Quantifying Meridional Advection in the Auroral E-Region For a Range of Geomagnetic Activity Levels

Abstract

The high-latitude E-region wind forcing has been studied extensively at large scales, but studies in auroral-oval-width scales are still sparse. In the auroral region, where the magnetospheric forcing is in the scale size of the aurora, winds can be forced to hundreds of meters per second in the auroral acceleration channel. This can result in large advective accelerations, where even a moderate cross-channel neutral wind could move momentum outside the acceleration channel through advection. In this paper, we use sounding rocket data from Alaska to estimate the meridional advective acceleration of horizontal momentum and other forcing terms for different geomagnetic activity levels. We used the Poker Flat Incoherent Scatter Radar measurements of F-region plasma drifts and E-region electron densities to calculate the magnetospheric Lorentz forcing (MLF). We interpret our results in terms of the gradient wind solution presented in recent study by Larsen et al. (2022, https://www.doi.org/10.1029/2021JA029936). We found that the magnitude of the advective acceleration and MLF generally increase with the sampled geomagnetic conditions in the non-storm time Quiet to Active range. We concluded that while a correlation between advection and geomagnetic activity is indicated but not the only factor at work with our results, the meridional advection can disturb the gradient balance and influence the neutral winds in both zonal and meridional directions. We also show that it is crucial to account for the time evolution of forcing of winds in the scale of 100–1,000s of kilometers when examining aurora-related events.