Publications by Karen Aplin

Measuring ionizing radiation in the atmosphere with a new balloon-borne detector


KL Aplin, AA Briggs, RG Harrison, GJ Marlton

Scientific rationale for Uranus and Neptune in situ explorations

Planetary and Space Science (2017)

O Mousis, DH Atkinson, T Cavalié, LN Fletcher, MJ Amato, S Aslam, F Ferri, JB Renard, T Spilker, E Venkatapathy, P Wurz, K Aplin, A Coustenis, M Deleuil, M Dobrijevic, T Fouchet, T Guillot, P Hartogh, T Hewagama, MD Hofstadter, V Hue, R Hueso, JP Lebreton, E Lellouch, J Moses, GS Orton, JC Pearl, A Sánchez-Lavega, A Simon, O Venot, JH Waite, RK Achterberg, S Atreya, F Billebaud, M Blanc, F Borget, B Brugger, S Charnoz, T Chiavassa, V Cottini, L d'Hendecourt, G Danger, T Encrenaz, NJP Gorius, L Jorda, B Marty, R Moreno, A Morse, C Nixon, K Reh, T Ronnet, FX Schmider, S Sheridan, C Sotin, P Vernazza, GL Villanueva

© 2017 Elsevier Ltd. The ice giants Uranus and Neptune are the least understood class of planets in our solar system but the most frequently observed type of exoplanets. Presumed to have a small rocky core, a deep interior comprising ~70% heavy elements surrounded by a more dilute outer envelope of H 2 and He, Uranus and Neptune are fundamentally different from the better-explored gas giants Jupiter and Saturn. Because of the lack of dedicated exploration missions, our knowledge of the composition and atmospheric processes of these distant worlds is primarily derived from remote sensing from Earth-based observatories and space telescopes. As a result, Uranus's and Neptune's physical and atmospheric properties remain poorly constrained and their roles in the evolution of the Solar System not well understood. Exploration of an ice giant system is therefore a high-priority science objective as these systems (including the magnetosphere, satellites, rings, atmosphere, and interior) challenge our understanding of planetary formation and evolution. Here we describe the main scientific goals to be addressed by a future in situ exploration of an ice giant. An atmospheric entry probe targeting the 10-bar level, about 5 scale heights beneath the tropopause, would yield insight into two broad themes: i) the formation history of the ice giants and, in a broader extent, that of the Solar System, and ii) the processes at play in planetary atmospheres. The probe would descend under parachute to measure composition, structure, and dynamics, with data returned to Earth using a Carrier Relay Spacecraft as a relay station. In addition, possible mission concepts and partnerships are presented, and a strawman ice-giant probe payload is described. An ice-giant atmospheric probe could represent a significant ESA contribution to a future NASA ice-giant flagship mission.

Lightning detection in planetary atmospheres

WEATHER 72 (2017) 46-50

KL Aplin, G Fischer

Evaluating stratiform cloud base charge remotely


RG Harrison, KA Nicoll, KL Aplin

Solar-Driven Variation in the Atmosphere of Uranus

Geophysical Research Letters (2017)

KL Aplin, RG Harrison

©2017. American Geophysical Union. Long-term measurements (1972-2015) of the reflectivity of Uranus at 472 and 551 nm display variability that is incompletely explained by seasonal effects. Spectral analysis shows that this nonseasonal variability tracks the 11 year solar cycle. Two mechanisms could cause solar modulation: (a) nucleation onto ions or electrons created by galactic cosmic rays (GCR) or (b) UV-induced aerosol color changes. Ion-aerosol theory is used to identify expected relationships between reflectivity fluctuations and GCR flux, tested with multiple regression and compared to the linear response predicted between reflectivity and solar UV flux. The statistics show that 24% of the variance in reflectivity fluctuations at 472 nm is explained by GCR ion-induced nucleation, compared to 22% for a UV-only mechanism. Similar GCR-related variability exists in Neptune's atmosphere; hence, the effects found at Uranus provide the first example of common variability in two planetary atmospheres driven through energetic particle modulation by their host star.

Atmospheric changes from solar eclipses.

Philosophical transactions. Series A, Mathematical, physical, and engineering sciences 374 (2016)

KL Aplin, CJ Scott, SL Gray

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 subset 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 that 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 ionization of the upper atmosphere are also briefly reviewed.This article is part of the themed issue 'Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse'.

Applications of Electrified Dust and Dust Devil Electrodynamics to Martian Atmospheric Electricity

SPACE SCIENCE REVIEWS 203 (2016) 299-345

RG Harrison, E Barth, F Esposito, J Merrison, F Montmessin, KL Aplin, C Borlina, JJ Berthelier, G Deprez, WM Farrell, IMP Houghton, NO Renno, KA Nicoll, SN Tripathi, M Zimmerman

Determining solar effects in Neptune's atmosphere.

