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Showing papers in "Earth Moon and Planets in 2000"


Book ChapterDOI
TL;DR: In the wake of a meteor, organic carbon appears to survive flash heating and rapid cooling as mentioned in this paper, and the resulting materials could account for the bulk of pre-biotic organic carbon on the early Earth at the time of the origin of life.
Abstract: All potential exogenous pre-biotic matter arrived to Earth by ways of our atmosphere, where much material was ablated during a luminous phase called "meteors" in rarefied flows of high (up to 270) Mach number. The recent Leonid showers offered a first glimpse into the elusive physical conditions of the ablation process and atmospheric chemistry associated with high-speed meteors. Molecular emissions were detected that trace a meteor's brilliant light to a 4,300 K warm wake rather than to the meteor's head. A new theoretical approach using the direct simulation by Monte Carlo technique identified the source-region and demonstrated that the ablation process is critical in the heating of the meteor's wake. In the head of the meteor, organic carbon appears to survive flash heating and rapid cooling. The temperatures in the wake of the meteor are just right for dissociation of CO and the formation of more complex organic compounds. The resulting materials could account for the bulk of pre-biotic organic carbon on the early Earth at the time of the origin of life.

74 citations


Book ChapterDOI
TL;DR: In this article, two video spectra of a Leonid afterglow were obtained for the first time during the 1999 Leonid aircraft campaign, and the train spectrum consisted of a red continuum, yellow continuum, and about 50 atomic lines between 3700-9000 A. The train was produced by a −13 magnitude Leonid fireball at a relatively low height between 91-75 km.
Abstract: Two video spectra of a meteoric afterglow were obtained for the first time during the 1999 Leonid aircraft campaign. The train was produced by a −13 magnitude Leonid fireball at a relatively low height between 91–75 km. The meteor spectrum has a strong hydrogen emission, proportional to 10–20 H atoms per one Fe atom The train spectrum consisted of a red continuum, yellow continuum, and about 50 atomic lines between 3700–9000 A. The yellow continuum, possibly due to NO2, was also detected in the persistent train. The red continuum is interpreted as a thermal radiation of dust from meteoric debris at about 1400 K. Evidence for secondary ablation is found in the afterglow. The atomic lines decayed within seconds of the meteor. The lines of Fe i, Mg i, Na i, Ca i, Ca ii, Cr i, Mn i, K i, and possibly Al i were present in the glow together with the 5577 A forbidden 01 line. The gas temperature in the train was close to 5000 K at the beginning and decayed to 1200 K within two seconds. However, thermal equilibrium was not satisfied for all populated levels.

46 citations


Book ChapterDOI
TL;DR: The first unambiguous detection of meteoroids impacting the night side of the Moon was obtained during the 1999 Leonid storm up to eight optical flashes were recorded with CCD video cameras attached to small telescopes on November 18, 1999 Six impacts were videotaped by at least two independent observers at the same times and lunar locations.
Abstract: The first unambiguous detection of meteoroids impacting the night side of the Moon was obtained during the 1999 Leonid storm Up to eight optical flashes were recorded with CCD video cameras attached to small telescopes on November 18, 1999 Six impacts were videotaped by at least two independent observers at the same times and lunar locations, which is perhaps the strongest evidence for their collisional nature The flashes were clearly above the noise and lasted for less than 002 s Although previous observational efforts did not succeed in detecting impact flashes, additional candidates have been reported in the literature The evidence accumulated so far implies that small telescopes equipped with high speed cameras can be used as a new tool for studying meteoroid streams, sporadic meteoroids, and hypervelocity collisions In this review we discuss the various intervening parameters for detectability of flashes on the night side of the Moon (geometrical effects, contamination by scattered light from the day side, and properties of the meteoroids such as speed and flux of particles) Particular emphasis is placed on the analysis of the observations in order to derive relevant physical parameters such as luminous efficiencies, impactor masses, and crater sizes Some of these parameters are of interest for constraining theoretical impact models From a simple analysis, it is possible to derive the mass distribution of the impactors in the kg range A more elaborate analysis of the data permits an estimate of the fraction of kinetic energy converted to radiation (luminous efficiency) if the meteoroid flux on the Moon is known Applied to the 1999 lunar Leonids, these methods yield a mass index of 16 ± 01 and luminous efficiencies of 2 × 10−3 with an uncertainty of about one order of magnitude Predictions of visibility of the major annual meteor showers are given for the next few years These include the forthcoming 2001 Leonid return, for which we estimate detection rates in the visible

