Author name code: carlqvist ADS astronomy entries on 2022-09-14 author:"Carlqvist, Per" ------------------------------------------------------------------------ Title: Twisted Crab fingers revisited Authors: Carlqvist, Per Bibcode: 2015Ap&SS.357...47C Altcode: Narrowband images of the Crab Nebula captured by the Hubble Space Telescope have earlier shown that the nebula does not only present a network of broad, bright filaments crossing the nebula but also numerous so-called fingers mostly pointing inwards. Using archival Hubble images we have in some detail studied the morphology of a great number of such fingers. This scrutiny has revealed that practically all the fingers are made up of filaments. Most of the larger fingers show overall shapes that are similar to either of the two letters V and Y. In many of these fingers it is also possible to see internal details. Interestingly, a number of the larger, Y-shaped fingers turn out to have a stem that consists of intertwined filaments. By contrast with this, the smaller fingers usually appear only as diffuse and sometimes incomplete pegs. In none of the smaller fingers is it possible to find any plain, internal structure. The observational results obtained are compared with the properties of a previously proposed model of the fingers. The model suggests that the fingers have evolved out of magnetized filaments. The evolution should lead to fingers with overall shapes that are similar to either a V or a Y, very much in agreement with the observations. In addition to this, the model prescribes that the stems of the Y-shaped fingers should be made up of intertwined filaments. From all these points of agreement we conclude that the properties of the fingers observed lend strong support to the model. Title: Model of outgrowths in the spiral galaxies NGC 4921 and NGC 7049 and the origin of spiral arms Authors: Carlqvist, Per Bibcode: 2013Ap&SS.343..689C Altcode: 2012Ap&SS.tmp..380C; 2012arXiv1211.3628C NGC 4921 and 7049 are two spiral galaxies presenting narrow, distinct dust features. A detailed study of the morphology of those features has been carried out using Hubble Space Telescope archival images. NGC 4921 shows a few but well-defined dust arms midway to its centre while NGC 7049 displays many more dusty features, mainly collected within a ring-shaped formation. Numerous dark and filamentary structures, called outgrowths, are found to protrude from the dusty arms in both galaxies. The outgrowths point both outwards and inwards in the galaxies. Mostly they are found to be V-shaped or Y-shaped with the branches connected to dark arm filaments. Often the stem of the Y appears to consist of intertwined filaments. Remarkably, the outgrowths show considerable similarities to elephant trunks in H ii regions. A model of the outgrowths, based on magnetized filaments, is proposed. The model provides explanations of both the shapes and orientations of the outgrowths. Most important, it can also give an account for their intertwined structures. It is found that the longest outgrowths are confusingly similar to dusty spiral arms. This suggests that some of the outgrowths can develop into such arms. The time-scale of the development is estimated to be on the order of the rotation period of the arms or shorter. Similar processes may also take place in other spiral galaxies. If so, the model of the outgrowths can offer a new approach to the old winding problem of spiral arms. Title: Dark mammoth trunks in the merging galaxy NGC 1316 and a mechanism of cosmic double helices Authors: Carlqvist, Per Bibcode: 2010Ap&SS.327..267C Altcode: 2010Ap&SS.tmp..120C; 2010arXiv1003.5818C NGC 1316 is a giant, elliptical galaxy containing a complex network of dark, dust features. The morphology of these features has been examined in some detail using a Hubble Space Telescope, Advanced Camera for Surveys image. It is found that most of the features are constituted of long filaments. There also exist a great number of dark structures protruding inwards from the filaments. Many of these structures are strikingly similar to elephant trunks in H ii regions in the Milky Way Galaxy, although much larger. The structures, termed mammoth trunks, generally are filamentary and often have shapes resembling the letters V or Y. In some of the mammoth trunks the stem of the Y can be resolved into two or more filaments, many of which showing signs of being intertwined. A model of the mammoth trunks, related to a recent theory of elephant trunks, is proposed. Based on magnetized filaments, the model is capable of giving an account of the various shapes of the mammoth trunks observed, including the twined structures. Title: Filamentary structures in planetary nebulae Authors: Dahlgren, Hanna; Carlqvist, Per; Gahm, Gösta F. Bibcode: 2007Ap&SS.310...65D Altcode: 2007Ap&SS.tmp..134D We have studied small-scale, filamentary features in 14 planetary nebulae and found that some structures are recurrent and shaped like the letters V and Y, with the apex or stem pointing toward the central parts of the nebula. Two such filaments containing dust, one in NGC 3132 and one in NGC 7293, were investigated in more detail. The mass and density of the filaments were obtained from extinction measurements, and their physical properties were derived. We propose that the structures are confined by magnetic fields, and derive magnetic field strengths of about 10−8 T, in line with earlier estimates. We also estimate the magnitude of the electric currents that we expect are generated in these dynamic systems. We propose a theory where the magnetic fields control the sculpting and evolution of small-scale filaments. This theory demonstrates how the substructures may form magnetized flux ropes that are twisted around each other, in the shape of double helices. Similar structures, and with similar origin, are found in many other astrophysical environments. Title: Rotating elephant trunks Authors: Gahm, G. F.; Carlqvist, P.; Johansson, L. E. B.; Nikolić, S. Bibcode: 2006A&A...454..201G Altcode: Aims.We investigate the structure and velocity of cold molecular pillars, "elephant trunks", in expanding H II regions.
