The Experts below are selected from a list of 28569 Experts worldwide ranked by ideXlab platform
Dale E Gary - One of the best experts on this subject based on the ideXlab platform.
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microwave Spectral imaging of an erupting magnetic flux rope implications for the standard solar flare model in three dimensions
2020Co-Authors: Bin Chen, Sijie Yu, Katharine K Reeves, Dale E GaryAbstract:We report microwave Spectral imaging observations of an erupting magnetic flux rope during the early impulsive phase of the X8.2-class limb flare on 2017 September 10, obtained by the Expanded Owens Valley Solar Array. A few days prior to the eruption, when viewed against the disk, the flux rope appeared as a reverse S-shaped dark filament along the magnetic polarity inversion line. During the eruption, the rope exhibited a "hot channel" structure in extreme ultraviolet and soft X-ray passbands sensitive to ~10 MK plasma. The central portion of the flux rope was nearly aligned with the line of sight, which quickly developed into a teardrop-shaped dark cavity during the early phase of the eruption. A long and thin plasma sheet formed below the cavity, interpreted as the reconnection current sheet viewed edge-on. A nonthermal microwave source was present at the location of the central current sheet, which extended upward encompassing the dark cavity. A pair of nonthermal microwave sources were observed for several minutes on both sides of the main flaring region. They shared a similar temporal behavior and Spectral Property to the central microwave source below the cavity, interpreted as the conjugate footpoints of the erupting flux rope. These observations are broadly consistent with the magnetic topology and the associated energy release scenario suggested in the three-dimensional standard model for eruptive solar flares. In particular, our detection of nonthermal emission at conjugate flux rope footpoints provides solid evidence of particle transport along an erupting magnetic flux rope.
Bin Chen - One of the best experts on this subject based on the ideXlab platform.
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microwave Spectral imaging of an erupting magnetic flux rope implications for the standard solar flare model in three dimensions
2020Co-Authors: Bin Chen, Sijie Yu, Katharine K Reeves, Dale E GaryAbstract:We report microwave Spectral imaging observations of an erupting magnetic flux rope during the early impulsive phase of the X8.2-class limb flare on 2017 September 10, obtained by the Expanded Owens Valley Solar Array. A few days prior to the eruption, when viewed against the disk, the flux rope appeared as a reverse S-shaped dark filament along the magnetic polarity inversion line. During the eruption, the rope exhibited a "hot channel" structure in extreme ultraviolet and soft X-ray passbands sensitive to ~10 MK plasma. The central portion of the flux rope was nearly aligned with the line of sight, which quickly developed into a teardrop-shaped dark cavity during the early phase of the eruption. A long and thin plasma sheet formed below the cavity, interpreted as the reconnection current sheet viewed edge-on. A nonthermal microwave source was present at the location of the central current sheet, which extended upward encompassing the dark cavity. A pair of nonthermal microwave sources were observed for several minutes on both sides of the main flaring region. They shared a similar temporal behavior and Spectral Property to the central microwave source below the cavity, interpreted as the conjugate footpoints of the erupting flux rope. These observations are broadly consistent with the magnetic topology and the associated energy release scenario suggested in the three-dimensional standard model for eruptive solar flares. In particular, our detection of nonthermal emission at conjugate flux rope footpoints provides solid evidence of particle transport along an erupting magnetic flux rope.
Gene H Golub - One of the best experts on this subject based on the ideXlab platform.
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structured inverse eigenvalue problems
2002Co-Authors: Gene H GolubAbstract:An inverse eigenvalue problem concerns the reconstruction of a structured matrix from prescribed Spectral data. Such an inverse problem arises in many applications where parameters of a certain physical system are to be determined from the knowledge or expectation of its dynamical behaviour. Spectral information is entailed because the dynamical behaviour is often governed by the underlying natural frequencies and normal modes. Structural stipulation is designated because the physical system is often subject to some feasibility constraints. The Spectral data involved may consist of complete or only partial information on eigenvalues or eigenvectors. The structure embodied by the matrices can take many forms. The objective of an inverse eigenvalue problem is to construct a matrix that maintains both the specific structure as well as the given Spectral Property. In this expository paper the emphasis is to provide an overview of the vast scope of this intriguing problem, treating some of its many applications, its mathematical properties, and a variety of numerical techniques.
Ka-sing Lau - One of the best experts on this subject based on the ideXlab platform.
