1. Usoskin, I. G., & Kovaltsov, G. A. (2021). Mind the gap: New precise 14C data indicate the nature of extreme solar particle events. Geophysical Research Letters, 48, e2021GL094848. doi:10.1029/2021GL094848 – the result suggests that the extreme solar events likely represent the high-energy/low-probability tail of the continuous distribution of solar eruptive events.
  2. Mishev, A., Poluianov, S. About the Altitude Profile of the Atmospheric Cut-Off of Cosmic Rays: New Revised Assessment. Solar Physics, 296 (8), 2021, doi: 10.1007/s11207-021-01875-5 – on the basis of Monte Carlo simulations with the PLANETOCOSMICS code and by the employment of a new verified neutron monitor yield function, we assessed the atmospheric cut-off as a function of the altitude, as well as for specific stations located in the polar region.
  3. Aguilar, M. … I.G. Usoskin and S. Poluianov et al. (AMS collaboration), Properties of a New Group of Cosmic Nuclei: Results from the Alpha Magnetic Spectrometer on Sodium, Aluminum, and Nitrogen, Phys. Rev. Lett., 127, 021101 (2021), doi: 10.1103/PhysRevLett.127.021101´- we report the properties of sodium (Na) and aluminum (Al) cosmic rays in the rigidity range 2.15 GV to 3.0 TV based on 0.46 million sodium and 0.51 million aluminum nuclei collected by the AMS.
  4. Velinov, Peter I. Y.; Mishev, Alexander (2021) Influence of forbush effect on atmospheric ionization due to solar energtic particles. Comptes rendus de l’Académie bulgare des Sciences 74(6): 868-878. – using Monte Carlo simulations and appropriate solar proton spectra we computed the ion production rate and the corresponding ionization effect in the Earth’s atmosphere during GLE-66.
  5. Kocharov, L., N. Omodei, A. Mishev, M. Pesce-Rollins, F. Longo, S. Yu, D.E. Gary, R. Vainio, I. Usoskin, Multiple Sources of Solar High-energy Protons, Astrophys. J., 915, 12 (2021) doi: 10.3847/1538-4357/abff57 – we find a good statistical correlation between the γ-ray fluences of the Fermi/LAT-observed delayed events and the products of corresponding CME speed and the square root of the soft X-ray flare magnitude.
  6. Krivova, N.A., S.K.  Solanki, B. Hofer, C.-J. Wu, I.G. Usoskin, R. Cameron, Modelling the evolution of the Sun’s open and total magnetic flux, Astron. Astrophys., 650 A70 (2021) doi: 10.1051/0004-6361/202140504 – we present a major update of a widely used simple model, which now takes into account the observation that the distribution of all magnetic features on the Sun follows a single power law. 
  7. Usoskin, I.G., S.K. Solanki, N.A. Krivova, B. Hofer, G A. Kovaltsov, L. Wacker, N. Brehm and B. Kromer, Solar cyclic activity over the last millennium reconstructed from annual 14C data, Astron. Astrophys., 649, A141 (2021) doi: 10.1051/0004-6361/202140711 – we reconstruct individual cycles for the last millennium using recent 14C data and state-of-the-art models.
  8. Mishev, A.L., Koldobskiy, S.A., Kocharov, L.Get al. GLE # 67 Event on 2 November 2003: An Analysis of the Spectral and Anisotropy Characteristics Using Verified Yield Function and Detrended Neutron Monitor Data. Sol Phys 296, 79 (2021). – on the basis of an analysis of neutron monitor and space-borne data we derived the spectra and pitch-angle distribution of high-energy solar particles with their dynamical evolution throughout the event.
  9. Väisänen, P., I. Usoskin, and K. Mursula, Seven decades of neutron monitors (1951-2019): Overview and evaluation of data sources. J. Geophys. Res. Space Phys., 126, e2020JA028941, 2021. doi: 10.1029/2020JA028941 – a list of 29 “prime” stations with the longest and most reliable data and tabulate here a recommendation for the optimal data source of NM.
  10. Similä, M., I. Usoskin, S. Poluianov, A. Mishev, G.A. Kovaltsov, D. Strauss, High-Altitude Polar NM With the New DAQ System as a Tool to Study Details of the Cosmic-Ray Induced Nucleonic Cascade, J. Geophys. Res. Space Phys., 126, e2020JA028959, 2021, doi: 10.1029/2020JA028959 – аn analysis of the pulse characteristics (viz. shape, magnitude, duration, waiting time) has been performed.
