146-day signal in the geomagnetic field—a probable association with the periodicity of the solar flare index

  • D. R. K. Rao
  • B. D. Kadam


Results on the spectral analysis using geomagnetic field at three low latitude stations and the planetary magnetic activity index have shown peaks in the power densities in a broad band centred around 146-day period. This periodic behaviour appears to be close to that shown by the solar flare activity index for the same interval. It is suggested that the geoeffectiveness of the flare activity signal in different phases of the solar cycle can be better worked out using long series of ground-based geomagnetic data.


Flare index 146-day period geomagnetic planetary index geomagnetic field 


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  1. Cooley J W and Tukey J W 1965Math. Compt. 19 297CrossRefGoogle Scholar
  2. Ichimoto K, Kubota J, Suzuki M, Tohmura I and Munokawa H 1985 Periodic behaviour of solar flare activity;Nature (London) 316 422–424CrossRefGoogle Scholar
  3. Munk W H, Snodgram F F and Tacker M J 1959 Spectra of low frequency ocean waves;Bull. Scripps Inst. Oceanogr. Univ. Calif. 7 283–362Google Scholar
  4. Rieger E, Share G H, Forrest D J, Kanbach G, Reppin C and Chupp E L 1984 A 154-day periodicity in the occurrence of hard solar flares;Nature (London) 312 623–625CrossRefGoogle Scholar
  5. Stuart W F, Sherwood V and Macintosh S M 1971 The power spectral density technique applied to micropulsation analysis;Pure Appl. Geophys. 92 150–154CrossRefGoogle Scholar
  6. Tukey J W 1961 Discussion emphasizing the connection between analysis of variance and spectrum analysis;Technometrics 3 210CrossRefGoogle Scholar

Copyright information

© Indian Academy of Sciences 1987

Authors and Affiliations

  • D. R. K. Rao
    • 1
  • B. D. Kadam
    • 1
  1. 1.Indian Institute of GeomagnetismBombayIndia

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