Particle flows in a dc discharge in laboratory and microgravity conditions

We describe a series of experiments on dust particles flows in a positive column of a horizontal dc discharge operating in laboratory and microgravity conditions. The main observation is that the particle flow velocities in laboratory experiments are systematically higher than in microgravity experiments, for otherwise identical discharge conditions. The paper provides an explanation for this interesting and unexpected observation. The explanation is based on a physical model, which properly takes into account main plasma-particle interaction mechanisms relevant to the described experimental study. Comparison of experimentally measured particle velocities and those calculated using the proposed model demonstrates reasonable agreement, both in laboratory and microgravity conditions, in the entire range of discharge parameters investigated.Comment: 9 pages, 7 figure

Shear flow in a three-dimensional complex plasma in microgravity conditions

Shear flow in a three-dimensional complex plasma was experimentally studied in microgravity conditions using Plasmakristall-4 (PK-4) instrument on board the International Space Station (ISS). The shear flow was created in an extended suspension of microparticles by applying the radiation pressure force of the manipulation-laser beam. Individual particle trajectories in the flow were analyzed and from these, using the Navier-Stokes equation, an upper estimate of the complex plasma's kinematic viscosity was calculated in the range of $0.2$--$6.7~{\rm mm^2/s}$. This estimate is much lower than previously reported in ground-based experiments with 3D complex plasmas. Possible reasons of this difference are discussed.Comment: 5 pages, 4 figure

BUILDING A TOMOGRAPHIC VELOCITY MODEL FOR SAMOYLOV ISLAND AREA (LENA DELTA) FROM LOCAL SEISMOLOGICAL DATA FOR THE PERIOD OF 2019–2021

In our paper we present the results of seismotomographic inversion for the local seismological monitoring data obtained in the area of the Samoylov Island (Lena River delta) in 2019–2021. Tomographic velocity model was used for refining hypocenter locations of local earthquakes and for geological interpretation. The results are shown as maps of anomalies of seismic waves and Vp /Vs ratios for the 5 and 10 km depths. The velocity anomalies structure made it possible to interpret low Vp /Vs ratio as rocks related to the Siberian platform, and to compare between the boundary of the low Vp /Vs area and the trace of the known geological fault running along the Olenekskaya Channel

ПОСТРОЕНИЕ СЕЙСМОТОМОГРАФИЧЕСКОЙ МОДЕЛИ РАЙОНА НАУЧНО-ИССЛЕДОВАТЕЛЬСКОЙ СТАНЦИИ «ОСТРОВ САМОЙЛОВСКИЙ» ПО ДАННЫМ ЛОКАЛЬНОГО СЕЙСМОЛОГИЧЕСКОГО МОНИТОРИНГА ЗА 2019–2021 гг.

In our paper we present the results of seismotomographic inversion for the local seismological monitoring data obtained in the area of the Samoylov Island (Lena River delta) in 2019–2021. Tomographic velocity model was used for refining hypocenter locations of local earthquakes and for geological interpretation. The results are shown as maps of anomalies of seismic waves and Vp /Vs ratios for the 5 and 10 km depths. The velocity anomalies structure made it possible to interpret low Vp /Vs ratio as rocks related to the Siberian platform, and to compare between the boundary of the low Vp /Vs area and the trace of the known geological fault running along the Olenekskaya Channel. В работе приведены результаты сейсмотомографической инверсии по данным локального сейсмологического мониторинга, полученным в районе научно-исследовательской станции «Остров Самойловский» (дельта р. Лены) в 2019–2021 гг. Полученная сейсмотомографическая модель была использована для уточнения гипоцентров локальных землетрясений и геологической интерпретации. Результаты приведены в виде скоростных аномалий P- и S-волн, а также их соотношения Vp /Vs , для глубин 5 и 10 км. Анализ структуры скоростных аномалий позволил интерпретировать зону пониженного соотношения Vp /Vs как слой пород, относящийся к Сибирской платформе, а также сопоставить границу области пониженного Vp /Vs с известным геологическим разломом, проходящим вдоль Оленёкской протоки.