MODEL OF FINITE INHOMOGENEOUS CAVITY CHAIN AND APPROXIMATE METHODS OF ITS ANALYSIS

A new approach to the description of an inhomogeneous chain of coupled resonators (inhomogeneous disk waveguides) is proposed. New matrix difference equations based on the technique of coupled integral equations and the decomposition method are obtained. Various approximate approaches have been developed, including the WKB approximation.

Photometry of WD 1145+017 in Early 2017

We present photometric observations of WD 1145+017 during six nights in early 2017. They exhibited asymmetric transits with durations of 10–50 mins and depths up to 50% in flux. We managed to track two deep features that drift in phase during 2.5-month season. This effect may be explained by period decreasing of the transiting formations due to their slow spiralling to the white dwarf. One of them seems to fragment in several smaller parts within a month. The structures causing the two deep transits have elongated shape whose sizes perpendicular and along the orbit are of the order of 1 R⊕ and 100 R⊕. They are parts of geometrically thin inhomogeneous disk (ring) around the white dwarf that is well within its Roche radius. This explains the observed dip activity of WD 1145+017 during the year 2017.

Localized S‐inversion of time‐domain electromagnetic data

Interpretation of time‐domain electromagnetic (TDEM) data over inhomogeneous geological structures is a challenging problem of geophysical exploration. The most widely used approach of interpreting TDEM data is based on the smooth 1‐D layered resistivity inversion. We have developed an effective technique of fast TDEM inversion based on thin‐sheet conductance approximation that we call S‐inversion. In this paper we extend the S‐inversion technique, approximating the conductivity cross‐section by adding a local inhomogeneous disk with an excess conductance ΔS to the horizontal conductive thin sheet used in S‐inversion. Localized S‐inversion determines the distribution of this excess conductance as a function of a depth and a horizontal coordinate. This new method takes into account the limited horizontal extent of the inhomogeneities, localizing inversion. The numerical modeling results and inversion of practical TDEM data demonstrate that the method resolves local geological targets better than traditional 1‐D inversion and original S‐inversion. The method can be applied to interpret both ground and airborne TDEM data sets.