A5040027409- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Geomagnetism and Paleomagnetism Studies
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Geophysics and Gravity Measurements
- Solar Radiation and Photovoltaics
- Space Satellite Systems and Control
- Atmospheric Ozone and Climate
- Laser-induced spectroscopy and plasma
- Magneto-Optical Properties and Applications
- Meteorological Phenomena and Simulations
- Astrophysical Phenomena and Observations
- Magnetic confinement fusion research
- Cardiovascular Health and Disease Prevention
- Market Dynamics and Volatility
- Astrophysics and Star Formation Studies
- Cardiovascular Disease and Adiposity
- Radiation Therapy and Dosimetry
- Spaceflight effects on biology
- Thin-Film Transistor Technologies
- Fluid Dynamics and Turbulent Flows
- Healthcare Systems and Challenges
- Magnetic Field Sensors Techniques
- Characterization and Applications of Magnetic Nanoparticles
University of Exeter
2014-2025
University of Warwick
2004-2013
University College London
2006-2011
Coventry University
2011
University of Buenos Aires
2010
University of New Hampshire
2010
Consejo Nacional de Investigaciones Científicas y Técnicas
2010
UCL Australia
2009
KU Leuven
2002-2005
University of St Andrews
2000-2005
Flows and instabilities play a major role in the dynamics of magnetized plasmas including solar corona, magnetospheric heliospheric boundaries, cometary tails, astrophysical jets. The nonlinear effects, multi-scale microphysical interactions inherent to flow-driven instabilities, are believed role, e.g., plasma entry across discontinuity, generation turbulence, enhanced drag. However, order clarify efficiency macroscopic these processes, we lack proper knowledge their overall morphological...
We propose a new model for quasi-periodic modulation of solar and stellar flaring emission. Fast magnetoacoustic oscillations non-flaring loop can interact with nearby active region. This interaction occurs when part the oscillation situated outside reaches regions steep gradients in magnetic field within an region produces periodic variations electric current density. The depth these is few orders magnitude greater than amplitude driving oscillation. induce current-driven plasma...
During propagation, Magnetic Clouds (MC) interact with their environment and, in particular, may reconnect the solar wind around it, eroding away part of its initial magnetic flux. Here we quantitatively analyze such an interaction using combined, multipoint observations same MC flux rope by STEREO A, B, ACE, WIND and THEMIS on November 19–20, 2007. Observation azimuthal imbalance inside a has been argued to stem from erosion due reconnection at front boundary. The present study adds...
Abstract Several recent studies suggest that magnetic reconnection is able to erode substantial amounts of the outer flux interplanetary clouds (MCs) as they propagate in heliosphere. We quantify and provide a broader context this process, starting from 263 tabulated coronal mass ejections, including MCs, observed over time period covering 17 years at distance 1 AU Sun with Wind (1995–2008) two STEREO (2009–2012) spacecraft. Based on several quality factors, careful determination MC...
Our purpose is to characterize the evolution of magnetopause Kelvin‐Helmholtz (KH) wave activity with changes in thickness adjacent boundary layer, geomagnetic latitude and interplanetary magnetic field (IMF) orientation. As IMF turns northward, may be generated at dayside before propagating down tail, where layer expected support longer wavelengths. We use two‐point observations on dusk low latitudes, from Geotail Cluster tailward terminator. quantify wavelength, power, wavefront steepness...
The first analysis of a transverse loop oscillation observed by both Solar TErrestrial RElations Observatories (STEREO) spacecraft is presented, for an event on the 2007 June 27 as seen Extreme Ultraviolet Imager (EUVI). three-dimensional geometry determined using reconstruction with semicircular model, which allows accurate measurement length. plane wave polarization found from comparison simulated model and shows that fundamental horizontally polarized fast magnetoacoustic kink mode....
Quasi-periodic pulsations (QPPs) of gamma-ray emission with a period about 40 s are found in single loop X-class solar flare on 2005 January 1 at photon energies up to 2–6 MeV the SOlar Neutrons and Gamma-rays (SONG) experiment aboard CORONAS-F mission. The oscillations also be present microwave detected Nobeyama Radioheliograph, hard X-ray low energy channels RHESSI. Periodogram correlation analysis shows that QPPs microwave, X-ray, almost synchronous all observation bands. Analysis spatial...
Electromagnetic (radio, visible-light, UV, EUV, x-ray and gamma-ray) emission generated by solar stellar flares often contains pronounced quasi-periodic pulsations (QPPs). Physical mechanisms responsible for the generation of long-period QPP (with periods longer than 1 s) are likely to be associated with MHD processes. The observed modulation depths, anharmonicity suggest that they can linked some kind auto-oscillations, e.g. an oscillatory regime magnetic reconnection. Such regimes, both...
Recent spectral observations of upward moving quasi-periodic intensity perturbations in solar coronal structures have shown evidence periodic line asymmetries near their footpoints. These challenge the established interpretation terms propagating slow magnetoacoustic waves. We show that waves inherently a bias toward enhancement emission blue wing due to in-phase behavior velocity and density perturbations. demonstrate cause when is averaged over an oscillation period or quasi-static plasma...
Aims. We investigate two successive trains of large amplitude transverse oscillations in an arched EUV prominence, observed with SoHO/EIT on the north-east solar limb 30 July 2005. The oscillatory are triggered by scale coronal waves, associated X-class and a C-class flare occurring same remote active region.