Methods: .The trunks are seen in silhouette against the bright background in our Hα images. All trunks are filamentary, and show signs of being twisted. Four such trunks in NGC 7822, IC 1805, the Rosette Nebula, and DWB 44 were selected, and then mapped mainly in 12CO and 13CO. We determine the mass and density of the trunks. Most of the mass is concentrated in a head facing the central cluster, and in sub-filaments forming the body of the trunk that is connected to V-shaped filaments to the outer expanding shell.
Results: .We discovered that all four trunks rotate as rigid bodies (to a first approximation) about their major axes, and that at least two trunks are stretching along their major axes, meaning that the massive heads are lagging behind in the general expansion of the H II regions. The rotational periods are of the order of a few million years - similar to the age of the clusters. Rotation, then, is responsible for the twisted appearance of many elephant trunks, since they are rooted in the outer shells. The trunks carry surprisingly large amounts of angular momentum, 3× 1048{-}2× 1050 kg m2 s-1, with corresponding rotational energies of up to 1037 J. However, we estimate the total magnetic energies to be even larger. The trunks continuously reshape, and the formation of twined, and in many cases helical, sub-filaments can be understood as a consequence of electromagnetic and inertia forces inside the trunks. A theory based on the concept of magnetically twisted trunks is developed further, where the initial angular momentum is a consequence of the twisting of parent filaments containing mass condensations. Our results also suggest a new process of removing angular momentum from parent molecular clouds.
Title: A remarkable double helix in the V838 Mon nebula Authors: Carlqvist, P. Bibcode: 2005A&A...436..231C Altcode: In the beginning of 2002 the previously unnoted star V838 Mon had a powerful outburst. The star is surrounded by pre-existing, dusty clouds which are illuminated by the star in an expanding, parabolic layer. Spectacular images captured by the Hubble Space Telescope Advanced Camera for Surveys show that the clouds are to a great extent built up by filaments and concentric shells. One of the most remarkable features is a filamentary structure forming a double helix. The structure, which has a projected length and width of ~ 9 arcsec and ∼ 1.4 arcsec, respectively, points almost radially towards V838 Mon. In order to reveal the geometry of the double helix in some more detail, a three-dimensional computer model of the structure has been constructed. The model also assists in determining the expansion rate of the light echoes along the double helix. By means of the expansion rate and the tilt of the double helix the distance to V838 Mon is determined to be 2.4 ± 0.5 kpc. A theory of the double helix, based on a magnetized and twisted filament, is presented. Dynamic and magnetic forces play an essential role in the shaping of the double helix. The theory is supported by a mechanical analogy model. Double helices in other cosmic environments are also discussed. Title: A new mechanism for the crab fingers Authors: Carlqvist, P. Bibcode: 2004Ap&SS.289...47C Altcode: Images of the outer filamentary parts of the Crab Nebula, earlier obtained with the Hubble Space Telescope WFPC2, are reconsidered. On inspection of the images it is found that most of the mainly radially oriented fingers possess an internal structure, usually in the form of two or more filaments.For some of the fingers there are clear signs that the filaments are twistedaround each other. A mechanism for the fingers taking the internal structureinto account is proposed. The mechanism is based on the reshaping of magnetizedfilaments under the influence of inertia and magnetic forces. When interacting with an expanding shell, driven by the pressure of the synchrotron nebula, part of such a filament may develop into a double helix pointing radially inwards. For this transformation to take place it is required that the magnetic field within the filament is sufficiently twisted and that the filament containsa mass condensation. The finger is identified with the double helix. Similar structures of double helices are found to be present also in other environments. Title: Theory of twisted trunks Authors: Carlqvist, P.; Gahm, G. F.; Kristen, H. Bibcode: 2003A&A...403..399C Altcode: Using the 2.6 m Nordic Optical Telescope we have observed a large number of elephant trunks in several H II regions. Here, we present a small selection of this material consisting of a few large, well-developed trunks, and some smaller ones. We find that: (i) the well-developed trunks are made up of dark filaments and knots which show evidence of twisted structures, (ii) the trunks are connected with essentially two filamentary legs running in V-shape, and (iii) all trunks have the maximum extinction in their heads. We advance a theory of twisted elephant trunks which is based on the presence of magnetic flux ropes in molecular clouds where hot OB stars are formed. If the rope contains a local condensation it may adopt a V-shape as the H II region around the hot stars expands. If, in addition, the magnetic field in the rope is sufficiently twisted, the rope may form a double helix at the apex of the V. The double helix is identified with the twisted elephant trunks. In order to illustrate the mechanisms behind the double helix we have constructed a mechanical analogy model of the magnetic flux rope in which the rope has been replaced by a bundle of elastic strings loaded by a weight. Experiments with the model clearly show that part of the bundle will transform into a double helix when the twist of the bundle is sufficiently large. We have also worked out a simple theoretical model of a mass-loaded magnetic flux rope. Numerical calculations show that a double helix will indeed form when the twist of the rope exceeds a certain critical limit. Numerical model calculations are applied to both the analogy model experiments and one of the well-developed elephant trunks. On the basis of our model we also suggest a new interpretation of the so called EGGs.

