Very precise orbits of 1998 Leonid meteors

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2003

Monthly Notices of the Royal Astronomical Society, 2000

We present a detailed activity profile for the 1998 Leonid shower from visual observations. The shower displayed at least two distinct components ± a broad component peaking between 2348 X 4 and 2358 X 0, and two narrower filaments near 2358 X 21 and 2358 X 33 probably of younger origin based on modelling results. This dual-peaked structure in the flux profile has peak fluxes to a limiting magnitude of 16.5 of 0.03 Leonid km 22 h 21 . The distribution of particles also changes dramatically across the stream in 1998, with large meteoroids dominating the early peak and smaller meteoroids relatively more abundant near the time of the nodal passage of the comet. Detailed comparison of the observed activity with models in 1998 shows that the early component comes from material ejected between 500 and 1000 yr ago. Our modelling results suggest that the later dual peaks are caused by high-b meteoroids with large ejection velocities released during the 1932 and 1965 passages of Comet 55P/ Tempel±Tuttle.

Meteoritics & Planetary Science, 2000

Two-station electro-optical observations of the 1998 Leonid shower are presented. Precise heights and light curves were obtained for 79 Leonid meteors that ranged in brightness (at maximum luminosity) from +0.3 to +6.1 astronomical magnitude. The mean photometric mass of the data sample was 1.4 × 10 -6 kg. The dependence of astronomical magnitude at peak luminosity on photometric mass and zenith angle was consistent with earlier studies of faint sporadic meteors. For example, a Leonid meteoroid with a photometric mass of ∼1.0 × 10 -7 kg corresponds to a peak meteor luminosity of about +4.5 astronomical magnitudes. The mean beginning height of the Leonid meteors in this sample was 112.6 km and the mean ending height was 95.3 km. The highest beginning height observed was 144.3 km. There is relatively little dependence of either the first or last heights on mass, which is indicative of meteoroids that have clustered into constituent grains prior to the onset of intensive grain ablation. The height distribution, combined with numerical modelling of the ablation of the meteoroids, suggests that silicate-like materials are not the principal component of Leonid meteoroids and hints at the presence of a more volatile component. Light curves of many Leonid meteors were examined for evidence of the physical structure of the associated meteoroids: similar to the 1997 Leonid meteors, the narrow, nearly symmetric curves imply that the meteoroids are not solid objects. The light curves are consistent with a dustball structure.

2000

In November 1997 a shower of bright Leonid mete- ors was observed from Spain. The visual and photographic mea- surements of the Zenital Hourly Rates (ZHRs) and the respective spatial number densities together with the meteor distribution characteristics indicate the existence of a broad component rich in large grains prior to the perihelion passage of P/Tempel-Tuttle comet. This dust component may be responsible for similar out- bursts in previous appearances. However, the Lunar conditions impeded in 1997 obtaining conclusive evidence of the presence of a component of small meteoroids from more recent ejecta, really responsible for past meteor storms. After comparing 1997 peak data with 1965 data, a very close pattern is detected that supports the presence of future storms.

Monthly Notices of the Royal Astronomical Society, 1998

The activity of the 1996 Leonid shower from two radars, global visual and single-station lowlight-level TV (LLTV) observations is presented and summarized. Radar observations from Ondřejov in the Czech Republic indicate a peak rate of (>+1) Leonids near l ᭪ ¼ 235Њ : 2Ϯ0.1 (Equinox 2000). As observed by this radar, this peak interval was characterized by a significant increase in the number of bright Leonids as demonstrated by a noticeable lowering of the mass index near the peak. From radar observations in Ontario, Canada (using the CLOVAR system), a raw peak flux of 1.3Ϯ0.3×10 ¹2 meteoroid km ¹2 h ¹1 brighter than radio magnitude +7.7 was reached at l ᭪ ¼ 235Њ : 3Ϯ0.1, uncorrected for initial train radius effects. Single-station LLTV observations suggest a peak shower flux of 1.8Ϯ0.4×10 ¹2 meteoroid km ¹2 h ¹1 brighter than absolute magnitude +5Ϯ0.5 between 235Њ : 3 and 235Њ : 39. The position of the radiant on the night of maximum of the shower is found to be a=152Њ : 9Ϯ1Њ : 0 and d=22Њ : 1Ϯ1Њ : 0 from CLOVAR observations and a=153Њ : 3Ϯ1Њ : 7 and d=22Њ : 1Ϯ1Њ : 7 from LLTVobservations. Visual observations of the shower yield a peak zenithal hourly rate (ZHR) of 86Ϯ22 at 235Њ : 17Ϯ0Њ : 07 or an equivalent flux of 1.2Ϯ0.4×10 ¹2 meteoroid km ¹2 h ¹1 brighter than absolute visual magnitude +6.5. The visual peak was short-lived (1.5 Ϯ 0.5 h HWHM) and richer in fainter meteors than neighbouring intervals. Discrepancies in the estimated absolute Leonid flux found using differing methods are noted and possible reasons for the differences discussed. The stream in 1996 showed two distinct meteoroid populations: a population of recently ejected meteoroids rich in smaller particles near 235Њ : 17 which is very narrow in nodal extent (HWHM 0Њ : 07Ϯ0Њ : 02), and an older component (of order 10 revolutions in age) peaking near 235Њ : 4 which is rich in larger stream meteoroids, of long duration (FWHM 1Њ : 2 Ϯ0Њ : 4), which contributed most to the total mass flux at Earth from the stream in 1996.

