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The post-noon region (around 14 MLT) seems to have a special significance in magnetospheric physics. The other R1 field-aligned current maxima occurs there (see also Bythrow et al, 1994), and measurements have shown strong particle precipitation occurring there (McDiarmid et al., 1975; Evans, 1985). These relate to a general enhancement of auroral intensity within this region (Snyder and Akasofu, 1976; Shepherd et al., 1976; Cogger et al., 1977; Murphree et al., 1981; Meng and Lundin, 1986). It is possible that this activity is somehow also linked with the nightside substorm activity (Lui et al., 1987).

The auroral activity consists often of separate bright spots with uniform spacing, estimated to be about 1.5 hours of local time by Lui et al. (1987). Similar spots have also been seen in the nightside, and they may correspond to deformed auroral arcs (folds etc.) when seen from the ground.


  • Bythrow, P. F., B. J. Anderson, T. A. Potemra, L. J. Zanetti, J. D. Winningham, and D. L. Chenette, Filamentary current structures in the postnoon sector: Observations from UARS, J. Geophys. Res., 99, 14917-14929, 1994.
  • Cogger, L. L., J. S. Murphree, S. Ismail, and C. D. Anger, Characteristics of dayside 5577 A and 3914 A aurora, Geophys. Res. Lett., 4, 413, 1977.
  • Evans, D. S., The characteristics of a persistent auroral arc at high latitude in the 1400 MLT sector, in The Polar Cusp, edited by J. A. Holtet and A. Egeland, p. 99, D. Reidel Pub. Co., Dordrecht, Holland, 1985.
  • Lui, A. T. Y., D. Venkatesan, and J. S. Murphree, Auroral bright spots on the dayside oval, J. Geophys. Res., 94, 5515-5522, 1989.
  • McDiarmid, I. B., J. R. Burrows, and E. E. Budzinski, Average characteristics of magnetospheric electrons (150 eV to 300 keV) at 1400 km, J. Geophys. Res., 80, 73, 1975.
  • Murphree, J. S., L. L. Cogger, and C. D. Anger, Characteristics of the instantaneous oval in 1200.1800 MLT sector, J. Geophys. Res., 86, 7657, 1981.
  • Shepherd, G. G., F. W. Thirkettle, and C. D. Anger, Topside optical view of the dayside cleft aurora, Planet. Space Sci., 24, 937, 1976.
  • Snyder, A. L., and S.-A. Akasofu, Auroral oval photographs from the DMSP 8531 and 10533 satellites, J. Geophys. Res., 81, 1799, 1976.
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