Abstract
Gamma-ray quanta, which occur during solar flares due to the interaction of accelerated protons with the photosphere and deeper layers of the sun, enter interplanetary space from a thickness ...of several tens of g/cm
2
. In the presented work, gamma quanta with energies of more than 511 keV are considered. This makes it possible to exclude from consideration the dependence of the probability of ortho- and parapositronium formation on the temperature and density of the solar matter. And also do not consider the probability of annihilation by two or 3 gamma quanta. Thus, the reactions of thermal neutrons remain dependent on the temperature. As the ambient temperature increases, the average number of elastic neutron scattering before capture increases. This leads to a more likely penetration of neutrons to a greater depth or their departure into the interplanetary space. The high temperature of the Sun below the photosphere may be one of the reasons for the absence of the 2.223 MeV line in solar flares with registered protons in the PAMELA and AMS2 experiments. Using the GEANT4 package, the spectra of gamma-quanta arising in nuclear interactions are calculated. The temperature-dependent features of the gamma-ray spectra are discussed.
We suggest an explanation of a sharp increase in the abundance of cosmogenic radiocarbon found in tree rings dated AD 775. The increase could originate from high-energy irradiation of the atmosphere ...by a Galactic gamma-ray burst. We argue that, unlike a cosmic ray event, a gamma-ray burst does not necessarily result in a substantial increase in long-lived 10Be atmospheric production. At the same time, the 36Cl nuclide would be generated in the amounts detectable in the corresponding ice-core samples from Greenland and Antarctica. These peculiar features allow experimental discrimination of nuclide effects caused by gamma-ray bursts and by powerful proton events.
Abstract
Analysis of the isotopic composition of nuclei in galactic cosmic rays (GCR) in the orbital experiment of the PAMELA collaboration makes it possible to study the problems of the origin and ...propagation of cosmic rays in the Galaxy. The data of the PAMELA magnetic spectrometer, due to their high statistical and methodological accuracy, ensured significant progress in the study of the isotopic composition of light nuclei from H to Be in GCR in the energy range ~ 0.1-1 GeV/nucleon and for the first time made it possible to estimate the contribution to GCR of Local Interstellar Sources (LIS) from close (∼ 100 pc) of recent (~ million years) supernova explosions. To date, the isotopic composition of beryllium nuclei in GCR has been measured only for
7
Be./
9
Be,
10
Be/
9
Be ratios in the energy range of ∼ 100 MeV/nucleon in the space experiments IMP 7/8, Voyager, Ulysses, ACE/CRIS and for
10
Be/
9
Be in balloon experiment with a superconducting magnet ISOMAX-98 for energies 0.2-1.0 and 1.1-2.0 GeV/nucleon. In this work, using flight data PAMELA 2006-2014, on the rigidity of the detected nuclei and their velocity (time-of-flight analysis and ionization losses in the multilayer calorimeter of the instrument), a new analysis of the isotopic composition of beryllium nuclei in the energy range of ~ 0.1-1.4 GeV/nucleon has been carried out. The results of isotopic analysis of beryllium nuclei in GCR (spectra
7
Be,
9
Be,
10
Be and
7
Be/
9
Be,
10
Be/
9
Be - ratio depending on the rigidity and energy of nuclei) in comparison with the existing measurement and calculation data will be presented.
Cosmic-ray electrons and positrons are a unique probe of the propagation of cosmic rays as well as of the nature and distribution of particle sources in our Galaxy. Recent measurements of these ...particles are challenging our basic understanding of the mechanisms of production, acceleration, and propagation of cosmic rays. Particularly striking are the differences between the low energy results collected by the space-borne PAMELA and AMS-02 experiments and older measurements pointing to sign-charge dependence of the solar modulation of cosmic-ray spectra. The PAMELA experiment has been measuring the time variation of the positron and electron intensity at Earth from July 2006 to December 2015 covering the period for the minimum of solar cycle 23 (2006-2009) until the middle of the maximum of solar cycle 24, through the polarity reversal of the heliospheric magnetic field which took place between 2013 and 2014. The positron to electron ratio measured in this time period clearly shows a sign-charge dependence of the solar modulation introduced by particle drifts. These results provide the first clear and continuous observation of how drift effects on solar modulation have unfolded with time from solar minimum to solar maximum and their dependence on the particle rigidity and the cyclic polarity of the solar magnetic field.
