The Experts below are selected from a list of 207 Experts worldwide ranked by ideXlab platform
Syun-ichi Akasofu - One of the best experts on this subject based on the ideXlab platform.
-
Energy Supply Processes for Solar Flares and Magnetospheric Substorms
Space Science Reviews, 2001Co-Authors: Syun-ichi AkasofuAbstract:It is shown that Solar Flares and magnetospheric substorms must primarily be caused by a dynamo process, rather than magnetic reconnection – a spontaneous, explosive annihilation of magnetic energy stored prior to the onset. Magnetic energy in the vicinity of Solar Flares and in the magnetotail shows often an increase at their onset, not a decrease. It is unfortunate that many observed features of Solar Flares and substorms have tacitly been ascribed to unproven (3-D) characteristics of the neutral line for a long time. In the future, it is necessary to study carefully their driving process and examine how the driven magnetic field system evolves, leading to Solar Flares and substorms.
Hugh S. Hudson - One of the best experts on this subject based on the ideXlab platform.
-
Solar Flares at submillimeter wavelengths
The Astronomy and Astrophysics Review, 2013Co-Authors: Säm Krucker, C. G. Giménez de Castro, G. Trottet, A. S. Hales, J. Kašparová, Thomas Luethi, T. S. Bastian, K L Klein, Seppo Pohjolainen, Hugh S. Hudson, Michael Kretzschmar, Andrew Mackinnon, S. M. WhiteAbstract:We discuss the implications of the first systematic observations of Solar Flares at submillimeter wavelengths, defined here as observing wavelengths shorter than 3 mm (frequencies higher than 0.1 THz). The events observed thus far show that this wave band requires a new understanding of high-energy processes in Solar Flares. Several events, including observations from two different observatories, show during the impulsive phase of the flare a spectral component with a positive (increasing) slope at the highest observable frequencies (up to 405 GHz). To emphasize the increasing spectra and the possibility that these events could be even more prominent in the THz range, we term this spectral feature a “THz component”. Here we review the data and methods, and critically assess the observational evidence for such distinct component(s). This evidence is convincing. We also review the several proposed explanations for these feature(s), which have been reported in three distinct flare phases. These data contain important clues to flare development and particle acceleration as a whole, but many of the theoretical issues remain open. We generally have lacked systematic observations in the millimeter-wave to far-infrared range that are needed to complete our picture of these events, and encourage observations with new facilities.
-
High-Energy Aspects of Solar Flares - High-energy aspects of Solar Flares
2012Co-Authors: A. Gordon Emslie, Brian R. Dennis, Robert P. Lin, Hugh S. HudsonAbstract:Preface.- Overview of the Volume.- An Observational Overview of Solar Flares.- Implications of X-ray Observations for Electron Acceleration and Propagation in Solar Flares.- Properties of Energetic Ions in the Solar Atmosphere from Gamma-ray and Neutron Observations.- The Relationship Between Solar Radio and Hard X-ray Emission.- MicroFlares and the Statistics of X-ray Flares.- Deducing Electron Properties from Hard X-ray Observations.- Recent Advances in Understanding Particle Acceleration Processes in Solar Flares.- Energy Release and Particle Acceleration in Flares: Summary and Future Prospects.- Index.
-
An Observational Overview of Solar Flares
Space Science Reviews, 2011Co-Authors: Lyndsay Fletcher, Säm Krucker, Brian R. Dennis, Hugh S. Hudson, K. J. H. Phillips, Astrid Veronig, Marina Battaglia, L. Bone, Amir Caspi, Qingrong ChenAbstract:We present an overview of Solar Flares and associated phenomena, drawing upon a wide range of observational data primarily from the RHESSI era. Following an introductory discussion and overview of the status of observational capabilities, the article is split into topical sections which deal with different areas of flare phenomena (footpoints and ribbons, coronal sources, relationship to coronal mass ejections) and their interconnections. We also discuss flare soft X-ray spectroscopy and the energetics of the process. The emphasis is to describe the observations from multiple points of view, while bearing in mind the models that link them to each other and to theory. The present theoretical and observational understanding of Solar Flares is far from complete, so we conclude with a brief discussion of models, and a list of missing but important observations.