  11. Golubenko, K., Rozanov, E., Kovaltsov, G., Leppänen, A.-P., Sukhodolov, T., and Usoskin, I.: Chemistry-climate model SOCOL-AERv2-BEv1 with the cosmogenic Beryllium-7 isotope cycle, Geosci. Model Dev. Discuss. [preprint], doi: 10.5194/gmd-2021-56, in review, 2021. – a new full 3D time-dependent model, based on SOCOL-AERv2, of beryllium atmospheric production, transport, and deposition has been developed and validated using directly measured data. 
  12. Koldobskiy, S., O. Raukunen, R. Vainio, G.A. Kovaltsov, I. Usoskin, New reconstruction of event-integrated spectra (spectral fluences) for major solar energetic particle events, Astron. Astrophys. 647, A132, 2021, doi: 10.1051/0004-6361/202040058 – we present the results of a full revision of the spectral fluences for most major SEP events (GLEs) for the period from 1956 to 2017 
  13. Mishev, A.L., S.A. Koldobskiy, I.G. Usoskin, L.G. Kocharov and G.A. Kovaltsov, Application of the Verified Neutron Monitor Yield Function for an Extended Analysis of the GLE # 71 on 17 May 2012, Space Weather, 19, e2020SW002626 (2021), doi: 10.1029/2020SW002626 – we computed the integrated exposure during the GLE # 71 and discussed the exposure of crew members/passengers to radiation at several altitudes.
  14. Aguilar, M. … S. Poluianov … I. Usoskin .. et al. (AMS Collaboration), Properties of Heavy Secondary Fluorine Cosmic Rays: Results from the Alpha Magnetic Spectrometer, Phys. Rev. Lett. 126, 081102, 2021, doi: 10.1103/PhysRevLett.126.081102 – we report the properties of heavy secondary cosmic ray fluorine F in the rigidity R range 2.15 GV to 2.9 TV based on 0.29 million events collected by the Alpha Magnetic Spectrometer experiment on the International Space Station. 
  15. Aguilar, M. et al. (AMS collaboration), The Alpha Magnetic Spectrometer (AMS) on the international space station: Part II— Results from the first seven years, Phys. Rep., 894, 1-116, 2021, doi: 10.1016/j.physrep.2020.09.003 – we present results based on 120 billion charged cosmic ray events up to multi-TeV energies. 
  16. Aguilar, M. et al. (AMS Collaboration), Properties of Iron Primary Cosmic Rays: Results from the Alpha Magnetic Spectrometer, Phys. Rev. Lett. 126, 041104, 2021, doi: 10.1103/PhysRevLett.126.041104 – reporting the observation of new properties of primary iron (Fe) cosmic rays in the rigidity range 2.65 GV to 3.0 TV with 0.62×106 iron nuclei collected by the Alpha Magnetic Spectrometer experiment on the International Space Station. 
  17. Usoskin, I.G., G.A. Kovaltsov, W. Kiviaho, Robustness of Solar-Cycle Empirical Rules Across Different Series Including an Updated Active-Day Fraction (ADF) Sunspot Group Series, Solar Phys., 296, 13, 2021. Doi: 10.1007/s11207-020-01750-9 – testing the robustness of empirical rules (Waldmeier rule and Gnevyshev–Ohl rule) for different sunspot (group) series for the period 1749 – 1996, using four classical and revised international sunspot-number and group sunspot-number series.
  18. Brehm, N., Bayliss, A., Christl, M., Synal, H., Adolphi, F., Beer, J, Kromer, B., Muscheler, R., Solanki, S.K., Usoskin, I., Bleicher, N., Bollhalder, S., Tyers, C. Wacker, L. Eleven-year solar cycles over the last millennium revealed by radiocarbon in tree rings. Nat. Geosci. (2021). – an annually resolved atmospheric 14C concentration (fractionation-corrected ratio of 14CO2 to CO2) record reconstructed from absolutely dated tree rings covering nearly all of the last millennium (AD 969–1933). 


  1. Terrasi, F., F. Marzaioli, R. Buompane, I. Passariello, G. Porzio, M. Capano, M., S Helama, M. Oinonen, P. Nöjd, J. Uusitalo, A.J.T. Jull, I.P. Panyushkina, C. Baisan, M. Molnar, T. Varga, G., S. Poluianov, I. Usoskin, Can the 14C production in 1055 CE be affected by SN1054? Radiocarbon, 62(5), 1403-1418, 2020. doi:10.1017/RDC.2020.58 – new results of annual and sub-annual 14C fluctuations in tree rings from a middle-latitude sequoia (California) and a high-latitude pine (Finland).
