Dye-laser observations of the nighttime atomic sodium layer

Abstract

Observations of the free atomic sodium layer near 90 km have been made as part of performance tests on a tunable dye‐laser radar. Altitude profiles of the layer obtained during parts of four nights in the fall of 1971 are consistent with those obtained by other groups but show two interesting additional features. The first is a sharp decrease in density that terminates the layer on the bottom side at a variable altitude near the mesopause. This decrease appears to become sharp only some time after twilight, suggesting that the sodium consumption mechanism undergoes a change as the nighttime chemistry is established. The second feature is a fourfold increase in sodium‐layer content during a 4‐hour period surrounding the transit of the radiant of the Geminids meteor shower on the night of December 13–14, 1971, when the shower was at its peak.

Development of the mesospheric Na layer at 69° N during the Geminids meteor shower 2010

“…We observe a similar tendency in 2009 and 2011. These three years are in contrast to an observation in 1971 by Hake et al (1972). The weak decrease of the number of sporadic meteors in 740 2010 as measured with the meteor radar correlates well with corresponding decreases of Na column density and meteoric smoke particle column density.…”

“…We observe a similar tendency in 2009 and 2011. These three years are in contrast to an observation in 1971 by Hake et al (1972).…”

“…Some of the authors report an influence (Uchiumi et al, 1993;Gerding et al, 1999;Höffner et al, 1999), but mostly for a very short time. From four hours of lidar measurements, a fourfold increase in Na density was reported by Hake et al (1972). No influence has been found by Höffner et al (2000) and .…”

“…However, our data does not show such an increase. Hake et al (1972) reported a more than fourfold increase of the Na layer during about four hours on 13/14 December 1971. This may suggest that the Na content of the Geminids varies from year to year, or even has decayed between 1971 and 2010.…”

Sporadic Enhancement of the Mesospheric Sodium during the Perseids .GAMMA. Meteor Shower.

“…Moreover, it gives information about the response of the sodium layer to the sporadic injection of sodium atoms. Enhancements of mesospheric sodium from permanent meteoric shower influxes have already been observed either by the photometric technique or the lidar technique (HAKE et al, 1972;MEGIE and BLAMONT, 1977). In addition to the enhancement of the sodium layer during meteor showers, the enhancement of lithium layer was already observed (JEGOU et al, 1980).…”