Existence and Charge State of Meteoric Dust Grains in the Middle Atmosphere

The Earth`s atmosphere receives between 10 and 100 tonnes a day of meteoric matter too small to reach the surface. This material evaporates and is thought to provide the nuclei for ice particles and to cause other phenomena which occur in the mesosphere (70 to 90 km). Under special conditions NLC (= noctilucent clouds) can form which are visible from the ground. The probability and the altitude of the clouds have - within the accuracy of the triangulations and observations - not changed for more than 100 years. However, the brightness has detectably increased since the advent of satellite borne measurements over only two decades. A connection of the variability of this phenomenon with anthropogenic interference in the atmosphere is the topic of many investigations. For a sound understanding of the formation of NLC and polar mesospheric radar echoes an investigation of the anticipated nuclei is essential. An instrument dedicated to study the nature of these meteoric nuclei will be flown in a series of sounding rockets. The mechanisms leading from these nuclei to ice crystals depend crucially on the electric charge of these particulates. Knowledge of the background plasma is therefore essential for the understanding of the growth of these ice crystals. The Austrian hardware contribution to this German-Norwegian series of rocket payloads consists of instruments to measure the number densities of electrons and positive ions. All experimenters will take part in the data analysis and interpretation using data from all instruments.

The Earth`s atmosphere receives between 10 and 100 tonnes a day of meteoric matter too small to reach the surface. This material evaporates and is thought to provide the nuclei for ice particles and to cause other phenomena which occur in the mesosphere (70 to 90 km). Under special conditions NLC (= noctilucent clouds) can form which are visible from the ground. The probability and the altitude of the clouds have - within the accuracy of the triangulations and observations - not changed for more than 100 years. However, the brightness has detectably increased since the advent of satellite borne measurements over only two decades. A connection of the variability of this phenomenon with anthropogenic interference in the atmosphere is the topic of many investigations. For a sound understanding of the formation of NLC and polar mesospheric radar echoes an investigation of the anticipated nuclei is essential. An instrument dedicated to study the nature of these meteoric nuclei will be flown in a series of sounding rockets. The mechanisms leading from these nuclei to ice crystals depend crucially on the electric charge of these particulates. Knowledge of the background plasma is therefore essential for the understanding of the growth of these ice crystals. The Austrian hardware contribution to this German-Norwegian series of rocket payloads consists of instruments to measure the number densities of electrons and positive ions. All experimenters will take part in the data analysis and interpretation using data from all instruments.