arXiv subjects

Karen Aplin

Publications and source records attributed to Karen Aplin.

7 recordsLinked to original sources

arXiv2021

Electric field measurements made on a robotic platform

This presentation reports the first known data from a field mill mounted on a ground-based robotic platform. The robot's motor and electrostatic charging of its wheels do not perturb the field mill data, and electric field varies smoothly whilst the robot is moving. Test measurements under a charged polystyrene plate are reduced in variability by a factor of 2 compared to a hand-held field mill. This technology has potential for autonomous measurements in inaccessible or hazardous environments.

cs.RO↗

arXiv2018

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.

physics.ins-det↗

arXiv2017

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.

physics.ao-ph↗

arXiv2017

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.

physics.ao-ph↗

arXiv2016

Atmospheric changes from solar eclipses

This article reviews atmospheric changes associated with 44 solar eclipses, beginning with the first quantitative results available, from 1834 (earlier qualitative, accounts also exist). Eclipse meteorology attracted relatively few publications until the total solar eclipse of 16 February 1980, with the 11 August 1999 eclipse producing the most papers. Eclipses passing over populated areas such as Europe, China and India now regularly attract scientific attention, whereas atmospheric measurements of eclipses at remote locations remain rare. Many measurements and models have been used to exploit the uniquely predictable solar forcing provided by an eclipse. In this paper we compile the available publications and review a sub-set of them chosen on the basis of importance and novelty. Beyond the obvious reduction in incoming solar radiation, atmospheric cooling from eclipses can induce dynamical changes. Observations and meteorological modelling provide evidence for the generation of a local eclipse circulation which may be the origin of the "eclipse wind". Gravity waves set up by the eclipse can, in principle, be detected as atmospheric pressure fluctuations, though theoretical predictions are limited, and many of the data are inconclusive. Eclipse events providing important early insights into the ionisation of the upper atmosphere are also briefly reviewed.

physics.ao-ph↗

arXiv2015

Further considerations of cosmic ray modulation of infra-red radiation in the atmosphere

Understanding effects of ionisation in the lower atmosphere is a new interdisciplinary area, crossing traditionally distinct scientific boundaries. Following the paper of Erlykin et al. (Astropart. Phys. 57--58 (2014) 26--29) we develop the interpretation of observed changes in long-wave (LW) radiation (Aplin and Lockwood, Env. Res. Letts. 8, 015026 (2013)), by taking account of cosmic ray ionisation yields and atmospheric radiative transfer. To demonstrate this, we show that the thermal structure of the whole atmosphere needs to be considered along with the vertical profile of ionisation. Allowing for ionisation by all components of a cosmic ray shower and not just by the muons, reveals that the effect we have detected is certainly not inconsistent with laboratory observations of the LW absorption cross section. The analysis presented here, although very different from that of Erlykin et al., does come to the same conclusion that the events detected were not caused by individual cosmic ray primaries -- not because it is impossible on energetic grounds, but because events of the required energy are too infrequent for the 12/hr rate at which they were seen by the AL experiment. The present paper numerically models the effect of three different scenario changes to the primary GCR spectrum which all reproduce the required magnitude of the observed effect. However, they cannot solely explain the observed delay in the peak effect which, if confirmed, would appear to open up a whole new and interesting area in the study of water oligomers and their effects on LW radiation. We argue that a technical artefact in the earlier experiment is highly unlikely and that our initial observations merit both follow-up experiments and more rigorous, self-consistent, three-dimensional radiative transfer modelling.

physics.ao-ph↗

arXiv2005

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.

physics.geo-ph↗