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All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

Noctilucent Clouds and Corresponding Meteorological Conditions

Temperature measurements obtained using the passive falling sphere technique in 1991, 1993, and again in 1999 are being used to study the relationship between the neutral atmosphere and Noctilucent Clouds (NLC) The earlier NLC studies provided useful information on the behavior of the neutral atmosphere. The recent study program, the Distribution and Role of Particles in the Polar Summer Mesosphere (DROPPS) produced additional significant information of the neutral atmosphere and Noctilucent Cloud (NLC) association. Temperature lapse rates from seven rocket observations that were generally monatonic indicated changes at the mesopause during the NLC event of 5 July. Between 5 July, 2313 UTC and 6 July 0209 UTC, the temperature lapse rate between about 85 and 92 km was different and the altitude of the minimum temperature changed by 5 km. Furthermore, change in wind direction and speed, although not yet fully analyzed, may be associated with the change of the temperature structure, possibly due to advection. Comparisons are made between the meteorological conditions during the NLC events of 1991, 1993, and 1999.

Schmidlin, F. J.↗
NASA NTRS1993

Electric field measurements in the vicinity of noctilucent clouds and PMSE

We report mesospheric electronic field structure in the vicinity of noctilucent clouds (NLC) and polar mesospheric summer echoes (PMSEs) measured on the DECIMALS-B rocket payload launched during the international rocket-radar campaign NLC-91 from Esrange, Sweden on August 10, 1991. Unusually large vertical E- fields, E(sub Z), about 100-300 mV/m on ascent and greater than 1 V/m on descent were detected at 82.5-84.5 km. The region of the large E(sub Z) was clearly limited by the NLC layer on the bottom and by the distinctly separated PMSE layer on the top. A narrow negative peak in the E(sub Z) height profile observed on ascent in the lower part of the NLC layer was apparently caused by the interaction of the field mill with impacting NLC particles possibly carrying negative charge. If the impact signature is due to single particles, their size is estimated to at least 0.5 microns and their concentration about 10(exp -4)/cu cm locally. Based on the light-scattering properties of NLC such massive particles can only be a minor part of the NLC population.

Zadorozhny, Alexander M.↗
NASA NTRS1973

Unusual chemical compositions of noctilucent-cloud particle nuclei

Two sounding rocket payloads were launched from the ESRO range in Sweden during a noctilucent cloud display. Large numbers of submicron particles were collected, most of which appear to be made up of a high density material coated with a low density material. Typical electron micrographs are shown. Particle chemical compositions have been measured by use of dispersive X-ray analysis equipment attached to an electron microscope and have revealed that most of the high density particle nuclei have atomic weights greater than iron.

Hemenway, C. L.↗
NASA NTRS1993

First height comparison of noctilucent clouds and simultaneous PMSE

On the night of August 9-10, 1991, two rocket payloads were launched into simultaneously occurring noctilucent clouds (NLC) and polar mesospheric summer echoes (PMSE) above Esrange, a third rocket payload was launched into a NLC where a PMSE was detected 5 minutes later above Esrange, in Sweden as part of the NLC-91 campaign. An aim of this experiment was to compare the vertical structures and locations of the NLC and PMSE events. To this end, in-situ optical photometers and particle impact sensors were used to measure the altitude and vertical structure of the NLC layer, while the Cornell University portable radar interferometer (CUPRI) was used to probe the PMSE. Although this comparison is complicated by the horizontal separations between the in-situ measurements and the radar volume, and low electron densities which reduced the overall radar reflectivity, we conclude that the PMSE layer in the CUPRI radar volume remained above the NLC layer detected by the in-situ instruments by 300 to 2000 m throughout the experiment. We interpret this result as supporting the view that PMSE are more likely to result from the presence of aerosols smaller than the ones optically detectable as NLCs.

Waelchli, Urs↗
NASA NTRS1985

Connection between mesopause temperature, circulation and noctilucent clouds

To investigate the connection between mesopause temperature in summer and the induced circulation upon possible formation of the observed polar mesospheric (noctilucent) cloud layer (PMC), a two-dimensional semiempirical model is used to calculate the zonally averaged diabatic circulation. On the basis of the calculations, one may draw the following conclusions: (1) if the large departures from radiative equilibrium which occur at the summer mesopause at high latitudes should be balanced by adiabatic processes of the mean circulation alone, a vigorous circulation is needed (there is some evidence that such a vigorous circulation has been observed); (2) the vertical velocities of some cm/s at the polar summertime mesopause will support the formation of polar mesospheric clouds, because those large wind speeds support larger ice particles against gravitational sedimentation; and (3) a region of mild subsidence in the summertime midlatitude mesosphere due to the effect of nonlinear temperature advection would tend to limit the occurrence of ice particles to latitudes poleward of about 55 deg.

Gartner, V.↗
NASA NTRS2024

Iridescence Reveals the Formation and Growth of Ice Aerosols in Martian Noctilucent Clouds

Water and carbon dioxide each form mesospheric clouds on Mars. At such altitudes (40–100 km), clouds may remain sunlit for part of the night. We describe a previously unreported, visually spectacular season of iridescent, noctilucent clouds visible in early southern autumn from the Curiosity rover's site in Gale crater. Ice nucleation begins near sunset with a narrow range of particle sizes, and the ice aerosols grow and precipitate. The iridescence, visible through three-color imaging, arises from locally uniform particle sizes resulting from similar growth histories. Colorful fall streaks show the clouds evolving, and a scattering corona shows size uniformity over large areas. The terminator was observed on the clouds, allowing the determination of cloud altitudes and a likely CO2 composition. This is the first observation of particle size variations within individual Martian clouds, allowing a new probe of Martian cloud physics.

