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FRINATEK-Fri prosj.st. mat.,naturv.,tek

Mesospheric Dust in the Small Size Limit: Radar Studies, Model Calculations and Supporting Observations

Alternative title: Mesosfærisk støv ved den nedre størrelsesgrensen: Radarstudier, modellberegninger og understøttende observasjoner

Awarded: NOK 10.2 mill.

This projects addresses the physics and interactions of small nanometer-sized solid particles in the upper atmosphere of Earth at 75 to 110 km altitude. These particles have different properties than the larger dust. They are important because they influence the physics and chemistry of the atmosphere. The dust in the mesosphere forms as a result of material deposited from meteors when cosmic dust enters the atmosphere. It was suggested that the solid particles facilitate the growth of ice particles when the temperatures are sufficiently low. This happens in the high latitude upper atmosphere during the summer, which is why ice particles can be observed above Northern Scandinavia. With recent work in the project, we have applied advanced condensation models to show that such solid particles are indeed needed to facilitate the formation of ice particles in the upper atmosphere. The ice particles are visible from ground as the Noctilucent Clouds (NLC) and can form radar echoes, i.e. Polar Mesospheric Summer Echoes (PMSE). Our recent analysis of selected PMSE shows their variation with particle precipitation influencing the ionospheric conditions. We have also developed data handling tools for a quantitative and qualitative analysis of large data sets of NLC and PMSE to be used with existing observations as well as the upcoming EISCAT_3D. We are investigating the incoherent scatter radar spectra in the presence of charged dust and prepare for more dedicated observations. To complement the remote observations with in-situ studies we develop in-situ instruments and prepare a rocket campaign with recovery from Andøya Space. Our goal is to collect dust from the mesosphere for laboratory analysis. A mini-workshop was conducted to compare the ionospheres on Earth with those of Saturn, Enceladus and Io. The discussion continues and we continue to collaborate with researchers in Japan, Sweden, the United Kingdom, and other countries over the Internet and have also participated in conferences in this way. Project results were presented at the European Union General Assembly, European Conference on Rocket and Balloon research, the International EISCAT Symposium and the International Workshop on Layered Phenomena in the Mesosphere. This interdisciplinary project brings together international experts from various disciplines such as atmospheric chemistry and physics, laboratory experiments, low-temperature studies, dust plasma and space physics. Several students are involved in the project.

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This study addresses the fundamental questions how particles of nanometer size form and interact in the partially ionized medium of Earth ionosphere. We analyze the incoherent scatter of radio waves from the mesosphere, a dusty plasma process, to study particles at the size transition from molecules to nanodust. The ionosphere at 75 to 110 km altitude, the mesosphere contains nanoparticles ranging from dust to few 100 amu. The polar mesosphere cools down to 120 K or lower during summer and nanoparticles that contain ice lead to the formation of the visible Noctilucent Clouds (NLC) and to Polar Mesospheric Summer Echoes (PMSE) observed with radar. Size and charge of nanoparticles influence their growth rates, chemical processes and PMSE formation. We study for the first time systematically the influence of charged nanoparticles on the incoherent scatter spectra with measurement at three different radar frequencies. We plan to observe during a rocket measurement and consider results from previous ones. We calculate height profiles of the nanoparticles using atmospheric models, simulate their nucleation and carry out dusty plasma simulations to analyze the observations. Based on this we will determine the size distribution, smallest size, and charging rates of the nanoparticles, parameters of fundamental importance for understanding the role of nanoparticles in mesospheric processes. We also plan first observations with the new EISCAT_3D radar. The project will be carried out at Tromsø University (UiT) with a long tradition in cosmic dusty plasma research and radar observations of the ionosphere. The project manager has long experience in cosmic dust research using space measurements, observations, model calculations and recently radar studies. This multidisciplinary project brings together international experts in the fields of atmospheric chemistry, laboratory experiments and low temperature studies, dusty plasma theory, space and atmospheric physics.

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FRINATEK-Fri prosj.st. mat.,naturv.,tek