Formation and large-scale patterns of filament channels and filaments

2015ASSL..415..355MThe properties and large-scale patterns of filament channels and filaments are considered. Initially, the global formation locations of filament channels and filaments are discussed, along with their hemispheric pattern. Next, observations of the formation of filament channels and filaments are described where two opposing views are considered. Finally, the wide range of models that have been constructed to consider the formation of filament channels and filaments over long time-scales are described, along with the origin of the hemispheric pattern of filaments

Future capabilities of CME polarimetric 3D reconstructions with the METIS instrument: A numerical test

Understanding the 3D structure of coronal mass ejections (CMEs) is crucial for understanding the nature and origin of solar eruptions. To derive information on the 3D structure of CMEs from white-light (total and polarized brightness) images, the polarization ratio technique is widely used. The soon-to-be-launched METIS coronagraph on board Solar Orbiter will use this technique to produce new polarimetric images. We determine the accuracy at which the position of the centre of mass, direction and speed of propagation, and the column density of the CME can be determined along the line of sight. We perform a 3D MHD simulation of a flux rope ejection where a CME is produced. From the simulation we (i) synthesize the corresponding METIS white-light (total and polarized brightness) images and (ii) apply the polarization ratio technique to these synthesized images and compare the results with the known density distribution from the MHD simulation. We find that the polarization ratio technique reproduces with high accuracy the position of the centre of mass along the line of sight. However, some errors are inherently associated with this determination. The polarization ratio technique also allows information to be derived on the real 3D direction of propagation of the CME. In addition, we find that the column density derived from white-light images is accurate and we propose an improved technique where the combined use of the polarization ratio technique and white-light images minimizes the error in the estimation of column densities. Our method allows us to thoroughly test the performance of the polarization ratio technique and allows a determination of the errors associated with it, which means that it can be used to quantify the results from the analysis of the forthcoming METIS observations in white light (total and polarized brightness)

Simulating AIA observations of a flux rope ejection

Extreme ultraviolet (EUV) images from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) are providing new insights into the early phase of CME evolution. Observations now show the ejection of magnetic flux ropes from the solar corona and how they evolve into CMEs. These observations are difficult to interpret in terms of basic physical mechanisms and quantities. To fully understand CMEs we need to compare equivalent quantities derived from both observations and theoretical models. To this end we aim to produce synthesised AIA observations from simluations of a flux rope ejection. To carry this out we include the role of thermal conduction and radiative losses, both of which are important for determining the temperature distribution of the solar corona during a CME. We perform a simulation where a flux rope is ejected from the solar corona. From the density and temperature of the plasma in the simulation we synthesise AIA observations. The emission is then integrated along the line of sight using the instrumental response function of AIA. We sythesise observations of AIA in the channels at 304 A, 171 A, 335 A, and 94 A. The synthesised observations show a number of features similar to actual observations and in particular reproduce the general development of CMEs in the low corona as observed by AIA. In particular we reproduce an erupting and expanding arcade in the 304 A and 171 A channels with a high density core. The ejection of a flux rope reproduces many of the features found in the AIA observations. This work is therefore a step forward in bridging the gap between observations and models, and can lead to more direct interpretations of EUV observations in terms of flux rope ejections. We plan to improve the model in future studies in order to perform a more quantitative comparison

The light-sense in strabismus : especially in the amblyopia of strabismus : examined by means of a new photometer

