Recent explosive volcanic episodes on the Island of Kos (Greece): associated hydrothermal parageneses and geothermal area of Volcania

Altered xenoliths in the 0.25–0.12 Myr non-welded ignimbrite deposits of the Island of Kos (Greece) provide evidence for a hydrothermal convective system in the basement complex. The conjunction of a potential heat source, high-temperature hydrothermal parageneses, permeable and porous bedded formations, continuing tectonic phenomena and successive fracturing and possible access by sea-waters, argues for a favourable geothermal potential. The hydrothermal area of Volcania, where mineralized and sometimes degassing waters circulate, could be regarded as a zone of lateral leakage from the hydrothermal convective system, which developed above the cooling magma chamber.     

Internal gravity waves in Titan's atmosphere observed by Voyager radio occultation

This paper discusses observational considerations in a search for extraterrestrial intelligence (SETI) program to detect extraterrestrial messenger probes in the solar system. Observable artifacts will most likely be found in a search space consisting of geocentric, selenocentric, Earth-Moon libration, and Earth-Moon halo orbits, which may be searched to a limiting artifact size of 1–10 m (p_v = 0.1) using existing or foreseeable instrumentation.     

Combining borehole temperature and meteorologic data to constrain past climate change

Geothermal observations from a suite of boreholes in western Utah, USA, combined with meteorologic data at nearby weather stations are used to test the hypothesis that temperatures in the earths subsurface contain an accurate record of recent climate change. The change in air temperature over the last hundred years successfully predicts detailed subsurface temperature profiles to better than ±0.05°C, indicating that ground temperatures tract air temperatures over long periods and that climate change signals are conducted into, and recorded in, the solid earth by the process of heat conduction. We combine borehole temperature data with meteorologic data from the nearest weather station to determine the time averaged difference between surface ground temperature and surface air temperature for borehole-weather station pairs and to infer the long term mean air temperature prior to the observational record. For our western Utah sites the preobservational mean temperature is close to the average surface air temperature for this century suggesting that up to 0.5°C of warming deduced from the last 100 years of weather station data may be attributed to recovery from a cool period at the turn of the century.     

Terrestrial paleoenvironmental effects of a late quaternary-age supernova

A chronology of the γ and X radiation incident upon the Earth from discrete supernova occurences is desirable for two reasons: (1) large but short-lived γ flashes should result in episodically increased atmospheric ¹⁴C production, and thus affect the ¹⁴C dating method, and (2) modeling of the other atmospheric effects to be expected from nearby supernovas indicates their possible importance as independent variables capable of causing climatic or other environmental changes. Presented here is a preliminary chronology of the larger inferred radiation events experienced by the Earth during the past 15, 000 years. This chronology illustrates the possible importance of the Vela optical-, radio-, and X-emitting supernova remnant (G263.9-3.3), and its associated pulsar (PSR-0833-45), which together record an unusually close (d = 500 pc supernova occuring sometime between 11,300 and 8,400 years B.P. The predicted terrestrial effects of a 10⁴⁹?1 10⁵⁰-erg γ- and X-emitting supernova at this distance include short-term increases in ¹⁴C activity (+3 to +6%), increases in aquatic productivity at some localities, and a brief global cooling. Such effects appear to be documented by many late Quaternary paleoenvironmental records dated between 11,000 and 10,000 ¹⁴C yr B.P.     

Characteristics of VLF emissions manifested by their cross-spectral phase information

Natural VLF emissions received by a single antenna can be characterised at each point in the emissions' frequency-time domain by a power and a phase. Emissions received at a single point by two antennae with a fixed relative orientation in space can be similarly described by the cross-spectral power and relative phase. It is shown that the cross-spectral phase contains information on the propagation characteristics of the waves which is better utilised in wave analysis than the power. In fact, the phase information allows weak signals to be identified more readily than is possible from a power spectrogram. It also allows the recognition of waves propagating with different wave normal directions. Data from the Geos-1 electric and magnetic antennae, pre-processed by the on-board correlator, are used to study the cross-spectral characteristics of VLF hiss and chorus in the Earth's magnetosphere.     

Comments on the paper ‘hydrodynamic and turbulent motions in the galactic disk’

Two comments are prompted by the recent paper of Quiroga (1983). First, it is pointed out that Quiroga's identification of two distinct types of motion (hydrodynamic and turbulent) within the galactic disk supports the suggestion that turbulent motions in the Galaxy are generated by the shearig action of differential galactic rotation. Secondly, as a result of these turbulent motions dominating the systematic hydrodynamics of galactic rotation at scale sizes below 100–300 pc, it appears that some process(es) associated with interstellar turbulence rather than with galactic rotation should play a dominant role in the establishment of the angular momentum of interstellar material.