Carbon Isotopes in the PAMELA Experiment Bogomolov, E A; Vasilyev, G I; Menn, W
Journal of physics. Conference series,
12/2020, Volume:
1697, Issue:
1
Journal Article
Peer reviewed
Open access
Abstract
An analysis of the isotopic composition of nuclei in galactic cosmic rays (GCR) in the orbital experiment of the PAMELA collaboration allows us to study the problems of the origin and ...propagation of cosmic rays in the Galaxy. Due to the high statistical and methodological accuracy, the data of the PAMELA magnetic spectrometer provided significant progress in studying the isotopic composition of light nuclei from H to Be in the GCR in the energy region of ∼ 0.1-1 GeV / nucleon and for the first time made it possible to estimate the contribution of local sources from close ones to the GCR (∼ 100 pc) of recent (∼ 10
6
yrs) supernova explosions. To date, the isotopic composition of carbon nuclei in the GCR has been measured only for the
13
C /
12
C ratio in the energy region ∼ 0.05-0.13 GeV / nucleon in the VOYAGER 1.2 space experiment and the upper limit for the
14
C /
12
C ratio was estimated in the ACE / CRIS experiment for energies 0.12-0.43 MeV / nucleon. In this work, using PAMELA flight data 2006-2014, on the rigidity of the detected nuclei and their speed (time-of-flight analysis and ionization losses in the multilayer calorimeter of the device), an attempt was made to determine the isotopic composition of carbon nuclei in the energy region of ∼ 0.1-1 GeV / nucleon. The half-life of
14
C nuclei is 5730 years and can be detected in the case of a supernova explosion in the last ∼ 5 10
4
years at a distance of ∼ 100 200 pc. The results of isotope analysis of carbon nuclei in GCR (spectra
12
C,
13
C,
14
C and
14
C /
12
C - ratio depending on the rigidity and energy of the nuclei) in comparison with the existing measurement data will be presented.
The extreme cosmic event that occurred in AD 775 was detected using 14C measurements in tree rings and 10Be, 36Cl abundances in polar ice cores. Perhaps it is the most powerful solar proton event in ...the past several thousands of years. Simulation of isotope production with the spectra of solar flares observed in the modern era (23.02.56, 04.08.72 etc.) showed that to produce the measured amount of radionuclides, the particle fluence in the AD 775 event has to be by tens - hundreds times greater than the modern powerful solar events. The results of calculations of long-lived cosmogenic radionuclides (14C, 10Be, 36Cl) production in the Earth's atmosphere are presented.
Boron Isotopes in the PAMELA Experiment Bogomolov, E A; Vasilyev, G I
Journal of physics. Conference series,
11/2019, Volume:
1400, Issue:
2
Journal Article
Peer reviewed
Open access
Analysis of the isotopic composition of nuclei in galactic cosmic rays (GCR) in the PAMELA orbital international experiment allows us to study the problems of the origin and propagation of cosmic ...rays in the Galaxy. Due to the high statistical and methodical accuracy, the PAMELA magnetic spectrometer data provided significant progress in the study of the isotopic composition of the light nuclei from H to Be in the GCR in the energy region of ∼0.1-1 GeV/nucleon and, for the first time, made it possible to estimate the contribution in GCR from local (∼100 pc) recent (∼106 years) interstellar sources (LS) from supernova explosions. An isotopic analysis of boron (B) nuclei in the GCR has so far been carried out only in the energy region ∼0.08-0.17 GeV/nucleon in the space experiments Voyager, Ulysses, ACE. In this work using the PAMELA data 2006-2014 about the rigidities of the detected nuclei and their speed (time of flight analysis (TOF) and ionization losses in a multilayer calorimeter) for the first time was made an attempt to determine the 11B/10B ratio in the energy range of ∼0.1-1.0 GeV/nucleon. The new PAMELA data are consistent with existing measurements and those expected from modeling, but the statistical and methodological accuracy of measurements does not allow us to separate the contribution of local boron sources to GCR. The results of the isotope analysis of boron nuclei in the GCR (spectra 10B, 11B and 11B/10B ratio depending on the rigidity and energy of the nuclei) in comparison with the existing measurement data and calculations will be presented.
