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The SIDC of the Royal Observatory of Belgium is a very active center for solar physics research, ... more The SIDC of the Royal Observatory of Belgium is a very active center for solar physics research, but also provides an operational service for data and services related to solar activity and space weather. In this poster we present the currently available data sets and products, with a focus on recent additions and new developments.
Prominentes and filaments are thought to arise as a consequence of a magnetized plasma undergoing... more Prominentes and filaments are thought to arise as a consequence of a magnetized plasma undergoing thermal instability. Therefore the thermal stability of a magnetized plasma is investigated under coronal conditions. The equilibrium structure of the plasma is approximated by a 1-D slab configuration. This is investigated on thermal instability taking into account optically thin plasma radiation and anisotropical thermal conduction. The thermal conduction perpendicular to the magnetic field is taken to be small but non-zero.
Computer Physics Communications, 1990
Telescopes and Instrumentation for Solar Astrophysics, 2004
Solar Physics, 1991
ABSTRACT
Physics of Plasmas, 1994
Multifaceted asymmetric radiation from the edge (MARFE) is studied as a radiative thermal instabi... more Multifaceted asymmetric radiation from the edge (MARFE) is studied as a radiative thermal instability in a one-dimensional (1-D) cylindrical equilibrium model. In order to get a global idea of the MARFE onset, a linear analysis is performed, using a full set of magnetohydrodynamic (MHD) equations. It is found that the onset of the MARFE is accompanied by perturbations of pressure and magnetic field. These characteristics seem especially important in case the MARFE leads to a disruption and rational surfaces are affected. The experimentally observed relation between critical density and plasma current [Nucl. Fusion 24, 977 (1984)] is studied. The particular role of perpendicular thermal conduction is considered separately. Correspondence with experimentally observed behavior, like toroidal symmetry and poloidal asymmetry, is discussed.
Multifaceted asymmetric radiation from the edge (MARFE) is studied as a radiative thermal instabi... more Multifaceted asymmetric radiation from the edge (MARFE) is studied as a radiative thermal instability in a one-dimensional (1-D) cylindrical equilibrium model. In order to get a global idea of the MARFE onset, a linear analysis is performed, using a full set of magnetohydrodynamic (MHD) equations. It is found that the onset of the MARFE is accompanied by perturbations of pressure and magnetic field. These characteristics seem especially important in case the MARFE leads to a disruption and rational surfaces are affected. The experimentally observed relation between critical density and plasma current [Nucl. Fusion 24, 977 (1984)] is studied. The particular role of perpendicular thermal conduction is considered separately. Correspondence with experimentally observed behavior, like toroidal symmetry and poloidal asymmetry, is discussed.
Solar Physics, 1992
The normal mode spectrum for the linearized MHD equations is investigated for a cylindrical equil... more The normal mode spectrum for the linearized MHD equations is investigated for a cylindrical equilibrium. This spectrum is examined for zero perpendicular thermal conduction, with both zero and non-zero scalar resistivity. Particular attention is paid to the continuous branches of this spectrum, or continuous spectra. For zero resistivity there are three types of continuous spectra present, namely the Alfvén, slow, and thermal continua. It is shown that when dissipation due to resistivity is included, the slow and Alfvén continua are removed and that the thermal continuum is shifted to a different position (where the shift is independent of the exact value of resistivity). The ‘old’ location of the thermal continuum is covered by a dense set of nearly singular discrete modes called a quasi-continuum. The quasi-continuum is investigated numerically, and the eigenfunctions are shown to have rapid spatial oscillating behaviour. These oscillations are confined to the most unstable part of the equilibrium based on the Field criterion, and may be the cause of fine structure in prominences.
Advances in Space Research, 2006
Solar Physics, 1994
A WKB approach, based on the method of Connor, Hastie, and Taylor (1979), is used to obtain simpl... more A WKB approach, based on the method of Connor, Hastie, and Taylor (1979), is used to obtain simple estimates of the critical conditions for the onset of ideal MHD instabilities in line-tied solar coronal loops. The method is illustrated for the constant twist, Gold-Hoyle (1960) field, and the critical conditions are compared with previous and new numerical results. For the
The SIDC of the Royal Observatory of Belgium is a very active center for solar physics research, ... more The SIDC of the Royal Observatory of Belgium is a very active center for solar physics research, but also provides an operational service for data and services related to solar activity and space weather. In this poster we present the currently available data sets and products, with a focus on recent additions and new developments.