43 citations


Book ChapterDOI
TL;DR: In this article, a simple model is described that predicts the time of occurrences and peak activity of Leonid shower outbursts by considering the role of non-isotropic effects in the interaction with the solar radiation on the dispersion of particles away from the dust trail center.
Abstract: A simple model is described that predicts the time of occurrences and peak activity of Leonid shower outbursts. It is assumed that the ejection speeds of escaping particles at each return of the parent comet near perihelion are very small, but solar radiation pressure acting differently on different particles causing a spread of particles into different period orbits. Earlier papers predicted the position of the resulting dust trails. This paper sets forth to better predict the strength of the expected outbursts by considering the role of non-isotropic effects in the interaction with the solar radiation on the dispersion of particles away from the dust trail center. This paper determines the approximate magnitude of the relevant effects. Predictions for the next few years are presented that include such considerations, for reasonable assumptions of particle properties. For example, earlier predictions for the 1999 storm of ZHR = 6,000–7,000 are now reduced by a factor of two, which is in better agreement with the observed ZHR ~ 4,000. The success of the technique, when applied to historic meteor storms and outbursts without need of additional free parameters, lends confidence to the soundness of the underlying model and to its application for future predictions. We predict that the best encounters of this return of the parent-comet will occur in the years 2001 and 2002.

41 citations


Book ChapterDOI
TL;DR: In this paper, the authors reported the detection of a broad continuum emission dominating the visual spectrum of a Leonid persistent train, which confirmed the classical mechanism of metal atom catalyzed recombination of ozone and oxygen atoms as the driving force behind optical emission.
Abstract: We report the detection of a broad continuum emission dominating the visual spectrum of a Leonid persistent train. A comparison with laboratory spectra of FeO "orange arc" emission at 1 mbar shows a general agreement of the band position and shape. The detection of FeO confirms the classical mechanism of metal atom catalyzed recombination of ozone and oxygen atoms as the driving force behind optical emission from persistent trains. Sodium and iron atoms are now confirmed catalysts.

39 citations


Book ChapterDOI
TL;DR: In this article, a particle beam model is developed that describes the air-meteoroid interaction and the physical parameters of the vapor cloud are calculated and compared with observations collected during the Leonid Multi-Instrument Aircraft Campaign.
Abstract: The ablation is calculated of non-fragmenting 10−2 to 10 cm sized meteoroids for typical Leonids with a velocity of 72 km/s at altitudes of about 90–110 km. At altitudes below the onset of intensive evaporation, a dense vapor cloud is formed around the body. This vapor cloud screens the meteoroid surface from direct impacts of air molecules. A particle beam model is developed that describes the air—meteoroid interaction. Based on this model, the physical parameters of the vapor cloud are calculated and compared with observations collected during the Leonid Multi-Instrument Aircraft Campaign. General agreement with measured temperatures is found. In addition, boundaries of the model’s applicability to specific encounter conditions are given.

34 citations


Book ChapterDOI
TL;DR: The bulk density and bulk porosity of IDPs and various meteorite classes show that protoplanet accretion and evolution were arrested at different stages as a function of parent body modification.
Abstract: The bulk density and bulk porosity of IDPs and various meteorite classes show that protoplanet accretion and evolution were arrested at different stages as a function of parent body modification The collected IDPs, micrometeorites and meteorites are aggregates of different structural entities that were inherited from the earliest times of solar system evolution These structural entities and the extent of parent body lithification will determine the material strength of the meteoroids entering the Earth’ s atmosphere There is a need for measurements of the material strength of collected extraterrestrial materials because they will in part determine the nature of the chemical interactions of descending meteors and fireballs in the atmosphere High—precision determinations of meteor and fireball compositions are required to search for anhydrous, carbon-rich proto-CI material that has survived in the boulders of comet nuclei

31 citations


Book ChapterDOI
TL;DR: In this article, low-light level video observations of 1999 Leonid storm meteors have been obtained from two airborne platforms during the Leonid multi-instrument aircraft campaign (Leonid MAC).
Abstract: Photometric low-light level video observations of 1999 Leonid storm meteors have been obtained from two airborne platforms during the Leonid multi-instrument aircraft campaign (Leonid MAC). The 1999 Leonid light curves tend to be skewed towards the end point of the trajectory, while the 1998 Leonid light curves were not. The variation in the light curves from 1998 and 1999 can be explained as an overall reduction in the mass distribution index, α from ~ 1.95 in 1998 to ~ 1.75 in 1999. We have interpreted this behaviour as being either indicative of a gradual loss of the “glue” that keeps the grains together, or the fact that the meteoroids sampled in 1998 had a different morphological structure to those sampled in 1999. The early fragmentation of a dustball meteoroid results in a light curve that peaks sooner than that predicted by classical single body ablation theory.