M T Lemmon↗
NASA NTRS2000

Aerosol and Plasma Measurements in Noctilucent Clouds

The purpose of this project was to develop rocket-borne probes to detect charged aerosol layers in the mesosphere. These include sporadic E layers, which have their origin in meteoric dust, and noctilucent clouds, which form in the arctic summer and are composed of ice crystals. The probe being developed consists of a charge collecting patch connected to a sensitive electrometer which measures the charge deposited on the patch by impacting aerosols. The ambient electrons and light ions in the mesosphere are prevented from being collected by a magnetic field. The magnetic force causes these lighter particles to turn so that they miss the collecting patch.

Robertson, Scott↗
NASA NTRS1987

The nonlinear thermodynamics of meteors, noctilucent clouds, enhanced airglow and global atmospheric circulation

Two types of fundamental topological junctions of elements are deduced from a nonlinear thermodynamical model. Using this scheme, the possibility of a causal relation between fireballs and faint meteors as nonlinear sources on the one hand, and noctilucent clouds (NC) and Hoffmeister's enhanced airglow (EA) as complementary formative processes in the middle atmosphere and ionosphere, on the other hand, is examined. The principal role of the global atmospheric circulation in this relation is demonstrated. Such circulation in the mesosphere appears to prevent the neutral dust dissipated by fireballs from becoming an efficient agent in NLC generation. In this case, the behavior of ionized material deposited by both the bright and faint meteors is more probably controlled, as shown from the annual variation of the E sub s layer by the darkness of lunar eclipses and the global circulation of the lower thermosphere. The role of fireballs and neutral dust might be more significant as a source of EA phenomenon.

Rajchl, J.↗
NASA NTRS1993

Small-scale structure of O2(+) and proton hydrates in a Noctilucent Cloud and polar mesospheric summer echo of August 9/10 1991 above Kiruna

A novel mass spectrometer designed to measure simultaneously positive ion composition in the mesosphere, was successfully launched during the NLC-91 project. Instruments supporting the mass spectrometer were a probed to measure both electrons and positive ions as well as a wave propagation experiment. The location of the Noctilucent Clouds (NLC) was determined by a particle impact sensor to detect secondary electrons and ions from the impact of NLC particle. The density of proton hydrates and of the related total ions is depleted in the NLC region at 83 km. An improved detection limit of 5 x 10(exp 4)/cu m for positive ions and improved height resolution revealed for the first time large gradients in the O2(+), H(+)(H2O)2 and H(+)(H2O)6 densities within a small height range of the order of 50 m. Such gradients at the altitude of NLC and Polar Mesospheric Summer Echoes (PMSE) are associated with strong variability of mesospheric water vapor, temperature and neutral air density.

Balsiger, F.↗
NASA NTRS1977

Ion composition in a noctilucent cloud region

Ion composition at mesospheric altitudes was measured at high-latitude (Kiruna, Sweden) and mid-latitude (Wallops Island, Virginia) sites under summer daytime conditions, using two sets of rocket measurements both made with pumped quadrupole ion mass spectrometers. Cluster ions of hydronium and of nitric oxide were observed at midlatitudes, while, in addition to these cluster ions, a preponderance of heavy ions between 90 and 145 amu, was observed at high latitudes. These latter results may suggest the presence of metallic particles and ions which form hydrated cluster ions within the noctilucent cloud region.

Goldberg, R. A.↗
NASA NTRS1976

Ion composition in a noctilucent cloud

Ion composition at mesospheric altitudes was measured and compared between high and mid-latitude sites under summer daytime conditions. Rocket-borne measurements were made with pumped quadrupole ion mass spectrometers. The mid-latitude data were obtained at Wallops Island, Virginia on June 30, 1973, at 1510 LMT. Large quantities of hydronium cluster ions were observed through 109+, with maximum concentrations at 55+ and 73+. Also, cluster ions of nitric oxide were observed through 84+. The high latitude launch occurred at Kiruna, Sweden on August 2, 1973, at 0700 LMT following visual sighting of a noctilucent cloud on the prior evening. The data near mesopause shows cluster ions, but also a preponderance of heavy ions between 90 and 145 AMU, with groupings 18 AMU apart but unrelated to the more typical cluster ions. One possible set of consistent identifications leads to iron and iron oxide hydrates. These results may suggest the presence of metallic particulates and ions which form hydrated clusters ions.

Goldberg, R. A.↗
NASA NTRS1963

Selected Papers on Noctilucent Clouds

The papers presented herein were taken from two Russian publications on the International Geophysical Year. The first four articles (footnoted Certain Articles Regarding Meteorology") are from Nekotoryye Problemy Meteorologii; Sbornik Statey, II Razdel Programmy MGG (Meteorologiya), No. 1, Izdat. Akademii Nauk SSSR (Certain Problems Regarding Meteorology; Collection of Articles, Second Section of the IGY Program (Meteorology), No. 1. Published by the Academy of Sciences Press) Moscow, 1960. The last two articles (footnoted "International Geophysical Year") are from Mezhdunarodnoy Geofizicheskiy God; Sbornik Statey i Materialov, Izdat. Leningradskogo Universiteta (International Geophysical Year; Collection of Articles and Materials. Published by the Leningrad University Press) 1960.

NOCTILUCENT CLOUD↗