Monthly Notices of the Royal Astronomical Society, 2001

Monthly Notices of the Royal Astronomical Society, 2000

We report observations of an unpredicted fine structure in the activity profile of the Leonid meteor storm of 1999 November 18. Our observations were obtained at three widely separated sites (on the Iberian peninsula, in Germany, and in northern Sweden) and with two totally different techniques (video cameras and meteor radars). The observations clearly show quasi-periodic variations of the meteor rate with temporal separations of individual maxima in the 6-to 9-min range. These temporal variations translate into spatial variations within the dust trail with scales between 10 000 and 30 000 km, depending in which reference frame or direction one chooses to compare. The times for the central three maxima as observed at the three sites agree within 2 min of each other after application of the appropriate topocentric time corrections. We consider a number of potential causes for the observed density variations within the meteor stream.

Monthly Notices of the Royal Astronomical …, 2002

Meteor activity profiles are reported for the three Leonid storms of 1999 and 2001 and the substorm of 2000. These yield information on the evolution of the shape of cross-sections through Leonid dust trails of known age. Leonid dust trails shed 4 or more revolutions of the parent comet ago, widen rather sudden, compared to the 3 revolutions old dust trail encountered in 1999. Trails shed 4 respectively 7 revolutions ago differ little from each other in width by contrast. It is proposed that the evolution of Leonid dust trail widths is not gradual with age but progresses by a process of ‘punctuated equilibria’, parallel to a similar pattern in the orbital evolution of the parent comet 55P/Tempel–Tuttle. Trails shed 4 to 7 revolutions ago appear to represent an equilibrium phase. The current series of encounters with these trails therefore yield a unique opportunity to investigate the spatial dust density distribution for trails in this age range. Minimum and maximum rate estimates are given for the upcoming 2002 Leonids. The minimum rates possible amount to zenith hourly rates of ∼3000 for the 4-revolution trail encounter and ∼2500 for the 7-revolution trail encounter. Maximum rates possible, but unlikely to be fulfilled, are ∼6500 for the 4-revolution trail and ∼7100 for the 7-revolution trail. We can look forward with confidence to two new Leonid storms in 2002 with rates at least equal to and perhaps above those of 2001.

Publications of the Astronomical Society of Japan, 2012

This paper presents an analysis of records obtained by video equipment of the 2001 Leonid meteor storm. Totally, 3712 meteors, including 22 non-Leonid ones, were recognized from the record of 247 min. The brightness of meteors was measured with the software "LIMovie", and a population index of r = 2.01˙0.05 (8 Ä mag Ä 3) was thus derived. We proposed a way to derive the mass-distribution index, s = 1.82, from only our one-station data. The maximum of the activity appeared at 18 h 25 m UT with an effective peak of ZHR 90 ı 67 ı = 52606 (mag Ä +6.5). There are also compatible sub-peaks and high plateaus beside the main peak. One of them may correspond to the predicted 9-revolution dust trail (ejection in 1699). In this article we treat the cross section of the influx zone as a trapezoid. The peak "influx rate" generated by the 4-revolution dust trail (ejection in 1866) thus derived would be 6.76 10 5 km 2 s 1 (mag Ä +6.5), and the corresponding "spatial number density" would be 9.52 10 7 km 3 (mag Ä +6.5).

Earth, Moon, and Planets, 1995

A procedure of selection of meteoroids from major streams is suggested and applied to the IAU Lund photographic database modified by a check for internal consistency among orbital elements (3411 orbits). Limits for choice of stream members were defined by break points on the plots of the cumulative number N c vs. the Southworth-Hawkins D discriminant. For the break points were considered the points from which the dependence Nc rs. D changes to a quasi-linear one, and with the increasing D, N c changes only moderately. Except for the Tanrids which desire a separate ana.lysis, the N c vs. D diagrams are presented for the foUowing major meteoroid streams: Quadrantids, Lyrids, r/Aquarids, c~ Capricornids, N and S ~ Aquarids, Perseids, Orionids, Leonids and Geminids. The mean orbits, velocities and radiartts of the streams are derived and compared with the osculating orbits of their patent bodies. The limiting DB was found to be a function of the number of the stream members NcB. Omitting the exceptionally concentrated Geminids, the relation is in the form DB -~ 0.058 * In(NcB) -0.04.