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<p>Forbush decreases (FDs) are short-term reductions in the time-intensity flux of cosmic rays (CRs). Their spectacular and unpredictable intensity variations present their detection, timing, magnitude estimation, and cataloging as one of the most difficult tasks in space weather research. Due to the paucity of accurate event lists, new methods of event detection and FD catalogs continue to appear in the literature. But validation of either the old or new lists remains an open field. This work intends to remind the astrophysicist and space weather community that dramatic modifications of the age-long manual/semi-manual FD event cataloging are long overdue. In this present era of extremely fast and sophisticated computer algorithms, a complementary automated list of all the manually created FD catalogs, especially the IZMIRAN (Pushkin Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation, Russian Academy of Sciences, <a href="http://spaceweather.izmiran.ru/eng/dbs.html">http://spaceweather.izmiran.ru/eng/dbs.html</a>) (which is the currently available and widely used lists) should have been developed, the old lists expanded and new catalogs created. A Fourier decomposition technique, which guarantees the sinusoidal fidelity of the input and output signals, is presented. This highlights the possibility of a complete algorithm-based FD cataloging with the aim of stimulating other automated methodological approaches. The impossibility of creating accurate FD lists without first disentangling the contribution from diurnal CR anisotropy and the 11-year solar oscillation was qualitatively analyzed. Using a set of CR data from Moscow station, we automatically created four different FD catalogs − FD1 from the raw data without adjusting for the contribution from the 11-year solar cycle oscillation or CR anisotropy, FD2 after adjusting for the 11-year solar cycle effects, FD3 after adjusting for CR anisotropy and FD4 after adjusting for both the 11-year and CR anisotropy. This allows us to practically demonstrate the possible discrepancies among different FD catalogs and the attendant bias implications on FD-based space weather investigation. Given the detailed analyses performed, FD4 is the most accurate FD list. This serves as an evidence that accurate FD catalog is realizable. We also establish that several of the events in FD1, FD2 and FD3 catalogs may be intensity reductions/spurious events arising from other CR phenomena like anisotropies.</p>

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Accurate cataloging of Forbush decreases: implications for space weather research

  • 期刊论文

  • 发表日期：

    2025年10月22日

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  • O. Okike,
  • O. C. Nwuzor,
  • P. I. Rowland,
  • O. Ogunjobi,
  • Z. Mtumela,
  • J. B. Habarulema,
  • F. M. Menteso,
  • R. E. Ugwoke,
  • C. J. Ugwu,
  • I. O. Eya,
  • J. A. Alhassan,
  • A. E. Chukwude,
  • E. U. Iyida,
  • P. A. Nwofe,
  • U. Iburu,
  • F. N. Anekwe,
  • C. I. Onah

摘要

Forbush decreases (FDs) are short-term reductions in the time-intensity flux of cosmic rays (CRs). Their spectacular and unpredictable intensity variations present their detection, timing, magnitude estimation, and cataloging as one of the most difficult tasks in space weather research. Due to the paucity of accurate event lists, new methods of event detection and FD catalogs continue to appear in the literature. But validation of either the old or new lists remains an open field. This work intends to remind the astrophysicist and space weather community that dramatic modifications of the age-long manual/semi-manual FD event cataloging are long overdue. In this present era of extremely fast and sophisticated computer algorithms, a complementary automated list of all the manually created FD catalogs, especially the IZMIRAN (Pushkin Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation, Russian Academy of Sciences, http://spaceweather.izmiran.ru/eng/dbs.html) (which is the currently available and widely used lists) should have been developed, the old lists expanded and new catalogs created. A Fourier decomposition technique, which guarantees the sinusoidal fidelity of the input and output signals, is presented. This highlights the possibility of a complete algorithm-based FD cataloging with the aim of stimulating other automated methodological approaches. The impossibility of creating accurate FD lists without first disentangling the contribution from diurnal CR anisotropy and the 11-year solar oscillation was qualitatively analyzed. Using a set of CR data from Moscow station, we automatically created four different FD catalogs − FD1 from the raw data without adjusting for the contribution from the 11-year solar cycle oscillation or CR anisotropy, FD2 after adjusting for the 11-year solar cycle effects, FD3 after adjusting for CR anisotropy and FD4 after adjusting for both the 11-year and CR anisotropy. This allows us to practically demonstrate the possible discrepancies among different FD catalogs and the attendant bias implications on FD-based space weather investigation. Given the detailed analyses performed, FD4 is the most accurate FD list. This serves as an evidence that accurate FD catalog is realizable. We also establish that several of the events in FD1, FD2 and FD3 catalogs may be intensity reductions/spurious events arising from other CR phenomena like anisotropies.