C-13/C-12 and N-15/N-14 isotopic ratios are pivotal for our understanding of the Martian carbon cycle, history of the Martian atmospheric escape, and origin of the organic compounds on Mars. Here we ...demonstrate that the carbon and nitrogen isotopic composition of the surface rocks on Mars can be significantly altered by the continuous exposure of Martian surface to cosmic rays. Cosmic rays can effectively produce C-13 and N-15 isotopes via spallation nuclear reactions on oxygen atoms in various Martian rocks. We calculate that in the top meter of the Martian rocks, the rates of production of both C-13 and N-15 due to galactic cosmic rays (GCRs) exposure can vary within 1.5-6 atoms/cm3/s depending on rocks' depth and chemical composition. We also find that the average solar cosmic rays can produce carbon and nitrogen isotopes at a rate comparable to GCRs in the top 5-10 cm of the Martian rocks. We demonstrate that if the total carbon content in a surface Martian rock is <10 ppm, then the "light," potentially "biological" C-13/C-12 ratio would be effectively erased by cosmic rays over 3.5 billion years of exposure. We found that for the rocks with relatively short exposure ages (e.g., 100 million years), cosmogenic changes in N-15/N-14 ratio are still very significant. We also show that a short exposure to cosmic rays of Allan Hills 84001 while on Mars can explain its high-temperature heavy nitrogen isotopic composition (N-15/N-14). Applications to Martian meteorites and the current Mars Science Laboratory mission are discussed.
Boron Isotopes in the PAMELA Experiment Bogomolov, E. A.; Vasilyev, G. I.; Menn, W. ...
Physics of atomic nuclei,
11/2019, Volume:
82, Issue:
6
Journal Article
Peer reviewed
Analysis of the isotope composition of nuclei in galactic cosmic rays (GCR) in the PAMELA orbital international experiment allows studying the problems of cosmic-ray origin and propagation in our ...Galaxy. PAMELA magnetic spectrometer data provided the significant progress in the study of the light nuclei isotope composition of GCR from H to Be in the energy range ∼0.1–1 GeV/nucleon. This makes it possible to estimate the contribution of local (∼100 pc) young (∼10
6
years) interstellar sources (LISS) into GCR fluxes from supernova explosions. The analysis of boron (B) isotope fluxes in the GCR has so far been carried out only in the energy range ∼0.08–0.17 GeV/nucleon in the space experiments Voyager, Ulysses, ACE. In the present contribution the attempt was done to determine the
11
B/
10
B ratio in the energy range ∼0.1–1.0 GeV/nucleon for the first time on the base of 2006–2014 PAMELA data using the measurements of the detected nuclei rigidities, velocities and ionization losses in a multilayer calorimeter. The new PAMELA results are consistent with existing as experimental data and those expected from simulations. However the statistical and systematic measurement uncertainties do not allow to separate the local boron source contributions into GCR fluxes. The preliminary results of the boron isotope flux analysis in GCR (
10
B,
11
B spectra and
11
B/
10
B ratio dependences on the rigidity and energy) are presented as well as the existing measurement data and simulation results.
High-resolution MRI is an important tool in the diagnosis of structural epilepsy |in determining the seizure initiation zones, identification of the mechanisms of epileptogenesis in predicting ...outcomes and preventing postoperative complications in patients. In this article we have tried to demonstrate the neuroradiological and pathohistological characteristics of the main epileptogenic substrates in children using modern classification. The second part of the article is devoted to the spectrum of epileptogenic cerebral disorders, in addition to cortical malformations.
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