The double helix mechanism is quite general, and should be active also in other suitable environments. One such environment may be the shell of supernova remnants. Another example is the expanding bubble outlined by the North Celestial Pole Loop.

Based on observations collected at the Nordic Optical Telescope, La Palma, Spain. Title: The threaded molecular clumps of Chamaeleon III Authors: Gahm, G. F.; Lehtinen, K.; Carlqvist, P.; Harju, J.; Juvela, M.; Mattila, K. Bibcode: 2002A&A...389..577G Altcode: We have mapped large areas in the Chamaeleon III complex of molecular clouds with the SEST in 13CO(J=1-0) and in C18O(J=1-0). The stronger CO emission coincides with areas of cold dust emission, which is distributed in long, but thin, wavy filaments. We identify some 40 clumps of enhanced CO emission in these filaments. In the southern part of Cha III the clumps are equidistant along the main zig-zag shaped filament. Here we find two systems of filaments moving at different radial velocities. At least part of the zig-zag patterns visible on optical images may be caused by overlapping filaments. All clumps are small (typically 0.02-0.05 pc in radius), and of small mass (typically 0.1-0.7 Msun, when assuming the ``standard'' C18O/H2 column density ratio). Also the average number densities are small, n(H2) = 1x 104 - 8x 104 cm-3, and the density contrast between clump and interclump gas is only ~ 10. In addition the values of |Epot|/Ekin are unusually small, 0.03-0.33. These clumps have smaller masses than those so far identified in other molecular clouds. Previously reported clumps of larger masses in Cha III turn out to be composed of assemblies of clumps. There are no signs of star formation in Cha III (unlike Cha I and Cha II), and our results indicate also that such activity is not expected. However, with the velocity dispersion of 0.2 km s-1 the clumps would leave the thin filaments on short timescales, and if the clumps as such are not confined by some external force, they would also lose their identity on even shorter timescales. We discuss the possibility that the clumps are confined by electromagnetic forces, and show that this may work with reasonable assumptions on the required magnetic field strength. We also discuss the possibility that the clumps are attached to magnetic ropes along the filamentary axis, in which case the clumps could swing back and forth perpendicularly to the axis, like they were threaded on elastic strings. Based on observations made with the Swedish ESO Submillimetre Telescope (SEST), Chile. Title: Formation of Twisted Elephant Trunks in the Rosette Nebula Authors: Carlqvist, P.; Gahm, G. F.; Kristen, H. Bibcode: 2002Ap&SS.280..405C Altcode: New observations show that dark elephant trunks in the Rosette nebula are often built up by thin filaments. In several of the trunks the filaments seem to form a twisted pattern. This pattern is hard to reconcile with current theory. We propose a new model for the formation of twisted elephant trunks in which electromagnetic forces play an important role. The model considers the behaviour of a twisted magnetic filament in a molecular cloud, where a cluster of hot stars has been recently born. As a result of stellar winds, and radiation pressure, electromagnetic forces, and inertia forces part of the filament can develop into a double helix pointing towards the stars. The double helix represents the twisted elephant trunk. A simple analogy experiment visualizes and supports the trunk model. Title: Linear polarization and molecular filamentary clouds Authors: Harjunpää, P.; Kaas, A. A.; Carlqvist, P.; Gahm, G. F. Bibcode: 1999A&A...349..912H Altcode: We have carried out deep CCD polarimetry in the I band in selected fields in three filamentary, molecular clouds: the L1400 complex, L204, and MBM25, at galactic latitudes 4degr , 21degr , and 31degr , respectively. I magnitudes and the degree and direction of linear polarization were measured with satisfactory accuracies for 387 stars down to I=19.5. Typical uncertainties of the degree and angle of polarization are ΔP{~}0.5% and Δθ{~}10degr . We also derived extinctions from star counts in and around the observed fields. In the L1400 complex we imaged a 48 arcmin(2) field in the H and K bands, providing independent measures of extinction based on the E(H-K) colour excess. Our measurements show that the patterns of polarization are remarkably smooth over the fields studied, particularly in the L1400 complex. There is no indication of any statistically significant difference in polarization angle and degree between obscured and non-obscured regions. MBM25, with the lowest levels of extinction and polarization, shows some anomalies in the polarization vectors, but the statistics is here less good. Our method opens the possibility to study small-scale irregularities in the polarization pattern on angular scales down to a few arcseconds. Comparing the extinction A_V and P/A_V in the field observed in the H and K bands we find that P/A_V can attain high values (close to the P=3 A_V relation) only for small values of A_V. Modelling the stellar content along the line of sight reveals that we, for magnitudes around I=19, sample stars at very large distances behind the clouds. Our general conclusion is that the interstellar filaments contribute very little to the polarization measured. This is in line with recent results obtained for other cloud regions comprising less detailed spatial scale and a smaller depth in brightness. Using a semi-empirical version of the Davis-Greenstein mechanism we have calculated the polarization for simple models of the three clouds studied, and find that it is considerably smaller than the typical background polarization, a result in consonance with the polarimetric measurements. For MBM25 we derive a new distance of ~ 145 pc from Hipparcos parallaxes of two stars surrounded by bright nebulosities, on the assumption that the stars are physically associated with the cloud. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. Title: Molecular Filamentary Clouds, Structures and Polarization Authors: Gahm, G. F.; Carlqvist, P.; Harjunpää, P.; Kaas, A. A.; Kristen, H. Bibcode: 1999anot.conf..155G Altcode: No abstract at ADS Title: Helical structures in a Rosette elephant trunk Authors: Carlqvist, Per; Kristen, Helmuth; Gahm, Gosta F. Bibcode: 1998A&A...332L...5C Altcode: We discuss small-scale, helical, interstellar filaments on the basis of optical observations of an elephant trunk in the Rosette nebula. The trunk studied is composed of a number of sinusoidal or serpentine-like dark filaments, preferentially in the outer part of the trunk, where their wavelength is 7-9 times the trunk radius. The diameters are down to the limit of resolution of 1.0 arcsec, corresponding to 1600 au, and ranging up to about 6400 au. At some positions filament crossings give rise to enhanced extinction. We suggest that the sinusoidal filaments are helices lined up by magnetic fields. We derive average extinctions of 0.5-1.0 mag in the filaments, implying molecular densities of n_H2 ~ 10(4) cm(-3) . From existing data on the Rosette HiI region, we conclude that the surrounding kinetic and dynamic pressure and the background radiation field suffice to balance even the denser filaments and to exert drag forces on the trunk as a whole, consistent with evidence of stretching of the trunk. The helical magnetic structures imply the presence of electric currents along the trunk axis. These currents should form a nearly force-free geometry and are consistent with a model consisting of 4-7 helical cables on the surface of a cylinder and which produce the observed wavelength of the helices. We suggest that the Rosette elephant trunks form an interconnected system of rope-like structures which are relics from filamentary skeletons of magnetic fields in the primordial cloud. Based on observations collected at the Nordic Optical Telescope, La Palma, Spain Title: Polarization models of filamentary molecular clouds. Authors: Carlqvist, P.; Kristen, H. Bibcode: 1997A&A...324.1115C Altcode: We study numerically the linear polarization and extinction of light from background stars in three types of models of elongated molecular clouds by following the development of the Stokes parameters. The clouds are assumed to be of cylindrical shape and penetrated by a helical magnetic field {vec}(B). In the first two models we study only the relative magnitude of the polarization assuming that the polarization is proportional to Bmu^, where primarily μ=2. Provided there is no background/foreground polarization present we find from the cylindrically symmetric Model I that the angle of polarization has a bimodal character with the polarization being either parallel with or perpendicular to the axis of the filament. For some magnetic-field geometries both angles may exist in one and the same filament. It is concluded that it is not a straightforward task to find the magnetic-field-line pattern from the polarization pattern. If a background/foreground polarization exists or, as in Model II, the filament is not cylindrically symmetric, the bimodal character of the angle of polarization is lost. By means of Model III we have, using semi-empirical methods based on the Davis-Greenstein mechanism, estimated the absolute degree of polarization in the filamentary molecular cloud L204. It is found that the polarization produced by the model is much less than the polarization observed. We therefore conclude that most of the polarization measured in the L204 cloud is not produced in the cloud itself but is constituted by a large-scale background/foreground polarization. Title: Multicomponent double layers and selective acceleration of charged particles Authors: Carlqvist, Per Bibcode: 1995JGR...100..205C Altcode: Multicomponent double layers, defined as layers composed of more than two kinds of charged particles, are supposed to constitute the predominant type of double layer in cosmic plasmas. A model of a steady and strong multicomponent double layer is studied in both the nonrelativistic and relativistic approximations. In particular, such properties of the layer as the structure, potential drop, and current composition are investigated. It is demonstrated that the density distribution of each kind of positive and negative particle in the nonrelativistic multicomponent layer is of the same shape as the density distribution of the ions and electrons, respectively, in Langmuir's two-component layer. Also, the shape of the distribution of the electric field corresponds to that of the two-component layer. In the relativistic layer the charges are distributed among two very thin layers of high positive and negative charge density close to the high-potential and low-potential boundaries of the layer, respectively, and a constant but low charge density in the rest of the layer. It is shown that the potential drop across the multicomponent layer is proportional to the