Relation of zonal plasma drift and wind in the equatorial F region as derived from CHAMP observations

Abstract

In this paper we estimate zonal plasma drift in the equatorial ionospheric F region without counting on ion drift meters. From June 2001 to June 2004 zonal plasma drift velocity is estimated from electron, neutral, and magnetic field observations of Challenging Mini-satellite Payload (CHAMP) in the 09:00–20:00 LT sector. The estimated velocities are validated against ion drift measurements by the Republic of China Satellite-1/Ionospheric Plasma and Electrodynamics Instrument (ROCSAT-1/IPEI) during the same period. The correlation between the CHAMP (altitude ~ 400 km) estimates and ROCSAT-1 (altitude ~ 600 km) observations is reasonably high (<I>R</I> &approx; 0.8). The slope of the linear regression is close to unity. However, the maximum westward drift and the westward-to-eastward reversal occur earlier for CHAMP estimates than for ROCSAT-1 measurements. In the equatorial F region both zonal wind and plasma drift have the same direction. Both generate vertical currents but with opposite signs. The wind effect (F region wind dynamo) is generally larger in magnitude than the plasma drift effect (Pedersen current generated by vertical E field), thus determining the direction of the F region vertical current

Influence of the Magnetic Field Strength and Solar Activity on the Thermospheric Zonal Wind

“…The corresponding superrotations are 15, 9, and 3 m/s. Park and Lühr (2013) compared the zonal wind and plasma drift observations of the CHAMP satellite and found that they exhibited the same diurnal variation. Both the plasma drift direction and the zonal wind reversed at 16 LT, and the velocities of the zonal wind during the daytime and nighttime were slightly larger than those of the plasma that is consistent with our simulation results.…”

“…The F‐region zonal wind dynamo can drive the vertical current in the radial direction at the equator, $${j}_{z}={\sigma }_{p}({E}_{z}-{U}_{y}{B}_{x})$$, where $${\sigma }_{p}$$ is the Pedersen conductivity in the F layer, $${E}_{z}$$ is the radial electric field, $${U}_{y}\hspace*{.5em}$$ is the zonal wind, and $${B}_{x}$$ is the geomagnetic field in the northward direction (Park & Lühr, 2013). The first term on the right‐hand side represents the contribution of the vertical electric field (that is, the zonal plasma drift), and the second term represents the contribution of the zonal wind in the F region.…”

“…The first term on the right-hand side represents the contribution of the vertical electric field (that is, the zonal plasma drift), and the second term represents the contribution of the zonal wind in the F region. Park and Lühr (2013) studied the relative contribution of these two components to the vertical current in the F region. They found that the current driven by the radial electric field is opposite to the wind dynamo current, while the vertical current of the F layer is mainly contributed by the wind dynamo.…”

The interhemispheric and F region dynamo currents revisited with the Swarm constellation

“…Zonal winds from CHAMP provide no suitable explanation for that longitudinal variation. Park and Lühr [] showed that E region dynamics has a strong influence on the F region currents. We may well see the response of a tidal effect at E layer altitude.…”

Local time and longitudinal variation of the ionospheric radial current: swarm observations and TIE–GCM simulations

“…The second term, −σ P E z , represents the current generated by the polarized electric field. Park and Lühr (2013) studied the relative contributions of these two components to the vertical current in the F region. They found that the current driven by the radial electric field is opposite to the wind dynamo current, whereas the vertical current of the F layer is mainly contributed by the wind dynamo.…”