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Model computations, based on the compound approach (Ferreira and Potgieter, 2004), shown with the Hermanus NM count rates expressed as percentage values for 1980–1992. Shaded areas indicate when the solar magnetic field polarity was not well defined.
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In recent years the variability of the cosmic ray flux has become one of the main issues interpreting cosmogenic elements
and especially their connection with climate. In this review, an interdisciplinary team of scientists brings together our
knowledge of the evolution and modulation of the cosmic ray flux from its origin in the Milky Way, during...
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... approach has so far provided the most successful modeling of the 11-year and 22-year cycles. An example is given in Figure 9, where the 11-year simulation done with the compound numerical model is shown compared to the Hermanus NM count rates expressed as percentage values for the period of 1980-1992. This inversion CR-B method is used to derive values of the solar magnetic field back in time, after the modulation model is calibrated to CR observations, typically for minimum modulation like in May 1965, and further by assuming a direct relation between CRs and the long-term cosmogenic isotope time-profiles. ...
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... ↔ κ is the momentum-average of the diffusion tensor given in Equation (2). A typical result for the plasma structure of the heliosphere at solar minimum activity is shown in Figure 19. ...
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... is the result of the interaction of the solar wind with the Earth's internal magnetic field and ionosphere (McPherron, 1995). From this complex interaction several dynamical magnetospheric current systems develop, resulting in several modifications of the Earth's magnetic field, among which are the compression of the magnetic field lines in the day-side and their stretching in the night-side, leading to a magnetosphere con- figuration as illustrated in Figure 29. The external geomagnetic field, also called the magnetospheric magnetic field, refers to the magnetic field induced by the magne- tospheric currents. ...
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... latitude dependence of fast neutrons as observed by Simpson (1951), taken from Simpson (2000). Figure 29. Configuration of the Earth's magnetosphere at 9 a.m. on January 1,2005 as obtained by using the IGRF and Tsyganenko96 models for describing the internal and external geomagnetic field respectively (Langel, 1992;Tsyganenko, 1996). ...
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... the Earth during a typical solar cycle, the low energy part of GCR particle flux (E < 1 GeV/nucleon ) varies by an order of magnitude. With increasing energy, the modulation effect becomes weaker (Figure 39). Solar modulation is taken into account in the expression for the differential primary GCR proton flux. ...
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... authors (e.g. Knauth and Lowe, 2003) even argued that the declining δ 18 O values in ancient cherts and carbonates (Figure 49) indicate that the Archean oceans may have been as warm as ≈70 ± 15 • C , but the clear evidence for ice ages at ≈2.9 Ga , 2.2-2.4 Ga and since ≈0.7 Ga ago (Frakes et al., 1992;Young et al., 1998) rules out such an interpretation. ...
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... and pH both affect the δ 18 O of marine carbonate minerals, but have opposing effects of similar magnitude, essentially canceling each other. The downward δ 18 O trend ( Figure 49) is therefore unlikely to be an outcome of the hot " CO 2 greenhouse" oceans, but rather of the changing oxygen isotopic composition of seawater Veizer and Mackenzie, 2004). The alternative proposition of a CH 4 or NH 3 greenhouse ( Sagan and Chyba, 1997;Kasting and Ono, 2005) faces the problem that such greenhouses could have been sustained only in an oxygen-free ocean/atmosphere system. ...
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... alternative proposition of a CH 4 or NH 3 greenhouse ( Sagan and Chyba, 1997;Kasting and Ono, 2005) faces the problem that such greenhouses could have been sustained only in an oxygen-free ocean/atmosphere system. This may have been Figure 49. Oxygen isotope record of CaCO 3 shells and sediments over geologic history (n = 9957). ...