thickness of the layer raised to 4/3 in the nonrelativistic case while it is directly proportional to the thickness in the relativistic case. Current conditions prescribing the allowed sets of current densities of the various kinds of particles in the layer are derived in the nonrelativistic and relativistic approximations. Correspondingly, abundance conditions for the particles accelerated through the layer are also obtained. The abundance of the particles accelerated by the double layer is expected generally to be different from the abundance of the ambient plasma. It is suggested that the abundance of the accelerated particles might serve as a means to detect double layers, especially in space plasmas. Title: Manifestations of electric currents in interstellar molecular clouds. Authors: Carlqvist, Per; Gahm, Gosta F. Bibcode: 1992ITPS...20..867C Altcode: The authors draw the attention to filamentary structures in molecular clouds and point out the existence of subfilaments of sinusoidal shape and also of helix like structures. For two dark clouds, the Lynds 204 complex and the Sandqvist 187-188 complex, they make a detailed study of such shapes and in addition they find the possible existence of helices wound around the main filaments. These features suggest the existence of electric currents and magnetic fields in these clouds. The authors derive the magnitudes of the currents expected to flow in the filaments. Values of column densities, magnetic field strengths, and directions of the fields are derived from observations. This study shows that axial currents of the order of a few times 1013A are necessary for the clouds to be in equilibrium. The corresponding mean current densities are very small and even at the very low values of the fractional abundance of electrons encountered in these clouds. Title: Manifestations of electric currents in interstellar molecular clouds Authors: Carlqvist, P.; Gahm, G. F. Bibcode: 1991STIN...9317638C Altcode: Filamentary structures in molecular clouds and the existence of subfilaments of sinusoidal shape and also of helixlike structures are investigated. For two dark clouds, the Lynds 204 complex and the Sandqvist 187-188 complex, such shapes and the possible existence of helices wound around the main filaments are studied. All these features suggest the existence of electric currents and magnetic fields in these clouds. On the basis of a generalization of the Bennett pinch model, the magnitudes of the currents expected to flow in the filaments are derived. Values of column densities, magnetic field strengths, and direction of the fields are derived from observations. Magnetic fields with both toroidal and axial components are considered. The study shows that axial currents of the order of a few times 10 to the 13th power A are necessary for the clouds to be in equilibrium. The mean electron velocities are of the order of 0.01 to 0.00001 m/s, much lower than the thermal velocities in the clouds. It is suggested that helical structures may evolve as a result of various instabilities in the pinched clouds. Attention is given to the kink instability in connection with the sinusoidal shapes. The existence of electromagnetically controlled features in the interstellar clouds can be tested by further observations. Title: Relativistic Fireworks Authors: Laurent, Bertel; Carlqvist, Per Bibcode: 1991Ap&SS.181..211L Altcode: We have studied a model of relativistic fireworks. In this model it is assumed that a series of explosions occur. In each explosion the fragments fly apart in arbitrary directions with a given velocity which is a parameter in the model. We have succeeded in obtaining an exact expression for the distribution of fragments in velocity space aftern explosions. We present an exact solution also in the limiting case of small velocity steps where the process turns into a diffusion in velocity space. The development in configuration space has been obtained through Monte-Carlo numerical simulations. The model has been applied to metagalactic cosmology. Although single explosions cannot reach the highest redshifts observed in the Hubble expansion the fireworks model offers a possibility to reach thesez-values in a few explosions. The model gives a density inhomogeneity of 20% over a tenth of the Hubble distance as seen from a typical position. Observations show a considerably greater irregular variation. The model gives a local velocity dispersion which is too great to comply with observations. A development of the model is suggested. Title: Cosmic electric currents and the generalized Bennett relation. Authors: Carlqvist, Per Bibcode: 1988Ap&SS.144...73C Altcode: A generalized form of the Bennett pinch is studied in both cylindrical geometry and plane-parallel geometry. In this kind of pinch electromagnetic forces, kinetic pressure gradient forces, centrifugal forces, and gravitational forces may act. For each of the two geometries considered a generalized Bennett relation is derived. By means of these relations it is possible to describe among other things the pure Bennett pinch, Jean's criterion in one and two dimensions, force-free magnetic fields, gravitationally balanced magnetic pressures, and continuous transitions between these states. The theory is applied to electric currents in the magnetosphere, in the solar atmosphere, and in the interstellar medium. It is pointed out that the currents in the solar atmosphere and in the interstellar medium may lead to pinches that