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On a recursive construction of Dirichlet form on the Sierpiński gasket
2019Co-Authors: Ka-sing Lau, Hua QiuAbstract:Abstract Let Γ n denote the n-th level Sierpinski graph of the Sierpinski gasket K. We consider, for any given conductance ( a 0 , b 0 , c 0 ) on Γ 0 , the Dirichlet form E on K obtained from a recursive construction of compatible sequence of conductances ( a n , b n , c n ) on Γ n , n ≥ 0 . We prove that there is a dichotomy situation: either a 0 = b 0 = c 0 and E is the standard Dirichlet form, or a 0 > b 0 = c 0 (or the two symmetric alternatives), and E is a non-self-similar Dirichlet form independent of a 0 , b 0 . The second situation has been studied in [13] , [9] as a one-dimensional asymptotic diffusion. The analytic approach here is more direct and yields sharper results; in particular, for the Spectral Property, we give a precise estimate of the eigenvalue distribution of the associated Laplacian, which improves a similar result in [9] .
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on a recursive construction of dirichlet form on the sierpi nski gasket
2017Co-Authors: Ka-sing Lau, Hua QiuAbstract:Let $\Gamma_n$ denote the $n$-th level Sierpinski graph of the Sierpinski gasket $K$. We consider, for any given conductance $(a_0, b_0, c_0)$ on $\Gamma_0$, the Dirchlet form ${\mathcal E}$ on $K$ obtained from a recursive construction of compatible sequence of conductances $(a_n, b_n, c_n)$ on $\Gamma_n, n\geq 0$. We prove that there is a dichotomy situation: either $a_0= b_0 =c_0$ and ${\mathcal E}$ is the standard Dirichlet form, or $a_0 >b_0 =c_0$ (or the two symmetric alternatives), and ${\mathcal E}$ is a non-self-similar Dirichlet form independent of $a_0, b_0$. The second situation has also been studied in [Hattori et al 1994][Hambley et al 2002] as a one-dimensional asymptotic diffusion process on the Sierpinski gasket. For the Spectral Property, we give a sharp estimate of the eigenvalue distribution of the associated Laplacian, which improves a similar result in [Hambley et al 2002].
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Spectral Property of the bernoulli convolutions
2008Co-Authors: Ka-sing LauAbstract:For 0<ρ<1, let μρ be the Bernoulli convolution associated with ρ. Jorgensen and Pedersen [P. Jorgensen, S. Pedersen, Dense analytic subspaces in fractal L2-spaces, J. Anal. Math. 75 (1998) 185–228] proved that if ρ=1/q where q is an even integer, then L2(μρ) has an exponential orthonormal basis. We show that for any 0<ρ<1, L2(μρ) contains an infinite orthonormal set of exponential functions if and only if ρ is the nth root of a fraction p/q where p is an odd integer and q is an even integer.
Sijie Yu - One of the best experts on this subject based on the ideXlab platform.
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microwave Spectral imaging of an erupting magnetic flux rope implications for the standard solar flare model in three dimensions
2020Co-Authors: Bin Chen, Sijie Yu, Katharine K Reeves, Dale E GaryAbstract:We report microwave Spectral imaging observations of an erupting magnetic flux rope during the early impulsive phase of the X8.2-class limb flare on 2017 September 10, obtained by the Expanded Owens Valley Solar Array. A few days prior to the eruption, when viewed against the disk, the flux rope appeared as a reverse S-shaped dark filament along the magnetic polarity inversion line. During the eruption, the rope exhibited a "hot channel" structure in extreme ultraviolet and soft X-ray passbands sensitive to ~10 MK plasma. The central portion of the flux rope was nearly aligned with the line of sight, which quickly developed into a teardrop-shaped dark cavity during the early phase of the eruption. A long and thin plasma sheet formed below the cavity, interpreted as the reconnection current sheet viewed edge-on. A nonthermal microwave source was present at the location of the central current sheet, which extended upward encompassing the dark cavity. A pair of nonthermal microwave sources were observed for several minutes on both sides of the main flaring region. They shared a similar temporal behavior and Spectral Property to the central microwave source below the cavity, interpreted as the conjugate footpoints of the erupting flux rope. These observations are broadly consistent with the magnetic topology and the associated energy release scenario suggested in the three-dimensional standard model for eruptive solar flares. In particular, our detection of nonthermal emission at conjugate flux rope footpoints provides solid evidence of particle transport along an erupting magnetic flux rope.
