Theories of the Origin of Pc 1 Pulsations

  • J. A. Jacobs
Part of the Physics and Chemistry in Space book series (SPACE, volume 1)


One model of Pc 1 pulsations is that they are the result of oscillations of bunches of monochromatic particles trapped by the Earth’s magnetic field. In this case the period of Pc 1’s is that of the oscillations of the bunch from one conjugate point to the other, and their amplitude is determined by the density and energy of the charged particles in the group, by the height of the mirror points and by the absorption of hydro-magnetic (hm) waves in the ionosphere. The basis for such a view is the morphological features of Pc 1’s and their connection with other upper atmospheric phenomena. It is further suggested that the spacing between successive “pearls” is the drift time of the particles around the Earth. R. C. Wentworth and L.R. Tepley (1962) assumed the particle bunches to consist of energetic electrons and Table 4.1 shows their calculated and the observed data for Pc 1’s. The mirror points of the particle bunches are thought to be situated above the F-2 layer of the ionosphere. As the ionosphere has high conductivity, the arrival of a diamagnetic bunch of particles at the mirror point cannot be recorded directly at the surface of the Earth. The disturbance must reach the E-layer as a hm wave. Propagation through the ionosphere reduces the disturbance because of absorption due to joule heating.
Table 4.1

Data for Pc 1 Oscillations (after R. C. Wentworth and L. R. Tepley, 1962)


Palo Alto




Geomagnetic latitude





Full length of arc (× 10-9 cm)





Energy of electrons for 1 Hz oscillations (kev)





Electron drift velocity for 1 Hz oscillations (× 10-5 rad/sec)





Maximum frequency of oscillations (Hz)





Maximum frequency of oscillations for a point 500 km distant (Hz)





Maximum observed frequency of hydromagnetic emissions (Hz)






External Magnetic Field Field Line Conjugate Point Magnetic Line Auroral Oval 
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.


