GPS Loss of Lock Events and Their Dependence on the Interplanetary Magnetic Field Orientation

Abstract

The study investigates the influence of interplanetary magnetic field (IMF) orientation on loss of lock (LoL) events in GPS signals. We analyzed LoLs recorded on two Swarm satellites between July 2014 and December 2021, examining how the signs of the IMF $B_x$, $B_y$, and $B_z$ components affect the distribution of events at high latitudes. Our results reveal an asymmetric distribution of LoL events over 75° magnetic latitude. In the Northern hemisphere, more events occur in the post-noon sector with negative IMF $B_y$, and in the pre-noon sector with positive IMF $B_y$. Conversely, in the Southern hemisphere, pre-noon events increase with negative IMF $B_y$, while post-noon events increase with positive IMF $B_y$. At lower latitudes (50°-75°), IMF $B_y$ does not significantly affect the event distribution, which mainly concentrates in the night sector for both hemispheres. Additionally, we found a connection between IMF $B_y$ and $B_x$, primarily due to the IMF spiral structure. Finally, we discuss our findings in the context of the SuperDARN data-driven model of ionospheric convection patterns, which shows that LoL events frequently cluster in the cusp region, as well as the area where the two convection cells separate.