One is now in a position to draw conclusions. I have put together all the cases of convergent strabismus with amblyopia, examined as to the light -sense either with or without glasses, which show a marked difference in their light-sense (groups 1 and 9).That is, of 15 cased (Divisions 1 and 2), in which the L.M. is affected markedly, 9 have it increased, and 6 have it diminished.On the other hand, of 20 cases (divisions 1 and 3), in which the L.D. is similarly affected, 15 have it increased, and 5 have it diminished.In like manner I put together those cases of convergent strabismus, without amblyopia, in which there was a marked difference in the light -sense of the two eyes. (Tables 14 and 37).Here then, of 7, which have a variation in the L.M., in 3 the L.M. is greater, and in 4 less. Of 6 which vary as to the L.D., in all the L.D. is increased.In the next place, I have made a similar summary of the cases of divergent strabismus, with amblyopia, which, with or without glasses, show a marked difference in the light-sense of the two eyes (Tables 21 and 42).That is, where the L. M. is affected- markedly, in 3 out of 4 it is increased, and in 1 diminished.Where the L.D. is markedly affected, out of 5 cases it is increased in 3, and diminished in 2.So far as it goes, this table points to defect in the L.T.C., and also, though in less degree, to defect in the L.P., but the number of cases is too small to permit of useful generalisation.Also, the number of cases of divergent strabismus without amblyopia (Group. 7.) is too small to be worth considering.Lastly, I may recall the fact (p.48) that, in amblyopic eyes without strabismus, there is no overwhelming evidence pointing either to the L.M. or the L.D., though either may be affected.This inquiry then has a negative result, for no abso- lute rule as to the light -sense in squinting or amblyó_ is eyes, as compared with the et in their normal fellows, has been revealed. In all the groups, a large proportion of the cases present equal or nearly equal light -sense in the two eyes. Of the remainder, some have defective L.7., and some defective L.D., some have more acute L.M. and some more acute L.D. And neither acutt: of vision, age, nor refractive error, seems to assist in determining any classification of each kind. Of those cases of Convergent Strabismus however, either with or without amblyopia, in which the light- sense is markedly different in the squint- ing eye from that in the normal eye, the majority show a defective L.D. In other words, these cases seem to have some affection of the optic nerve or nervous elements of the retina.One is forced to the conclusion, therefore, that probably the light -sense is not primarily responsibe for the squint or for the amblyopia. The explanation of squint is still hidden.PHOTOMETRY OF NORMAL EYES:- In order that I might report on the cases cf toxic amblyopia, which I have examined the light -sense of, it is necessary to determine the average of the normal eyes, as to their L.M. and L.D.In doing this, I have included all the eyes of the preceding study, which did not squint, and a few extra ones which were seen during the same time.All were perfectly healthy, as evidenced by the ophthalmoscope and the visual acuity. I have accordingly made tables of 73 eyes,whose light -sense was examined while they wore the correcting glasses necessary, and of 29 eyes which were examined naked. I have tabulated each lot in accordance with their decades of life, having sub- tables of the different acuities of vision under each decade.The figure in the third column is the area of the circular ring formed by the partly opened diaphragm and the central cylinder of wood. That in the fourth column is the proportion expressed as a decimal fraction, of the extra area, needed to enable the observer to note a difference in the brilliancy of the discs, to the L.M. The figure in the fifth column is the diameter of the diaphragmatic aperture at the first reading, and that in the sixth column is the diameter at the second reading (p.16)The form-sense is that obtained by correcting the refractive error with glasses, which were removed before introduction to the photometer.These two tables collected into one, ,under the decades of age, give a result as follows:These, again collected together under the decades, give the following figures as the averages for the five decades named, and they are seen to be all similar;We can now reckon the cases of Tobacco amblyopia, of which I have 12 eyes to report on.3 of these eyes have distinct increase in the L M. one of 6 them seeing Ja, and two 6/36.3 have markedly increased L.D. one seeing 6/6-0, one of them seeing 6/36, and one 6/24.In most of these eyes, therefore, there is no affection of the L.M. or the L, D., so that neither the retina nor the optic nerve, so far as its connection with the light-sense centre is concerned, need be affected. The cases are too few, however, to permit of dogmatism. So far as the observation goes, it is in accord with Henry's (op.cit.), who also found with his photometer that the L.M. was not affected in toxic-amblyopia

On the Bergman-Milton bounds for the homogenization of dielectric composite materials

The Bergman-Milton bounds provide limits on the effective permittivity of a composite material comprising two isotropic dielectric materials. These provide tight bounds for composites arising from many conventional materials. We reconsider the Bergman-Milton bounds in light of the recent emergence of metamaterials, in which unconventional parameter ranges for relative permittivities are encountered. Specifically, it is demonstrated that: (a) for nondissipative materials the bounds may be unlimited if the constituent materials have relative permittivities of opposite signs; (b) for weakly dissipative materials characterized by relative permittivities with real parts of opposite signs, the bounds may be exceedingly large

Properties of the prominence magnetic field and plasma distributions as obtained from 3D whole-prominence fine structure modeling

Aims. We analyze distributions of the magnetic field strength and prominence plasma (temperature, pressure, plasma beta, and mass) using the 3D whole-prominence fine structure model. Methods. The model combines a 3D magnetic field configuration of an entire prominence, obtained from non-linear force-free field simulations, with a detailed semi-empirically derived description of the prominence plasma. The plasma is located in magnetic dips in hydrostatic equilibrium and is distributed along multiple fine structures within the 3D magnetic model. Results. We show that in the modeled prominence, the variations of the magnetic field strength and its orientation are insignificant on scales comparable to the smallest dimensions of the observed prominence fine structures. We also show the ability of the 3D whole-prominence fine structure model to reveal the distribution of the prominence plasma, with respect to its temperature within the prominence volume. This provides new insights into the composition of the prominence-corona transition region. We further demonstrate that the values of the plasma beta are small throughout the majority of the modeled prominence when realistic photospheric magnetic flux distributions and prominence plasma parameters are assumed. While this is generally true, we also find that in the region with the deepest magnetic dips, the plasma beta may increase towards unity. Finally, we show that the mass of the modeled prominence plasma is in good agreement with the mass of observed non-eruptive prominences.Publisher PDFPeer reviewe