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Lunar Leonids: 
Encounters of the Moon with Leonid dust trails
Robert H. McNaught, Siding Spring Observatory
Last update 2000/10/27

The following table lists all encounters of the Moon with dust trails
within 0.0010 AU during the current epoch.  Only the trails discussed
in ref [1] are considered.  The calculations are based on the formulae
given in [2].  In every year, a test date was used to derive the
approximate magnitude of the Moon's distance towards (-ve) or away
from (+ve) the Sun in relation to the Earth (rE-rM).  This was
then directly compared with values for dust trail encounters with
the Earth given in [1] and close approaches were further investigated.

An iterative process is necessary, as the motion of the Moon during
the tens of minutes between Earth and Moon encounters with dust trails
must be taken into account.

The resulting time correction (dt) from the Earth encounter time in [1]
is given along with the distance of the nominal trail center from the
Moon (rM-rD).

Finally, an approximate ZHR indicates the relative activity of these
encounters.  This is derived using the same form of analysis as in [1]
and can be compared with the predicted values for the Earth [3].  It
seems clear that 1999 was the year for lunar Leonids but the years
2000 and 2001 could have some substantial activity.

It is notable that several of these encounters are unlikely to produce
meteor showers on the Earth, but as the Earth-Moon system is passing
through the midst of the comet 55P/Temple-Tuttle dust trail complex in
2000 and 2001, several encounters occur in each year for both the Earth
and Moon.

The circumstance of resonant Leonids striking the Moon in 1998 may require
further examination.  The 1333 trail is at a distance rE-rM = +0.0026 AU,
so it may not have been the culprit of the enchanced sodium tail.  However,
another resonant trail may have passed closer to the Moon and I've asked
David Asher about this.  David has noted that these old resonant trails are
broader than the young trails, so perhaps this greater miss distance is less
relevant.  It is also the case that the greater mass of the particles in
these resonant trails could result in substantially more mass impacting the
Moon in 1998 despite this greater miss distance than the probable lunar
Leonid storm in 1999.

                  re-rm            rm-rd    dt   Time of
                    AU    trails     AU     min  lunar max.        "ZHR"
1997 Nov. 18.0   -0.0018   none

1998 Nov. 17.013 +0.0025   none
                         (20-rev  +0.0026   -31)
1999 Nov. 18.089 -0.0009   3-rev  +0.0002  +163  Nov. 18 04:51 UT  50,000

2000 Nov. 17.327 -0.0006   2-rev  -0.0006  -175  Nov. 17 04:58 UT   1,000
          18.156 -0.0002   8-rev  +0.0010  -172       18 03:52 UT      10
          18.327 -0.0001   4-rev  +0.0009  -170       18 05:01 UT      50

2001 Nov. 17.595 +0.0022   1-rev   0.0000  +106  Nov. 17 16:03 UT     500
          18.505 +0.0020   6-rev  -0.0006  +128       18 14:16 UT   1,000
          18.595 +0.0020   5-rev  -0.0003  +130       18 16:28 UT   5,000

2002 Nov. 19.44  -0.0027   none

2003 Nov. 18.1   +0.0006   none

2004 Nov. 19.0   +0.0002   none

2005 Nov. 19.0   -0.0021   none

2006 Nov. 19.2   +0.0025   none

[1] R.H. McNaught, D.J. Asher, "Leonid dust trails and meteor storms",
    WGN 27, 1999, pp. 85-102.
[2] R.H. McNaught, D.J. Asher, "Variation of Leonid maximum times with
    location of observer", Meteorit. Planet. Sci. 34, 1999, pp. 975-978
[3] D.J. Asher, R.H. McNaught, "Expectations for the 2000 Leonids",
    WGN 28, 2000, pp. 134-139