Complex dynamics emerging in Rule 30 with majority memory

In cellular automata with memory, the unchanged maps of the conventional cellular automata are applied to cells endowed with memory of their past states in some specified interval. We implement Rule 30 automata with a majority memory and show that using the memory function we can transform quasi-chaotic dynamics of classical Rule 30 into domains of travelling structures with predictable behaviour. We analyse morphological complexity of the automata and classify dynamics of gliders (particles, self-localizations) in memory-enriched Rule 30. We provide formal ways of encoding and classifying glider dynamics using de Bruijn diagrams, soliton reactions and quasi-chemical representations

Effect of stellar flares on the upper atmospheres of HD 189733b and HD 209458b

Stellar flares are a frequent occurrence on young low-mass stars around which many detected exoplanets orbit. Flares are energetic, impulsive events, and their impact on exoplanetary atmospheres needs to be taken into account when interpreting transit observations. We have developed a model to describe the upper atmosphere of Extrasolar Giant Planets (EGPs) orbiting flaring stars. The model simulates thermal escape from the upper atmospheres of close-in EGPs. Ionisation by solar radiation and electron impact is included and photochemical and diffusive transport processes are simulated. This model is used to study the effect of stellar flares from the solar-like G star HD209458 and the young K star HD189733 on their respective planets. A hypothetical HD209458b-like planet orbiting the active M star AU Mic is also simulated. We find that the neutral upper atmosphere of EGPs is not significantly affected by typical flares. Therefore, stellar flares alone would not cause large enough changes in planetary mass loss to explain the variations in HD189733b transit depth seen in previous studies, although we show that it may be possible that an extreme stellar proton event could result in the required mass loss. Our simulations do however reveal an enhancement in electron number density in the ionosphere of these planets, the peak of which is located in the layer where stellar X-rays are absorbed. Electron densities are found to reach 2.2 to 3.5 times pre-flare levels and enhanced electron densities last from about 3 to 10 hours after the onset of the flare. The strength of the flare and the width of its spectral energy distribution affect the range of altitudes that see enhancements in ionisation. A large broadband continuum component in the XUV portion of the flaring spectrum in very young flare stars, such as AU Mic, results in a broad range of altitudes affected in planets orbiting this star.Comment: accepted for publication in A&

Electromagnetic Coupling through Arbitrary Apertures in Parallel Conducting Planes

We propose a numerical methodto solve the problem of coupling through finite, but otherwise arbitrary apertures in perfectly conducting and vanishingly thin parallel planes. The problem is given a generic formulation using the Method of Moments and the Green's function in the region between the two planes is evaluated using Ewald's method. Numerical applications using Glisson's basis functions to solve the problem are demonstrated and compared with previously published results and the output of FDTD software