are of vital importance to the phenomena of solar flares and star formation, respectively. Title: On the Dynamics of the Metagalaxy Authors: Laurent, B. E.; Bonnevier, B.; Carlqvist, P. Bibcode: 1988Ap&SS.144..639L Altcode: The dynamical aspects of the metagalactic model are studied. In particular, the consequences of high galaxy and quasar red shifts are considered. A number of explosion mechanisms are investigated and limits are given for the velocities they can produce. In case of constant density in the local rest frame limits are also given for the parameter Ω0, for our position in the metagalaxy, and for the initial mass. Title: On the dynamics of the metagalaxy Authors: Laurent, B. E.; Bonnevier, B.; Carlqvist, P. Bibcode: 1988STIN...8828852L Altcode: The dynamical aspects of the metagalactic model are studied. The consequences of high galaxy and quasar red shifts are considered. Explosion mechanisms are investigated and limits for the velocities they can produce are given. In the case of constant density in the local rest frame, limits are also given for the parameter omegao, for our position in the metagalaxy, and for the initial mass. Title: On the acceleration of energetic cosmic particles by electrostatic double layers. Authors: Carlqvist, Per Bibcode: 1986ITPS...14..794C Altcode: The capability of electrostatic double layers of accelerating charged particles to high energies is investigated. Starting from a one-dimensional relativistic double-layer model, a two-dimensional relativistic double layer in a current filament is studied. It is found that the filamentary double layer has a maximum potential drop that depends both on the magnitude of the filamentary current and on the composition of the layer. The results are applied to two cosmic double layers - one in a solar electric circuit and another in a galactic circuit. If the layers are composed of protons and electrons, these particles may be accelerated to 10 to the 11th eV in the solar layer, and to 10 to the 14th eV in the galactic layer. It is suggested that the solar double layer may account for the acceleration of solar cosmic rays, while the galactic layer may contribute to the generation of cosmic radiation. Title: On the acceleration of energetic cosmic particles by electrostatic double layers Authors: Carlqvist, Per Bibcode: 1986oaec.rept.....C Altcode: The capability of electrostatic double layers of accelerating charged particles to high energies is investigated. Starting from a one-dimensional, relativistic double layer model, a two-dimensional, relativistic double layer in a current filament is studied. It is found that the filamentary double layer has a maximum potential drop that depends on the magnitude of the filamentary current and on the composition of the layer. The results are applied to two cosmic double layers: one in a solar electric circuit and another in a galactic circuit. If the layers are composed of protons and electrons these particles may be accelerated to 10 to the 11th power eV in the solar layer and to 10 to the 14th power eV in the galactic layer. It is suggested that the solar double layer may account for the acceleration of solar cosmic rays while the galactic layer may contribute to the generation of cosmic radiation. Title: On the physics of relativistic double layers. Authors: Carlqvist, P. Bibcode: 1982Ap&SS..87...21C Altcode: A model of a strong, time-independent, and relativistic double layer is studied. Besides double layers having the electric field parallel to the current the model also describes a certain type of oblique double layers. The ‘Langmuir condition’ (ratio of ion current density to electron current density) as well as an expression for the potential drop of the double layer are derived. Furthermore, the distributions of charged particles, electric field, and potential within the double layer are clarified and discussed. It is found that the properties of relativistic double layers differ substantially from the properties of corresponding non-relativistic double layers. Title: Transition from the dusty plasma state to the planetesimal state of the early solar system Authors: Carlqvist, P.; Alfven, H. Bibcode: 1981STIN...8226133C Altcode: The agreement to within a few percent between the theoretically predicted cosmogonic shadow effect and observations of large scale structures of the Saturnian rings and the asteroidal region is discussed. Although the theory has to be modified, its observationally confirmed core remains valid. A transformation from the fixed coordinate system to a system which corotates with the plasma shows that in the latter system the orbits of the condensed particles contain a number of cusps where the condensed material is focused and stays for a comparatively long time. As a result, radiative cooling decreases the temperature, possibly by one or several orders of magnitude. This makes the cusps form small cold high density regions in a plasma, the major part of which is hot and dilute. Title: Electrostatic double layers and a plasma evacuation process. Authors: Raadu, M. A.; Carlqvist, P. Bibcode: 1981Ap&SS..74..189R Altcode: An evacuation process due to the growth of current driven instabilties in a plasma is discussed. The process, which leads to localized extreme density reductions, is related to the formation of electrostatic double layers. The initial linear phase is treated using the superposition of unstable plasma waves. In the long wavelength, non-dispersive