3 research outputs found
The longitudinal variability of equatorial electrojet and vertical drift velocity in the African and American sectors
While the formation of equatorial electrojet (EEJ) and its temporal
variation is believed to be fairly well understood, the longitudinal
variability at all local times is still unknown. This paper presents a case
and statistical study of the longitudinal variability of dayside EEJ for all
local times using ground-based observations. We found EEJ is stronger in the
west American sector and decreases from west to east longitudinal sectors.
We also confirm the presence of significant longitudinal difference in the
dusk sector pre-reversal drift, using the ion velocity meter (IVM)
instrument onboard the C/NOFS satellite, with stronger pre-reversal drift in
the west American sector compared to the African sector. Previous satellite
observations have shown that the African sector is home to stronger and
year-round ionospheric bubbles/irregularities compared to the American and
Asian sectors. This study's results raises the question if the vertical
drift, which is believed to be the main cause for the enhancement of
RayleighâTaylor (RT) instability growth rate, is stronger in the American
sector and weaker in the African sector â why are the occurrence and
amplitude of equatorial irregularities stronger in the African sector
Response of the equatorial ionosphere to the geomagnetic DP 2 current system
The response of equatorial ionosphere to the magnetospheric origin DP 2 current system fluctuations is examined using groundâbased multiinstrument observations. The interaction between the solar wind and magnetosphere generates a convection electric field that can penetrate to the ionosphere and cause the DP 2 current system. The quasiperiodic DP 2 current system, which fluctuates coherently with fluctuations of the interplanetary magnetic field (IMF) Bz, penetrates nearly instantaneously to the dayside equatorial region at all longitudes and modulates the electrodynamics that governs the equatorial density distributions. In this paper, using magnetometers at high and equatorial latitudes, we demonstrate that the quasiperiodic DP 2 current system penetrates to the equator and causes the dayside equatorial electrojet (EEJ) and the independently measured ionospheric drift velocity to fluctuate coherently with the highâlatitude DP 2 current as well as with the IMF Bz component. At the same time, radar observations show that the ionospheric density layers move up and down, causing the density to fluctuate up and down coherently with the EEJ and IMF Bz.Key PointsThe solar windâmagnetosphere interaction generates DP 2 current fluctuationThe DP 2 current fluctuations penetrate to the equator and cause the equatorial electrodynamics to fluctuateIt also causes the equatorial density to fluctuate which might affect the communication and navigation systemsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134255/1/grl54722.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134255/2/grl54722_am.pd