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  1. Akasofu, S.-I.: The auroral oval, the auroral sub-storm and their relations with the internal structure of the magnetosphere. Planet. Space Sci. 14, 587–595 (1966).ADSCrossRefGoogle Scholar
  2. Bostick, F. X., Jr.: Private communication 1963.Google Scholar
  3. Brice, N.: Fundamentals of very low frequency emission generation mechanisms. J. Geophys. Res. 69, 4515–4522 (1964).ADSCrossRefGoogle Scholar
  4. Brice, N.: Discrete VLF emissions from the upper atmosphere. Stanford Electronics Lab. Tech. Rept. No. 3412–6, Stanford Univ. 1964.Google Scholar
  5. Carpenter, D. L.: Whistler studies of the plasmapause in the magnetosphere 1. Temporal variations in the position of the knee and some evidence on plasma motions near the knee. J. Geophys. Res. 71, 693–709 (1966).ADSCrossRefGoogle Scholar
  6. Cornwall, J. M.: Micropulsations and the outer radiation zone. J. Geophys. Res. 71, 2185–2199 (1966).ADSCrossRefGoogle Scholar
  7. Criswell, D. R.: Pc 1 micropulsation activity and magnetospheric amplification of 0.2 to 5.0 Hz hydromagnetic waves. J. Geophys. Res. 74, 205–224 (1969).ADSCrossRefGoogle Scholar
  8. Davis, L. R., Williamson, J. M.: Space Research III. (Ed. W. Priester.) North Holland Publ. Co. 1963.Google Scholar
  9. Dessler, A. J.: The propagation velocity of world wide sudden commencements of magnetic storms. J. Geophys. Res. 63, 507–511 (1958).ADSCrossRefGoogle Scholar
  10. Dowden, R. L.: Micropulsation mode propagations in the magnetosphere. Planet. Space Sci. 13, 761–772 (1965).ADSCrossRefGoogle Scholar
  11. Dowden, R. L., Emery, M. W.: The use of micropulsation whistlers in the study of the outer magnetosphere. Planet. Space Sci. 13, 773–779 (1965).ADSCrossRefGoogle Scholar
  12. Field, E. C., Greifinger, C.: Transmission of geomagnetic micropulsations through the ionosphere and lower exosphere. J. Geophys. Res. 70, 4885–4899 (1965).ADSCrossRefGoogle Scholar
  13. Gendrin, R.: Sur une théorie des pulsations rapides structurées du champ magnétique terrestre. Ann. Geophys. 19, 197–214 (1963).Google Scholar
  14. Greifinger, C., Greifinger, P. S.: Theory of hydromagnetic propagation in the ionospheric waveguide. J. Geophys. Res. 73, 7473–7490 (1968).ADSCrossRefGoogle Scholar
  15. Heacock, R. R.: Notes on pearl-type micropulsations. J. Geophys. Res. 68, 589–591 (1963).ADSCrossRefGoogle Scholar
  16. Heacock, R. R.: The 4-second summertime micropulsation band at College. J. Geophys. Res. 71, 2763–2775 (1966).ADSCrossRefGoogle Scholar
  17. Helliwell, R. A.: Whistler-triggered periodic very low frequency emissions. J. Geophys. Res. 68, 5387–5395 (1963).ADSGoogle Scholar
  18. Hines, C. O.: Internal atmospheric gravity waves at ionospheric heights. Can. J. Phys. 38, 1441–1481 (1960).ADSCrossRefGoogle Scholar
  19. Jacobs, J. A., Watanabe, T.: Propagation of hydromagnetic waves in the lower exosphere and the origin of shortperiod geomagnetic pulsations. J. Atmos. Terr. Phys. 24, 413–434 (1962).ADSCrossRefGoogle Scholar
  20. Jacobs, J. A., Watanabe, T.: Trapped charged particles as the origin of short period geomagnetic pulsations. Planet. Space Sci. 11, 869–878 (1963).ADSCrossRefGoogle Scholar
  21. Jacobs, J. A., Watanabe, T.: Micropulsation whistlers. J. Atmos. Terr. Phys. 26, 825–829 (1964).ADSCrossRefGoogle Scholar
  22. Jacobs, J. A., Watanabe, T.: Amplification of hydromagnetic waves in the magnetosphere by a cyclotron instability process with application to the theory of hydromagnetic whistlers. J. Atmos. Terr. Phys. 28, 235–253 (1966).ADSCrossRefGoogle Scholar
  23. Jacobs, J. A., Watanabe, T.: Theoretical notes on whistlers and periodic emissions in the hydromagnetic regime. Planet. Space Sci. 15, 799–809 (1967).ADSCrossRefGoogle Scholar
  24. Kenney, J. F., Knaflich, H. B.: A systematic study of structured micropulsations. J. Geophys. Res. 72, 2857–2869 (1967).ADSCrossRefGoogle Scholar
  25. Kimura, I.: Meeting on cosmic plasma physics. Inst. Plasma Phys., Nagoya Univ., Japan, 1962.Google Scholar
  26. Lokken, J. E.: Private communication 1963.Google Scholar
  27. MacDonald, G. J. F.: Spectrum of hydromagnetic waves in the exosphere. J. Geophys. Res. 66, 3639–3670 (1961).MathSciNetADSCrossRefGoogle Scholar
  28. Manchester, R. N.: Propagation of Pc 1 micropulsations from high to low latitudes. J. Geophys. Res. 71, 3749–3754 (1966).ADSCrossRefGoogle Scholar
  29. Manchester, R. N.: Correlation of Pc 1 micropulsations at spaced stations. J. Geophys. Res. 73, 3549–3556 (1968).ADSCrossRefGoogle Scholar
  30. Matveeva, E. T., Troitskaya, V. A.: Investigations of pearl type pulsations for the years 1957–1964. Rep. Inst. Phys. Earth, Moscow 1965.Google Scholar
  31. Obayashi, T.: Hydromagnetic whistlers. J. Geophys. Res. 70, 1069–1082 (1965).ADSCrossRefGoogle Scholar
  32. Prince, C. E., Bostick, F. X., Jr., Smith, H. W.: A study of the transmission of plane hydromagnetic waves through the upper atmosphere. Elec. Eng. Res. Lab., Univ. Texas Rept. No. 134, 1964.Google Scholar
  33. Sen, A. K.: Pearl time geomagnetic oscillations. J. Atmos. Terr. Phys. 30, 439–451 (1968).ADSCrossRefGoogle Scholar
  34. Smith, R. L.: Properties of the outer ionosphere deduced from nose whistlers. J. Geophys. Res. 66, 3709–3716 (1961).ADSCrossRefGoogle Scholar
  35. Sturrock, P. A.: Kinematics of growing waves. Phys. Rev. 112, 1488–1503 (1958).MathSciNetADSMATHCrossRefGoogle Scholar
  36. Tepley, L. R., Heacock, R. R., Fraser, B. J.: Hydromagnetic emissions (Pc 1) observed simultaneously in the auroral zone and at low latitudes. J. Geophys. Res. 70, 2720–2725 (1965).ADSCrossRefGoogle Scholar
  37. Tepley, L. R., Landshoff, R. K.: Waveguide theory for ionospheric propagation of hydromagnetic emissions. J. Geophys. Res. 71, 1499–1504 (1966).ADSCrossRefGoogle Scholar
  38. Watanabe, T.: Determination of the electron distribution in the magnetosphere using hydromagnetic whistlers. J. Geophys. Res. 70, 5839–5848 (1965).ADSCrossRefGoogle Scholar
  39. Watanabe, T.: Quasi linear theory of transverse plasma instabilities with applications to hydromagnetic emissions from the magnetosphere. Can. J. Phys. 44, 815–835 (1966).ADSCrossRefGoogle Scholar
  40. Wentworth, R. C.: Evidence for maximum production of hydromagnetic emissions above the afternoon hemisphere of the Earth, I, Extrapolation to the base of the exosphere. J. Geophys. Res. 69, 2689–2698 (1964a).ADSCrossRefGoogle Scholar
  41. Wentworth, R. C.: Evidence for maximum production of hydromagnetic emissions above the afternoon hemisphere of the Earth, II, Analysis of statistical studies. J. Geophys. Res. 69, 2699–2705 (1964b).ADSCrossRefGoogle Scholar
  42. Wentworth, R. C.: Recent investigations of hydromagnetic emissions. Part II. J. Geomag. Geoelect. 18, 257–273 (1966).CrossRefGoogle Scholar
  43. Wentworth, R. C., Tepley, L. R.: Hydromagnetic emissions, X-ray bursts and electron bunches, Part 2., Theoretical interpretation. J. Geophys. Res. 67, 3335–3343 (1962).ADSCrossRefGoogle Scholar
  44. Wentworth, R. C., Tepley, L. R., Amundsen, K. D.: Intra-and inter hemisphere differences in occurrence times of hydromagnetic emissions. J. Geophys. Res. 71, 1492–1498 (1966).ADSCrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin · Heidelberg 1970

Authors and Affiliations

  • J. A. Jacobs
    • 1
  1. 1.Killam Memorial Professor of ScienceThe University of AlbertaEdmontonCanada

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