29 citations


Journal ArticleDOI
TL;DR: The cometary Leonid meteoroids as discussed by the authors represent a size range in between largest carbon-rich IDPs and the smallest CI meteorites, and their dustball structure and chemistry offer anopportunity to constrain hierarchical dust accretion inferred from petrologic studies of aggregates and cluster IDPs.
Abstract: The cometary Leonid meteoroids represent a size range in between largest carbon-richIDPs and the smallest CI meteorites. Their dustball structure and chemistry offer anopportunity to constrain hierarchical dust accretion inferred from petrologic studies ofaggregate and cluster IDPs. The Leonid shower meteoroids of known ``comet ejection''ages provide an opportunity to study space weathering of cometary dust over periodsof up to several hundred years. The meteors and aggregate and cluster IDPs displaycontinuous thermal modification of organics and volatile element (Na, K-bearing phases), that occur as discrete minerals and amorphous solids each different response during kinetically controlled ablation. Leonid meteoroids are not excessively Na-rich. The occurrences of Leonid meteors can now be accurate predicted and combined withknowledge better models for the settling rates, collections of surviving dust becomea comet nucleus-sampling mission.

26 citations


Book ChapterDOI
TL;DR: Two B707-type research aircraft of the 452nd Flight Test Squadron at Edwards Air Force Base were deployed to study the Leonid meteor storm of 1999 over the Mediterranean Sea on Nov. 18 as discussed by the authors.
Abstract: Two B707-type research aircraft of the 452nd Flight Test Squadron at Edwards Air Force Base were deployed to study the Leonid meteor storm of 1999 over the Mediterranean Sea on Nov. 18. The mission was sponsored by various science programs of NASA, and offered an international team of 35 researchers observing conditions free of clouds and low altitude extinction at a prime location for viewing the storm. This 1999 Leonid Multi-Instrument Aircraft Campaign followed a similar effort in 1998, improving upon mission strategy and scope. As before, spectroscopic and imaging experiments targeted meteors and persistent trains, but also airglow, aurora, elves and sprites. The research aimed to address outstanding questions in astrobiology, planetary science, astronomy, and upper atmospheric research. In addition, USAF co-sponsored the mission to provide near real-time flux measurements for space weather awareness. First results are presented in these issues of Earth, Moon, and Planets in preparation for future missions that will target the exceptional Leonid returns of 2001 and 2002. An early review of the scientific achievements in the context of campaign objectives is given.

22 citations


Book ChapterDOI
TL;DR: In this paper, continuous measurements of low frequency electromagnetic waves were performed during the Leonids meteor storm on the night of 18 November, 1999, and analyses of the data indicate distinct electromagnetic pulses produced by the incoming meteors.
Abstract: For more than 200 years large meteors entering the atmosphere have been observed to produce audible sounds simultaneously with the optical flash. Since sound waves travel much slower that visible light, the only explanation was that electromagnetic waves produced by the meteors induce a vibration in a transducer close to the observer, producing an audible sound, known as electrophonics. To check this hypothesis, continuous measurements of low frequency electromagnetic waves were performed during the Leonids meteor storm on the night of 18 November, 1999. The analyses of the data indicate distinct electromagnetic pulses produced by the incoming meteors. Many of the weaker incoming meteors that could not be seen visibly were also detected electromagnetically, with a peak rate of approximately 15,000 meteors per hour occurring at the peak of the storm, nearly 50 times the visible rate.

Book ChapterDOI
TL;DR: In this article, a summary of comet nucleus and dust properties is used to suggest a basis for predicting the properties of meteor shower particles originating as comet debris, based on which a meteor shower is predicted.
Abstract: A summary of comet nucleus and dust properties is used to suggest a basis for predicting the properties of meteor shower particles originating as comet debris.

Book ChapterDOI
TL;DR: The first infrared spectroscopy in the 3-13 micron region has been obtained of several persistent Leonid meteor trains with two different instrument types, one at a desert ground-based site and the other on-board a high-flying aircraft.
Abstract: The first infrared spectroscopy in the 3–13 micron region has been obtained of several persistent Leonid meteor trains with two different instrument types, one at a desert ground-based site and the other on-board a high-flying aircraft. The spectra exhibit common structures assigned to enhanced emissions of warm CH4, CO2, CO and H2O, which may originate from heated trace air compounds or materials created in the wake of the meteor. This is the first time that any of these molecules has been observed in the spectra of persistent trains. Hence, the raid-IR observations offer a new perspective on the physical processes that occur in the path of the meteor at some time after the meteor itself has passed by. Continuum emission is observed also, but its origin has not yet been established. No 10 micron dust emission feature has been observed.

