Meteor Path Research Articles

The Spectrum and Orbit of a Fireball Producing Mesospheric Irregularity and Implications for Meteor Mass Deposition

The physical properties of meteoroids producing meteor plasma non-field-aligned irregularities (NFAI) in the Earth’s atmosphere are poorly known. Here we report a complete picture of a fireball and mesospheric NFAI that it produced for the first time. Simultaneous radar and optical observations were made by the recently completed facility, Meteor and ionospheric Irregularity Observation System. The observations show that the mesospheric NFAI were clustered into three patches where the optical meteor flares took place, instead of being generated continuously along the whole meteor path. It is very likely that nanometer-or-larger-sized dust particles could be directly generated via meteoroid fragmentation at the flaring points and thus promote the generation of NFAI patches. The properties of the parent meteoroid show a chondrite type and a Jupiter family comet orbit, with Na/Mg and Fe/Mg intensity ratios of 1.5 and 1, respectively, photometric mass of about 4 g, and fragmentation strengths of around 10–74 kPa. The results suggest that the direct generation of dust particles, which was previously observed in the atmospheric disintegration of a kiloton-scale meteoroid, could be extended to the much smaller gram-scale meteoroids. Since meteoroids having such characteristics or more fragile material are not unusual, further studies leading to a better understanding of meteor mass deposition in the upper atmosphere, which consider the dust particles directly generated via gram-scale meteoroid fragmentation, are extremely important.

Atmospheric gravity waves excited by a fireball meteor: Observations and modeling

AbstractIn a companion paper, Suzuki et al. (2013) studied an expanding circular train observed in the Na airglow for 9 min above Syowa Station, Antarctica, on 7 June 2008. This train was created by a southwestward moving fireball meteor. Here we report on “V”‐shaped faint gravity waves (GWs) partially visible in many of the Na airglow images 8 to 43 min after the meteor. The GW phase lines appear to originate from the horizontal projection of the meteor path, with angles −42 to −52° south and 10 to 20° north of the path. The GWs south of the path propagated southwestward with a horizontal phase speed of cH∼80–100m/s, while those north of the path propagated northwestward with cH∼20–40m/s. Those south (north) of the path had horizontal wavelengths λH∼25–35km (λH∼18 km) and periods τr∼5–6 min (τr∼7–15 min). We then model the GWs excited by idealized horizontal and slanted heatings and body forces. We show that the GW phase lines form Vs when the heat/force is slanted vertically. If the central altitude of the heat/force is z0>92 km, the open ends of the Vs are mainly directed away from the meteor trajectory. If the heat/force is long enough, two oppositely directed Vs are created, forming an “X” at the center of the structure. We find that λH depends sensitively on the width of the heating. We obtain heating parameters which compare reasonably well with the Na observations: z0∼120 km, half‐length half maximum of ∼25–35km, and half width half maximum of ∼2–3km.

Some results from the quantitative analysis of meteor spectra

Monochromatic light curves for the H and K spectral lines of the ionized calcium doublet are derived from the prism spectra of two bright meteors photographed by small cameras. Using a new method of meteor spectroscopy the column N CaII and the volume n CaII concentrations of calcium ions are determined. The results obtained confirm that there is almost full ionization of calcium atoms in the radiating meteor plasma. The volume concentration of free electrons is measured. The excitation temperature of the meteor plasma and its variation along the meteor path is calculated.

Thermalization of sputtered particles as the source of diffuse radiation from high altitude meteors

High altitude meteors become luminous at altitudes above ∼130 km, where the standard ablation theory of meteor light production is not applicable. The physical mechanism responsible for their glow has not been known. We present a model that explains their existence, morphology and lightcurves. The model is based on particles ejected from the meteoroid surface through the sputtering process. The kinetic energy of such a sputtered particle is typically more than 1000 times larger than the energy of particles in the surrounding atmosphere. Thus, the sputtered particle creates a cascade of collisions in the atmosphere during thermalization. We show analytically that this process is capable of producing enough light for detection. We also explain the observed relationship between the beginning height of high altitude meteors and their maximum brightness. In addition, meteors are modeled with a Monte Carlo code developed specifically for this phenomenon. Theoretical images reproduce the observed shapes and sizes of high altitude meteors. Their exact shape depends on the relative angle between the meteor path and observer’s line of sight.

