Occurrence of metal ions in the descending layers over Arecibo
Abstract
Descending layers are a common feature at Arecibo, and act as a coupling mechanism between E and F region of the ionosphere. In this paper, we present novel results of metal ions in the valley region obtained using a resonance lidar at Arecibo. The lidar was tuned to 393 nm resonance wavelength of calcium ion for these observations. Metals and their ions are deposited in the mesosphere and lower thermosphere region (between 80 - 120 km) through meteoric ablation. Ca+ is the only ion that can be observed using a ground-based instrument since all other major ions have their resonance wavelength deep in UV, which is attenuated by ozone. Simultaneous observations of Ca and its ions along with electron density measurements from Arecibo have been crucial in demonstrating its association with Sporadic - E layers. Recent upgrades to the lidar receiver allowed the first detection of Ca+ within descending layers in the valley region. Three nights in November 2016 will be presented that showed occurrence of Ca+ between 150 - 180 km altitude regions on two nights during dawn periods. The Ca+ to Ne abundance ratio is found to range between 0.4% to 3% below 120 km regions, but decreases by a factor of 10 at higher altitudes. Combined ISR and lidar observations revealed that these high altitude/descending ion layers occurred on the nights with stronger downward ion drifts.On 30 Nov 2016, Ca+ observations revealed interesting features in the E and the valley region with structures resembling field aligned irregularities that are more prominent in this metal ion distribution. This work highlights the significance of metal ions observations that promises new insights into the valley region dynamics.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSA51B3167R
- Keywords:
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- 2415 Equatorial ionosphere;
- IONOSPHERE;
- 2431 Ionosphere/magnetosphere interactions;
- IONOSPHERE;
- 6969 Remote sensing;
- RADIO SCIENCE;
- 7944 Ionospheric effects on radio waves;
- SPACE WEATHER