High altitude large-scale plasma waves in the equatorial electrojet at twilight

J. L. Chau (1) , D. L. Hysell (2)

1 Radio Observatorio de Jicamarca
2 EAS - Department of Earth and Atmospheric Sciences [Ithaca)

Jicamarca radar observations of a new class of large-scale plasma waves in the equatorial electrojet (EEJ) are presented and characterized. The study is based on long-term (204 days), single-baseline interferometry observations made in 2003 using a low-power radar mode, also known as JULIA mode, along with a few hours of observations made in an aperture synthesis imaging mode. The large-scale waves are found to occur at high altitudes in the E-region, mainly between 120 and 140km, around twilight (between 18:30 and 20:00 LT), with durations of a few minutes to an hour. In our long-term observations, these large-scale waves occur very often (between 1 and 5 out 10 nights), drift westward (~70 ms^?1), exhibit very narrow spectral widths, and have both positive and negative Doppler shifts. The imaging results show that the large-scale waves occur along tilted bands that sweep westward and downward (~30?60ms^?1), with a horizontal separation between bands of about 10?15km. The cause of the waves remains unknown.

Domaines: Océan, Atmosphère; Sciences de la Terre

J. L. Chau, D. L. Hysell. High altitude large-scale plasma waves in the equatorial electrojet at twilight. Annales Geophysicae, 2004, 22 (12), pp.4071-4076. ⟨hal-00317758⟩