Learmonth Observations - 1999 Leonid Meteor Storm

The following are observations of the 1999 Leonid Meteor storm made from the Learmonth Solar Observatory in Western Australia.

The computed Zenithly Hourly Rates (ZHR) below have been supplied with a standard deviation estimate based upon a Poisson distribution.

15 November 1999
 
  1900-2000 UT
    Visual Observations
        Raw counts:
                Leonids = 4             Sporadic = 7
        Leonid ZHR: 8 +/- 4
    
16 November 1999

  1900-2000 UT
    Visual Observations
        Raw counts:
                Leonids = 2             Sporadic = 15
        Leonid ZHR:  4 +/- 3

17 November 1999

  1900-2000 UT
    Visual Observations
        Raw counts:
                Leonids = 8             Sporadic = 13
        Leonid ZHR:  17 +/- 6

18 November 1999

  1900-2000 UT
    Visual Observations
        Raw counts:
                Leonids = 34            Sporadic = 21
        Leonid ZHR: 70 +/- 12

Summary

The histogram below shows the Leonid Zenithal Hourly Rate from 15 to 18 November 1999 for visual observations between 1900-2000 UT each day.

            Leonid Zenithal Hourly Rate  (1900-2000 UT)
   Date     0    10   20   30   40   50   60   70   80
            I----I----I----I----I----I----I----I----I
            I
   Nov 15   IXXXX
   Nov 16   IXX
   Nov 17   IXXXXXXXXX
   Nov 18   IXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
            I

The histogram below shows the sporadic meteor hourly rate from 15 to 18 November 1999 for visual observations between 1900-2000 UT each day.

              Sporadic Meteor Hourly Rate  (1900-2000 UT)
   Date       0    5    10   15   20   25   30
              I----I----I----I----I----I----I
              I
   Nov 15     IXXXXXXX
   Nov 16     IXXXXXXXXXXXXXXX
   Nov 17     IXXXXXXXXXXXXX
   Nov 18     IXXXXXXXXXXXXXXXXXXXXX
              I

Comments

For the first three days of observations at Learmonth, the Leonid shower produced significantly fewer meteors than seen over the last four years. The meteors were in general fainter and less likely to produce trains - a feature common with Leonids in 1997 and 1998. However on the 18th the count was much higher with an approximate zenithal hourly rate of 70. However, even at this higher rate the Leonids were still in general fainter, and shorter in length than in 1998. No fireballs (mag < -4) were observed and just under 50% of the observed leonids had trains, all trains lasting only a short time (typically < 2 seconds). It appears that the increase we observed at 18/1900-2000 UT was associated with a secondary peak following the very short duration storm which peaked at a ZHR of 5400 near 18/0200 UT. This peak was observed over Europe. An anomalously high number of sporadic meteors (21) was observed on the 18th. None of these had any noticeable shower association.

Material prepared by John Kennewell (thanks to Alex Liu for great support)