We report the first observation at high spatial resolution of long-period quasi-periodic pulsations (QPP) X-ray radiation during solar flares, made possible with Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), supported by complementary data other wavelengths from space-based and ground-based telescopes. Evidence for presence a transequatorial loop possibly responsible detected periodicity connected its kink mode is found. Our findings suggest that QPP can be interpreted as...
A study of vertically polarised fast magnetoacoustic waves in a curved coronal loop is presented. The modeled as semi-circular magnetic slab the zero plasma-β limit. governing equations for linear are derived. We show that wave mode behaviour depends on slope equilibrium density profile, which piece-wise continuous power law curve index α. For all profiles, except , modes not trapped and leak out into external medium through tunneling. particular case corresponds to linearly increasing...
Abstract Previous works have emphasized the significant influence of solar wind Alfvén Mach number ( M A ) on magnetospheric dynamics. Here we report statistical, observational results that pertain to changes in magnetosheath flow distribution and magnetopause shape as a function interplanetary magnetic field (IMF) clock angle orientation. We use all Cluster 1 data during period 2001–2010, using an appropriate spatial superposition procedure, produce distributions location relative IMF other...
We present a study of transverse loop oscillations in large coronal arcade, using observations from the Transition Region And Coronal Explorer (TRACE) and Extreme-ultraviolet Imaging Telescope (EIT). For first time we reveal presence long-period with periods between 24 minutes 3 hr. One bundle, 690 Mm long an oscillation period 40 minutes, is analyzed detail its characteristics are determined automated manner. The quality factor similar to what has been found earlier for much shorter loops....
Two transversely oscillating coronal loops are investigated in detail during a flare on the 2011 September 6 using data from Atmospheric Imaging Assembly (AIA) board Solar Dynamics Observatory. We compare two independent methods to determine Alfvén speed inside these loops. Through period of oscillation and loop length, information about each is deduced seismologically. This compared with profiles magnetic extrapolation spectral AIA bandpass. find that for both consistent. Also, we average...
Aims. We report and analyse the first observation of a transverse oscillation in hot coronal loop with Atmospheric Imaging Assembly (AIA) on Solar Dynamics Observatory (SDO), following linked coronal-flare mass-ejection event 3 November 2010. The oscillating is observed off east solar limb exclusively 131 Å 94 bandpasses, indicating plasma temperature range 9–11 MK. Furthermore, not to cool into other AIA channels, but just disappears from all bandpasses at end oscillation.
New capabilities for studying the Sun allow us to image first time magnetic Kelvin–Helmholtz (KH) instability developing at surface of a fast coronal mass ejecta (CME) less than 150 Mm above solar surface. We conduct detailed observational investigation this phenomenon, observed off east limb on 2010 November 3, in EUV with SDO/AIA. In conjunction STEREO-B/EUVI, we derive CME source position. ascertain timing and early evolution outflow leading onset. perform spectral analysis, exploring...
Long-period oscillations in a coronal diffuse structure are detected with the Transition Region And Coronal Explorer (TRACE). The EUV images of NOAA active region 8253 available 171 Å and 195 bandpasses from 30 June to 4 July 1998. average intensity variation is found be connected CCD temperature, which varies orbital motion spacecraft. Hence, period its higher harmonics appear as artifacts light curves. After exclusion effects, we identified several long-period fan-like region. Similar...
Abstract Kelvin‐Helmholtz instability (KHI) and associated magnetic reconnection diffusion processes provide plasma transport from solar wind into the magnetosphere. The efficiency of this depends on magnetosheath magnetospheric field properties at vicinity magnetopause. Our recent statistical study using data Time History Events Macroscale Interactions during Substorms spacecraft indicates that amplitude velocity fluctuations perpendicular to magnetopause can be substantial. We have...
Abstract Automated detection schemes are nowadays the standard approach for locating coronal holes in extreme-UV images from Solar Dynamics Observatory (SDO). However, factors such as noisy nature of solar imagery, instrumental effects, and others make it challenging to identify using these automated schemes. While discrepancies between have been noted literature, a comprehensive assessment is still lacking. The contribution Coronal Hole Boundary Working Team COSPAR ISWAT initiative close...
We investigate whether or not ultra-long-period oscillations in EUV filaments can be related to their eruption. report new observations of long-period (∼10–30 hr) oscillatory motions an apparently quiescent filament, as it crosses the solar disk a 12 minute cadence SOHO/Extreme-Ultraviolet Imaging Telescope (EIT) 195 Å uninterrupted data set. This set is chosen explore characteristics filament depending on its eruptive behavior, which observed while still disk. The periods are found increase...
Aims.Using a model of vertically polarised fast magnetoacoustic waves in curved coronal loops, the method seismology is applied to observations transverse loop oscillations.
We report the first detection of long-period (8–27 h) oscillatory intensity variations in a coronal filament. The filament is observed continuously as it crosses solar disk 12-min-cadence SoHO/EIT 195 Å uninterrupted data set. Cyclic are found to be correlated along filament, while most pronounced oscillations detected at its southern end for nearly 6 days. dominant period these 12.1 h and amplitude reaches approximately 10% background intensity. ultra-long-period may interpreted terms slow...
Aims. Fast magnetoacoustic waves in curved coronal loops are investigated and the role of lateral leakage wave damping, which includes mechanism tunneling, is explored. Methods. A loop modeled as a curved, magnetic slab zero plasma-β limit. In this model for an arbitrary piece-wise continuous power law equilibrium density profile, equation governing linear vertically polarised fast solved analytically. An associated dispersion relation derived frequencies eigenfunctions modes characterised....