Pi C pulsations
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Introduction
ULF range continuous Pi C geomagnetic pulsations are
generally seen in the morning sector and at the low-frequency end
of the Pi 1 (1-40 s) range (Heacock, 1967).
The magnetic activity consists of pulses spaced irregularly about 10 s apart
and lasts up to several hours.
A very good correlation has been observed between the PiC and the auroral luminosity
variation (Oguti et al., 1979, 1984; Arnoldy et al., 1982; Engebretson et al., 1983, 1986;
Oguti and Hayashi, 1984; Burns and Cole, 1985; Burns and Craven, 1988; Grant and Burns, 1995).
Thus it seems obvious that the pulsations are created by the
pulsating auroras
as the conductivity changes driven by the precipitation pulsations modulate both the
ionospheric currents and field-aligned currents
(see the model calculations by, e.g., Oguti and Hayashi (1984) and Grant and Burns (1995).
It has been suggested that the 3-s enhancement seen in the Pi1B
should be called a special type of PiC related to resonant cavities, e.g.,
IAR (Grant and Burns, 1995; Arnoldy et al., 1998).
References
- Arnoldy, R. L., K. Dragoon, L. J. Cahill Jr., S. B. Mende, and T. J. Rosenberg,
Detailed correlations of magnetic field and riometer observations at L = 4.2 with pulsating
aurora, J. Geophys. Res., 87, 10449-10456, 1982.
- Arnoldy, R. L., J. L. Posch, M. J. Engebretson, H. Fukunishi, and
H. J. Singer, Pi1 magnetic pulsations in space and at high latitudes on
the ground, J. Geophys. Res., 103, 23581-23591, 1998.
- Åsheim, S. and K. Aarsnes, Optical and magnetic pulsations,
Planet. Space Sci., 32, 735-, 1984.
- Burns, G. B., and K. D. Cole, Ionospheric sources of Pi(c) magnetic pulsations,
J. Atmos. Terr. Phys., 47, 587-599, 1985.
- Burns, G. B., and M. Craven, Pi(c) magnetic pulsations: Their relation to
ionospheric currents, J. Atmos. Terr. Phys., 50, 231-241, 1988.
- Grant, I. F. and G. B. Burns, Observations and modeling of correlated
Pi B magnetic and auroral luminosity pulsations,
J. Geophys. Res., 100, 19387-19404, 1995.
- Engebretson, M. J., L. J. Cahill Jr., R. L. Arnoldy, S. B. Mende, and T. J. Rosenberg,
Correlated irregular magnetic pulsations and optical emissions observed at Siple station,
Antarctica, J. Geophys. Res., 88, 4841-4852, 1983.
- Engebretson, M. J., L. J. Cahill Jr., J. D. Winningham, T. J. Rosenberg, R. L. Arnoldy,
N. C. Maynard, M. Sugiura, and J. H. Doolittle,
Relations between morning sector Pi 1 pulsation activity and particle and field characteristics
observed by the DE 2 satellite, J. Geophys. Res., 91, 1535-1547 1986.
- Heacock, R. R., Two subtypes of Pi micropulsations, J. Geophys. Res.,
72, 3905, 1967
- Oguti, T. et al., Auroral and magnetic pulsations, Proceedings of the
International Workshop on Selected Topics of the Magnetospheric Physics, Tokyo, May 1979,
Jap. IMS-commity., 1979.
- Oguti, T., J. H. Meek, and K. Hayashi, Multiple correlations between auroral and magnetic
pulsations, J. Geophys. Res., 89, 2295-2303, 1984.
- Oguti, T., and K. Hayashi, Multiple correlation between auroral and magnetic
pulsations, 2, Determination of electric currents and electric fields around a pulsating
auroral pathc, J. Geophys. Res., 89, 7467-7481, 1984.
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