Acoustic observations of suspended participate matter in the ocean
CLOUDS of suspended particulate matter in the ocean have been observed by satellite1, sensed by nephelometers2, and sampled by water bottles. We present here evidence that it may be possible to observe oceanic suspended particulate matter acoustically. The particulate matter discussed is thought to have arisen from a dredging operation. It is also thought that the suspended matter is present at lower concentrations than any in any other case recorded acoustically3. Certain questions, as yet unresolved, regarding acoustic scattering strengths are also discussed.
Acoustic imaging of the New England shelf-slope water mass interfaces
PULSED high frequency acoustics has been shown to have unique applications in the detection and measurement of oceanic phenomena such as internal waves1–3 and dispersion of ocean-dumped sewage sludge4,5 or dredge material6. With moderate to high pulse repetition rates, a virtually continuous record of water column scattering strength is available to depths of the order of 500 m from a ship travelling at speeds of 4 or 5 knots. We used this feature to detect acoustically the interfaces associated with an intrusion of cold New England shelf water into the warmer slope water during a 9-d period in June 1976.
Atmospheric drag effects on the KOMPSAT-1 satellite during geomagnetic superstorms
We examine the atmospheric drag on the low earth-orbiting satellite, KOMPSAT-1 in a sun-synchronous orbit at ~685-km altitude starting in 1999, during a 3-month (October-December) period in 2003. This 3-month interval includes the October 29-30 and November 20 magnetic superstorms and weak to moderate storms. We observed that the daily KOMPSAT-1 drag acceleration transiently responses to transient storm-time disturbances. That is, there is an one-to-one correspondence between the KOMPSAT-1 drag accelerations and the storm events. We find that the drag acceleration correlates strongly with the level of geomagnetic disturbance. This indicates that the trajectory of KOMPSAT-1 is significantly perturbed during extremely disturbed intervals because of atmospheric density increase. The main contributor to the density increase is Joule heating associated with the geomagnetic activity rather than the solar EUV radiation, as reported by previous studies. We suggest that understanding how the upper atmosphere responses to the geomagnetic-associated heating is important to predict space weather impacts on low earth-orbiting satellites.