limit, a density dip — which is initially present as a small disturbance — grows rapidly and remains localized in the plasma. The process works for a variety of plasma conditions provided a certain current density is exceeded. For a particular choice of plasma parameters the non-linear development is followed, by solving the coupled Vlasov-Poisson equations by finite difference methods. The evacuation process is found to work even more effectively in the non-linear phase and leads to an extreme density reduction within the dip. It is suggested that the growth of such structures produces weak points within the plasma that can lead to the formation of double layers. Title: Energy Source of the Solar Wind Authors: Carlqvist, P.; Alfven, H. Bibcode: 1980Ap&SS..71..203C Altcode: A direct transfer of energy from photospheric activity to the solar wind by means of electric currents is discussed. Currents are assumed to flow in quiescent prominences which occasionally erupt and give rise to expanding loop-like structures in the corona, as observed from Skylab. Due to expansion, the legs of the loops are transformed into coronal rays which carry currents from the photosphere to the outer parts of the corona or interplanetary medium and then back again to the photosphere. It is proposed that energy is transferred from photospheric activity to the solar wind in the following ways: (1) as kinetic energy of the ejected loop matter; (2) as electric power directly fed into the extended loops; and (3) as torsional waves produced by fluctuations in the loop currents. Title: Energy source of the solar wind Authors: Carlqvist, P.; Alfven, H. Bibcode: 1979STIN...8025266C Altcode: A direct transfer of energy from photospheric activity to the solar wind by means of electric currents is discussed. Currents are assumed to flow in quiescent prominences which occasionally erupt and give rise to expanding looplike structures in the corona as observed from Skylab. Due to the expansion the legs of the loops are transformed into coronal rays which carry currents from the photosphere to the outer parts of the corona or interplanetary medium and then back again to the photosphere. It is proposed that energy is transferred from photospheric activity to the solar wind (1) as kinetic energy of the ejected loop matter; (2) as electric power directly fed into the extended loops; and (3) as torsional waves produced by fluctuations in the loop currents. Title: A flare-associated mechanism for solar surges. Authors: Carlqvist, P. Bibcode: 1979SoPh...63..353C Altcode: An ejection mechanism for solar surges is discussed. The mechanism is closely related to an earlier proposed model for solar flares founded on current disruption. Hence, the observed connection between surges and flares may be explained in a simple way. The mechanism can also offer explanations of other questions connected with surges such as why surges tend to grow up from small bright knots emitting moustache spectra, why strong magnetic field concentrations are observed near the base of surges, why surges often exhibit a helical motion, and why homologous surges are produced. Finally it is pointed out that spicules might be generated by a mechanism similar to that discussed for surges. Title: Some Theoretical Aspects of Electrostatic Double Layers Authors: Carlqvist, P. Bibcode: 1979wisp.proc...83C Altcode: A review is presented of the main results of the theoretical work on electrostatic double layers. The general properties of double layers are first considered. Then the time-independent double layer is discussed. The discussion deals with the potential drop, the thickness, and some necessary criteria for the existence and stability of the layer. As a complement to the study of the time-independent double layer a few remarks are also made upon the time-dependent double layer. Finally the question of how double layers are formed and maintained is treated. Several possible formation mechanisms are considered. Title: Some Theoretical Aspects of Electrostatic Double Layers Authors: Carlqvist, P. Bibcode: 1979ASSL...74...83C Altcode: No abstract at ADS Title: Some theoretical aspects of electrostatic double layers Authors: Carlqvist, P. Bibcode: 1978STIN...7917790C Altcode: The general properties of electrostatic double layers are considered. The time-independent double layer is discussed with emphasis on the potential drop, the thickness, and some necessary criteria for the existence and stability of the layer. Properties of the time-dependent double layer are also reviewed. The question of how double layers are formed and maintained is treated. Several possible formation mechanisms are examined. Title: Interstellar Clouds and the Formation of Stars Authors: Alfven, H.; Carlqvist, P. Bibcode: 1978Ap&SS..55..487A Altcode: Part I gives a survey of the drastic revision of cosmic plasma physics which is precipitated by the exploration of the magnetosphere throughin situ measurements. The ‘pseudo-plasma formalism’, which until now has almost completely dominated theoretical astrophysics, must be replaced by an experimentally based approach involving the introduction of a number of neglected plasma phenomena, such as electric double layers, critical velocity, and pinch effect. The general belief that star light is the main ionizer is shown to be doubtful; hydromagnetic conversion of gravitational and kinetic energy may often be much more important. In Part II the revised plasma physics is applied to