A quiet time empirical model of equatorial vertical plasma drift in the Peruvian sector based on 150 km echoes

Equatorial vertical plasma drift is an important consequence of the E and F region dynamos. Understanding the climatology of vertical drift can provide significant insight into many ionospheric phenomena. In this study we present the first empirical model of vertical plasma drifts at 150 km altitude, observed by the Jicamarca Unattended Long-term studies of the Ionosphere and Atmosphere (JULIA) coherent scatter radar located in Peru. The model, called JULIA Vertical Drift Model (JVDM), describes the local time, seasonal, and solar flux behavior of the equatorial vertical drifts in the Peruvian sector. The model is valid from 0800 through 1600 local time, which is typically when JULIA makes vertical drift measurements. During very high solar flux conditions, however, the model is unreliable before 1000 local time owing to a lack of JULIA data. The model includes a climatology of the 150 km equatorial vertical drifts as well as an estimate of the day-to-day variability, which can be significant. The daytime drifts typically peak between 1000 and 1200 LT and have amplitudes of 25-30 m/s +/- 10 m/s. The model has been validated against the global empirical model of Scherliess and Fejer, with a total rms difference of under 4 m/s for 1000 to 1600 LT. This model will allow researchers to study daily variations in the equatorial electric field by subtracting the climatological mean. Model coefficients and software are available online at http://geomag.org/models and http://www.earthref.org.