The transition from laminar to complex spatio-temporal dynamics of plumes due to a localized buoyancy source is studied numerically. Several experiments have reported that this transition is sensitive to external perturbations. Therefore, a well-controlled set-up has been chosen for our numerical study, consisting of a localized heat source at the bottom of an enclosed cylinder whose sidewall i...

Buoyant plumes, evolving free of boundary constraints, may develop well-defined mushroom-shaped heads. In conventional plumes, overturning flow in the head entrains less buoyant fluid from the surroundings as the head rises, robbing the plume of its driving force. We consider here a new type of plume in which the source of buoyancy is an autocatalytic chemical reaction. The reaction occurs at a...

We present observations by the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission of a substantial plume-like distribution of escaping ions from the Martian atmosphere, organized by the upstream solar wind convection electric field. From a case study of MAVEN particle-and-field data during one spacecraft orbit, we identified three escaping planetary ion populations: plume fluxes mainly alon...

A complex thermodynamic–microphysical package has been formulated that is able to deal with the microphysical processes of condensed water vapour in a volcanic plume. The microphysics follows a prognostic bulk approach for cloud water, cloud ice, rain and graupel and the interaction between them. In a standard experiment, this module, applied within a Ž . new nonhydrostatic volcano plume model,...

A time-accurate 2D axisymmetric Hybrid PIC-MCC model is used to simulate the plasma flow in the acceleration channel and near-field plume of a Hall thruster. The model is applied to the P5 Hall thruster due to known magnetic configuration and the availability of experimental data on the plasma properties in the interior and near-field plume for this thruster. Results for thruster performance an...

A steady source of buoyancy creates a plume. Experi­ mental and theoretical studies of plumes have been mainly concerned with the far-field (self-similar) velocity and den­ sity profiles. •-3 Yet in many practical situations, knowledge regarding the rate of molecular scale mixing of the buoyant fluid with its environment is needed. This is especially true in the context of atmospheric studies, ...

Iron is a scarce but essential micronutrient in the oceans that limits primary productivity in many regions of the surface ocean. The mechanisms and rates of Fe supply to the ocean interior are still poorly understood and quantified. Iron isotope ratios of different Fe pools can potentially be used to trace sources and sinks of the global Fe biogeochemical cycle if these boundary fluxes have di...

New H2O, CO2 and S concentration data for basaltic glasses from ‘hotspot’, with temperature differences of 200°C or more between hotter upwelling plumes and the ambient mantle Loihi seamount, Hawaii, allow us to model degassing, assimilation, adiabat (e.g. White & McKenzie, 1989; Campbell, 1998; and the distribution of major volatiles within and around the Davies, 1998). In contrast, it has lon...

[1] The pyrocumulonimbus storm near Chisholm, Alberta, on 28 May 2001 has been studied in depth. However, the impact of this eruption on the lower stratosphere has not been characterized. Here and in a companion paper we explore this topic. This paper focuses on the ‘‘young’’ Chisholm smoke plume, from the age of 3 h to 1 week, as observed by Earth-viewing satellite instruments. (The companion ...

[1] We measure expansion rate and bending in a 23-hour time series of acoustic images of the lower 25 m section of a buoyant hydrothermal plume rising from Grotto vent in the Main Endeavour Field, Juan de Fuca Ridge. We then calculate entrainment coefficient, the constant of proportionality relating mean inflow velocity at the plume edge to maximum mean upward velocity within the plume. The plu...