Investigation of localized 2D convection mapping based on artificially generated Swarm ion drift data

• Ionospheric convection mapping based on a Swarm satellite data set.
• Spherical cap harmonic analysis for mapping plasma flow within a localized spherical cap.
• Parameters determining goodness-of-fit for ionospheric convection mapping.

Ionospheric plasma flow is an indicator of the interconnection between the solar wind, interplanetary magnetic field (IMF), and Earth’s magnetosphere. Ionospheric convection has been mapped in the past using either a widespread data set for instantaneous convection mapping over a short time period or data from an instrument measuring convection in a spatially confined region over a long time period for the purpose of building a statistically averaged convection pattern. This study explores convection mapping using a spherical cap harmonic analysis (SCHA) technique within a localized spherical cap based on data that will be available from the Swarm three-satellite constellation. Convection is mapped in the vicinity of hypothetical Swarm satellite tracks where it is adequately constrained by data. By using statistical models to emulate Swarm measurements, we demonstrate that such mapping can be successful based on data from the Swarm A and Swarm B satellites. Convection is divided into well constrained and poorly constrained subsets to determine parameters characterizing goodness-of-fit based on known quantities. Using the subset of well constrained maps, it is determined that convection is best mapped for a spherical cap having an angular radius of θc=10°. The difference between the maximum mapped convection and the maximum velocity measured along the satellite track (Δv) is introduced to evaluate goodness-of-fit. For the examples presented in this paper, we show that a threshold value of Δv=281 m/s successfully differentiates between well and poorly constrained maps 77.6% of the time. It is shown that convection can be represented over a larger region through the use of multiple spherical caps.