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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, A03307, doi:10.1029/2007JA012661, 2008

Optical observations of the growth and day-to-day variability of equatorial plasma bubbles

J. J. Makela

Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA


E. S. Miller

Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA


Abstract

A new narrow-field ionospheric imaging system, the Portable Ionospheric Camera and Small-Scale Observatory, has been installed at the Cerro Tololo Inter-American Observatory near La Serena, Chile (geographic 30.17°S, 289.19°E; geomagnetic 16.72°S, 0.42°E). We present observations of the naturally occurring nightglow emission at 630.0 nm on three consecutive nights demonstrating the day-to-day variability in the occurrence of equatorial plasma bubbles or depletions. On two nights, large-scale undulations with a wavelength on the order of 300–600 km are observed in the emission regions magnetically connected to the bottomside of the equatorial F layer. We demonstrate that at each crest of these large-scale waves, zero, one, or multiple depletions may grow. Thus, the presence of a large-scale wave on the bottomside alone is not sufficient for irregularity growth. This variability is presumably due to the presence, or lack, of small-scale seed waves or some other mechanism needed to increase the instability growth rate past the critical threshold.

Received 19 July 2007; accepted 20 December 2007; published 19 March 2008.

Keywords: equatorial plasma bubbles; airglow; equatorial irregularities.

Index Terms: 2439 Ionosphere: Ionospheric irregularities; 2415 Ionosphere: Equatorial ionosphere; 2494 Ionosphere: Instruments and techniques; 7999 Space Weather: General or miscellaneous.

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Citation: Makela, J. J., and E. S. Miller (2008), Optical observations of the growth and day-to-day variability of equatorial plasma bubbles, J. Geophys. Res., 113, A03307, doi:10.1029/2007JA012661.