A5070351489- Astro and Planetary Science
- Ionosphere and magnetosphere dynamics
- Geomagnetism and Paleomagnetism Studies
- Solar and Space Plasma Dynamics
- Planetary Science and Exploration
- Dust and Plasma Wave Phenomena
- Magnetic confinement fusion research
- Earthquake Detection and Analysis
- Stellar, planetary, and galactic studies
- Plasma Diagnostics and Applications
- Laser-induced spectroscopy and plasma
- Space Exploration and Technology
- High-pressure geophysics and materials
- Geology and Paleoclimatology Research
- Astronomical Observations and Instrumentation
- Astrophysics and Star Formation Studies
- Atomic and Subatomic Physics Research
- GNSS positioning and interference
- Spacecraft and Cryogenic Technologies
- Laser-Plasma Interactions and Diagnostics
- Geochemistry and Geologic Mapping
- Astronomy and Astrophysical Research
- Characterization and Applications of Magnetic Nanoparticles
- Image Processing and 3D Reconstruction
- Geophysics and Gravity Measurements
University College London
2014-2024
UiT The Arctic University of Norway
1996-2024
Lancaster University
2024
University of Bergen
2005-2020
Birkbeck, University of London
2011-2019
Institute of Theoretical Physics
2017
UCL Australia
2010-2012
University of Oslo
2000-2008
The University of Sydney
2008
Université Grenoble Alpes
1998
We present calculations of magnetic potential associated with the perturbation Saturn's field by a rotating, equatorially-situated disc plasma. Such structures are central to dynamics rapidly rotating magnetospheres Saturn and Jupiter. They `fed' internally sources plasma from moons such as Enceladus (Saturn) Io (Jupiter). use scaled form Euler potentials for Jovian magnetodisc (Caudal, 1986). In this formalism, is assumed be azimuthally symmetric about planet's axis rotation, temperature...
This study is based on multi‐planet multi‐wavelength observations of planetary aurorae throughout the heliosphere, acquired along propagation path a series consecutive interplanetary shocks. The underlying motivation to track shocks was increase probability detection auroral emissions at Uranus. Despite several Earth‐based attempts in past few years, Far‐UV (FUV) and Near‐IR (NIR) wavelengths, such have never been unambiguously re‐observed since their discovery by Voyager 2 1986. Here, we...
Abstract Saturn's magnetic field acts as an obstacle to solar wind flow, deflecting plasma around the planet and forming a cavity known magnetosphere. The magnetopause defines boundary between planetary dominated regimes, so is strongly influenced by variable nature of pressure sources both outside within. Following from Pilkington et al. (2014), crossings are identified using 7 years particle data Cassini spacecraft providing unprecedented spatial coverage boundary. These observations...
Abstract. In the ionosphere, a sustained population of suprathermal electrons arises due to photoionization or electron precipitation. The presence such enhances scattered power in plasma line spectrum, thus making it possible detect them. Plasma measurements improve accuracy density and temperature estimates. We investigate enhancements EISCAT Tromsø UHF radar observations, using two image processing methodologies for detection: supervised morphological technique an unsupervised connected...
Previously, we have presented the first study to investigate response of Jovian thermosphere transient variations in solar wind dynamic pressure, using a coupled, azimuthally symmetric global circulation model coupled with simple magnetosphere model. This work (Yates et al., 2013, submitted) described thermospheric flows, momentum sources, and magnetosphere-ionosphere coupling currents compressions expansions magnetosphere. The present describes heating, cooling auroral emissions...
Abstract. Results on the formation and propagation of electron phase space vortices from laboratory experiments are summarized. The were excited in a strongly magnetized Q-machine plasma by applying pulse to segment waveguide surrounding plasma. Depending temporal variation applied pulse, one or more can be excited, their interaction followed time. We able demonstrate, for instance, an irreversible coalescence two such vortices. These results extended numerical simulations, showing how also...
Using a model of force balance in Saturn's disk-like magnetosphere, we show that variations hot plasma pressure can change the magnetic field configuration. This effect changes (i) location magnetopause, even at fixed solar wind dynamic pressure, and (ii) mapping between ionosphere disk. The uses equatorial observations as boundary condition-we test its predictions over wide latitude range by comparison with Cassini high-inclination orbit data. We find reasonable agreement time scales larger...
The aurorae of Uranus were recently detected in the far ultraviolet with Hubble Space Telescope (HST) providing a new, so unique, means to remotely study asymmetric Uranian magnetosphere from Earth. We analyze here two new HST campaigns executed Sept. 2012 and Nov. 2014 different temporal coverage under variable solar wind conditions numerically predicted by three MHD codes. Overall, images taken Imaging Spectrograph reveal auroral emissions pairs successive (one pair acquired 2014), hence...
We present the first ever measurement of full thermal plasma properties, an ionospheric patch in darkness noon region where patches are believed to form. Further these data experimental evidence for Lockwood and Carlson class mechanisms forming by injection. These were possible only because a new capability we had develop. introduce here it crosses high‐speed threshold that now allows study broader mesoscale flow‐transients, which thought occur over time scales near 2 minutes vice 8–10...
This paper presents a numerical study of the effect Langmuir turbulence on incoherent scatter spectra. The is driven by low energy beams electrons in Earth’s upper ionosphere above 300km. nonlinear coupling between waves and ion-acoustic governed Zakharov system equations. model enhanced with stochastic forcing order to estimate how much over thermal level spectrum seen an radar will be enhanced. also allows us directly compare modeled spectra observed collected scattering technique, as well...
