New Lidar Observations of Ca<sup>+</sup> in the Mesosphere and Lower Thermosphere Over Arecibo
S. Raizada, John A. Smith, J. Lautenbach, N. Aponte, Phil Perillat, M. P. Sulzer, J. D. Mathews
Abstract
Abstract This paper presents the first high‐resolution resonance lidar measurements of calcium ion (Ca + ) layers in the F region valley (140–180 km) over Arecibo. Unique, simultaneous Ca + , neutral sodium (Na), and potassium (K) lidar observations, along with incoherent scatter radar electron concentration (N e ) covering 80‐ to 180‐km altitudes for three consecutive nights, are reported here. At E region altitudes, the Ca + distribution follows sporadic E activity on these nights. Thin Ca + layers (widths < 150 m) imply wind reversals to be occurring over this short height range. Ca + above 140 km do not always correspond to N e layers but are detected only during presunrise hours. The average Ca + column abundance below 120 km is highly variable but during high‐altitude Ca + event decreases by a factor of 2 above 120 km. Both N e and Ca + display similar descent rates of ~7 m/s at altitudes >150 km during these events.