Parallel plate capacitor analogy of equatorial plasma bubble and associated fringe fields with implications to equatorial valley region irregularities

TL;DR

This study uses a capacitor analogy to analyze how fringe fields of equatorial plasma bubbles vary with latitude, explaining why irregularities are observed near the equator but not at lower latitudes.

Contribution

It introduces a capacitor-based model to quantify fringe field variations, revealing the influence of magnetic field alignment on plasma irregularities at different latitudes.

Findings

Fringe field decreases with altitude and latitude.

Magnetic field alignment reduces fringe field magnitude at low latitudes.

Results support the fringe field effect in plasma irregularities near the equator.

Abstract

VHF radar echoes from the valley region plasma irregularities, displaying ascending pattern, are often observed during the active phase of equatorial plasma bubble in the close vicinity of the geomagnetic equator and have been attributed to bubble-related fringe field effect. These irregularities however are not observed at a few degrees away from the equator. In this paper, we attempt to understand this contrasting observational result by comparing fringe field at the geomagnetic equator and low latitudes. We use parallel plate capacitor analogy of equatorial plasma bubble and choose a few capacitor configurations, consistent with commonly observed dimension and magnetic field-aligned property of plasma bubble, for computing fringe field. Results show that fringe field decreases significantly with decreasing altitude as expected. Further, fringe field decreases remarkably with latitude, which clearly indicates the role of magnetic field-aligned property of plasma bubble in reducing the magnitude of fringe field at low latitudes compared to that at the geomagnetic equator. The results are presented and discussed in the light of current understanding of plasma bubble-associated fringe field-induced plasma irregularities in the valley region.