SA035-0002
Quantitative Remote Sensing of Nighttime Ionospheric Electron DensityUsing GOLD 135.6 nm Airglow Observations

Wednesday, 16 December 2020
Poster
Robert Edward Daniell Jr1, Carlos R. Martinis2, Richard Eastes3, Deepak Kumar Karan4 and William E McClintock3, (1)Self Employed, Washington, DC, United States, (2)Boston University, Center for Space Physics, Boston, MA, United States, (3)University of Colorado, Laboratory for Atmospheric and Space Physics, Boulder, CO, United States, (4)University of Colorado at Boulder, Laboratory for Atmospheric and Space Physics, Boulder, United States
Abstract:
Global-scale Observations of the Limb and Disk (GOLD) Images of the nighttime OI 135.6 nm emission have proven very useful in the study of the Equatorial Ionospheric Anomaly (EIA) and associated phenomena, especially the formation and evolution of plasma bubbles. Since the basic chemistry and physics of the production of OI 135.6 nm emissions are well understood, GOLD images can be used to provide quantitative estimates of the electron content of the nighttime ionosphere and especially the EIA. We have undertaken a study to test the viability of this effort by comparing the OI 135.6 nm radiance calculated from measured electron density profiles with the actual radiances observed by GOLD.

We have begun our study by making use of electron density profiles (EDPs) measured by the Incoherent Scatter Radar (ISR) at the Jicamarca Radio Observatory (JRO). Since the JRO is located on the geomagnetic equator, it is normally situated in the low density trough between the two peaks of the EIA, so we have also used the co-located ionosonde and GNSS TEC measurements to assess the viability of obtaining approximate EDPs for use at other locations.

We have found large numerical discrepancies between the radiance calculated from the measured EDPs and the values observed by GOLD. The calculated values are consistently smaller than the observed values by a median factor of 0.6.

The GOLD instrument has been carefully calibrated by both laboratory measurements before launch and by stellar observations during the mission. This large discrepancy is not easily explained by calibration uncertainties, nor by uncertainties in the neutral atmosphere model used in the calculations. Therefore, we are undertaking a full error analysis of both the measurements and the calculations, as well as extending the analysis to other parts of the EIA where electron densities and nightglow radiances are larger. To this end, we are extending the measurements to include ionosondes and GNSS/TEC as well as ground-based nightglow observations at 630 nm and 777.4 nm.

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