(meteorobs) What caused Draconids 2012 outburst?

[Mikhail Maslov]

Hello,

After the strong outburst of Draconids 2012 it was wide announced that
it is 1959 trail of the comet 21P which is responsible for what
happened. However, this explanation was confusing me a bit as this
trail contains a large hole (caused by previous encounter with the
Earth) in its part, encountered the Earth in 2012. Meanwhile the 1966
trail is unperturbed but its distance to the Earth as well as maximum
time are not so good considering the real peak time detected by CMOR.
But this is particles ejected exactly at the moment of perihelion.
However the comet is active quite a long time around its perihelion,
for many months. So far I decided if the particles ejected before and
after the perihelion could come to the Earth closer. I've made some
computations and got the following results:

particles ejected at perihelion
trail  rD_rE,AU  Vej,m/s  f_M(fMD)  S.l.,°   Max. time, UT
1966    0.00416   43.20   3.636    195.580 08.10.2012 15:37
                                                
particles ejected 60 days before perihelion
trail  rD_rE,AU  Vej,m/s  f_M(fMD)  S.l.,°   Max. time, UT
1966    0.00287   80.60   6.759    195.595 08.10.2012 15:59

particles ejected 90 days before perihelion
trail  rD_rE,AU  Vej,m/s  f_M(fMD)  S.l.,°   Max. time, UT
1966   -0.00156  145.90  11.830    195.650 08.10.2012 17:20

We can see, that the farther the particles were ejected before the
perihelion, the higher is ejection velocity of their particles
encountering the Earth. Also the density of them increases (computed
density, not considering lower comet activity during this period), and
the maximum time shifts closer to the peak detected by CMOR.
Finally,  we can see that particles ejected 60 and 90 day before
perihelion pass outside and inside the Earth's orbit, respectively
(the first ones have positive rD-rE value and the second ones -
negative). It means that some particles ejected somewhere between 90
and 60 day before 21P perihelion in 1966 come very close to the Earth.
I computed particles evelution one more time - for those of them
ejected 80 days before perihelion and got almost ideal encounter
(rD-rE close to 0):

particles ejected 80 days before perihelion
trail  rD_rE,AU  Vej,m/s  f_M(fMD)  S.l.,°   Max. time, UT
1966    0.00056    117.40  9.666   195.624 08.10.2012 16:41

And maximum time also coincides with maximum detected by CMOR almost
ideally. The pic for comparison can be found here:
http://fireballs.ndc.nasa.gov/special/DRA_2012/Draconids_2012.png

Very high ejection velocity and very high trail density are also in
good accordance with a strong radiostorm observed by the Canadian radar. So I
suppose it gives substantial reasons to claim that the Draconids 2012
outburst was caused not by 1959 trail, but by 1966 trail, namely its
particles ejected ~80 days before the comet 21 periheion in 1966.

Best regards,
Mikhail Maslov