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(meteorobs) Re: Oct. 3/4 bolide swarm?



This is from sci.astro.....thought we might find it interesting
Wayne

In article <32B61596.53F1@sandiadot gov> Mark Boslough <mbboslo@sandiadot gov> 
writes:>From: Mark Boslough <mbboslo@sandiadot gov>
>Subject: Oct. 3/4 bolide swarm?
>Date: Mon, 16 Dec 1996 20:37:58 -0700

>October 3/4 Bolide Swarm?
>                         Mark Boslough, SNL

>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.


>=====================================================================

>                  October 4th Infrasound Summary
>                        Doug ReVelle, LANL


>      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.

>=====================================================================

>         Unusual Haze Streamers Above Cirrus Level Seen 
>                 Near Boston On October 3, 1996.

>                        FREDERIC E. VOLZ
>               24 Tyler Road, Lexington MA 02173

>  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.

>====================================================================