Spectroscopic anatomy of a meteor trail cross section with the European Southern Observatory Very Large Telescope

Abstract— A meteor spectrum was recorded serendipitously at the European Southern Obrervatory (ESO) Very Large Telescope (VLT) during a long exposure in long‐slit spectroscopic mode with FORS1. The −8 magnitude fireball crossed the narrow 1Î × 7î slit during the observation of a high z supernova in normal service mode operation on May 12, 2002. The spectrum covered the range of 637–1050 nm, where the meteor's air plasma emissions from N2, N, and O dominate. Carbon atom emission was not detected in the relatively unexplored wavelength range above 900 nm, but the observed upper limit was only 3 sigma less than expected from the dissociation of atmospheric CO2. The meteor trail was resolved along the slit, and the emission had a Gaussian distribution with a dimension of FWHM = 7.0 (±0.4) * sin(α) * H (km)/90 m, where α is the unknown angle between the orientation of the meteor path and slit and H the assumed altitude of the meteor in km. To our knowledge, this is the first observation of a spatially resolved spectrum across a meteor trail. Unlike model predictions, the plasma excitation temperature varied only from about 4,300 to 4,365 K across the trail, based on the ratio of atomic and molecular nitrogen emissions. Unfortunately, we conclude that this was because the meteor at 100 km altitude was out of focus.

An analysis of photographic observations of the Leonid meteoric shower in 1999

Photographic observations of meteors can provide more information than visual observations. In this paper, two photographs of Leonid meteoric shower taken on 1999 November 19 have been analyzed. The maximal angular velocity of meteoroids that cancan show up on films has been evaluated. The elevation of the beginning point, angular distance between the ending point and the radiant, angular velocity and arc length of the meteor's path are calculated for the two observed meteors. In addition, the observed short duration of about 0.65 second for the ablation of the meteoroids in the atmosphere means that the path length of ablation is about 40–50 kilometers. Through digitized processing of the photographs, photographic magnitudes of −10.3±0.2 and −4.8 ± 0.2 have been measured for the two Leonid meteors, from which their masses and electric line densities can be derived. The procedure given in this paper could be used for photographic observations of other meteors. We also discuss how to select a camera lens for meteor observations.

An artificial meteor database as a test for the presence of weak showers

We have constructed an artificial meteor database resembling in all details the real sample collected by the observers of the Comets and Meteors Workshop in the years 1996-1999. The artificial database includes the sporadic meteors and also events from the following showers: Perseids, Aquarid complex, Alpha Capricornids, July Pegasids and Sagittarids. This database was searched for the presence of the radiants of two weak showers: Alpha Cygnids and Delphinids. The lack of these radiants in the artificial database and their existence in the real observations suggests that Alpha Cygnids and Delphinids are the real showers and their radiants could not be formed as an effect of intersections of back prolongated paths of meteors belonging to other showers.

Airborne intensified charge‐coupled device observations of the 1998 Leonid shower

