Interhemispheric Asymmetry of Equatorial Plasma Bubbles in the American Sector

Abstract

Observations from the Global‐scale Observations of the Limb and Disk (GOLD) mission in 2023 reveal a pronounced interhemispheric asymmetry in the poleward extension of Equatorial Plasma Bubbles (EPBs) within the American longitude sector. To investigate this phenomenon, we extracted EPB structures and their maximum Quasi‐Dipole (QD) latitude boundaries using the Depletion Index (DI), and conducted statistical analyses with three asymmetry indices. Results suggest that EPBs tend to extend farther toward the hemisphere where the Equatorial Ionization Anomaly (EIA) crest is located at a higher absolute QD latitude and exhibits lower radiance. The prevalent southward bias in EPB extension may be related to the weaker magnetic field at conjugate southern locations, which may favor enhanced upward E × B drift and higher EPB apex altitudes. Seasonal variation in EIA radiance asymmetry is associated with summer‐to‐winter transequatorial neutral winds, which transport plasma toward and enhance the winter EIA crest. Analysis of two representative cases further suggests that EPB extension may be influenced by the combined effects of conjugate magnetic‐field‐strength asymmetry and wind‐modulated EIA density distributions.