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(meteorobs) Interaction with Leonid dust trails in 1971?



    Gary Kronk was kind enough to go through some of the references that he 
used in compiling his 1988 Meteor Showers book, scanning them and e-mailing 
them directly to me.  Of particular interest was a short paper printed in Solar 
System Research, 10 (1976): "Structure and Relative Activity of Radiants of 
Leonids in 1971" by N.M. Kremneva, V.V. Martynenko, and N.V. Smirnov.

    Observations of the Leonids were carried out between November 15 and 19, 
1971 in Sudak and Simferopol by N.V. Smirnov, S.N. Yu, V. Lyzhin and others.  

    According to their observations, it appears that there were two peaks of 
activity.  To quote from the paper:  "The maximum activity of the Leonids in 
1971 probably occurred in the interval 00h40m - 02h00mUT on November 17 
(longitudinal zone 234 deg. 02').  During this time more than 30 meteors brighter 
than 1m were observed."

    "The hourly number of Leonids for zenith magnitudes, including the 
correction for the zenith distance of the radiant for the nights of November 16-17 
and 18-19 (on November 17-18 the cloudiness was 100%), are given in Table 3."

    What is interesting is that observations on the first night (November 
16-17), made between 23:00 and 01:50 UT, gave a ZHR of 170.  

    On the second night (November 18-19), observations made between 22:00 and 
01:00 UT gave a ZHR of 145.  

    The night of November 16-17 also saw brighter Leonids (referred to as 
flights of bright meteor "packs") as compared to the night of November 18-19.

    So the question is, could this activity be attributable to Earth's 
interaction with one or possibly two hitherto unknown dust trails?  

    A check of Sky & Telescope (January 1972, pages 57-58) did not reveal 
anything out of the ordinary, at least over North America.  The short article 
indicates that the 1971 Leonids were expected to peak during the daylight hours, 
and counts that were reported to S&T on the mornings of the 17th and 18th were 
low.  "However, a number of bright fireballs were seen which is typical for 
this shower."  The highest counts came from two observers watching from Newton, 
North Carolina on the morning of the 17th.  Between 10:00 and 11:00 UT they 
made independent hourly counts, the average of which was listed at 27. Other 
observers from around the country generally saw 10 to 20 per hour on the morning 
of the 17th.

    What the Soviets reported, however, was a significantly stronger display 
about 10-11 hours earlier . . . and another strong surge of activity two 
mornings later.

    This unusual bevy of Leonids was also briefly cited in the IMOs "Handbook 
For Visual Meteor Observations" edited by Paul Roggemans (1989 Sky Publishing 
Corp.).  On page 163, for 1971 November 17, an hourly rate of 90 is 
attributed to "USSR Smirnov."

-- joe rao


  

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