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pure and applied geophysics

, Volume 65, Issue 1, pp 102–124 | Cite as

Spectral analysis of geomagnetic pulsations from 0.5 to 100 sec in period for the quiet sun condition

  • Takeo Hirasawa
  • Takesi Nagata
Article

Summary

A special technique is introduced to observe continuously dynamic spectra of geomagnetic pulsations from 0.002 to 2.0 cps in frequency. Observation and analyses of these spectra have been continued on semi-routine basis in the authors' observatory since April 1964. Main observed results are as follows:
  1. a)

    Pc-4 pulsations of 0.015 cps in average frequency appear almost throughout a day, being the most active around 09 h LT; their frequency is maximum about 07 h and minimum about 19 h.

     
  2. b)

    Pi-2 pulsations with noise-burst-like high frequency components are the most active around the midnight; these irregular pulsations excite the regular pc-4 band.

     
  3. c)

    Pc-3 pulsations of 0.035 cps in average frequency appear only in the daytime with a positive correlation with the geomagnetic activity; their frequency decreases almost parallel to that of pc-4 from the morning to the evening.

     
  4. d)

    The well-known pulsations of pc-1, pc-2 and pi-1 ranges are also observed. Owing to the attenuation by the ionosphere, their activity is dominant only in the night time. In addition to the pearl-necklace type, noise bursts of 0.2 to 2.0 cps are particularly characteristic in this rauge. The frequency of pc-2 has a regular daily variation which is parallel to that of pc-4.

     

Keywords

Geomagnetic Activity Noise Burst Geomagnetic Pulsation Irregular Pulsation Regular Daily Variation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Zusammenfassung

Eine neue Technik ist vorgeschlagen, mit der das dynamische Spektrum der erdmagnetischen Pulsationen mit der Frequenz von 0.002 bis 2.0 Hz fortlaufend aufgenommen wird. Seit April 1964 sind die Beobachtung und die Analyse der Pulsationsspektra in unserem Observatorium durchgeführt worden. Die Hauptresultate der Analyse sind folgende:
  1. a)

    Pc-4 Pulsationen mit durchschnittlicher Frequenz von 0.015 Hz treten fast den ganzen Tag durch auf, mit der stärksten Aktivität um 09 Uhr lokale Zeit. Die Frequenz dieser Pulsationen ist am längsten um 07 Uhr, am kürzesten um 19 Uhr.

     
  2. b)

    Pi-2 Pulsationen mit geräuschausbruchähnlichen Hochfrequenz-Komponenten zeigen den häufigsten Auftritt gegen Mitternacht. Diese unregelmässigen Pulsationen regen die üblichen pc-4 auf.

     
  3. c)

    Pc-3 Pulsationen mit der Durchschnittsfrequenz von 0.035 Hz treten nur am Tage mit einer positiven Korrelation mit der erdmagnetischen Unruhe auf. Ihre Frequenz nimmt fast parallel zur Frequenz von pc-4 von Morgen bis Abend ab.

     
  4. d)

    Die bekannten Pulsationen von pc-1-, pc-2- und pi-1-Gruppen mit kürzeren Perioden werden auch registriert. Ihre Aktivität ist bemerkbar nur in der Nacht, wegen ihrer Verkleinerung durch die Ionosphäre. Ausser den Perlenhalskettenpulsationen treten die Geräuschausbrüche mit Frequenzen von 0.2 bis 2.0 Hz oft merkwürdig auf. Die Wellenfrequenz von pc-2 zeigt einen regel mässigen Tagesgang, der parallel zur Frequenzvariation von pc-4 ist.

     

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Copyright information

© Birkhäuser Verlag 1966

Authors and Affiliations

  • Takeo Hirasawa
  • Takesi Nagata
    • 1
  1. 1.Geophysics Research LaboratoryUniversity of TokyoTokyoJapan

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