A5014076704- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Gamma-ray bursts and supernovae
- Solar Radiation and Photovoltaics
- Dark Matter and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Calibration and Measurement Techniques
- Lower Extremity Biomechanics and Pathologies
- History and Developments in Astronomy
- Geophysics and Gravity Measurements
- Oil, Gas, and Environmental Issues
- Geomagnetism and Paleomagnetism Studies
- Astronomy and Astrophysical Research
- Spacecraft and Cryogenic Technologies
- Adaptive optics and wavefront sensing
- Advanced X-ray Imaging Techniques
- Atmospheric and Environmental Gas Dynamics
- Radiation Therapy and Dosimetry
- Spacecraft Design and Technology
- Cosmology and Gravitation Theories
- Earthquake Detection and Analysis
- Particle Detector Development and Performance
University of Glasgow
2014-2024
University of Sheffield
2015-2017
Insigneo
2015-2017
Loughborough University
2011-2015
University of California, Berkeley
2006-2008
Netherlands Institute for Radio Astronomy
2008
We develop and apply an enhanced regularization algorithm, used in RHESSI X-ray spectral analysis, to constrain the ill-posed inverse problem that is determining DEM from solar observations. demonstrate this computationally fast technique applied a range of models simulating broadband imaging data SDO/AIA high resolution line spectra Hinode/EIS, as well actual active region observations with Hinode/EIS XRT. As method naturally provides both vertical horizontal (temperature resolution) error...
We present X-ray imaging and spectral analysis of all microflares the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observed between March 2002 2007, a total 25,705 events. These are small flares, from low GOES C Class to below A (background subtracted) associated with active regions. They were found by searching 6-12 keV energy range during periods when full sensitivity RHESSI's detectors was available (see paper I). Each microflare is automatically analyzed at peak time...
We present the first in-depth statistical survey of all X-ray microflares observed by RHESSI between 2002 March and 2007 March, a total 25,705 events, an order magnitude larger then previous studies. These were found using new flare-finding algorithm designed to search 6-12 keV count rate when RHESSI's full sensitivity was available in find smallest events. The peak are automatically obtained along with spectra at microflare centroid position. Our magnitudes below GOES C class, on average A...
Abstract The Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory ( SDO ) has been providing high-cadence, high-resolution, full-disk UV-visible/extreme ultraviolet (EUV) images since 2010, with best time coverage among all solar missions. A number of codes have developed to extract plasma differential emission measures (DEMs) from AIA images. Although widely used, they cannot effectively constrain DEM at flaring temperatures data alone. This often results in much higher...
Aims. The aim of this work is to determine the multi-thermal characteristics and plasma energetics an eruptive plasmoid occulted flare observed by Solar Dynamics Observatory's Atmospheric Imaging Assembly (SDO/AIA).
The fan-spine magnetic topology is believed to be responsible for many curious features in solar explosive events. A spine field line links distinct flux domains, but direct observation of such a feature has been rare. Here we report unique event observed by the Solar Dynamic Observatory where set hot coronal loops (over 10 MK) connected quasi-circular chromospheric ribbon at one end and remote brightening other. Magnetic extrapolation suggests that these are partly tracers evolving line....
In this paper we investigate the formation of white-light (WL) continuum during solar flares and its relationship to energy deposition by electron beams inferred from hard X-ray emission. We analyze nine spanning GOES classifications C4.8 M9.1, seven which show clear cospatial RHESSI TRACE WL footpoints. characterize WL/UV under two simplifying assumptions: (1) a blackbody function, or (2) Paschen-Balmer model. These set limits on in continuum, compare with that provided flare electrons...
Aims. We study the physical properties of a recurring solar active region jet observed in X-rays and extreme-ultraviolet (EUV).
ABSTRACT We present results from the first campaign of dedicated solar observations undertaken by Nuclear Spectroscopic Telescope ARray ( NuSTAR ) hard X-ray (HXR) telescope. Designed as an astrophysics mission, nonetheless has capability directly imaging Sun at HXR energies (>3 keV) with increase in sensitivity least two magnitude compared to current non-focusing telescopes. In this paper we describe scientific areas where will make major improvements on existing measurements. report...
ABSTRACT We present the first observations of quiescent active regions (ARs) using Nuclear Spectroscopic Telescope Array ( NuSTAR ), a focusing hard X-ray telescope capable studying faint solar emission from high-temperature and non-thermal sources. analyze directly imaged spectrally resolved X-rays above 2 keV non-flaring ARs, observed near west limb on 2014 November 1. The images match bright features seen in extreme ultraviolet soft X-rays. imaging spectroscopy is consistent with...
ABSTRACT The study of the localized plasma conditions before impulsive phase a solar flare can help us understand physical processes that occur leading up to main energy release. Here, we present evidence hot X-ray ‘onset’ interval enhanced isothermal temperatures in range 10–15 MK over period time prior flare’s phase. This ‘hot onset’ occurs during initial soft increase and definitely any detectable hard emission. temperatures, estimated by Geostationary Operational Environmental Satellite...