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... Specifically, the atmospheric ionization may alter the physical and chemical properties of the atmosphere and affect several processes, such as aerosol and cloud formation, atmospheric transparency, cloud cover, cyclogenesis and precipitation, especially in regions of middle and high geographic latitudes. Therefore, several numerical models were created and validated via comparison with direct observations and measurements of the CRII, e.g., the Sofia model [8,9], the Bern model, also called ATMOCOSMIC [10,11] and the Oulu model, also called CRAC:CRII [12,13]. Results from the latter model [14] are used in this work. ...
The main source of the ionization of the Earth’s atmosphere is the cosmic radiation that depends on solar activity as well as geomagnetic activity. Galactic cosmic rays constitute a permanent radiation background and contribute significantly to the radiation exposure inside the atmosphere. In this work, the cosmic-ray-induced ionization of the Earth’s atmosphere, due to both solar and galactic cosmic radiation during the recent solar cycles 23 (1996–2008) and 24 (2008–2019), was studied globally. Estimations of the ionization were based on the CRAC:CRII model by the University of Oulu. The use of this model allowed for extensive calculations from the Earth’s surface (atmospheric depth 1033 g/cm2) to the upper limit of the atmosphere (atmospheric depth 0 g/cm2). Monte Carlo simulations were performed for the estimation quantities of radiobiological interest with the validated software DYASTIMA/DYASTIMA-R. This study was focused on specific altitudes of interest, such as the common flight levels used by commercial aviation.
... Consequently, the magnetic field that should be used in the calculations is not the Earth's internal magnetic field but a modified version of it, usually called the external geomagnetic field or magnetospheric field. For more details on magnetospheric and atmospheric effects see, e.g., Scherer et al. (2006). ...
Simulating the irradiation of planetary atmospheres by cosmic ray particles requires, among others, the ability to understand and to quantify the interactions of charged particles with planetary magnetic fields. Here we present a process that is very often ignored in such studies: the dispersion and focusing of cosmic ray trajectories in magnetospheres. The calculations were performed using our new code CosmicTransmutation, which has been developed to study cosmogenic nuclide production in meteoroids and planetary atmospheres and which includes the computation of the irradiation spectrum on top of the atmosphere. Here we discuss effects caused by dispersion and focusing of cosmic ray particle trajectories.
... When a CME strikes Earth, this causes a worldwide temporary disturbance of Earth's magnetic field. The battle between charged particles and magnetic fields shake the Earth's magnetic field over a period of several hours or days (Scherer et al., 2006;Marusek, 2007). ...
Evolutionarily, a human organism is adapted to the natural geomagnetic environment and its slight alterations. However, during geomagnetic storms (GMSs), the strength of the geomagnetic field (GMF) sharply increased hundreds of times and can pose a serious threat to people. We examine the effects of controlled compensation in the time-varying components of the GMF, using a specially created experimental setup with electrically shielding solutions, providing an electromagnetically quiet environment. The measurement of heart rate variability (HRV) on 25 healthy young male volunteers was carried out in the laboratory using the experimental setup at different levels of outdoor geomagnetic activity (GMA). The geomagnetic K-index was used to characterize the magnitude of GMSs; volunteers were tested during quiet magnetic days (K=1-3), days with K=4, and days with GMSs (K≥5) in the period of solar cycle maximum. During quiet magnetic days, the comparison between HRV baseline values with values measured under GMF time-varying components compensation mode (CM) did not reveal any changes. On days with K=4 some HRV indices shifted from their initial values, but it was statistically not significant. However, on days with GMSs statistically significant changes in SDNN* (p=0.033) and LF* (p=0.011) indices of HRV were observed in the GMS CM compared to their baseline values. The experiments showed that GMSs cause a sensitive reaction of the heart rate regulatory mechanism, the effect of which can be canceled in the GMS CM. The efficiency of the used technology is supported by the results of this study. * SDNN (Standard Deviation Normal to Normal R-R of cardiointervals), LF (Low frequency spectral band of cardiointervals).
... Consequently, the magnetic field that should be used in the calculations is not the Earth's internal magnetic field but a modified version of it, usually called external geomagnetic field or magnetospheric field. For more details on magnetospheric and atmospheric effects see, e.g., [12]. ...