Langmuir cavitons have been artificially produced in the earth's ionosphere, but evidence of naturally-occurring cavitation has elusive. By measuring and modeling spectra electrostatic plasma modes, we show that natural cavitating, or strong, turbulence does occur via a process which beam auroral electrons drives waves, turn produce cascading ion-acoustic excitations cavitating turbulence. The data presented here are first direct occurring naturally any space astrophysical plasma.
The coupling of Jupiter's magnetosphere and ionosphere plays a vital role in creating its auroral emissions. strength these emissions is dependent on the difference speed rotational flows within high-latitude thermosphere planet's magnetodisc. Using an azimuthally symmetric global circulation model, we have simulated how upstream solar wind conditions affect energy direction atmospheric flows. In order to simulate effect varying dynamic pressure wind, calculated three magnetic field profiles...
High resolution spectra of Comet 8P/Tuttle were obtained in the frequency range 3440.6-3462.6 cm-1 on 3 January 2008 UT using CGS4 with echelle grating UKIRT. In addition to recording strong solar pumped fluorescent (SPF) lines H2O, long integration time (152 miutes target) enabled eight weaker H2O features be assigned, most which had not previously been identified cometary spectra. These transitions, are from higher energy upper states, similar character so-called 'SH' recorded post Deep...
Abstract For over 10 years, the Cassini spacecraft has patrolled Saturn's magnetosphere and observed its magnetopause boundary a wide range of prevailing solar wind interior plasma conditions. We now have data that enable us to resolve significant dawn‐dusk asymmetry find extends farther from planet on dawnside by 7 ± 1%. In addition, an opposing in suprathermal pressure adjacent been observed. This probably acts reduce size may explain discrepancy between degree found here similar Kivelson...
Abstract In order to analyze varying plasma conditions upstream of Titan, we have combined a physical model Saturn's disk with geometrical the oscillating current sheet. During modeled oscillation phases where Titan is farthest from sheet, main sources pressure in near‐Titan space are magnetic and, for disturbed conditions, hot pressure. When at center dynamic associated cold, subcorotating and under conditions. Total (dynamic plus thermal magnetic) typically increases by factor up about 3...
Under Horizon 2020, the Europlanet 2020 Research Infrastructure (EPN2020-RI) will include an entirely new Virtual Access Service, "Planetary Space Weather Services" (PSWS) that extend concepts of space weather and situational awareness to other planets in our Solar System particular spacecraft voyage through it. PSWS make twelve services accessible research community, agencies, industrial partners planning for missions. These be dedicated following key planetary environments: Mars (in...
Abstract The location of a planetary magnetopause is principally determined by the balance between solar wind dynamic pressure D P and magnetic plasma pressures inside boundary. Previous empirical studies assumed that Saturn's standoff distance varies as measured constant compressibility parameter α corresponding to behavior intermediate vacuum dipole appropriate for Earth ( ≈6) more easily compressible case Jupiter ≈4). In this study we employ 2‐D force model magnetosphere investigate...
An important property associated with turbulence in plasmas and fluids is anomalous transport. Plasma, being a good conductor, can addition be affected by causing an resistivity that significantly exceed its classical counterpart. While turbulent transport may adequately described configuration space, some aspects of the are best accounted for phase space. Kinetic phenomena like electron ion space vortices thus act as obstacles free flow slow charged particles. Plasma instabilities large...
We present an application of the latest UCL-AGA magnetodisc model (MDISC) to study magnetic and plasma conditions in near-Ganymede space. By doing this, we provide a comparison with measurements from Juno’s most recent flyby Jovian moon, perijove 34 (PJ34). find good agreement between results magnetometer data, pointing towards hot index value $K_h = \SI{2.719(24)e7}{\pascal\,\meter\,\tesla^{-1}}$ effective radius $r_{\text{max}} \SI{79.5(11)}{}$ Jupiter radii for magnetosphere, duration...
Abstract The WHAMP (Rönnmark, 1982, https://inis.iaea.org/search/search.aspx?orig_q=RN:14744092 ) and LEOPARD (Astfalk & Jenko, 2017, https://doi.org/10.1002/2016ja023522 dispersion relation solvers were used to evaluate the growth rate scale size for mirror mode (MM) ion cyclotron (IC) instabilities under plasma conditions resembling Saturn's magnetosheath in order compare observations predictions from linear kinetic theory. Instabilities waves are prevalent planetary magnetosheaths....
Abstract. The dynamic behavior of a collisionless plasma flowing around an obstacle is investigated by numerical methods. In the present studies, formed absorbing cylinder, and 2-D electrostatic particle-in-cell simulation used to study flow characteristics, with extensions fully 3-D generalization problem demonstrated as well. formation irregular filamented density depletions, oblique flow, observed. structures form behind obstacle, in region strong velocity shear, but also other...
The electrostatic potential and plasma density variations around a pointlike charged object in flow are studied. These objects can represent small dust particles, for instance. radiation patterns be interpreted as the result of sound waves being radiated by obstacle. Two limits considered: one where electron-ion temperature ratio is large, ${T}_{e}⪢{T}_{i}$, ${T}_{e}∕{T}_{i}\ensuremath{\approx}1$. former limit described simple model based on geometrical optics, while latter requires kinetic...