Abstract— We have used dual coaxial microchannel plate image‐intensified monochrome charge‐coupled device (CCD) detectors run at standard NTSC frame rates (30 frames per second, fps) to study the Leonid meteor shower on 1998 November 17 from an airborne platform at an altitude of ∼13 km. These observations were part of NASA's 1998 Leonid multi‐instrument aircraft campaign (MAC). The observing systems had fields of view (width) of 16.3° and 9.5°, and limiting stellar sensitivities of +8.3m and +8.9m. During 12 h of recording, 230 meteors were detected, of which 65 were Leonid meteors. Light curves are presented for 53 of these meteors. The magnitudes at peak brightness of the meteors investigated were generally in the range from +4.0m to +6.0m. The mass distribution indices for the two samples are 1.67 and 1.44, with the former being based on the wider field of view dataset. The light curves were skewed with the brightest point towards the beginning of the meteor trail. The F parameter for points one magnitude below maximum luminosity had a mean value of 0.47 for the wider field system and 0.37 for the more sensitive narrower field system. We provide leading and trailing edge light curve slopes for each meteor as another indication of light curve shape. There were few obvious flares on the light curves, indicating that in‐flight fragmentation into a large number of grains is not common. There is variability in light curve shape from meteor to meteor. The light curves are inconsistent with single, compact body meteor theory, and we interpret the data as indicative of a two‐component dustball model with metal or silicate grains bonded by a lower boiling point, possibly organic, substance. The variation in light curve shape may be indicative of differences in mass distribution of the constituent grains. We provide trail length vs. magnitude data. There is only a slight hint of a bend at +5m in the data, representing the difference between meteors that have broken into a cluster of grains prior to grain ablation, and those that continue to fragment during the grain ablation phase. Two specific meteors show interesting light curve features. One meteor is nebulous in appearance, with significant transverse width. The apparent light production region extends for 450 m from the center of the meteor path. Another meteor has several main fragments, and evidence of significant separated fragments. We offer several suggestions for improvements for the 1999 Leonid MAC light curve experiment.

Structure of Perseids from visual observations

A new method of processing of visual meteor data has been worked outand applied to Perseid meteor shower observations. Reduced meteor hourly rates with magnitudes brighter than +3 are proportional to meteor flux densities with a coefficient equals to the effective collecting area. Corrections due to moon light and for meteor path lenghts were applied. Our observations 1972–1979 and 1982–1990 gave similar hourly rate profiles with a maximum rate of 71 meteors at solar longitude L=140.36°. Perseids 1980 and 1981 were about 1.5 times more active. The maximum Perseid activity in 1991–1992 was 119 meteors at solar longitude 139.54° and narrow peaks are observed at the same longitude showing an enhanced activity up to 225 meteors.

21. The separation of small particles from meteor bodies, and its influence on some parameters of meteors

The separation of very small particles from meteor bodies as a part of the process of their ablation in the Earth's atmosphere is assumed by many investigators. But when the particle is small relative to the meteor body the path of the particle is a priori thought to be small relative to the length of the meteor path, i.e. the particle is expected to evaporate in close proximity to the point of separation. This assumption is not acceptable after McCrosky's work (1958) that has shown for one particular case the small particles (m = 10−5−10−6 g) go a long path before their mass is exhausted. The assumption made until now has caused incorrect conclusions, e.g. the luminosity at any point of the meteor path is proportional to the mass ablated from the meteor body at that point (Kramer, 1965).

Visual and photographic observations of meteors and noctilucent clouds

The visible paths of meteors appear generally in the region from 110 km to 60 km above sea level. The relations between meteor height and meteor velocity, brightness, and angle of the path to the vertical are discussed. Persistent meteor trains show a height distribution similar to that of meteors and reveal differential wind motions of various types, as well as giving evidence of a rapid increase in the train diameter during the first few minutes. A vertical spacing of about 6 km between major wind currents seems typical. Noctilucent clouds exhibit velocities comparable to those of meteor trains and often reveal a pattern of roughly parallel lines with a spacing of 9 km.

DETERMINATION OF THE ELEMENTS OF METEOR PATHS FROM RADAR OBSERVATIONS

Methods of determining meteor velocities from single-station observations are discussed. Where three-station observations are available both the velocity and the elements of the meteor's path through the atmosphere can be computed in favorable cases. These methods are applied to a selected daytime meteor, recorded by the three radar stations at 17h 59m 48s E.S.T., Aug. 4, 1948. The following elements of the meteor's path have been obtained from the radar data:—Apparent geocentric velocity 35.0 ± 0.4 km. per sec.True bearing of apparent radiant 074° ± 2°Elevation of apparent radiant 2° ± 2°Total radar path length 270 km.Height above sea level 108 − 104 km.These values lead to an orbit similar to one of the short-period comets, with these elements:—Semi-major axis a 2.66Eccentricity e 0.87Angle node to perihelion ω 294°.9Longitude of node 132°.4Inclination i 33°.6Period P 4.33 years