Simulating the irradiation of planetary atmospheres by cosmic ray particles requires, among others, the ability to understand and to quantify the interactions of charged particles with planetary magnetic fields. Here we present a process that is very often ignored in such studies; the dispersion and focusing of cosmic ray trajectories in magnetospheres. The calculations were performed using our new code CosmicTransmutation, which has been developed to study cosmogenic nuclide production in meteoroids and planetary atmospheres and which includes the computation of the irradiation spectrum on top of the atmosphere. Here we discuss effects caused by dispersion and focusing of cosmic ray particle trajectories.
... Several galactic processes affect the GCR flux in the inner Solar System, operating on a range of timescales [52][53][54]. On the longest timescales (>1 Gyr), the average GCR flux may reflect the galactic star formation rate, which could provide useful constraints on models of galactic evolution (although it would be necessary to account for an expected secular increase in GCR flux reaching the inner Solar System due to decreasing solar activity [11]). ...
The lunar surface has been exposed to the space environment for billions of years and during this time has accumulated records of a wide range of astrophysical phenomena. These include solar wind particles and the cosmogenic products of solar particle events which preserve a record of the past evolution of the Sun, and cosmogenic nuclides produced by high-energy galactic cosmic rays which potentially record the galactic environment of the Solar System through time. The lunar surface may also have accreted material from the local interstellar medium, including supernova ejecta and material from interstellar clouds encountered by the Solar System in the past. Owing to the Moon's relatively low level of geological activity, absence of an atmosphere, and, for much of its history, lack of a magnetic field, the lunar surface is ideally suited to collect these astronomical records. Moreover, the Moon exhibits geological processes able to bury and thus both preserve and ‘time-stamp' these records, although gaining access to them is likely to require a significant scientific infrastructure on the lunar surface.
This article is part of a discussion meeting issue ‘Astronomy from the Moon: the next decades'.
... Several galactic processes affect the GCR flux in the inner Solar System, operating on a range of timescales [52][53][54]. On the longest timescales (>1 Gyr), the average GCR flux may reflect the galactic star formation rate, which could provide useful constraints on models of galactic evolution (although it would be necessary to account for an expected secular increase in GCR flux reaching the inner Solar System due to decreasing solar activity [11]). ...
The lunar surface has been exposed to the space environment for billions of years and during this time has accumulated records of a wide range of astrophysical phenomena. These include solar wind particles and the cosmogenic products of solar particle events which preserve a record of the past evolution of the Sun, and cosmogenic nuclides produced by high-energy galactic cosmic rays which potentially record the galactic environment of the Solar System through time. The lunar surface may also have accreted material from the local interstellar medium, including supernova ejecta and material from interstellar clouds encountered by the Solar System in the past. Owing to the Moon's relatively low level of geological activity, absence of an atmosphere, and, for much of its history, lack of a magnetic field, the lunar surface is ideally suited to collect these astronomical records. Moreover, the Moon exhibits geological processes able to bury and thus both preserve and 'time-stamp' these records, although gaining access to them is likely to require a significant scientific infrastructure on the lunar surface.
... In addition to providing information about the history of the Sun, noble gases have the potential to provide insight into the history of the Galaxy and its implications for the development of life on Earth. The Solar System has been subject to a wide range of galactic environments as it orbits the Galaxy, and the GCR flux is sensitive to a variety of astrophysical processes including the star formation rate and nearby supernova explosions (e.g., Scherer et al., 2006;Shaviv, 2006). As the Moon possesses some of the most ancient surfaces in the Solar System, it may preserve a record of enhanced galactic cosmic ray fluxes in cosmogenic noble gas isotopes, which could potentially provide information on the structure and evolution of the Galaxy (e.g. ...
