Morphological indictors of the chirality of solar filaments

Abstract

There is no doubt that the structural features of filaments reflect properties of their magnetic fields, such as chirality and helicity. However, the interpretation of some morphological features can lead to incorrect conclusions when the observing time is limited and the spatial resolution is insufficiently high. In spite of the relative constancy of their overall shapes, filaments are dynamical formations with inhomogeneities moving along the threads making them up. Therefore, it is possible to observe material concentrated not only in magnetic traps, but also along curved arcs. Difficulties often arise in determining the chirality of filaments with anomalous “barbs”; i.e., those whose jagged side is located on the opposite side of the axis compared to most (“normal”) filaments. A simple model is used to show that anomalous barbs can exist in an ordinary magnetic flux rope, with the threads of its fine structure oriented nearly perpendicular to its length. A careful analysis of images with the maximum available spatial resolution and with information about temporal dynamics, together with comparisons with observations in various spectral lines, can enable a correct determination of the chirality of filaments.