented. Some peculiarities of electromagnetic structure of the heliosphere are derived.

While poor statistics preclude arriving at unequivocal conclusions regarding the H chondrites, it is surmised here that about 2 percent of the parent body from which the H chondrites originate was significantly heated about 200 million years ago. This heating was collisional, and resulted in almost complete loss of radiogenic He from this region of...