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Be is a cosmogenic isotope continuously produced in the Earth’s atmosphere by galactic cosmic rays (GCRs) and sporadically by solar energetic particles (SEPs). The long-living isotope, as measured in polar ice cores, typically with an annual resolution, serves as a proxy for long-term cosmic-ray variability, whose signal can, however, be distorted by atmospheric transport and deposition that need to be properly modelled. Atmospheric transport of 10Be depends on production, atmospheric circulation, and local orography. For an accurate physical description of the isotope's transport and deposition, we use the chemical climate model (CCM) SOCOL-AER2-BE. In combination with the production model CRAC, our model was verified using real measurements of beryllium in ice cores for Antarctic and Greenland locations. The model results agree with the measurements at the absolute level, implying that the production, decay, and lateral deposition are correctly reproduced. However, the exact time variability is not always well reproduced, particularly for the Greenland shore sites implying significant regional effects. Potentially, extreme SPEs that are orders of magnitude stronger than those observed during the recent decades can be recorded in cosmogenic isotope data, and a proper model is needed to study them. Here we present a model of the production and transport of 10Be for a major solar energetic particle event (GLE 69) and analyze the geographical pattern of the beryllium concentration.

For many reasons, from solar physics to terrestrial and engineering applications, it is important to estimate the total fluences of solar energetic particles (SEPs) especially for the strongest hard-spectrum events known as ground-level enhancements (GLEs). Here we present a revised reconstruction of the SEP spectral fluences using a recently developed probabilistic Monte-Carlo method, applied to major GLE events of the last decades. The method utilizes data from the ground-based neutron-monitor network in the higher-energy range and revised space-borne/ionospheric data for the lower-energy part. The fluences are reconstructed along with realistic uncertainty estimates which appear large for weak events and small for strong events.

Heavier-than-proton nuclei in cosmic rays are responsible for up to 45% of neutron monitor (NM)response depending on the level of solar modulation as well as the geomagnetic rigidity cutoffand altitude of a given NM location. Therefore, careful consideration of these heavy species isimportant for an accurate analysis of NM data, including a reconstruction of the solar modulationpotential using the worldwide NM network data. Recently, the AMS-02 experiment allowed usto directly verify the NM response to heavy particles. In this work, we evaluate the expectedcontribution of heavy nuclei into the NM response considering different models of the localinterstellar spectrum and also for different levels of solar activity.

Here we report a new reconstruction of the event-integrated spectra of solar energetic particles(SEP) detected by neutron monitor (NM) network and space-borne detectors (mainly GOESdata) during ground-level enhancement (GLE) events. The reconstruction of SEP fluences isbased on the “bow-tie” method employing the latest advances in the NM data analysis (a time-dependent GCR background and the use of the NM yield function directly verified with theAMS-02 experiment data), usage of different space-borne detectors data and a detailed study ofdifferent uncertainties. As a result of this work, we obtained integral fluences of SEPs in theenergy range from 30 MeV to a few GeV for 58 moderate and strong GLE events since 1956.The results were fitted with the modified Band-function (a double power-law function with twoexponential cutoffs). An easy-to-use presentation of SEP fluences in the form of an analyticalexpression forms a solid basis for new studies in different fields, such as the influence of SEPs onthe atmosphere and a statistical study of extreme solar activity.

We discuss the possibility of the enrichment of solar energetic particles (SEP) with trans-iron ions in impulsive events. Aiming to estimate the acceleration of ions in the weight range of 84–210 atomic units, we calculated the energy dependences of the ionization and recombination rates of energetic ions of Kr, Te, and Pb. On the basis of the charge-consistent model of the stochastic acceleration of ions in Alfven turbulence (including the spatial diffusion of ions and Coulomb losses of energy), we calculated energy spectra of O, Fe, Kr, Re, and Pb at various values of the spectral index of turbulence for a wide range of parameters of plasma in the acceleration region. It was demonstrated that the Coulomb losses could be one reason for the observed significant SEP enrichment with trans-iron ions in impulsive events.

The stochastic acceleration of heavy ions by Alfven turbulence is considered with allowance for Coulomb losses. The pattern of energy dependence of these losses gives rise to characteristic features in the energy spectra of the accelerated particles at energies of the order of several MeV nucleon−1. The manifestation of these features in the spectra is sensitive to the temperature and density of the medium, which can serve as a basis for plasma diagnostics in the flare region. Some impulsive solar energetic particle events during which features in the spectra of 3He and 4He were observed are considered as an example.