The lunar regolith provides a temporal archive of the evolution of the Moon and inner Solar System over the last ∼4 billion years. During this time, noble gases have been trapped and produced within soils and rocks at the lunar surface. These noble gas concentrations can be used to unravel the history of lunar material and shed light on processes that have evolved the surface of the Moon through time. We have collected published noble gas data for a range of lunar samples including soils, regolith breccias, crystalline (e.g., mare basalts, anorthosite) and impact-melt rocks. The compilation includes noble gas concentrations and isotope ratios for He, Ne, Ar, Kr and Xe; trapped, cosmogenic and radiogenic isotopes; and cosmic ray exposure ages. We summarise the significance of these data, which can be used as a baseline for expected noble gas concentrations in a range of lunar samples, and provide a framework for future in situ noble gas measurements on the lunar surface.
... The data, however, indicate differently; there is a large spread of data over the entire x-axis, indicating that there is no apparent periodicity. We found the same result for periods of 147 Ma (Scherer et al. 2006) and for 400 and 500 Ma (Alexeev 2016). Consequently, from our data, there is no indication for a periodicity in the CRE age data, which is in clear contradiction to the proposals by Shaviv (2002Shaviv ( , 2003, Scherer et al. (2006), andAlexeev (2016). ...
... We found the same result for periods of 147 Ma (Scherer et al. 2006) and for 400 and 500 Ma (Alexeev 2016). Consequently, from our data, there is no indication for a periodicity in the CRE age data, which is in clear contradiction to the proposals by Shaviv (2002Shaviv ( , 2003, Scherer et al. (2006), andAlexeev (2016). Furthermore, our result nicely confirms the earlier findings by Rahmstorf et al. (2004) and Jahnke (2005). ...
We measured the He, Ne, and Ar isotopic concentrations and the 10Be, 26Al, 36Cl, and 41Ca concentrations in 56 iron meteorites of groups IIIAB, IIAB, IVA, IC, IIA, IIB, and one ungrouped. From 41Ca and 36Cl data, we calculated terrestrial ages indistinguishable from zero for six samples, indicating recent falls, up to 562 ± 86 ka. Three of the studied meteorites are falls. The data for the other 47 irons confirm that terrestrial ages for iron meteorites can be as long as a few hundred thousand years even in relatively humid conditions. The 36Cl‐36Ar cosmic ray exposure (CRE) ages range from 4.3 ± 0.4 Ma to 652 ± 99 Ma. By including literature data, we established a consistent and reliable CRE age database for 67 iron meteorites. The high quality of the CRE ages enables us to study structures in the CRE age histogram more reliably. At first sight, the CRE age histogram shows peaks at about 400 and 630 Ma. After correction for pairing, the updated CRE age histogram comprises 41 individual samples and shows no indications of temporal periodicity, especially not if one considers each iron meteorite group separately. Our study contradicts the hypothesis of periodic GCR intensity variations (Shaviv 2002, 2003), confirming other studies indicating that there are no periodic structures in the CRE age histogram (e.g., Rahmstorf et al. 2004; Jahnke 2005). The data contradict the hypothesis that periodic GCR intensity variations might have triggered periodic Earth climate changes. The 36Cl‐36Ar CRE ages are on average 40% lower than the 41K‐K CRE ages (e.g., Voshage 1967). This offset can either be due to an offset in the 41K‐K dating system or due to a significantly lower GCR intensity in the time interval 195–656 Ma compared to the recent past. A 40% lower GCR intensity, however, would have increased the Earth temperature by up to 2 °C, which seems unrealistic and leaves an ill‐defined 41K‐K CRE age system the most likely explanation. Finally, we present new 26Al/21Ne and 10Be/21Ne production rate ratios of 0.32 ± 0.01 and 0.44 ± 0.03, respectively.
... As discussed above, the Sun is traveling through the shell of the Loop I superbubble that resulted from stellar evolution in the ScoCen OB2 association. It was recognized long ago that extreme variations in the physical properties of interstellar material interacting with the solar system would probably affect the terrestrial climate [1,205,206,207,208,209,3]. These effects are mediated by the interaction between the heliosphere and interstellar medium [210,207,3,208,211,212]. ...
