Morphology of the postsunset vortex in the equatorial ionospheric plasma drift

The postsunset vortex in the equatorial ionosphere exhibits clockwise plasma motions after sunset in longitude (time) and altitude coordinates when the equatorial ionosphere is viewed looking northward. We describe the typical morphology of the postsunset vortex using incoherent scatter radar observations at Jicamarca in Peru during the previous solar maximum (2000–2002). A pronounced vortical plasma motion appears around 1700 LT along with the onset of the prereversal enhancement (PRE). The center of this vortex is located near an altitude of 270 km. A smaller‐scale vortex also appears about 0.5 ~ 1 h later at higher altitudes. However, the morphology and occurrence time of this small vortex depend on the characteristics of the coherent backscatter region. We find that the earlier vortex is the major feature of the postsunset vortices because it is repeatable, associated with the PRE, and independent to the occurrence of the coherent backscatter region.

[1]  Yongliang Zhang,et al.  The zonal motion of equatorial plasma bubbles relative to the background ionosphere , 2014 .

[2]  G. Crowley,et al.  On TIE‐GCM simulation of the evening equatorial plasma vortex , 2012 .

[3]  David L. Hysell,et al.  Equatorial spread-F initiation: Post-sunset vortex, thermospheric winds, gravity waves , 2007 .

[4]  C. Swenson,et al.  Onset conditions for equatorial spread F determined during EQUIS II , 2005 .

[5]  David L. Hysell,et al.  Collisional shear instability in the equatorial F region ionosphere , 2004 .

[6]  J. Eccles,et al.  Study of the evening plasma drift vortex in the low‐latitude ionosphere using San Marco electric field measurements , 1999 .

[7]  Erhan Kudeki,et al.  Postsunset vortex in equatorial F‐region plasma drifts and implications for bottomside spread‐F , 1999 .

[8]  J. Vincent Eccles,et al.  Modeling investigation of the evening prereversal enhancement of the zonal electric field in the equatorial ionosphere , 1998 .

[9]  G. Haerendel,et al.  Theory for modeling the equatorial evening ionosphere and the origin of the shear in the horizontal plasma flow , 1992 .

[10]  Ronald F. Woodman,et al.  Average vertical and zonal F region plasma drifts over Jicamarca , 1991 .

[11]  E. Bonelli,et al.  The prereversal enhancement of the zonal electric field in the equatorial ionosphere , 1986 .

[12]  Donald T. Farley,et al.  Equatorial F region zonal plasma drifts , 1985 .

[13]  C. Rino,et al.  Evidence of a velocity shear in bulk plasma motion associated with the post‐sunset rise of the equatorial F‐layer , 1981 .

[14]  D. T. Farley,et al.  Interferometer studies of equatorial F region irregularities and drifts , 1981 .

[15]  Ronald F. Woodman,et al.  Dependence of equatorial F region vertical drifts on season and solar cycle , 1979 .

[16]  J. Jasperse,et al.  Electron distribution function and ion concentrations in the earth's lower ionosphere from Boltzmann-Fokker-Planck theory , 1977 .

[17]  P. C. Kendall,et al.  Electrical coupling of the E- and F-regions and its effect on F-region drifts and winds , 1974 .

[18]  Henry Rishbeth,et al.  Polarization fields produced by winds in the equatorial F-region , 1971 .