Calculation of the trail in which the appearance of Draconids (Giacobinids) originates in 1998 and 1999

Mikiya Sato (FAS - Fuchu Astronomical Society)

[Outline]

In Japan, the large appearance [HR=50-100] of Draconids was observed in 1998, and the outbreak appearance [HR=20-30] of it was observed in 1999.
I examined the trail of the reason of these appearances.

[Outline calculation]

I calculated the outline about the trail from the Comet 21P/Giacobini-Zinner using Excel.
The released speed was assumed to be -30 to +30 m/s.


fig.1 The distribution of a trail.

A trail is is complicated the reason of greatly influenced of Jupiter (Fig.1).
Some trails have passed through near an earth orbit in 1998.

[Accurate calculation in 1998]

In outline calculation, some trails which pass error within the limits were seen.
I calculated with still more sufficient accuracy about these trails using the NIPE which is a calculation program of perturbation.

Table.1 The precise calculation result of a trail in 1998.

Released
year		Released
speed		PositionDateTime
(UT)		Ls.
(2000.0)		Distance
(AU)
1907+6.0m/sDescending node.
Minimum point.		Oct. 8
Oct. 8		16h15m
12h20m		195.202
195.045		+0.0135
+0.0134
1913+6.7m/sDescending node.
Minimum point.		Oct. 8
Oct. 8		15h22m
12h20m		195.166
195.045		+0.0108
+0.0107
1920+8.2m/sDescending node.
Minimum point.		Oct. 8
Oct. 8		14h34m
12h25m		195.133
195.049		+0.0066
+0.0066
1926+10.8m/sDescending node.
Minimum point.		Oct. 8
Oct. 8		13h33m
13h25m		195.091
195.090		+0.0004
+0.0004
1933+15.4m/sDescending node.
Minimum point.		Oct. 8
Oct. 8		11h56m
14h35m		195.025
195.138		-0.0094
-0.0094


Fig.2@The position of trails in 1998.

According to the calculation result, The trail which approaches the earth most was a trail of the 1926 origin.
It was that the earth passed descending node of this trail at 13:33(UT) and was minimum point around 13:25(UT) on October 8. Approach distance was +0.0004 AU. This distance was smaller than the calculation error (about 0.001 AU).
The peak from the observation result in 1998 was around 13:10(UT), the difference was in agreement with dozens of minutes.

[Accurate calculation in 1999]

The trail which is likely to approach about 1999 was only the thing of the 1894 discharge. However, about this, the position of descending node did not suit actual observation.
Although it was outside the calculation range as a result of uniting and examining the position of descending node, it became clear that it is likely to approach, when speed was enlarged and was made to emit further from 1959 and 1966.

Table.2 The precise calculation result of a trail in 1999.

Released
year		Released
speed		PositionDateTime
(UT)		Ls.
(2000.0)		Distance
(AU)
1959+60.0m/sDescending node.
Minimum point.		10/9
10/9		10h48m
11h25m		195.712
195.740		-0.0027
-0.0026
1966+69.5m/sDescending node.
Minimum point.		10/9
10/9		11h57m
12h25m		195.760
195.782		-0.0015
-0.0015


Fig.3@The position of trails in 1999.

According to the calculation result, approaching to 0.001 to 0.003 AU was proved that they are both these two trails. However, the released speed is over +60 m/s, and the dust is likely to be distributed by low density.
The peak from the observation result in 1999 was around 11:00(UT) on October 9, the hourly rate(HR) was about 20 to 30. The approach time with the trail from 1959 was in agreement with the error of dozens of minutes.
And, the hourly rate(HR) was about 5 to 10 around 12:00(UT) , a possibility that this originates in the trail from 1966 is also considered.

In addition, the influence of radiation pressure is not included in these calculation. If calculation is further advanced including this influence, the still better result will be drawn.

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