Tuesday, 29 March 2011

Do meteors smoke?

Meteor smoke originates to the meteor ablation which takes place typically between 70 and 120 km. Estimates for the total meteoric input to the atmosphere vary from few tens to hundreds of tons per day.

After metal species are evaporated into atoms they start to interact with the atmospheric species forming metal oxides, hydroxides and carbonates which tend to coagulate by Brownian collisions into nm-scale particles called meteor smoke. Formation of the smoke takes place in timescales of a week, while the meteor smoke is redistributed by the global air circulation to maximize its concentration in the polar wintertime. In fact, due to sedimentation of the large meteor smoke particles, some fraction of the smoke will eventually enter to the ground level, especially in the polar regions and found from the ice-core drilling samples.

In general, the meteor smoke particles are of versatile scientific interest in the upper atmospheric research. As said, meteor smoke plays a key role in the chemistry of metallic species. Meteoric dust is thought to play a role in formation of noctilucent clouds and closely related anomalous polar mesospheric summer (and possibly winter) radar echoes (PMSE and PMWE). Charged meteor smoke particles, positive or negative, obviously contribute to the electron density budget of the D-region ionosphere which must be taken into account in the modelling. Despite of the scientific interest, relatively little is known about the meteor smoke properties. Even the fundamentals, like the actual chemical composition, size distribution, charging and finally what is the daily meteoric input to the atmosphere - all these are more or less open questions at the moment.

Charged meteor smoke can be detected in the incoherent backscattering as a narrow peak in the ion line. Novel radar techniques applied in the KAIRA will potentially provide a new insight to the meteors smoke and its role in the polar atmosphere.

Related links: http://www.sgo.fi/~j/kaira_ks.png

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