Digital multichannel spectrometer for solar microwave observations

Observations of solar microwave bursts have shown fine structures (e.g., the millisecond spikes), not resolvable in time and frequency by existing instruments. In order to investigate these features in greater detail we have developed a spectrometer with high temporal and spectral resolution. The frequency range from 3000 to 4000 MHz is covered by 32 channels with different bandwidths (0.1, 5, and 20 MHz). The instrument is fully controlled by a multiprocessor computer system and allows the recording of about 200 000 measurements per second. Thus it is possible to observe the intensity and the circular polarization of all the 32 channels with a time resolution of about 350 s. A very flexible frequency selection system allows the use of many different observation modes.     

Long-term changes of the surface air temperature in relation to solar inertial motion

The inertial motion of the Sun around the barycentre, or centre of mass, of the Solar System has been employed as the base in searching for possible influence of the Solar System as a whole on climatic processes, especially on the changes in surface air temperature. A basic cycle of about 180–200 years and its higher harmonics up to 30 years have been found in surface air temperature of central Europe since 1753, established from 13 continuous instrumental time series. These periods correspond to the periods of solar inertial motion. In the first half of the 19th century, when the solar motion was chaotic, this temperature was about 0.75°C lower than that in the 20th (1940–50) and the 18th (1760–70) centuries. The mentioned decades of long-term temperature maxima coincide with the central decades of the ordered (trefoil) motion of the Sun. The temperatures in coastal Europe have been found to have slightly different properties, especially on a long-time scale. The periods of 35–45 years are significantly pronounced in the coastal Europe temperature spectrum. The chaotic motion of the Sun in the next decades could decrease both the solar forcing and global surface air temperature.This research was performed with support of the Grant Agency of the Czech Republic, Grant No. 205/93/0417, I. Charvátová: Prognosis of climate development in central Europe.     

A porosity mapping survey in Hecate Strait using a seafloor electro-magnetic profiling system

A newly developed marine electromagnetic (E-M) system was used to create apparent porosity maps of the uppermost 20 m of sediments on the seafloor. Measurements of electrical conductivity were interpreted to give the porosity of the bottom sediments and underlying units. The data were collected continuously in a surveying mode using two receivers at different spacings to improve the resolution of porosity as a function of depth. The variations in apparent porosity over the area correlate well with information obtained from cores and acoustic profiles.

Acoustic profiles indicated the presence of biogenic gas in the central region of the survey area. The absence of distinct changes in apparent porosity over regions of gas allows us to conclude that the concentration of gas trapped within the Queen Charlotte muds does not exceed about 4% of the sediment by volume if we assume that the gas displaces fluid in the sediment.

A buried, lower porosity layer was detected, its position reflecting changes in the depth to the glaciomarine layer. Mapped variations in apparent porosity are well correlated with features on the acoustic record. This illustrates the system's ability to obtain continuous profiles of apparent porosity over seafloor features. The marine E-M survey provided rapid areal coverage, and, combined with the acoustic profiles, information on the porosity of deeper units.     

Diffusion and heat flow equations for the mid-latitude topside ionosphere

For application to the mid-latitude topside ionosphere, we have derived diffusion and heat flow equations for a gas mixture composed of two major ions, electrons and a number of minor ions. These equations were derived by expanding the velocity distribution of each constituent about its 13 lower order velocity moments. As a consequence, each constituent was allowed to have its own temperature and drift velocity. The restriction to mid-latitudes results because we have assumed that the species temperature and drift velocity differences were small. In deriving the diffusion and thermal conduction equations, we have discovered some new transport effects. For the major ions, we have found that: (1) a temperature gradient in either gas causes thermal diffusion in both gases; (2) a temperature gradient in either gas causes heat to flow in both gases; and (3) a relative drift between the major ion gases induces a heat flow in both gases. Similar transport effects have also been found for the minor ions.     

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