SA42A-04
Optical imaging of airglow structure in equatorial plasma bubbles at radio scintillation scales

Thursday, 17 December 2015: 11:05
2016 (Moscone West)
Jeffrey M Holmes1, Todd Pedersen2, Richard Todd Parris2, Brett Stephens2, Ronald G Caton2, Eugene V Dao3, Scott Kratochvil3, Yu Morton4, Donyang Xu4, Yu Jiao4, Steve Taylor4 and Charles Salvatore Carrano5, (1)Air Force Research Laboratory Albuquerque, Albuquerque, NM, United States, (2)Air Force Research Laboratory, Kirtland Afb, NM, United States, (3)Air Force Research Laboratory, Kirtland AFB, NM, United States, (4)Colorado State University, Electrical and Computer Engineering, Fort Collins, CO, United States, (5)Boston College, Institute for Scientific Research, Chestnut Hill, MA, United States
Abstract:
Imagery of optical emissions from F-region plasma is one of the few means available to
determine plasma density structure in two dimensions. However, the smallest spatial scales
observable with this technique are typically limited not by magnification of the lens or resolution
of the detector but rather by the optical throughput of the system, which drives the integration
time, which in turn causes smearing of the features that are typically moving at speeds of 100
m/s or more. In this paper we present high spatio-temporal imagery of equatorial plasma bubbles
(EPBs) from an imaging system called the Large Aperture Ionospheric Structure Imager
(LAISI), which was specifically designed to capture short-integration, high-resolution images of
F-region recombination airglow at λ557.7 nm. The imager features 8-inch diameter entrance
optics comprised of a unique F/0.87 lens, combined with a monolithic 8-inch diameter
interference filter and a 2x2-inch CCD detector. The LAISI field of view is approximately 30
degrees.

Filtered all-sky images at common airglow wavelengths are combined with magnetic
field-aligned LAISI images, GNSS scintillation, and VHF scintillation data obtained at
Ascension Island (7.98S, 14.41W geographic). A custom-built, multi-constellation GNSS data
collection system was employed that sampled GPS L1, L2C, L5, GLONASS L1 and L2, Beidou
B1, and Galileo E1 and E5a signals. Sophisticated processing software was able to maintain
lock of all signals during strong scintillation, providing unprecedented spatial observability of
L band scintillation.

The smallest-resolvable scale sizes above the noise floor in the EPBs, as viewed by
LAISI, are illustrated for integration times of 1, 5 and 10 seconds, with concurrent
zonal irregularity drift speeds from both spaced-receiver VHF measurements and single-station
GNSS measurements of S4 and σφ. These observable optical scale sizes are placed in the
context of those that give rise to radio scintillation in VHF and L band signals.

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