... It was recognized long ago that extreme variations in the physical properties of interstellar material interacting with the solar system would probably affect the terrestrial climate [1,205,206,207,208,209,3]. These effects are mediated by the interaction between the heliosphere and interstellar medium [210,207,3,208,211,212]. The 18 km s −1 motion of the solar system through the LSR and the 7-47 km s −1 LSR velocities of nearby interstellar clouds [121] lead to variations in the heliospheric boundary conditions over geological timescales of order ≤ 30 kyr [213]. ...
A range of astronomical data indicates that ancient supernovae created the galactic environment of the Sun and sculpted the physical properties of the interstellar medium near the heliosphere. In this paper we review the characteristics of the local interstellar medium that have been affected by supernovae. The kinematics, magnetic field, elemental abundances, and configuration of the nearest interstellar material support the view that the Sun is at the edge of the Loop I superbubble, which has merged into the low density Local Bubble. The energy source for the higher temperature X-ray emitting plasma pervading the Local Bubble is uncertain. Winds from massive stars and nearby supernovae, perhaps from the Sco-Cen Association, may have contributed radioisotopes found in the geologic record and galactic cosmic ray population. Nested supernova shells in the Orion and Sco-Cen regions suggest spatially distinct sites of episodic star formation. The heliosphere properties vary with the pressure of the surrounding interstellar cloud. A nearby supernova would modify this pressure equilibrium and thereby severely disrupt the heliosphere as well as the local interstellar medium.
... The analysis of the distribution of this set led to contradictory conclusions regarding the variations of the GCR intensity. For example, Shaviv (2002;2003) concluded that this distribution of ages is the evidence for variations of the GCR intensity with the period of 143 ± 10 Myr (or, according to more recent data (Scherer et al., 2006), with the period of 143 ± 6 Myr), which are caused by presumed periodic passages of the Solar System through the spiral arms of the Galaxy. However, the very fact of variations with such a period, as well as the authors' conclusion about the supposed correlation between periodic changes in the GCR intensity and climatic changes on the Earth, are disputed by many researchers, as both the procedure of sampling the ages for analysis and the interpretation of the data are considered poorly grounded (Rahmstorf et al., 2004;Jahnke, 2005;Bailer-Jones, 2009;Overholt et al., 2009;Wieler et al., 2013). ...
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 ages (106 values) has an exponential shape, similar to that for ordinary chondrites, but different from the distribution of TK ages (80 values). The difference is most likely due to small amounts of data for meteorites with low TK ages (less than ~200–300 Myr). The latter can be ascribed to the difficulty of measurement of small concentrations of cosmogenic potassium isotopes. This circumstance makes the selection of meteorites with ⁴⁰K/K ages nonrepresentative and casts doubt on the correctness of conclusions about the variations of the intensity of galactic cosmic rays (GCR) based on the analysis of distribution of these ages. (2) The magnitude of the known effect (systematic overestimation of TK ages in comparison with TRS ages) has been refined. The value k = TK/TRS = 1.51 ± 0.03 is acquired for the whole population of data. We have shown the inefficiency of the explanation of this effect on account of an exponential change in the GCR intensity (IT) with time (T) according to the relation IT = I0exp(–γT) over the whole range of ages of iron meteorites. (3) In order to explain the overestimation of TK ages in comparison with TRS ages, a model has been proposed, according to which the GCR intensity has exponentially increased in the interval of 0–1500 Myr governed by the relation: IT = IT = 1500 (1 + αexp(–βT)). For one of the variants of this model, the GCR intensity has exponentially increased by a factor of two only over the recent ~300 Myr, remaining approximately constant for the rest of the time. The data acquired with the use of this model indicate that the measured TK ages are close to the actual time that the meteorites existed in space; the data are in agreement with the observed exponential distribution of TRS ages.
