Temporal and Periodic Variations of the Solar Flare Index During the Last Four Solar Cycles and Their Association with Selected Geomagnetic-Activity Parameters

Ozguc A., KILÇIK A., Yurchyshyn V.

Solar Physics, cilt.297, sa.9, 2022 (SCI-Expanded) identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 297 Sayı: 9
  • Basım Tarihi: 2022
  • Doi Numarası: 10.1007/s11207-022-02049-7
  • Dergi Adı: Solar Physics
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Aerospace Database, INSPEC
  • Anahtar Kelimeler: Active regions, Flares, Geomagnetic activity, Observations, Oscillations, Solar, Solar cycle
  • Akdeniz Üniversitesi Adresli: Evet

Özet

© 2022, The Author(s), under exclusive licence to Springer Nature B.V.We studied the temporal and periodic variations of the monthly solar flare index (FI) and selected geomagnetic-activity parameters (Ap, Dst, Scalar B, and aa) measured during Solar Cycles 21 – 24 (from January 1, 1975 to December 31, 2020) and report the following findings: 1) all data sets except the FI peak values gradually decreased after 1992, while the FI peak values began their gradual decrease in 1982; 2) all data sets show double or multiple peaks during the maximum phase of solar cycles; 3) the FI shows meaningful correlations with the investigated geomagnetic-activity parameters; 4) the 11-year sunspot-cycle periodicity and periodicities lower than 3.9 months were observed in all data sets without exception; 5) the FI time series exhibits a unique period of 4.8 – 5.2 months that is not present in all the other indices, while geomagnetic aa, Ap, and Dst indices show a unique 6 – 6.1 months periodicity that does not appear in the scalar B and FI; 6) crosswavelet transform (XWT) spectra between FI and other parameters generally show phase mixing in the short (2 – 8 months) period range, while all parameters used in this study were found to be inphase and highly correlated with the 11-year solar-activity period. All these results show that the FI variations are one of the main drivers of the geomagnetic activity.