EDP Sciences
Free access
Volume 365, Number 3, January III 2001
Page(s) 622 - 626
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20000151

A&A 365, 622-626 (2001)
DOI: 10.1051/0004-6361:20000151

Radar observation of the Leonids in 1998 and 1999

M. Simek and P. Pecina

Astronomical Institute of the Academy of Sciences of the Czech Republic, 251 65 Ondrejov, Czech Republic

(Received 26 June 2000 / Accepted 22 October 2000)

Results of Ondrejov radar observations of Leo nid meteor shower in 1998 and 1999 are presented. It was found that while the activity in 1998 was dominated by the long-duration echoes resulting in a low mass distribution index averaged over an interval 23 h UT November 16 to 12 h UT November 17 as $s = 1.23 \pm 0.02$ with the peak at $L_{\odot}
= 234\hbox{$.\!\!^\circ$ }633 \pm 0\hbox{$.\!\!^\circ$ }004$. The 1999 activity culminated at $L_{\odot}
= 235\hbox{$.\!\!^\circ$ }285 \pm 0\hbox{$.\!\!^\circ$ }002$ and was mainly due to prevailing of fainter echoes yielding a mean mass distribution index $s = 1.58 \pm 0.05$ between 23 h UT November 17 8 h UT November 18. The activity pattern in 1998 showed a multiple peak structure while the corresponding 1999 pattern showed only one distinct peak. The 1998 activity rates were lower than those in 1999 by the ratio of 2.8. Our observations indicate that the main outburst of this Leonid return occurred in 1999. The 1998 activity is characterized by a large scatter of observed hourly echo counts while the ones in 1999 possessed only one sharp maximum. The flux curve in 1998 shows multiple peak character while in 1999 the activity patterns of echoes with duration in excess of 0.4 s even though their peaks do not coincide generally with the activity maxima. The 1998 flux reached 3.34 10-12 m-2 s-1 for a limiting mass of m0= 10-5 kg while for 1999 it was determined as 37.41 10-12 m-2 s-1.

Key words: comets: individual: 55P/Tempel-Tut tle -- Leonids -- me te ors, me te or oids

Offprint request: P. Pecina, ppecina@asu.cas.cz

© ESO 2001

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