Aims. A novel method of using hard X-rays as a diagnostic for chromospheric density and magnetic structures is developed to infer sub-arcsecond vertical variation flux tube size neutral gas density.
Plasma turbulence is thought to be associated with various physical processes involved in solar flares, including magnetic reconnection, particle acceleration and transport. Using Ramaty High Energy Solar Spectroscopic Imager ({\it RHESSI}) observations the X-ray visibility analysis, we determine spatial spectral distributions of energetic electrons for a flare (GOES M3.7 class, April 14, 2002 23$:$55 UT), which was previously found consistent reconnection scenario. It demonstrated that...
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...
Juvenile idiopathic arthritis (JIA) is the leading cause of childhood disability from a musculoskeletal disorder. It generally affects large joints such as knee and ankle, often causing structural damage. Different factors contribute to damage onset, including altered joint loading other mechanical factors, associated with pain inflammation. The prediction patients' can hence be valuable tool in understanding disease mechanisms involved progression. A number lower-limb models have been...
We report a NuSTAR observation of solar microflare, SOL2015-09-01T04. Although it was too faint to be observed by the GOES X-ray Sensor, we estimate event an A0.1 class flare in brightness. This with only 5 counts per second detector RHESSI, is fainter than any hard (HXR) existing literature. The microflare occurred during pointing highly sensitive astrophysical observatory, which used its direct focusing optics produce detailed HXR spectra and images. exhibits properties commonly larger...
The chromospheric Lyman-alpha line of neutral hydrogen (\lya; 1216\AA) is the strongest emission in solar spectrum. Fluctuations \lya\ are known to drive changes planetary atmospheres, although few instruments have had ability capture rapid enhancements during flares. In this paper we describe flare-associated emissions via a statistical study 477 M- and X-class flares as observed by EUV Sensor on board 15th Geostationary Operational Environmental Satellite, which has been monitoring...
We study the solar source of 3He-rich energetic particle (SEP) event observed on 2006 November 18. The SEP showed a clear velocity dispersion at energies below 1 MeV nucleon−1, indicating its origin. associate with coronal jet in an active region heliographic longitude W50°, as soft X-rays. This was only noticeable activity full-disk X-ray images around estimated release time ions. It temporally correlated series type III radio bursts detected metric and longer wavelength ranges followed by...
The newly developed X-ray visibility forward fitting technique is applied to Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) data of a limb flare investigate the energy and height dependence on sizes, shapes, position hard chromospheric footpoint sources. This provides information about electron transport density structure. spatial distribution two sources analyzed using PIXON, Maximum Entropy Method, CLEAN fit algorithms at nonthermal energies from $\sim 20$ 200$ keV. We...
The sites of chromospheric excitation during solar flares are marked by extended extreme ultraviolet ribbons and hard X-ray (HXR) footpoints. standard interpretation is that these the result heating bremsstrahlung emission from non-thermal electrons precipitating corona. We examine this picture using multi-wavelength observations early phase an M-class flare SOL2010-08-07T18:24. aim to determine properties heated plasma in ribbons, understand partition power input into radiative conductive...
Context. The impulsive phase of solar flares is a time rapid energy deposition and heating in the lower atmosphere, leading to changes temperature, density, ionisation velocity structure this region.
Abstract NuSTAR is a highly sensitive focusing hard X-ray (HXR) telescope and has observed several small microflares in its initial solar pointings. In this paper, we present the first joint observation of microflare with Hinode /XRT on 2015 April 29 at ∼11:29 UT. This shows heating material to million Kelvin, soft X-rays /XRT, was faintly visible extreme ultraviolet SDO /AIA. For three four observations region (pre-flare, decay, post-flare phases), spectrum well fitted by single thermal...
Extreme-Ultraviolet (EUV) waves are globally propagating disturbances that have been observed since the era of Solar and Heliospheric Observatory/Exteme-ultraviolet Imaging Telescope instrument. Although kinematics wave front secondary components widely studied, there is not much known about generation plasma properties wave. In this paper we discuss effect an EUV on local as it passes through corona. We studied wave, generated during 2011 February 15 X-class flare/coronal mass ejection...
We investigate the spatial, temporal, and spectral properties of 10 microflares from AR12721 on 2018 September 9 observed in X-rays using Nuclear Spectroscopic Telescope ARray (NuSTAR) Solar Dynamic Observatory's Atmospheric Imaging Assembly Helioseismic Magnetic Imager (SDO/AIA HMI). find GOES sub-A class equivalent microflare energies 10$^{26}$-10$^{28}$ erg reaching temperatures up to MK with consistent quiescent or hot active region core plasma 3-4 MK. One (SOL2018-09-09T10:33), an A0.1,...