Prominentes and filaments are thought to arise as a consequence of a magnetized plasma undergoing... more Prominentes and filaments are thought to arise as a consequence of a magnetized plasma undergoing thermal instability. Therefore the thermal stability of a magnetized plasma is investigated under coronal conditions. The equilibrium structure of the plasma is approximated by a 1-D slab configuration. This is investigated on thermal instability taking into account optically thin plasma radiation and anisotropical thermal conduction. The thermal conduction perpendicular to the magnetic field is taken to be small but non-zero.
Computer Physics Communications, 1990
Telescopes and Instrumentation for Solar Astrophysics, 2004
Solar Physics, 1991
ABSTRACT
Physics of Plasmas, 1994
Multifaceted asymmetric radiation from the edge (MARFE) is studied as a radiative thermal instabi... more Multifaceted asymmetric radiation from the edge (MARFE) is studied as a radiative thermal instability in a one-dimensional (1-D) cylindrical equilibrium model. In order to get a global idea of the MARFE onset, a linear analysis is performed, using a full set of magnetohydrodynamic (MHD) equations. It is found that the onset of the MARFE is accompanied by perturbations of pressure and magnetic field. These characteristics seem especially important in case the MARFE leads to a disruption and rational surfaces are affected. The experimentally observed relation between critical density and plasma current [Nucl. Fusion 24, 977 (1984)] is studied. The particular role of perpendicular thermal conduction is considered separately. Correspondence with experimentally observed behavior, like toroidal symmetry and poloidal asymmetry, is discussed.
Multifaceted asymmetric radiation from the edge (MARFE) is studied as a radiative thermal instabi... more Multifaceted asymmetric radiation from the edge (MARFE) is studied as a radiative thermal instability in a one-dimensional (1-D) cylindrical equilibrium model. In order to get a global idea of the MARFE onset, a linear analysis is performed, using a full set of magnetohydrodynamic (MHD) equations. It is found that the onset of the MARFE is accompanied by perturbations of pressure and magnetic field. These characteristics seem especially important in case the MARFE leads to a disruption and rational surfaces are affected. The experimentally observed relation between critical density and plasma current [Nucl. Fusion 24, 977 (1984)] is studied. The particular role of perpendicular thermal conduction is considered separately. Correspondence with experimentally observed behavior, like toroidal symmetry and poloidal asymmetry, is discussed.
Solar Physics, 1992
The normal mode spectrum for the linearized MHD equations is investigated for a cylindrical equil... more The normal mode spectrum for the linearized MHD equations is investigated for a cylindrical equilibrium. This spectrum is examined for zero perpendicular thermal conduction, with both zero and non-zero scalar resistivity. Particular attention is paid to the continuous branches of this spectrum, or continuous spectra. For zero resistivity there are three types of continuous spectra present, namely the Alfvén, slow, and thermal continua. It is shown that when dissipation due to resistivity is included, the slow and Alfvén continua are removed and that the thermal continuum is shifted to a different position (where the shift is independent of the exact value of resistivity). The ‘old’ location of the thermal continuum is covered by a dense set of nearly singular discrete modes called a quasi-continuum. The quasi-continuum is investigated numerically, and the eigenfunctions are shown to have rapid spatial oscillating behaviour. These oscillations are confined to the most unstable part of the equilibrium based on the Field criterion, and may be the cause of fine structure in prominences.
Advances in Space Research, 2006
Solar Physics, 1994
A WKB approach, based on the method of Connor, Hastie, and Taylor (1979), is used to obtain simpl... more A WKB approach, based on the method of Connor, Hastie, and Taylor (1979), is used to obtain simple estimates of the critical conditions for the onset of ideal MHD instabilities in line-tied solar coronal loops. The method is illustrated for the constant twist, Gold-Hoyle (1960) field, and the critical conditions are compared with previous and new numerical results. For the