[In the wake of controversy over sightings of bright "fireball" objects over much of western North America the night of October 3, this report from Mark Boslough supports a possible, unusual but natural explanation. Then follow two further reports which underscore the unusual characteristics of the purported fireballs. CNI News can neither confirm nor deny the validity of this information. Mark Boslough can be reached by email at mbboslo@sandia.gov.]
There is some evidence for a swarm of particularly bright bolides on the evening of Oct. 3 over North America, several of which generated infrasound signals (see ReVelle report, below). One (in California) exploded at an altitude of about 40 km and generated a sonic boom that was detected by Caltech's seismic array, allowing its time (8:45 pm PDT) and location (near Little Lake) to be precisely determined. Eyewitness reports are consistent with a ENE near-grazing trajectory. An earlier fireball (at 8:01 pm MDT) was observed over New Mexico and the Texas Panhandle, also on an ENE near-grazing trajectory, and videotaped from El Paso, TX. Infrasound instruments detected an event 20 minutes before that over Utah (see below), which may not have been observed from the ground due to cloudcover. Eyewitnesses reported bright fireballs that same evening over Nevada, Indiana, Ohio, and later events in California. Finally, there were unusual high-altitude haze streaks observed earlier in the day near Boston (see Volz report, below). These observations may or may not all be related; the purpose of this summary is simply to report what was seen and detected.
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October 4th Infrasound Summary
Doug ReVelle
Los Alamos National Laboratory
During the period from 0000 Z to 0600 Z on October 4, (the evening of Oct. 3 in the western U.S.) 1996, infrasound arrays operated by Los Alamos National Laboratory detected a number signals whose characteristics were relatively unusual. This behavior included unusually large trace velocity (indicating either a source at large heights or waveguide propagation with returns from the Earth's Thermosphere) and in some cases a source azimuth which was shifting significantly during the detection. Taken together these characteristics indicate a source that is also quite close, i.e., near-field type propagation. In addition to detecting a number of events with these unusual characteristics, we also detected two of the largest of the many fireball sightings that were reported on that night. We detected the entry of the New Mexico fireball at the Los Alamos array with the correct directions, but with no physical time delay between the fireball appearance and the detection of the infrasound (detection at 02:00 Z, or 8:00 pm MDT, Oct. 3). This by itself is very puzzling. We also detected the California fireball of 03:45 Z (or 8:45 pm, PDT) at three arrays (operating in Nevada, Utah and in Wyoming). The azimuth intersections of these three detections converge very near to Little Lake, California, which is also the ground projection of the seismic detections from 31 sensors operating in the Los Angeles area. Prior to the New Mexico fireball, there was an infrasound detection of a moving elevated source at 0140 Z (or 7:40 MDT, Oct. 3) from St. George Utah and also at the array at Pinedale, Wyoming later that night. The bearing and elevation angles are changing rapidly at St. George, but not at Pinedale so the suspicion is that the source is closer to St. George.
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Unusual Haze Streamers Above Cirrus Level Seen Near Boston On October 3, 1996.
by FREDERIC E. VOLZ
24 Tyler Road, Lexington MA 02173
Phone: 617-861-8849, day phn: 617-377-3666
During a period of clear, cold weather, thin haze streaks already visible by noon had developed by 1500 LT to become very long and strange, especially near the northern horizon. Having worked formerly in atmospheric optics, I am always looking for such events. Observations happened to be made at a playfield in in western Lexington and access to a high roof provided a mostly free horizon. The rather broad streamers converged to the WSW to a knotty, fibrous structure of considerable density, but lacked horizontal layering usually associated with tropospheric and stratospheric (volcanic) haze. Isolated patches could be seen between the sun and the horizon, but I missed the opportunity to determine their drift direction. The upper edge of cirrus in the far North was banded, too, but structure and direction of the bands was clearly different from those of the streamers. The cirrus also was at a lower altitude, as were a few short contrails and small patches of lenticular clouds in other parts of the sky. Photos by automatic exposure show the broad streamers farther from the sun, but the more interesting regions near the sun were overexposed. The haze streamers faded in the eastern direction, but the lower horizon was hidden by trees.
By about 1630 LT, the last traces seemed to disappear in the WSW. However, these must have been the last patches arriving from that direction. According to the evening sounding at Brookhaven on Long Island, the wind, about 20 km/hour from about 250 deg, was steady up to the top of the sounding at 16 km. There was a strong inversion at about 7 km, probably related to the lenticular clouds. In mostly clear skies, no haze streaks were seen in the days following the event.
The streamers seemed to have had no relation to condensation or icing processes but rather looked like sheets of poorly dispersed dust, which possibly was still in the process of turbulent mixing as indicated by the contorted fibers.
There has been some recent volcanic activity. At Soufriere Hills, Montserrat, West Indies, some moderate ash eruptions occurred from 11 to 22 August, but only those on the 12th reached 10 km. On Iceland, an eruption in the morning hours of October 3 also went to about 10 km, but that haze could not have arrived within a few hours. Also, meteor events over Texas and California in the evening of the same day, widely reported in the media occurred several hours after my sighting. However, more meteor sightings in the same night have been reported. In view of these events, and the possibility that meteors also arrived at earlier times, I should like to add that my streamers could well have been much higher than the tropopause. However, the smoke trail at about 60 km of the daytime meteor of August 10, 1972, starting as a very bright narrow line, only lasted about 90 minutes when it looked like a "diffused single-jet contrail", but apparently was not much distorted (Sky and Telescope, Oct.1972, 269-272). On this basis, and the probably bigger size of the 1972 meteor, my streamers are expected to have had 1.) several sources (as from a split meteor); 2.) probably much more total smoke mass, and 3.) been in a much more turbulent environment. Trails of micrometeorites, or shooting stars, usually become strongly distorted within their liftime of about 60 seconds.
FREDERIC E. VOLZ Telephone 617 861 8849, daytime 617 377 3666.
Original file name: CNI - Bolides Oct 3?
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