An Empirical Model of the Midlatitude Ionospheric Trough Based on Swarm Observations

The subauroral ionosphere is the transition zone between the convecting and corotating plasma and plays an important role in the magnetosphere - ionosphere (MI) interaction. The midlatitude ionospheric trough (MIT), a longitudinally extended depletion in electron density, is an important feature of this region. Various formation mechanisms have been proposed but some of their underlying physics remains unknown. 

 

The MIT exhibits a strong dependence on magnetospheric activity and magnetic local time (MLT). This dependence has been captured by empirical models describing the location of the MIT (e.g., Deminov and Shubin, 2018; Werner and Prössl 1997).

 

In this study, we present a new empirical model that describes the location of the MIT electron density minimum and its associated equatorward and poleward walls.  The model is based on empirical observations combined with ionospheric physics. The dataset is derived from the Swarm-PRISM MIT product (https://earth.esa.int/eogateway/activities/swarm-prism)  where MIT features are identified using Langmuir probe measurements from the ESA Swarm mission. The model input parameters are MLT and a time weighted average of the geomagnetic activity represented by the Hp30 index (Yamazakiet et al., 2022).  More than 170 000 of MIT events have been identified which is a large dataset compared to previous models allowing our model to provide a more precise and more featured description of the MIT compared to existing models. Our model can also provide a tool for monitoring magnetospheric processes and can advance the understanding of MIT formation mechanisms.