Separation and Quantification of Ionospheric Convection Sources: 2. The Dipole Tilt Angle Influence on Reverse Convection Cells During Northward IMF

TL;DR

This study examines how Earth's dipole tilt angle affects reverse ionospheric convection cells during northward IMF, revealing a linear relationship and seasonal variation in cell potential, with implications for understanding magnetic reconnection.

Contribution

It introduces a novel technique to isolate and quantify reverse convection cells and demonstrates the dipole tilt's significant influence on their potential during northward IMF.

Findings

Reverse cell potential is twice as high in summer than in winter.

Dipole tilt angle has a linear influence on reverse cell potential.

Results suggest dipole tilt modifies reconnection rates beyond known factors.

Abstract

This paper investigates the influence of Earth's dipole tilt angle on the reverse convection cells (sometimes referred to as lobe cells) in the Northern Hemisphere ionosphere during northward IMF, which we relate to high-latitude reconnection. Super Dual Auroral Radar Network plasma drift observations in 2010-2016 are used to quantify the ionospheric convection. A novel technique based on Spherical Elementary Convection Systems (SECS) that was presented in our companion paper (Reistad et al., 2019, https://doi.org/10.1029/2019JA026634) is used to isolate and quantify the reverse convection cells. We find that the dipole tilt angle has a linear influence on the reverse cell potential. In the Northern Hemisphere the reverse cell potential is typically two times higher in summer than in winter. This change is interpreted as the change in interplanetary magnetic field-lobe reconnection rate due to the orientation of the dipole tilt. Hence, the dipole tilt influence on reverse ionospheric convection can be a significant modification of the more known influence from v(O$_{sw}$)B(O$_{z}$). These results could be adopted by the scientific community as key input parameters for lobe reconnection coupling functions.