Separation and Quantification of Ionospheric Convection Sources: 1. A New Technique

Abstract

This paper describes a novel technique that allows separation and quantification of different sources of convection in the high‐latitude ionosphere. To represent the ionospheric convection electric field, we use the Spherical Elementary Convection Systems representation. We demonstrate how this technique can separate and quantify the contributions from different magnetospheric source regions to the overall ionospheric convection pattern. The technique is in particular useful for distinguishing the contributions of high‐latitude reconnection associated with lobe cells from the low‐latitude reconnection associated with Dungey two‐cell circulation. The results from the current paper are utilized in a companion paper (Reistad et al., 2019, https://doi.org/10.1029/2019JA026641) to quantify how the dipole tilt angle influences lobe convection cells. We also describe a relation bridging other representations of the ionospheric convection electric field or potential to the Spherical Elementary Convection Systems description, enabling a similar separation of convection sources from existing models.

Quantifying the Lobe Reconnection Rate During Dominant IMF By Periods and Different Dipole Tilt Orientations

“…As explained by Reistad, Laundal, Østgaard, Ohma, Haaland, et al. (2019), the potential $${\Phi}(\overrightarrow{r})$$ is found by summing the potential from each SECS node, which is given by the integral of the SECS curl‐free elementary function from the node to $$\overrightarrow{r}$$. The general two‐cell convection pattern is seen, with a round cell at dusk and a crescent cell at dawn due to the positive IMF B y conditions.…”

“…The top row shows the solution of the inversion described in Section 2.5. In our application, these SECS amplitudes are proportional to $$\nabla \cdot \overrightarrow{E}$$ (Reistad, Laundal, Østgaard, Ohma, Haaland, et al., 2019) and hence also $$\nabla \times \overrightarrow{v}$$, where $$\overrightarrow{E}$$ and $$\overrightarrow{v}$$ are the convection electric field and ionospheric convection field, respectively. Hence, the amplitudes reflect the degree of vorticity in the ionospheric convection.…”

“…This study was designed to target this gap in knowledge by developing methods that allow for quantitative estimates of the average ionospheric plasma circulation solely within the polar cap when IMF B y dominates. We largely build on previous work (Reistad, Laundal, Østgaard, Ohma, Haaland, et al., 2019; Reistad, Laundal, Østgaard, Ohma, Thomas, et al., 2019) that used the same SECS representation of the ionospheric convection as presented here. Reistad, Laundal, Østgaard, Ohma, Thomas, et al.…”

“…The analysis presented in this paper is based on the same technique as described in Reistad, Laundal, Østgaard, Ohma, Haaland, et al. (2019); Reistad, Laundal, Østgaard, Ohma, Thomas, et al. (2019) to represent the average convection pattern based on the selection of observations described above using Spherical Elementary Current Systems (SECS) (Amm, 1997; Amm & Viljanen, 1999; Amm et al., 2010).…”

Electrojet estimates from mesospheric magnetic field measurements

“…We also believe that the ideas behind the grid and inversion, including possible improvements described in Section 3.4, will be useful in other analyses of regional ionospheric electrodynamics. The technique could be applied with both ground and space magnetometers, or for estimating ionospheric convection using the The Super Dual Auroral Radar Network (e.g., Reistad et al, 2019).…”