Nature communications 7 (2016) 11976-

KL Aplin, RG Harrison

Long-duration observations of Neptune's brightness at two visible wavelengths provide a disk-averaged estimate of its atmospheric aerosol. Brightness variations were previously associated with the 11-year solar cycle, through solar-modulated mechanisms linked with either ultraviolet or galactic cosmic ray (GCR) effects on atmospheric particles. Here, we use a recently extended brightness data set (1972-2014), with physically realistic modelling to show, rather than alternatives, ultraviolet and GCR are likely to be modulating Neptune's atmosphere in combination. The importance of GCR is further supported by the response of Neptune's atmosphere to an intermittent 1.5- to 1.9-year periodicity, which occurred preferentially in GCR (not ultraviolet) during the mid-1980s. This periodicity was detected both at Earth, and in GCR measured by Voyager 2, then near Neptune. A similar coincident variability in Neptune's brightness suggests nucleation onto GCR ions. Both GCR and ultraviolet mechanisms may occur more rapidly than the subsequent atmospheric particle transport.

Weather scientists cite Bob Dylan too.

BMJ (Clinical research ed.) 532 (2016) i265-

S Brown, KL Aplin, K Jenkins, S Mander, C Walsh, PD Williams

Atmospheric Electrification in Dusty, Reactive Gases in the Solar System and Beyond

SURVEYS IN GEOPHYSICS 37 (2016) 705-756

C Helling, RG Harrison, F Honary, DA Diver, K Aplin, I Dobbs-Dixon, U Ebert, S-I Inutsuka, FJ Gordillo-Vazquez, S Littlefair

Electrostatics and In Situ Sampling of Volcanic Plumes

in Volcanic Ash: Hazard Observation, (2016) 99-113

KL Aplin, AJ Bennett, RG Harrison, IMP Houghton

© 2016 Elsevier Ltd. All rights reserved. The spectacular lightning displays that can sometimes be seen during volcanic eruptions demonstrate that the emitted plumes readily become electrically charged, but the relationships between volcanic parameters, meteorological conditions, and lightning type and rate are not well understood. The variability and range of physical processes involved, and difficulties of in situ measurements-here defined as those made in and near the plume-are the major reasons for this uncertainty. Lightning in volcanic plumes has now been measured in some detail using established remote sensing systems that can characterize both lightning location and flash rate. It seems likely that the meteorological mechanisms generating lightning in thunderstorms are enhanced by the presence of ash, a mechanism that we refer to as the ash-rich icy electrification system (ARIES). The ash brings its own fractoemission and triboelectric (frictional) charging mechanisms, which are thought to dominate close to the vent where large numbers of weaker lightning strikes are seen. Charging in distal plumes has been detected by enhanced meteorological radiosondes, indicating that self-charging continues during dispersion. Laboratory measurement of ash samples under controlled conditions suggest that the self-charging efficiency of atmospheric plumes is related to the size distribution of the particles and therefore that self-charging can occur in all plumes. Measurements of laboratory electrical charging alone are inadequate to fully characterize plume electrostatics, which has motivated integrated radiosonde packages for in situ plume measurements, such as particle size and location, turbulence, and thermodynamic structure.

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


KL Aplin, M Lockwood

Is there a Rhythm Of The Rain? An analysis of weather in popular music

WEATHER 70 (2015) 198-204

S Brown, KL Aplin, K Jenkins, S Mander, C Walsh, PD Williams

Let's share our music of the spheres


K Aplin, D Williams

Energetic Particle Influence on the Earth's Atmosphere


IA Mironova, KL Aplin, F Arnold, GA Bazilevskaya, RG Harrison, AA Krivolutsky, KA Nicoll, EV Rozanov, E Turunen, IG Usoskin

Cosmic ray measurements in the atmosphere at several latitudes in October, 2014

Proceedings of Science 30-July-2015 (2015)

V Makhmutov, G Bazilevskaya, Y Stozhkov, M Philippov, Y Yair, R Yaniv, G Harrison, K Nicoll, K Aplin

Cosmic ray fluxes in the atmosphere were recorded during balloon flights in October 2014 in northern Murmansk region, Apatity (Russia; 67o33'N, 33o24'E), in Antarctica (observatory Mirny; 66o33'S, 93o00'E), in Moscow (Russia; 55o45'N, 37o37'E), in Reading (United King- dom; 51o27'N, 0o 58'W), in Mitzpe-Ramon (Israel; 30o36'N, 34o48'E) and in Zaragoza (Spain; 41o9'N, 0o54'W). Two type of cosmic ray detectors were used, namely, (1) the standard ra- diosonde and its modification constructed at the Lebedev Physical Institute (Moscow, Russia) and (2) the device manufactured at the Reading University (Reading, United Kingdom). We compare and analyze obtained data and focus on the estimation of the cosmic ray latitudinal effect in the atmosphere.

Modelling of an asteroid photoelectron sheath and implications for a sample return mission


KL Aplin, AJ Macfaden, NE Bowles

Vertical profile measurements of lower troposphere ionisation


RG Harrison, KA Nicoll, KL Aplin

Atmospheric electric fields during the Carrington flare


KL Aplin, RG Harrison

Brief Communication: Earthquake-cloud coupling through the global atmospheric electric circuit


RG Harrison, KL Aplin, MJ Rycroft