Automated Detection and Tracking of Low Latitude Plasma Bubbles
Utilizing Global-Scale Observations of the Limb and Disk (GOLD) 135.6 nm
Data
Abstract
Plasma bubbles are regions of depleted plasma within the upper
thermosphere/ionosphere that form during post-sunset hours near the
magnetic equator. These structures tend to align with local geomagnetic
field lines, extend upwards hundreds of kilometers along geomagnetic
longitudes, and thousands of kilometers along geomagnetic latitudes.
These large scale plasma density gradients can attenuate lower frequency
radio waves, while small scale structures along the walls can interfere
with centimeter scale wavelengths via Fresnel and Bragg scattering.
Large scale statistical analysis of this phenomenon can further
understanding of their occurrence and subsequent behavior. The current
study utilizes Global-Scale Observations of the Limb and Disk (GOLD)
135.6 nm nightglow data from October 5, 2018 to September 30, 2022. GOLD
has a unique perspective from geostationary orbit, allowing a constant
and consistent view of nightglow and structures over the Americas and
Atlantic. A plasma bubble detection method is developed and used to
generate a database of plasma bubble occurrences. Occurrences are used
to calculate plasma bubble drift speeds and separations. Clear
seasonality in plasma bubble occurrence rate is evident. Overall
occurrences peak during December solstice months and minimize during
June solstice for longitudes seen by GOLD. Within GOLD’s field of view,
higher occurrences are seen to the west during December solstice and
east during June solstice. Plasma bubble drift speeds and separations
show consistent distributions regardless of magnetic region, geographic
region, season, or local time. This suggests plasma bubbles behave
consistently and regularly once formed, at least on spatial scales seen
by GOLD.