Visual Observations Of The Leonid Meteors 1998 In Yunnan

The 1998 Leonid meteor shower was observed at the Gaomeigu station of Yunnan Observatory during five successive days in November. The visual records indicate that the number of meteors increased suddenly, from a ZHR of about 140 to over 400, in the early morning of November 17th, Beijing time. But it decreased slowly in the following two days. During the maximum there was a high proportion – about 10 percent – of very bright fireballs with enduring trains. The brightest one was about -10 magnitude with a smoke train fading about three minutes after. This revised version was published online in July 2006 with corrections to the Cover Date.     

Updates to the MSFC Meteoroid Stream Model

The Marshall Space Flight Center (MSFC) Meteoroid Stream Model simulates particle ejection and subsequent evolution from comets in order to provide meteor shower forecasts to spacecraft operators for hazard mitigation and planning purposes. The model, previously detailed in Moser and Cooke (Earth Moon Planets 95, 141 (2004)), has recently been updated; the changes include the implementation of the RADAU integrator, an improved planetary treatment, and the inclusion of general relativistic effects in the force function. The results of these updates are investigated with respect to various meteoroid streams and the outcome presented.     

Video Observations Of Leonids 1999

We analyse data obtained by different ground-based video camera systems during the 1999 Leonid meteor storm. We observe similar activity profiles at nearby observing sites, but significant differences over distances in the order of 4,000 km. The main peak occured at 02:03 UT (λ_⊙=235.286, J2000, corrected for the time of the topocentric stream encounter). At the Iberian peninsula quasi-periodic activity fluctuations with a period of about 7 min were recorded. The camera in Jordan detected a broad plateau of activity at 01:39–01:53 UT, but no periodic variations. The Leonid brightness distribution derived from all cameras shows a lack of faint meteors with a turning point close to +3^m, which corresponds to meteoroids of approximately 10^-3 g. We find a pin-point radiant at αalpha=153.65 ±0.1, δ=21.80 ±0. (λ_⊙=235.290). The radiant positionis identical before and after the storm, and also during the storm no driftis observed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Natural Variations in Comet-Aggregate Meteoroid Compositions

Bulk compositions of aggregate meteoroids made of the originally accreted dust with its highly varied in mineral content and chemistry and considerable grain size variations do not have a chondritic bulk composition. Deviations from CI element abundances reflect indigenous variations within and among comet nuclei. These unmodified meteoroids that are heterogeneous in all their properties are fundamentally different from meteoroids with a CI bulk composition that are fine-grained, equigranular materials and chemically and mineralogically homogeneous. Collection and data reduction bias exists but the compositions of individual fast meteors are entirely constrained by the measured main component meteor abundances.     

Activity of the Leonid meteor shower in the years 1944–1953

The activity of the Leonid shower in the years 1944–1953 was derived from visual records obtained at the Skalnaté Pleso Observatory, using the zenithal exponent = 1.47 in the reduction factor cos z _R.     

Analysis of historical meteor and meteor shower records: Korea, China, and Japan

We have compiled and analyzed historical Korean meteor and meteor shower records in three Korean official history books, Samguksagi which covers the three Kingdoms period (57 B.C.-A.D. 935), Goryeosa of Goryeo dynasty (A.D. 918-1392), and Joseonwangjosillok of Joseon dynasty (A.D. 1392-1910). We have found 3861 meteor and 31 meteor shower records. We have confirmed the peaks of Perseids and an excess due to the mixture of Orionids, north-Taurids, or Leonids through the Monte Carlo test. The peaks persist from the period of Goryeo dynasty to that of Joseon dynasty, for almost one thousand years. Korean records show a decrease of Perseids activity and an increase of Orionids/north-Taurids/Leonids activity. We have also analyzed seasonal variation of sporadic meteors from Korean records. We confirm the seasonal variation of sporadic meteors from the records of Joseon dynasty with the maximum number of events being roughly 1.7 times the minimum. The Korean records are compared with Chinese and Japanese records for the same periods. Major features in Chinese meteor shower records are quite consistent with those of Korean records, particularly for the last millennium. Japanese records also show Perseids feature and Orionids/north-Taurids/Leonids feature, although they are less prominent compared to those of Korean or Chinese records.     

MSFC Stream Model Preliminary Results: Modeling Recent Leonid and Perseid Encounters

The cometary meteoroid ejection model of Jones and Brown [Physics, Chemistry, and Dynamics of Interplanetary Dust, ASP Conference Series 104 (1996b) 137] was used to simulate ejection from comets 55P/Tempel-Tuttle during the last 12 revolutions, and the last 9 apparitions of 109P/Swift-Tuttle. Using cometary ephemerides generated by the Jet Propulsion Laboratory’s (JPL) HORIZONS Solar System Data and Ephemeris Computation Service, two independent ejection schemes were simulated. In the first case, ejection was simulated in 1 h time steps along the comet’s orbit while it was within 2.5 AU of the Sun. In the second case, ejection was simulated to occur at the hour the comet reached perihelion. A 4th order variable step-size Runge–Kutta integrator was then used to integrate meteoroid position and velocity forward in time, accounting for the effects of radiation pressure, Poynting–Robertson drag, and the gravitational forces of the planets, which were computed using JPL’s DE406 planetary ephemerides. An impact parameter (IP) was computed for each particle approaching the Earth to create a flux profile, and the results compared to observations of the 1998 and 1999 Leonid showers, and the 1993 and 2004 Perseids.     

Radar Observations of Leonid Meteor Shower 2003

Observations carried out during Leonid meteor shower 2003, by using Indian MST radar (13.46^N, 79.18^E; dip 12.5^N) are used to determine the number density of meteoroids through the cross section of the meteor streams. Cross sections are calculated for a number of classes of echo duration (particle size). They are also used to determine the relative flux of the shower in particle size ranges producing radar meteor echoes having durations <0.4 s, 0.4–1 s and >1 s. Mean activity profiles along the Earth's passage through the stream show a systematic change of the peak activity and the width of the stream depending on the distribution of echo durations across the stream. The patterns of mass distribution index s are presented and discussed.