108 research outputs found
Atmospheric electrification in the Solar System
Atmospheric electrification is not a purely terrestrial phenomenon: all Solar
System planetary atmospheres become slightly electrified by cosmic ray
ionisation. There is evidence for lightning on Jupiter, Saturn, Uranus and
Neptune, and it appears likely to exist on Mars, Venus and Titan. Atmospheric
electricity has controversially been implicated in climate on Earth; here, a
comparative approach is employed to review the role of electrification in the
atmospheres of other planets and their moons. This paper reviews planetary
atmospheric electricity including ionisation and ion-aerosol interactions. The
conditions necessary for a global electric circuit, and the likelihood of
meeting these conditions in other planetary atmospheres are briefly discussed.
Atmospheric electrification could be important throughout the Solar System,
particularly at the outer planets which receive little solar radiation,
increasing the significance of electrical forces. Nucleation onto atmospheric
ions has been predicted to affect the evolution and lifetime of haze layers on
Titan, Neptune, and Triton. Atmospheric electrical processes on Titan,
pre-Huygens, are summarised. Closer to Earth, heating from solar radiation
dominates planetary meteorology; however Mars may have a global circuit based
on electrical discharges from dust storms. There is a need for direct
measurements of planetary atmospheric electrification, in particular on Mars,
to assess the risk for future missions. Theoretical understanding could be
increased by cross-disciplinary work to modify and update models and
parameterisations initially developed for specific planetary atmospheres to
make them more broadly applicable.Comment: Submitted to Surveys in Geophysics. Abstract shown here is slightly
abridged for brevit
Remote sensing of cloud base charge
Layer clouds are abundant in the Earth's atmosphere. Such clouds do not
become sufficiently strongly charged to generate lightning, but they show weak
charging along the upper and lower cloud boundaries where there is a
conductivity transition. Cloud edge charging has recently been observed using
balloon-carried electrometers. Measurement of cloud boundary charging without
balloons is shown to be possible here for low altitude (<1km) charged cloud
bases, through combining their effect on the surface electric field with laser
time of flight cloud base height measurements, and the application of simple
electrostatic models.Comment: Proceedings of the Electrostatics Society of America conference,
Ottawa, June 201
Electrical charging of ash in Icelandic volcanic plumes
The existence of volcanic lightning and alteration of the atmospheric
potential gradient in the vicinity of near-vent volcanic plumes provides strong
evidence for the charging of volcanic ash. More subtle electrical effects are
also visible in balloon soundings of distal volcanic plumes. Near the vent,
some proposed charging mechanisms are fractoemission, triboelectrification, and
the so-called "dirty thunderstorm" mechanism, which is where ash and convective
clouds interact electrically to enhance charging. Distant from the vent, a
self-charging mechanism, probably triboelectrification, has been suggested to
explain the sustained low levels of charge observed on a distal plume. Recent
research by Houghton et al. (2013) linked the self-charging of volcanic ash to
the properties of the particle size distribution, observing that a highly
polydisperse ash distribution would charge more effectively than a monodisperse
one. Natural radioactivity in some volcanic ash could also contribute to
self-charging of volcanic plumes. Here we present laboratory measurements of
particle size distributions, triboelectrification and radioactivity in ash
samples from the Gr\'{i}msv\"{o}tn and Eyjafjallaj\"{o}kull volcanic eruptions
in 2011 and 2010 respectively, and discuss the implications of our findings.Comment: XV Conference on Atmospheric Electricity, 15-20 June 2014, Norman,
Oklahoma, US
Lord Kelvinâs atmospheric electricity measurements
Lord Kelvin (William Thomson) made important contributions to the study of atmospheric elec-
tricity during a brief but productive period from 1859â1861. By 1859 Kelvin had recognised the need for
âincessant recordingâ of atmospheric electrical parameters, and responded by inventing both the water dropper
equaliser for measuring the atmospheric potential gradient (PG), and photographic data logging. The water
dropper equaliser was widely adopted internationally and is still in use today. Following theoretical consid-
erations of electric field distortion by local topography, Kelvin developed a portable electrometer, using it to
investigate the PG on the Scottish island of Arran. During these environmental measurements, Kelvin may
have unwittingly detected atmospheric PG changes during solar activity in August
/
September 1859 associated
with the âCarrington eventâ, which is interesting in the context of his later statements that solar magnetic influ-
ence on the Earth was impossible. Kelvinâs atmospheric electricity work presents an early representative study
