Zonal drift of plasma particles inside equatorial plasma bubbles and its relation to the zonal drift of the bubble structure

Abstract

[1] It has been observed that the zonal drift velocity of equatorial plasma bubbles is generally eastward. However, it has not been well understood whether the zonal drift of plasma bubbles is the same as the ambient plasma drift and what process causes differences in the drift velocities of the ambient plasma and bubbles. In this study we analyze the ion drift velocities measured by the Defense Meteorological Satellites Program and ROCSAT-1 satellites and the electric fields measured by the Communications/ Navigation Outage Forecasting System (C/NOFS) satellite in the presence of equatorial spread F. We find that the zonal drift velocity of the plasma particles inside plasma bubbles is significantly different from the ambient plasma drift. The relative zonal velocity of the ions inside the depletion region with respect to the ambient plasma is generally westward. In most cases it can be as high as several hundreds of meters per second. The plasma bubbles detected by the C/NOFS satellite in the midnight-dawn sector are still growing, and the polarization electric field inside the postmidnight bubbles is much stronger than the electric field in the ambient plasma. We suggest that the zonal drift velocity of the plasma particles inside the depletion region is driven by polarization electric field. When a plasma bubble is tilted, the E × B drift velocity caused by the polarization electric field has an upward component and a zonal component. Because of the zonal motion of the plasma particles inside the bubble, the eastward drift velocity of the bubble structure is faster than the ambient plasma drift for a west-tilted bubble and slower than the ambient plasma drift for an east-tilted bubble.

A study of GPS ionospheric scintillations observed at Shenzhen

“…Thus, those irregularities generated further to the west of Shenzhen are causing more scintillation on the GPS signals than those irregularities that drifted eastward toward midnight. Huang et al (2010) showed evidence that the eastward drift velocity of the irregularities is faster than that of the ambient plasma drifts when the bubbles are tilted westward. Muella et al (2014) revealed that the scintillations are more likely to be observed in the west sector of the sky above Sao Luis, a station located close to the geomagnetic dip equator.…”

Occurrence of Equatorial Plasma Bubbles during Intense Magnetic Storms

“…Equatorial plasma bubbles result from the nonlinear evolution of the Rayleigh-Taylor instability. A unique feature of plasma bubbles is the existence of large upward ion drift caused by polarization electric field inside the depletion region (e.g., [43]). In order to show this feature, we plot the ion density and ion vertical velocity in The very large upward ion velocity is the plasma E × B drift caused by the polarization electric field and is the evidence that the plasma depletions are bubbles.…”

Zonal velocity of the equatorial plasma bubbles over Kolhapur, India

“…The zonal plasma drift speeds of equatorial nighttime plasma depletions observed using the imager aboard a highapogee IMAGE satellite during March-May 2002 had a strong longitudinal dependence and are maximum over the Indian sector (Immel et al, 2004). Martinis et al (2003) presented studies of plasma drift using OI 630.0 nm measurements from South American Sector.…”

“…Strong equatorial spread F (ESF)/EPBs typically arise soon after the PRE of the zonal electric field (Heelis et al, 1974;Fejer et al, 1999). Huang (2010) reported that more EPBs, expected during the main phase of magnetic storm, are generated more rapidly under stronger southward interplanetary magnetic field (IMF) conditions. However, all of these relate to the same physical process commonly believed to be associated with the RayleighTaylor (RT) instability (e.g., Kelley, 1989).…”