Protocols for UV camera volcanic SO2 measurements

Ultraviolet camera technology offers considerable promise for enabling 1 Hz timescale acquisitions of volcanic degassing phenomena, providing two orders of magnitude improvements on sampling frequencies from conventionally applied scanning spectrometer systems. This could, for instance enable unprecedented insights into rapid processes, such as strombolian explosions, and non-aliased corroboration with volcano geophysical data. The uptake of this technology has involved disparate methodological approaches, hitherto. As a means of expediting the further proliferation of such systems, we here study these diverse protocols, with the aim of suggesting those we consider optimal. In particular we cover: choice and set up of hardware, calibration for vignetting and for absolute concentrations using quartz SO2 cells, the retrieval algorithm and whether one or two filters, or indeed cameras, are necessary. This work also involves direct intercomparisons with narrowband observations obtained with a scanning spectrometer system, employing a differential optical absorption spectroscopic evaluation routine, as a means of methodological validation

X-Ray Fluoroscopy Measurements and CFD Simulation of Hydrodynamics in a Two Dimensional Gas-Solids Fluidized Bed

X-ray fluoroscopy measurements and CFD simulation were used to characterize the hydrodynamics in a pseudo 2-D gas-solids bubbling fluidized bed using polyethylene resin and glass beads. Bubble properties, such as bubble frequency, bubble size, bubble number distribution and bubble diameter distribution, were estimated from X-ray images and compared to those from CFD simulation

Passive vs. active degassing modes at an open-vent volcano (Stromboli, Italy)

We report here on a UV-camera based field experiment performed on Stromboli volcano during 7 days in 2010 and 2011, aimed at obtaining the very first simultaneous assessment of all the different forms (passive and active) of SO2 release from an open-vent volcano. Using the unprecedented spatial and temporal resolution of the UV camera, we obtained a 0.8 Hz record of the total SO2 flux from Stromboli over a timeframe of 14 h, which ranged between 0.4 and 1.9 kg s 1 around a mean value of 0.7 kg s 1 and we concurrently derived SO2 masses for more than 130 Strombolian explosions and 50 gas puffs. From this, we show erupted SO2 masses have a variability of up to one order of magnitude, and range between 2 and 55 kg (average 20 kg), corresponding to a time integrated flux of 0.0570.01 kg s 1. Our experimental constraints on individual gas puff mass (0.03–0.42 kg of SO2, averaging 0.19 kg) are the first of their kind, equating to an emission rate ranging from 0.02 to 0.27 kg s 1. On this basis, we conclude that puffing is two times more efficient than Strombolian explosions in the magmatic degassing process, and that active degassing (explosionsþpuffing) accounts for 23% (ranging from 10% to 45%) of the volcano’s total SO2 flux, e.g., passive degassing between the explosions contributes the majority ( 77%) of the released gas. We furthermore integrate our UV camera gas data for the explosions and puffs, with independent geophysical data (infrared radiometer data and very long period seismicity), to offer key and novel insights into the degassing dynamics within the shallow conduit systems of this open-vent volcano

Exploring the role of composition and mass loading on the properties of hadronic jets

Astrophysical jets are relativistic outflows that remain collimated for remarkably many orders of magnitude. Despite decades of research, the origin of cosmic rays (CRs) remains unclear, but jets launched by both supermassive black holes in the centre of galaxies and stellar-mass black holes harboured in X-ray binaries (BHXBs) are among the candidate sources for CR acceleration. When CRs accelerate in astrophysical jets, they initiate particle cascades that form gamma-rays and neutrinos. In the so-called hadronic scenario, the population of accelerated CRs requires a significant amount of energy to properly explain the spectral constraints, similarly to a purely leptonic scenario. The amount of energy required often exceeds the Eddington limit or even the total energy available within the jets. The exact energy source for the accelerated protons is unclear, but due to energy conservation along the jets, it is believed to come from the jet itself via transfer of energy from the magnetic fields or kinetic energy from the outflow. To address this hadronic energy issue and to self-consistently evolve the energy flux along the flows, we explore a novel treatment for including hadronic content, in which instabilities along the jet/wind border play a critical role. We discuss the impact of the different jet compositions on the jet dynamics for a pair dominated and an electron-proton jet and, consequently, the emitted spectrum, accounting for both leptonic and hadronic processes. Finally, we discuss the implications of this mass-loading scenario to address the proton energy issue

Comparison of Low Cost Miniature Spectrometers for Volcanic SO2 Emission Measurements

Miniature ultraviolet USB coupled spectrometers have become ubiquitously applied over the last decade for making volcanic SO2 emission rate measurements. The dominantly applied unit has recently been discontinued however, raising the question of which currently available devices should now be implemented. In this paper, we consider, and make recommendations on this matter, by studying a number of inexpensive compact spectrometers in respect of measurement performance and thermal behaviour. Of the studied units, the Avaspec demonstrated the best prospects for the highest time resolution applications, but in the majority of cases, we anticipate users likely preferring the less bulky USB2000+s

Vulcamera: a program for measuring volcanic SO2 using UV cameras

We report here on Vulcamera, a stand-alone program for the determination of volcanic SO2 fluxes using ultraviolet cameras. The code enables field image acquisition and all the required post-processing operations

Recent advances in ground-based ultraviolet remote sensing of volcanic SO2 fluxes

Measurements of volcanic SO2 emission rates have been the mainstay of remote-sensing volcanic gas geochemistry for almost four decades, and they have contributed significantly to our understanding of volcanic systems and their impact upon the atmosphere. The last ten years have brought stepchange improvements in the instrumentation applied to these observations, which began with the application of miniature ultraviolet spectrometers that were deployed in scanning and traverse configurations, with differential optical absorption spectroscopy evaluation routines. This study catalogs the more recent empirical developments, including: ultraviolet cameras; wideangle field-of-view differential optical absorption spectroscopy systems; advances in scanning operations, including tomography; and improved understanding of errors, in particular concerning radiative transfer. Furthermore, the outcomes of field deployments of sensors during the last decade are documented, with respect to improving our understanding of volcanic dynamics and degassing into the atmosphere