A 2-dimensional Data Detrending Technique for Equatorial Plasma Bubble
Studies Using GOLD Far Ultraviolet Observations
Abstract
We formulate a numerical data detrending technique that can be used to
help reveal large-scale equatorial plasma bubble (EPB) structures in
2-dimensional data from the Global-scale Observations of the Limb and
Disk (GOLD) mission. This GOLD data detrending technique is inspired by
and is a generalization of a previous rolling-barrel data detrending
method for 1-dimensional total electron content (TEC) observations on
individual global positioning system (GPS) satellite passes. This
2-dimensional GOLD data detrending technique treats the observed 135.6
nm radiance as a function of longitude and latitude as an uneven
terrain, where EPBs appear as deep but narrow elongated valleys. The
unperturbed background radiance is inferred by rolling a ball on the
2-dimensional terrain to skip over the EPB valleys. The two
degrees-of-freedom possessed by the rolling ball allow it to smoothly
trace the edges of EPB depletions, without falling into the deep
valleys. Surface interpolation of radiance values at the ball’s contact
points onto the whole domain produces the baseline radiance. Subtracting
the baseline from the original radiance data yields the net detrended
radiance. As a result of the detrending, sharper contrast is present
between EPB depletions and the ambient surroundings. As such, this new
2-dimensional GOLD data detrending may potentially open the door to the
development of other more advanced techniques for automated EPB
detection and tracking, or data assimilation into low-latitude space
domain awareness (SDA) information ecosystems.