Threshold in solar wind dynamic pressure for bulge occurrence

Ascertain whether a clear threshold value of the adjusted solar wind dynamic pressure P_SW exists at Venus that governs the occurrence of the topside bulge in dayside ionospheric electron density profiles, and quantify this threshold if present.

Background

The study relates bulge morphology and occurrence to solar wind conditions measured by ASPERA-4, applying a geometric correction (flow solar zenith angle) to derive P_SW at the occultation point. Profiles under enhanced solar wind dynamic pressure often show a Type 1 bulge or disturbed topside structure.

Despite observing correlations, the authors could not identify a definitive pressure threshold that triggers bulge formation, leaving the existence and value of such a threshold unresolved.