in quantitative environmental physics, through the application of mathematical principles to an environmental
problem, the design and construction of bespoke instrumentation for real world measurements and recognising
the limitations of the original theoretical view revealed by experimental wor
Miniaturized atmospheric ionization detector
A small scintillator-based detector for atmospheric ionization measurements
has been developed, partly in response to a need for better ionization data in
the weather-forming regions of the atmosphere and partly with the intention of
producing a commercially available device. The device can measure both the
count rate and energy of atmospheric ionizing radiation. Here we report results
of a test flight over the UK in December 2017 where the detector was flown with
two Geiger counters on a meteorological radiosonde. The count rate profile with
height was consistent both with the Geigers and with previous work. The energy
of incoming ionizing radiation increased substantially with altitude.Comment: Proc 18th Conference on Atmospheric Electricity, Nara, Japan, June
201
Electrical processes in planetary atmospheres
Lightning is common throughout the Solar System, and charging of particles
occurs in all atmospheres due to ionization from galactic cosmic rays. Here,
some electrical processes relevant to the atmosphere of Venus are outlined and
discussed in a comparative planetology context.Comment: Proceedings of the Electrostatics Society of America Conference,
Ottawa, June 201
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Recent advances in global electric circuit coupling between the space environment and the troposphere
The global atmospheric electric circuit is driven by thunderstorms and electrified rain/shower clouds and is also influenced by energetic charged particles from space. The global circuit maintains the ionosphere as an equipotential atâŒ+250 kV with respect to the good conducting Earth (both land and oceans). Its âloadâ is the fair weather atmosphere and semi-fair weather atmosphere at large distances from the disturbed weather âgeneratorâ regions. The main solar-terrestrial (or space weather) influence on the global circuit arises from spatially and temporally varying fluxes of galactic cosmic rays (GCRs) and energetic electrons precipitating from the magnetosphere. All components of the circuit exhibit much variability in both space and time. Global circuit variations between solar maximum and solar minimum are considered together with Forbush decrease and solar flare effects. The variability in ion concentration and vertical current flow are considered in terms of radiative effects in the troposphere, through infra-red absorption, and cloud effects, in particular possible cloud microphysical effects from charging at layer cloud edges. The paper identifies future research areas in relation to Task Group 4 of the Climate and Weather of the Sun-Earth System (CAWSES-II) programme
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A scientific career launched at the start of the space age: Michael Rycroft at 80
The scientific career of Michael Rycroft (born in 1938) spans the space age, during which significant changes have occurred in how scientists work, experiment, and interact. Here, as part of his 80th birthday celebrations, we review his career to date in terms of the social and structural changes in collaborative international science. His contributions to research, teaching, and management across solarâterrestrial and ionospheric physics as well as atmospheric and space science are also discussed
Response and Resistance to Paradox-Breaking BRAF Inhibitor in Melanomas
FDA-approved BRAF inhibitors produce high response rates and improve overall survival in patients with BRAF V600E/K-mutant melanoma, but are linked to pathologies associated with paradoxical ERK1/2 activation in wild-type BRAF cells. To overcome this limitation, a next-generation paradox-breaking RAF inhibitor (PLX8394) has been designed. Here, we show that by using a quantitative reporter assay, PLX8394 rapidly suppressed ERK1/2 reporter activity and growth of mutant BRAF melanoma xenografts. Ex vivo treatment of xenografts and use of a patient-derived explant system (PDeX) revealed that PLX8394 suppressed ERK1/2 signaling and elicited apoptosis more effectively than the FDA-approved BRAF inhibitor, vemurafenib. Furthermore, PLX8394 was efficacious against vemurafenibresistant BRAF splice variant-expressing tumors and reduced splice variant homodimerization. Importantly, PLX8394 did not induce paradoxical activation of ERK1/2 in wild-type BRAF cell lines or PDeX. Continued in vivo dosing of xenografts with PLX8394 led to the development of acquired resistance via ERK1/2 reactivation through heterogeneous mechanisms; however, resistant cells were found to have differential sensitivity to ERK1/2 inhibitor. These findings highlight the efficacy of a paradox-breaking selective BRAF inhibitor and the use of PDeX system to test the efficacy of therapeutic agents. © 2017 American Association for Cancer Research
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