摘要:

It has been suggested that a non‐linear, multi‐channel summation process increases the signal‐to‐noise ratio of small coherent signals. Using the data base of the International Seismic Month, it is shown conclusively that a logarithmic beamforming process increases the detection probability for seismic events for a specified false alarm rate by at least a factor of two. A detector based on this process is working on‐line at the Yellowknife seis

ISSN:0094-8276    

DOI:10.1029/GL002i004p00121

年代:1975

数据来源: WILEY

摘要:

The September 5, 1970 Sea of Okhotsk earthquake consisted of two possibly causally related but dissimilar events: a small (Mag 4.5) event at the hypocenter given by the International Seismologic Centre (52.28 N, 151.49 E, 560 km) followed 5.16±.06 seconds later by a larger (Mag 5.7) event almost at the same epicenter but 23.0±1 km deeper. The fault planes and the principal stress axes of the two events are significantly different; furthermore, the second event does not lie on either of the nodal planes of the first event. We interpret this as a possible triggering of the second event by the smaller first event and not as a change in direction of rupture propagation during a single continuous faulting episod

ISSN:0094-8276    

DOI:10.1029/GL002i004p00124

年代:1975

数据来源: WILEY

摘要:

Internal waves on the continental shelf off New York have been observed from ship and the ERTS‐1 spacecraft, and positive correlations made between surface and subsurface measurements of temperature, acoustic volume reflectivity, and surface slicks. The spacecraft imagery senses the quasi‐periodic variations in surface optical reflectivity induced by the internal waves. The waves appear to be tidally generated at the shelf edge and occur intermittently in packets, which propagate shoreward and disappear in water near 50‐m

ISSN:0094-8276    

DOI:10.1029/GL002i004p00128

年代:1975

数据来源: WILEY

摘要:

The environmental satellites NOAA‐2 and ERTS‐1 observed flooding in United States' rivers such as the Mississippi during 1973. Combination of NOAA‐2 observation frequency and the ERTS‐1 resolution provides an adequate satellite system for monitoring floods. Several polar‐orbiting satellites of the ERTS type could view flooded areas at a reasonably high resolution every three to five days. A high‐resolution Earth‐synchronous satellite would further enhance flood mapping by providing observations whenever clou

ISSN:0094-8276    

DOI:10.1029/GL002i004p00132

年代:1975

数据来源: WILEY

摘要:

Utilizing the daily analyzed zonal and meridional wind components at 200 mb for the year 1970 (available from the tropical analysis program of the National Meteorological Center) daily estimates of the meridional eddy momentum transfer have been computed at 33, 29, 24, 20, 15, 10, 5 and 0°N. The momentum transfers were then subjected to conventional spectrum analysis and the results indicate a coherent relationship from 33N into the subtropics at 14–16 and 4.35 days. This suggests a form of mid‐latitude tropical interaction that should be considered in investigation of tropical variations at these per

ISSN:0094-8276    

DOI:10.1029/GL002i004p00136

年代:1975

数据来源: WILEY

摘要:

A transparent whitish cloud veil was observed over Hawaii from early October throughout January 2, 1975, the date of submission of this paper. Lidar measurements made from the Mauna Loa Observatory during this period established the height of the layer at about 19.5 km MSL with a typical thickness at half maximum of 800 meters. The nearest Rawinsonde data clearly indicated this height to be above the tropopause. During the month of November, a stratospheric layer was observed by several other workers in the United States which has been attributed to the eruption of Fuego volcano in Guatemala during the month of October. However, the backscatter coefficient observed in the layer over Hawaii was occasionally 20 times greater than that observed at other locations. Although our data support the volcanic hypothesis, there are still some unanswered questions. For example, we observed the layer prior to the major eruption period and the time of appearance of the layer over other observatories in the United States. Furthermore, high altitude aircraft were operating in the stratosphere over Hawaii during the first two weeks of October which may have influenced the cloud formation.

ISSN:0094-8276    

DOI:10.1029/GL002i004p00139

年代:1975

数据来源: WILEY

摘要:

During geomagnetic disturbed periods, the q type of sporadic E layer near the dip equator is shown to disappear with maximum error of five minutes during the period when the difference of the geomagnetic H field between the equatorial and non‐equatorial station decreases below the night level. These periods are identified with the reversal to westward direction of the electrojet currents at the base of the E region around 100 km level irrespective of the changes in the Sqcurrent system which might be produced by the disturbanc

ISSN:0094-8276    

DOI:10.1029/GL002i004p00142

年代:1975

数据来源: WILEY

摘要:

Initial results are presented from an experiment to generate artificial ultra‐low‐frequency (ULF) hydromagnetic waves in the magnetosphere and ionosphere by means of specially modulated very‐low‐frequency (VLF) transmissions into the magnetosphere. The data were obtained predominantly during the interval September 1–7, 1973, when frequency‐shift‐keyed (FSK) VLF transmissions were made from Siple Station, Antarctica, and simultaneous VLF and ULF recordings were made at the conjugate point (Roberval, Quebec). The same 8‐hour transmission schedule was followed each day; it consisted primarily of intervals of FSK transmission (pulse lengths in the range 200 msec to 3.2 sec) interspersed with intervals of no transmission. All ULF pulsations with frequencies in the Pc 1 range (0.2 to 5 Hz) that occurred during the experiment started in an interval of FSK transmission and the average rate of occurrence of the ULF activity was about twice the rate observed on days with n

ISSN:0094-8276    

DOI:10.1029/GL002i004p00146

年代:1975

数据来源: WILEY

摘要:

Strong electron precipitation fluxes are frequently accompanied by strong downward heat conduction fluxes, deduced from simultaneous high and low altitude electron temperature measurements. It is shown that the heat input due to beam‐plasma interactions is of the correct order of magnitude to sustain the observed heat flu

ISSN:0094-8276    

DOI:10.1029/GL002i004p00150

年代:1975

数据来源: WILEY

摘要:

The question of possible energy dissipation that might be associated with the dayside magnetopause current requires consideration of the tangential component of the electric field. If the total current of 9 × 106amperes flowed through the average magnetospheric dawn‐dusk potential difference of 6 × 104volts the power dissipation would be 5 × 1011watts. We might expect this energy to be carried away by energized particles, perhaps as increased thermal or flow energy at or near the magnetopause boundary layer or mantle. Satellite observations are available, but they do not provide evidence of such energization. This failure leads us to conclude that the magnetopause current does not flow through the magnetospheric potential difference, and that the magnetopause is approximately an equipotential surface. Because of the necessary continuity of the tangential component of the electric field, this conclusion implies that there is no steady state electric field along the neutral or X‐line that must be located near the dayside magnetopause in an open magnetospheric model (which is clearly supported by other evidence). Such an electric field is an essential part of the theory of merging or reconnection of magnetic field lines, and it is therefore concluded that the merging model for the electric field is not correct. This conclusion could be avoided if some evidence for the implied energy dissipation were

ISSN:0094-8276    

DOI:10.1029/GL002i004p00154

年代:1975

数据来源: WILEY