Skip to main content

Advertisement

You are viewing the new article page. Let us know what you think. Return to old version

Article | Open | Published:

Local time dependence of the dominant frequency of Pi2 pulsations at mid- and low-latitudes

Abstract

We carried out a statistical analysis of Pi2 pulsations using the geomagnetic field data obtained at three ground stations. A local time dependence of the dominant frequency of Pi2 was found on the nightside. The frequency of mid-latitude Pi2 pulsations is lower on the dusk side than that on the dawn side. This tendency is attributed to the shape of the plasmasphere which bulges out to the dusk side. It was confirmed that the Pi2 frequency depends also on the geomagnetic activity measured with Kp index. During the disturbed periods, Pi2 pulsations have higher frequency than that in the quiet periods. This dependence is interpreted to be caused by the size of the plasmapause which is smaller under the disturbed conditions than that under the quiet conditions. The dominant frequency of Pi2 pulsations at lower latitudes has a peak in post-midnight, and a Kp dependence similar to that at mid-latitudes is also observed. However, the result for low-latitude Pi2’s is different from that for mid-latitude Pi2. We consider that the dominant mechanism of mid-latitude Pi2 is the plasmaspheric surface wave. In order to examine the idea that the surface wave on the plasmapause is the dominant mechanism of Pi2 pulsations at mid-latitudes, we estimated the resonance frequency of the surface wave on the plasmapause using a plasmaspheric model which includes the effect of the plasmaspheric bulge. The estimated frequency of the surface wave is higher on the dawn side than that on the dusk side, which is essentially consistent with the observational results. The predicted frequency under quiet conditions (Kp ≤ 3) is nearly equal to the observed Pi2 frequency at mid-latitudes. These results suggest that the dominant frequency of Pi2 pulsations at mid-latitudes depends on the structure of the plasmapause.

References

  1. Carpenter, D. L., Whistler studies of the plasmapause in the magnetosphere, 1, Temporal variations in the position of the knee and some evidence on the plasma motions on near knee, J. Geophys. Res., 71, 693–709, 1966.

  2. Carpenter, D. L. and R. R. Anderson, An ISEE/whistler model equatorial electron density in the magnetosphere, J. Geophys. Res., 97, 1097–1108, 1992.

  3. Chappell, C. R., K. K. Harris, and G. W. Sharp, A study of the influence of magnetic activity on the location of plasmasphere, J. Geophys. Res., 75, 3848–3861, 1970.

  4. Chen, L. and A. Hasegawa, A theory of long-period magnetic pulsations, 2. Impulse excitation of surface eigenmode, J. Geophys. Res., 79, 1033–1037, 1974.

  5. Cheng, C.-C., J.-K. Chao, and K. Yumoto, Spectral power of low-latitude Pi2 pulsations at the 210° magnetic meridian stations and plasmaspheric cavity resonances, Earth Planets Space, 52, 615–627, 2000.

  6. Decreau, P. M. E., D. L. Carpenter, C. R. Chappell, R. H. Comfort, J. Green, R. C. Olsen, and J. H. Waite, Jr., Latitudinal plasma distribution in the dusk plasmaspheric bulge: Refilling phase and quasi-equilibrium state, J. Geophys. Res., 91, 6929–6943, 1986.

  7. Fujita, S., H. Nakata, M. Itonaga, A. Yoshikawa, and T. Mizuta, A numerical simulation of the Pi2 pulsations associated with the substorm current wedge, J. Geophys. Res., 107(A3), 10.1029/2001JA900137, 2002.

  8. Fukunishi, H., Polarization changes of geomagnetic Pi2 pulsations associated with the plasmapause, J. Geophys. Res., 80, 98–110, 1975.

  9. Gallagher, D. L., P. D. Craven, and R. H. Comfort, Global core plasma model, J. Geophys. Res., 105, 10819–10833, 2000.

  10. Kepko, L., M. G. Kivelson, and K. Yumoto, Flow bursts, braking, and Pi2 pulsations, J. Geophys. Res., 106, 1903–1915, 2001.

  11. Kuwashima, M. and T. Saito, Spectral characteristics of magnetic Pi2 pulsations in the auroral region and lower latitudes, J. Geophys. Res., 86, 4686–4696, 1981.

  12. Lester, M. and D. Orr, Correlation between ground observations of Pi2 geomagnetic pulsations and satellite plasma density observations, Planet. Space Sci., 31, 143–160, 1983.

  13. Moore, T. E., D. L. Gallagher, J. L. Horwitz, and R. H. Comfort, MHD wave breaking in the outer plasmasphere, Geophys. Res. Lett., 14, 1007–1010, 1987.

  14. Nosé, M., T. Iyemori, M. Takeda, T. Kamei, D. K. Milling, D. Orr, H. J. Singer, E. W. Worthington, and N. Sumitomo, Automated detection of Pi2 pulsations using wavelet analysis: 1. Method and an application for substorm monitoring, Earth Planets Space, 50, 773–783, 1998.

  15. Olson, J. V, Pi2 pulsations and substorm onsets: A review, J. Geophys. Res., 104, 17499–17520, 1999.

  16. Osaki, H., K. Takahashi, H. Fukunishi, T. Nagatsuma, H. Oya, A. Matsuoka, and D. K. Milling, Pi2 pulsations observed from the Akebono satellite in the plasmasphere, J. Geophys. Res., 103, 17605–17615, 1998.

  17. Saito, T., Geomagnetic pulsations, Space Sci. Rev., 10, 319–412, 1969.

  18. Saito, T., T. Sakurai, and Y. Koyoma, Mechanism of association between Pi2 pulsation and magnetospheric substorm, J. Atmos. Terr. Phys., 38, 1265–1277, 1976.

  19. Sutcliffe, P. R., The association of harmonics in Pi2 power spectra with the plasmapause, Planet. Space Sci., 23, 1581–1587, 1975.

  20. Takahashi, K., W. J. Hughes, B. J. Anderson, and S. I. Solovyev, CRRES satellite observations associated with low-latitude Pi2 pulsations, J. Geophys. Res., 104, 17431–17440, 1999.

  21. Tarcsai, Gy., Ionosphere-plasmasphere electron fluxes at middle latitudes obtained from whistlers, Advances in Space Research, 5, 155–158, 1985.

  22. Yeoman, T. K. and D. Orr, Phase and spectral power of mid-latitude Pi2 pulsations: Evidence for a plasmaspheric cavity resonance, Planet. Space Sci., 37, 1367–1383, 1989.

  23. Young, D. T., H. Balsiger, and J. Geiss, Correlations of magnetospheric ion composition with geomagnetic and solar activity, J. Geophys. Res., 87, 9077–9096, 1982.

  24. Yumoto, K. and the CPMN Group, Characteristics of Pi2 magnetic pulsations observed at the CPMN stations: A review of the STEP results, Earth Planets Space, 53, 981–992, 2001.

Download references

Author information

Correspondence to Kazuhiro Kosaka.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Keywords

  • Surface Wave
  • Local Time
  • Dominant Frequency
  • Geomagnetic Activity
  • Disturbed Condition