Rapidly propagating fast magnetoacoustic wave trains guided by field-aligned plasma non-uniformities are confidently observed in the Sun’s corona. Observations at large heights suggest that fast wave trains can travel long distances from the excitation locations. We study characteristic time signatures of fully developed, dispersive fast magnetoacoustic wave trains in field-aligned zero-β plasma slabs in the linear regime. Fast wave trains are excited by a spatially localised impulsive driver and propagate along the waveguide as prescribed by the waveguide-caused dispersion. In slabs with steeper transverse density profiles, developed wave trains are shown to consist of three distinct phases: a long-period quasi-periodic phase with the oscillation period shortening with time, a multi-periodic (peloton) phase in which distinctly different periods co-exist, and a short-lived periodic Airy phase. The appearance of these phases is attributed to a non-monotonic dependence of the fast wave group speed on the parallel wavenumber due to the waveguide dispersion, and is shown to be different for axisymmetric (sausage) and non-axisymmetric (kink) modes. In wavelet analysis, this corresponds to the transition from the previously known tadpole shape to a new boomerang shape of the wave train spectrum, with two well-pronounced arms at shorter and longer periods. We describe a specific previously published radio observation of a coronal fast wave train, highly suggestive of a change of the wavelet spectrum from a tadpole to a boomerang, broadly consistent with our modelling. The applicability of these boomerang-shaped fast wave trains for probing the transverse structuring of the waveguiding coronal plasma is discussed.

The case for applying correlation techniques to gas chromatography has been re-examined following the introduction of on-line cross-correlators, and it is concluded that there is still little scope for these techniques in a normal chromatograph situation. A series of experiments designed to demonstrate the feasibility of applying cross-correlation to trace analysis by gas chromatography is reported and, from these experiments, it is concluded that correlation offers considerable advantages over the conventional single-sample injection method when minute quantities of a component in a sample gas are being sought. With the continuing interest in environmental pollution, there appears to be much scope for correlation techniques in this area.

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<p>Ice shelves encircling the Antarctic perimeter buttress ice flow from the continent towards the ocean, and their evolution and integrity are governed by surface accumulation, basal melting, and ice dynamics. The disintegration of ice shelves, caused by future changes in the climate, leads to an increase in ice discharge towards the ocean and a consequent increase in global sea level – making their future stability important.</p> <p>In this study we focus on the structure and composition of ice shelves. We model ice shelf stratigraphy for all ice shelves around Antarctica using a simplistic and observationally driven ice-dynamic forward model (validated on the Roi Baudouin Ice Shelf, Visnjevic et al., 2022), and map spatial variations in the percentage of locally accumulated ice on the ice shelf (local meteoric ice - LMI) compared to the ice inflowing from the continental ice sheet (continental meteoric ice - CMI). We investigate differences between LMI and CMI dominated ice shelves in the context of ice shelf stability, and discuss their susceptibility to future atmospheric and oceanic changes in climate. Expanding the analysis to the continental scale allows us to identify zones where future changes in climate might strongly impact ice shelf geometry and composition.</p>