dark clouds and star formation. Magnetic fields do not necessarily counteract the contraction of a cloud; they may just as well ‘pinch’ the cloud. Magnetic compression may be the main mechanism for forming interstellar clouds and keeping them together. Part III treats the formation of stars in a dusty cosmic plasma cloud. Star formation is due to an instability, but it is very unlikely that it has anything to do with the Jeans instability. A reasonable mechanism is that the sedimentation of ‘dust’ (including solid bodies of different size) is triggering off a gravitationally assisted accretion. A ‘stellesimal’ accretion analogous to the planetesimal accretion leads to the formation of a star surrounded by a very low density hollow in the cloud. Matter falling in from the cloud towards the star is the raw material for the formation of planets and satellites. The study of the evolution of a dark cloud leads to a scenario of planet formation which is reconcilable with the results obtained from studies based on solar system data. This means that the new approach to cosmical plasma physics discussed in Part I logically leads to a consistent picture of the evolution of dark clouds and the formation of solar systems. Title: Interstellar clouds and the formation of stars Authors: Alfven, H.; Carlqvist, P. Bibcode: 1977STIN...7827037A Altcode: The theory and properties of cosmic plasma are reviewed and the general belief that star light is the main ionizer is shown to be doubtful. The magnetohydrodynamic aspects of cosmic plasma clouds are discussed and it is concluded that magnetic fields may pinch the cloud, while magnetic compression may be the main mechanism for forming interstellar clouds and keeping them together. The formation of stars in a dusty cosmic plasma cloud is also discussed. Title: The cosmic X-ray background (reply) Authors: Carlqvist; Laurent Bibcode: 1976Natur.262..822C Altcode: No abstract at ADS Title: Annihilation of matter and antimatter and the cosmic X-ray background Authors: Carlqvist, P.; Laurent, B. Bibcode: 1976Natur.260..225C Altcode: When optical photons are scattered against the relativistic electrons produced by the annihilation of matter and antimatter, X-rays are produced by the inverse Compton effect. The efficiency of this X-ray mechanism in intergalactic space is investigated on the basis of a simplified model. The inverse Compton spectrum obtained from the model is in good agreement with observational data on the cosmic X-ray background over the interval 1 keV to 100 keV. A mean electron density calculated for the energy interval 10 MeV to 100 MeV is about two orders of magnitude smaller than the mean atom density of galactic material throughout the Universe. The magnetic field required to yield a stationary spectrum for the electron energies of interest is calculated to be greater than .00002 Gauss, indicating an intensity of synchrotron radiation in the radio band produced by the annihilation electrons necessary to produce the X-rays which is higher than experiment allows. Annihilation electrons may be created in quasars and galactic nuclei where a rapid decay in the electron energy occurs. The annihilation electrons escape into intergalactic space, become uniformly distributed, and produce the X-ray background by interacting with optical photons. Title: Annihilation of matter and antimatter and the cosmic X-ray background. Authors: Carlqvist, P.; Laurent, B. Bibcode: 1975amac.book.....C Altcode: 1975STIN...7623146C A cosmologic model for the cosmic X-ray background radiation mechanism is suggested. This model is based on inverse Compton scattering of galactic photons on relativistic annihilation electrons. Title: On the formation of double layers in plasmas. Authors: Carlqvist, P. Bibcode: 1972CosEl...3..377C Altcode: No abstract at ADS Title: Space-charge regions above the aurora Authors: Carlqvist, Per; Boström, Rolf Bibcode: 1970JGR....75.7140C Altcode: Observations have shown that field-aligned currents above auroras reach such magnitudes that space-charge regions of high potential drops can be expected. Effects of the electric fields associated with such a space-charge region are acceleration of auroral electrons and horizontal motions in the visual aurora. Title: Current Limitation and Solar Flares Authors: Carlqvist, P. Bibcode: 1969SoPh....7..377C Altcode: A flare model based on force-free currents in the solar atmosphere is considered. The energy of the flare is supposed to be stored as magnetic energy in the current system. If the current density exceeds a certain critical limit an over-voltage may arise in the circuit which will give rise to a rapid release of the stored energy. At the end of the paper some results yielded by the model are compared with observational evidence of flares. Title: Solar flares caused by high impedance regions in current filaments Authors: Carlqvist, P. Bibcode: 1968mmsf.conf..193C Altcode: No abstract at ADS Title: Currents in the Solar Atmosphere and a Theory of Solar Flares Authors: Alfvén, H.; Carlqvist, P. Bibcode: 1967SoPh....1..220A Altcode: No abstract at ADS Title: Solar Flares Caused by Circuit Interruptions Authors: Jacobsen, C.; Carlqvist, P. Bibcode: 1964Icar....3..270J Altcode: Interruptions in inductive electric current circuits in the Sun are considered as possible causes of solar flares. The currents are assumed to have a filamentary structure and the interruption to be related to an instability well known in gas discharge physics.