The Theory of the Radio Detection of Meteors

The methods of observation are described both for ``bursts'' of signal strength and ``whistles'' caused by reflection of radio waves from meteoric ionization. Consideration is given to the geometry of reflection, and it is shown that meteoric velocity and range can be accurately determined by combined pulse and whistle observations. The possibility of determining the direction and position of a meteor path by observations at three receiving locations is examined, and a method for interpreting such data is developed. An investigation is made of the fraction of meteors capable of producing bursts, and the important effect of the meteoric radiant is emphasized.

Prof. Frantisek Nusl

IN honour of Prof. F. Nusl, director of the National Observatory of Prague and professor in the Charles University, who has entered on his seventieth year, a composite work has been compiled with the title “Prage venovaneDr.FrantiskuNuglovi”. Prof. Null's interest in astronomy is well known; he was vice-president of the International Astronomical Union for the Leyden meeting held in 1928. His circum-zenithal instrument for the determination of time was described before the Czech Academy in Prague (see NATURE, 68, 376; 1903) and also in a number of other papers. Twelve authors have contributed to the volume and their papers embrace a wide range of subjects. Z. Kopal discusses the two-bodies problem where the central body is an oblate spheroid, not homogeneous, and shows that a steady advance of periastron will take place. V. Guth develops a graphical method for determining the heights and paths of meteors, and J. StSpanek has a most interesting paper showing the results of photographing Comet Finsler (1937f) from July 13 until August 15, 1937. It is easy to follow the developments of various parts of the head and tail of the comet by examining these photographs, and also the variations of the different luminous rays. J. Prochazka explains his method for investigating the stability of the Bouty meridional telescope at Paris by means of two auxiliary telescopes provided with micrometers, and has found that the stability of the instrument is excellent. J. Svoboda supplies a detailed account of his experimental method for finding the personal error in observations with the NuSl-Fri8 circum-zenithal instrument. Z. Horák deals with Svoboda's method for determining the radiant of a meteor stream with a minimum of error, and towards the end of his paper shows how very satisfactory results can be obtained by a graphical method. These as well as the other papers, with all of which it is impossible to deal in the limited space, form most interesting reading.

Probable Errors in Determinations of the Real Paths of Meteors

Probable Errors in Determinations of the Real Paths of Meteors

Our Astronomical Column

THE AUGUST PERSEIDS.—One result of the recent observations of this shower will be the determination of a large number of real paths of meteors not belonging to the Perseid swarm. The minor radiants visible between August 10–20 were very numerous and interesting. In several cases, however, the meteors doubly observed do not work out very well, and these await further investigation. Some of the other observers have not yet sent in their results.

Real Paths of Brilliant Meteors observed in 1908

Real Paths of Brilliant Meteors observed in 1908

Real paths of Meteors observed in England, November 14–18 1903.

Real paths of Meteors observed in England, November 14–18 1903.

Real paths of meteors observed in England in April, July and August 1903

Astronomische NachrichtenVolume 164, Issue 14 p. 213-214 Miscellaneous Real paths of meteors observed in England in April, July and August 1903 W. F. Denning, W. F. Denning Bishopston, BristolSearch for more papers by this author W. F. Denning, W. F. Denning Bishopston, BristolSearch for more papers by this author First published: 1903 https://doi.org/10.1002/asna.19031641403AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume164, Issue141903Pages 213-214 RelatedInformation

Daylight Meteor, April 12

THE meteor referred to in NATURE of April 23 (p. 581), was seen by me in Glasgow, low down on the S.E. horizon, at 8.5 p.m. The position of its visible path was carefully noted at the time in relation to a church spire, which it just seemed to touch. On April 27, at 10.30 p.m. the centre of the full moon was 2° above this point, its declination was therefore 22° 13′ S., and its R.A. on April 12 at 8.5 p.m. was 10h. 39m. On account of some intervening shrubs the meteor's path was only visible over a distance of 10°, but the declination seemed to remain unchanged.