  2. A. Mishev and P.I.Y. Velinov Ionization effect in the Earth’s atmosphere during the sequence of October–November 2003 Halloween GLE events JASTP, Volume 211, December 2020, 105484 – quantification and comparison the 24 h and event averaged ionization effects.
  3. Mishev, A.L., S.A. Koldobskiy, I.G. Usoskin, L.G. Kocharov and G.A. Kovaltsov, Application of the Verified Neutron Monitor Yield Function for an Extended Analysis of the GLE # 71 on 17 May 2012, Space Weather, 19, e2020SW002626 (2021), doi: 10.1029/2020SW002626 – we derived the spectral and angular characteristics, and apparent source position of the solar protons during the GLE # 71, employing verified newly computed NM yield function and sophisticated unfolding procedure.
  4. Poluianov, S.V., G.A. Kovaltsov, I.G. Usoskin, A new full 3-D model of cosmogenic tritium 3H production in the atmosphere (CRAC:3H). J Geophys. Res. Atmos., 125, e2020JD033147, 2020. doi: 10.1029/2020JD033147 – a new model of cosmogenic tritium production in the atmosphere is presented.
  5. Strauss, D. T., S. Poluianov, C. van der Merwe, H. Krüger, C. Diedericks, H. Krüger, I. Usoskin, B. Heber et al., The mini-neutron monitor: a new approach in neutron monitor design, J. Space Weather Space Clim., 10, 39, 2020, doi: 10.1051/swsc/2020038. — the technical details of the mini-NM’s design and operation.
  6. Usoskin, I., S. Koldobskiy, G.A. Kovaltsov, A. Gil, I. Usoskina, T. Willamo and A. Ibragimov, Revised GLE database: Fluences of solar energetic particles as measured by the neutron-monitor network since 1956, Astron. Astrophys., 640, A17, 2020, doi; 10.1051/0004-6361/202038272. — all available data are collected in the International GLE Database (IGLED), which provides formal NM count-rate increases above the constant pre-increase level which is due to galactic cosmic rays (GCR).
  7. Usoskin, I.G., S.A. Koldobskiy, G.A. Kovaltsov, E.V. Rozanov, T.V. Sukhodolov, A.L. Mishev, I.A. Mironova, Revisited Reference Solar Proton Event of 23 February 1956: Assessment of the Cosmogenic‐Isotope Method Sensitivity to Extreme Solar Events, J. Geophys. Res., 125, e2020JA027921. doi: 10.1029/2020JA027921. — a study of proxy-method sensitivity to identify extreme SPEs.
  8. K. Golubenko, E. Rozanov, I. Mironova, A. Karagodin, I. Usoskin Natural sources of ionization and their impact on atmospheric electricity doi: 10.1029/2020GL088619 — a study of atmospheric electricity using the chemistry‐climate model SOCOL.
  9. M. Aguilar et al. (AMS Collaboration), Properties of Neon, Magnesium, and Silicon Primary Cosmic Rays Results from the Alpha Magnetic Spectrometer, Phys. Rev. Lett. 124, 211102, 2020, doi; 10.1103/PhysRevLett.124.211102. — measurements of neon (Ne), magnesium (Mg), and silicon (Si) in primary cosmic rays by the AMS-02 experiment.
  10. Mishev, A.L., I.G. Usoskin, Current status and a possible extension of the global neutron monitor network (Strategic and programming article), J. Space Weather Space Clim. 10, 17, 2020, doi: 10.1051/swsc/2020020. — the ability of the optimized global neutron monitor network to study various populations of solar energetic particles and to provide reliable space weather services.
  11. Mishev, A.L., S.A. Koldobskiy, G.A. Kovaltsov, A. Gil, I.G. Usoskin, Updated Neutron-Monitor Yield Function: Bridging Between In Situ and Ground-Based Cosmic Ray Measurements, J. Geophys. Res. Space Phys., 125, e2019JA027433, 2020, doi: 10.1029/2019JA027433 — The new YF is tabulated and parameterized and is ready to use.
  12. Kocharov, L. M. Pesce-Rollins, T. Laitinen, A. Mishev, P. Kühl, A. Klassen, M. Jin, N. Omodei, F. Longo, D.F. Webb, H.V. Cane, B. Heber, R. Vainio, and I. Usoskin, Interplanetary Protons versus Interacting Protons in the 2017 September 10 Solar Eruptive Event, Astrophys. J., 890, 13, 2020, doi: 10.3847/1538-4357/ab684e
  13. Frick, P., D. Sokoloff, R. Stepanov, V. Pipin and I. Usoskin, Spectral characteristic of mid-term quasi-periodicities in sunspot data, Mon. Not. R. Astron. Soc., 491, 5572–5578, 2020, doi: 10.1093/mnras/stz3238 — this paper presents an analysis of mid-term solar variability.