-
Global Properties of Solar Flares
Space Science Reviews, 2011Co-Authors: Hugh S. HudsonAbstract:This article broadly reviews our knowledge of Solar Flares. There is a particular focus on their global properties, as opposed to the microphysics such as that needed for magnetic reconnection or particle acceleration as such. Indeed Solar Flares will always remain in the domain of remote sensing, so we cannot observe the microscales directly and must understand the basic physics entirely via the global properties plus theoretical inference. The global observables include the general energetics—radiation in Flares and mass loss in coronal mass ejections (CMEs)—and the formation of different kinds of ejection and global wave disturbance: the type II radio-burst exciter, the Moreton wave, the EIT “wave”, and the “sunquake” acoustic waves in the Solar interior. Flare radiation and CME kinetic energy can have comparable magnitudes, of order 10^32 erg each for an X-class event, with the bulk of the radiant energy in the visible-UV continuum. We argue that the impulsive phase of the flare dominates the energetics of all of these manifestations, and also point out that energy and momentum in this phase largely reside in the electromagnetic field, not in the observable plasma.
-
Solar physics: Solar Flares add up
Nature Physics, 2010Co-Authors: Hugh S. HudsonAbstract:Solar Flares are the most energetic events in our Solar System, but relatively little is known about their contribution to the total energy the Earth receives from the Sun. The detection of a moderate Solar flare in the total Solar irradiance suggests their impact on the variability of the Sun's output could be larger than expected.
Alberto Sorrentino - One of the best experts on this subject based on the ideXlab platform.
-
Sparse Bayesian Imaging of Solar Flares
SIAM Journal on Imaging Sciences, 2019Co-Authors: Federica Sciacchitano, Silvio Lugaro, Alberto SorrentinoAbstract:We consider imaging of Solar Flares from NASA Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) data as a parametric imaging problem, where Flares are represented as a finite collection...
-
Sparse Bayesian Imaging of Solar Flares.
arXiv: Instrumentation and Methods for Astrophysics, 2018Co-Authors: Federica Sciacchitano, Silvio Lugaro, Alberto SorrentinoAbstract:We consider imaging of Solar Flares from NASA RHESSI data as a parametric imaging problem, where Flares are represented as a finite collection of geometric shapes. We set up a Bayesian model in which the number of objects forming the image is a priori unknown, as well as their shapes. We use a Sequential Monte Carlo algorithm to explore the corresponding posterior distribution. We apply the method to synthetic and experimental data, largely known in the RHESSI community. The method reconstructs improved images of Solar Flares, with the additional advantage of providing uncertainty quantification of the estimated parameters.
Federica Sciacchitano - One of the best experts on this subject based on the ideXlab platform.
-
Sparse Bayesian Imaging of Solar Flares
SIAM Journal on Imaging Sciences, 2019Co-Authors: Federica Sciacchitano, Silvio Lugaro, Alberto SorrentinoAbstract:We consider imaging of Solar Flares from NASA Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) data as a parametric imaging problem, where Flares are represented as a finite collection...
-
Sparse Bayesian Imaging of Solar Flares.
arXiv: Instrumentation and Methods for Astrophysics, 2018Co-Authors: Federica Sciacchitano, Silvio Lugaro, Alberto SorrentinoAbstract:We consider imaging of Solar Flares from NASA RHESSI data as a parametric imaging problem, where Flares are represented as a finite collection of geometric shapes. We set up a Bayesian model in which the number of objects forming the image is a priori unknown, as well as their shapes. We use a Sequential Monte Carlo algorithm to explore the corresponding posterior distribution. We apply the method to synthetic and experimental data, largely known in the RHESSI community. The method reconstructs improved images of Solar Flares, with the additional advantage of providing uncertainty quantification of the estimated parameters.
Silvio Lugaro - One of the best experts on this subject based on the ideXlab platform.
-
Sparse Bayesian Imaging of Solar Flares
SIAM Journal on Imaging Sciences, 2019Co-Authors: Federica Sciacchitano, Silvio Lugaro, Alberto SorrentinoAbstract:We consider imaging of Solar Flares from NASA Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) data as a parametric imaging problem, where Flares are represented as a finite collection...
-
Sparse Bayesian Imaging of Solar Flares.
arXiv: Instrumentation and Methods for Astrophysics, 2018Co-Authors: Federica Sciacchitano, Silvio Lugaro, Alberto SorrentinoAbstract:We consider imaging of Solar Flares from NASA RHESSI data as a parametric imaging problem, where Flares are represented as a finite collection of geometric shapes. We set up a Bayesian model in which the number of objects forming the image is a priori unknown, as well as their shapes. We use a Sequential Monte Carlo algorithm to explore the corresponding posterior distribution. We apply the method to synthetic and experimental data, largely known in the RHESSI community. The method reconstructs improved images of Solar Flares, with the additional advantage of providing uncertainty quantification of the estimated parameters.
