Radio Echo Signals Research Articles

Mesospheric observations by a forward scattering meteor radar basic setup

The durations of radio echo signals scattered from meteor ionized trails might not show a consistent increase corresponding to higher density trails due to the rapid removal of meteor ions at certain heights. Several studies have concluded the dominant role of the secondary ozone layer over diffusion in the removal of the meteor trails below 95 km through chemical oxidization of the meteor ions. Using a basic setup configuration of a forward scattering receiver, a trial to observe the mesospheric ozone concentration was performed by analyzing the meteor echo duration distributions. The forward scattered meteor echoes have the advantage of long durations that can enable observing the transition from the diffusion-removal regime to the chemistry-removal regime. The cumulative meteor echo duration distribution of two meteor showers, the Perseids and the Geminids, were analyzed over 10 years and the chemistry-removal regime in each shower was observed. The knee duration position at which a drop in the number of long overdense meteor echoes starts differed by around 30 seconds between the two showers. As the secondary ozone concentration is inversely related to the solar activity level, the Geminids 2011 corresponding to a high solar activity level showed a significant higher counts of long duration echoes compared to the Geminids 2006 during a low activity level, with the knee position shifted to longer duration. The knee positions obtained during the two distinct meteor showers and the two half solar cycle points are generally in agreement with the mesospheric ozone conditions expected in each case. However, continuous data record is required for the other meteor showers and the sporadic meteors at different heights to observe the mesospheric ozone concentration vertically and the full 11-years solar cycle.

Electromagnetic reflecting properties of sub-ice surfaces

AbstractThe power strength of the radio-echo signal coming from reflecting sub-ice surfaces is used to determine the nature of the reflecting surface, i.e. rock, water or sea water. Electromagnetic analysis shows that the amplitude variations detected by radio-echo sounding are mainly due to the nature of the interface as well as the concave or convex shape of the reflectors. In this paper, some relevant profiles showing the power variations due to the different nature of the interface and the shape of the reflectors are presented. These results are important both for surface shape determination and for subglacial lake detection.

Internal radio-echo layering at Vostok station, Antarctica, as an independent stratigraphie control on the ice-core record

Antarctic radio-echo sounding (RES) data at 60 MHz have been used to determine an independent stratigraphy for the ice core at Vostok station, based on internal radio-echo layering. A-scope RES data allow the amplitude of reflected electromagnetic (e/m) waves to be measured and, by accounting fur geometric spreading and absorption losses of the e/m wave, power reflection coefficients (PRCs) to be calculated. This information is compared with time-continuous Z-scope RES data in order to trace continuous e/m reflectors across the ice sheet. Internal ice-sheet horizons deeper than 800 m are caused by layers of ice that possess distinctly different dielectric properties (i.e. acidic layers) compared with ice above and/or below. Comparison of four PRC samples, located ~ 5 km from Vostok station, revealed five distinct internal reflections between 1000 and 2200 m. Z-scope data from directly over the Vostok station site show the same five prominent internal radio-echo layers. The depth-related radio-echo signals were then compared with chemical records from the Vostok ice core, including the H2SO4 signal, a major component of which is derived from volcanic events. From this procedure, internal radio-echo reflectors and Vostok ice-core acid measurements were correlated. Avery good match was made between Z-scope and ice-core data. However, vertical offsets observed between A-scope-derived RES layers and peaks in the chemical signal of up to 100 m are probably due to the general Inkling of the ice-sheet layering between the core site and the RES flight-line. We conclude that 60 MHz RES layering may be regarded as a stratigraphy independent of palaeoclimate, and may be used to correlate other deep Southern Hemisphere ice cores.

Focusing-defocusing phenomena of radio echo signal after passage of the morning solar terminator

Campaign results of high-repetition ionospheric soundings, performed at the ionospheric station of Rome using a Digisonde 128P, are presented. We introduce an index derived from run rapid ionograms that can be used to detect oscillations of isodensity surfaces ofF ionospheric region started by morning solar terminator.

Statistical Method of Radio-Echo Sounding Temperate Mountain Glaciers and Portable Equipment for That

Abstract Field experimental data show the possibility of using standard radio-echo sounding equipment of relatively low power to sound through a temperate mountain glacier. The main problem of sounding is the interpretation of echo signals, because they are a mixture of visually indiscernible echoes from the bed and from inhomogeneities in the body of the glacier. To get information about ice thickness and other things from such echo data, a method based on a statistical analysis of echo-signal fluctuations is proposed. As a main criterion the stability of echo-signal statistical characteristics is used. Special portable equipment was designed based on this method. The equipment makes the interpretation of radio-echo sounding data simple. It eliminates distortions of echo signals because of receiver overloading by powerful impulses, automatically records the form and intensity of signals, makes its amplitudes proportional to reflection characteristics of the ice bed and inhomogeneities of the glacier body, and makes automatic statistical analysis. The thickness of a glacier, and the position of inhomogeneities within its body, are determined given more than ten radio-echo signal positions. The method and the equipment have been used to determine thicknesses of Lednik Dzhankuat (Caucasus). Radio-echo sounding data have been compared with data obtained by other geophysical methods and thermal drilling. There is a good agreement (±10 m when the ice thickness is about 100 m).

Statistical Method of Radio-Echo Sounding Temperate Mountain Glaciers and Portable Equipment for That

AbstractField experimental data show the possibility of using standard radio-echo sounding equipment of relatively low power to sound through a temperate mountain glacier. The main problem of sounding is the interpretation of echo signals, because they are a mixture of visually indiscernible echoes from the bed and from inhomogeneities in the body of the glacier. To get information about ice thickness and other things from such echo data, a method based on a statistical analysis of echo-signal fluctuations is proposed. As a main criterion the stability of echo-signal statistical characteristics is used.Special portable equipment was designed based on this method. The equipment makes the interpretation of radio-echo sounding data simple. It eliminates distortions of echo signals because of receiver overloading by powerful impulses, automatically records the form and intensity of signals, makes its amplitudes proportional to reflection characteristics of the ice bed and inhomogeneities of the glacier body, and makes automatic statistical analysis. The thickness of a glacier, and the position of inhomogeneities within its body, are determined given more than ten radio-echo signal positions.The method and the equipment have been used to determine thicknesses of Lednik Dzhankuat (Caucasus). Radio-echo sounding data have been compared with data obtained by other geophysical methods and thermal drilling. There is a good agreement (±10 m when the ice thickness is about 100 m).