A list of non-referenced publications

  1. S. Koldobskiy, G. Kovaltsov, I. Usoskin, Role of heavier-than-proton nuclei in neutron monitor response, Proc. Of Sci., 395 (ICRC2021), 1284, 2021.
  2. S. Koldobskiy, O. Raukunen, R. Vainio, G. Kovaltsov, I. Usoskin, New reconstruction of the event-integrated spectra for GLE events, Proc. Of Sci., 395 (ICRC2021), 1273, 2021.
  3. A. Mishev, S. Koldobskiy, G. Kovaltsov, A. Gil, I. Usoskin, New neutron monitor altitude-dependent yield function and its application to an analysis of neutron-monitor data, Proc. Of Sci., 395 (ICRC2021), 1247, 2021.
  4. Similä, M., Poluianov, S. Usoskin, I., Mishev, A., Kovaltsov, G., Strauss, D.T. Pulse height-length analysis of data from neutron monitors DOMC/DOMB with a new data acquisition system, Proc. Of Sci., 395 (ICRC2021), 1237, 2021. doi:10.22323/1.395.1237
  5. Poluianov, S. and Mishev, A. The altitude profile of the cosmic ray atmospheric cutoff, Proc. Of Sci., 395 (ICRC2021), 1331, 2021. doi:10.22323/1.395.1331
  6. Usoskin, I., S. Koldobskiy, G. Kovaltsov, E. Rozanov, T. Sukhodolov, A. Mishev and I. Mironova, Strongest directly observed Solar Proton Event of 23-Feb-1956: Revised reference for the cosmogenic-isotope method, Proc. Of Sci., 395 (ICRC2021), 1319, 2021.
  7. Usoskin, I., S. Koldobskiy, A. Gil, G. Kovaltsov, I. Usoskina, T. Willamo and A. Ibragimov, A major update of the International GLE Database: Correction for the variable GCR background, Proc. Of Sci., 395 (ICRC2021), 1241, 2021.
  8. Kasztelan, M. M. Kasztelan, T. Enqvist, K. Jędrzejczak, J. Joutsenvaara, O. Kotavaara, P. Kuusiniemi, K.K. Loo, J. Orzechowski, J. Puputti, A. Sobkow, M. Słupecki, J. Szabelski, I. Usoskin, W.H. Trzaska and T.E. Ward, High-multiplicity neutron events registered by NEMESIS experiment, Proc. Of Sci., 395 (ICRC2021), 497, 2021.
  9. Trzaska, W.H. T. Enqvist, K. Jedrzejczak, J. Joutsenvaara, M. Kasztelan, O. Kotavaara, P. Kuusiniemi, K.K. Loo, J. Orzechowski, J. Puputti, A. Sobkow, M. Slupecki, J. Szabelski, I. Usoskin and T. E. Ward, New NEMESIS results, Proc. Of Sci., 395 (ICRC2021), 514, 2021.
  10. Poluianov, S., I. Usoskin, A. Ibragimov, Data management at the Oulu cosmic ray station, in: Cosmic ray studies with neutron detectors, pp. 205-207, Kiel University Publ. (2021) doi: 10.38072/2748-3150/p25.
  11. Similä, M., S. Poluianov, I. Usoskin, Study of individual pulses at the Antarctic high-altitude neutron monitor DOMC, in: Cosmic ray studies with neutron detectors, pp. 173-176, Kiel University Publ. (2021) doi: 10.38072/2748-3150/p22.
  12. Poluianov, S., I. Usoskin, D.T. Strauss, Upgrade of electronics of neutron monitors DOMC and DOMB, in: Cosmic ray studies with neutron detectors, pp- 167-172, Kiel University Publ. (2021) doi: 10.38072/2748-3150/p21.
  13. Abunina, M. R. Bütikofer, K.L. Klein, O. Kryakunova, M. Laurenza, D. Ruffolo, D. Sapundjiev, C. Steiges, I. Usoskin, 1st virtual symposium on cosmic ray studies with neutron detectors, in: Cosmic ray studies with neutron detectors, pp. 7-12, Kiel University Publ. (2021) doi: 10.38072/2748-3150/p1.