Book ChapterDOI
TL;DR: In this article, multi-station observations of 47 Leonid meteors are presented that were obtained from two ground locations in Spain during the 1999 meteor storm, and they find an unresolved compact cluster of radiants at α = 153.67 ± 0.05 and δ = 21.70 ± 0.282 (J2000).
Abstract: Photographic multi-station observations of 47 Leonid meteors are presented that were obtained from two ground locations in Spain during the 1999 meteor storm. We find an unresolved compact cluster of radiants at α = 153.67 ± 0.05 and δ = 21.70 ± 0.05 for a mean solar longitude of 235.282 (J2000). The position is identical to that of the Nov. 17/18 outburst of 1998, which implies that both are due to comet 55P/Tempel-Tuttle's ejecta from 1899. We also find a halo which contains about 28% of all meteors. The spatial distribution of radiant positions appears to be Lorentzian, with a similar fraction of meteors in the profile wings as the meteor storm activity curve.

Book ChapterDOI
TL;DR: In this article, an intensified HDTV camera was used for slitless meteor spectroscopy at visible and near-UV wavelengths in three night flights of the Leonid Multi-instrument Aircraft Campaign.
Abstract: During the 1999 Leonids, an intensified HDTV camera was used for slitless meteor spectroscopy at visible and near-UV wavelengths in three night flights of the Leonid Multi-instrument Aircraft Campaign. The HDTV system provided a high dynamic range (digital 10-bit) and a wide field of view of 37 x 21 degrees. The maximum spectral sensitivity is at 405 nm, while the resolving power of the spectrograph was λ/Δλ ~ 250. Here, we report on the results for one particularly nice spectrum from a Leonid meteor at 03:24:40 UT. Numerous atomic emission lines of magnesium and iron were detected, with an excitation temperature of T = 5,000 ± 1,000. It is confirmed that sodium is released from the meteoroid earlier than iron and magnesium, just as in meteors of the 1998 Leonid shower. Rovibrational bands of N2 dominate the spectrum in the visible and near-IR. We searched for CN band emission at 389 nm, but could not detect it due to the overlap of numerous iron lines.

Journal ArticleDOI
TL;DR: In this article, the authors have produced top ten ranked lists of impact velocity, main belt asteroid region dwell times and impact probabilities for a selection of short period comets, including Comet C/1766 G1 Helfenzrieder and Comet 28P/Neujmin 1.
Abstract: We have produced top ten ranked lists of impact velocity, mainbelt asteroid region dwell times and impact probabilities for a selection of short period comets. The comet with the combined highest ranking with respect to impact probability and impact velocity is Comet C/1766 G1 Helfenzrieder. Since it is not clear that this comet still exists, the highest ranked, presently active, comet with respect to the likelihood of suffering impacts from meter-sized objects while in the main belt asteroid region is Comet 28P/Neujmin 1. We find no evidence to support the existence of a distinctive sub-set of the short period comets liable to show repeated outburst or splitting behavioursdue to small body, meter-sized, asteroid impacts.

Book ChapterDOI
TL;DR: In this paper, three chemical groups of primary "silicate" spheres < 30 µm in diameter of cometary origin were collected in the lower stratosphere between 1981 May and 1994 July.
Abstract: Three chemical groups of primary “silicate” spheres < 30 µm in diameter of cometary origin were collected in the lower stratosphere between 1981 May and 1994 July. The “silicate” sphere abundances represent an annual background from contributions by sporadic meteor and weak annual meteor shower activities. During two collection periods, from 06/22 until 08/18, 1983 (U2015), and from 09/15–12/15, 1981 (W7027/7029), a higher number of spheres was collected compared to other periods of the year represented by the other collectors studied here. This study links two different data sets, viz. the NASSA/JSC Cosmic Dust Catalogs and peak activities of annual meteor showers, and identified high-velocity cometary sources for collected stratospheric “silicate” spheres. The majority of spheres on flag U2015 may originate from comet P/Swift-Tuttle (Perseids), while the majority of spheres on flags W7027/7029 could be from comet P/Halley (Orionids) or comet P/Tempel-Tuttle (Leonids). Variations in relative proportions of the Mg,Si,Ca ± Al, Mg,Si ± Fe and Al, Si,Ca spheres may offer a hint of chemical differences among high-velocity comets. Proof for the findings reported here might be obtained by targeted cosmic dust collections in the lower stratosphere including periods of meteor shower and storm activity.

Book ChapterDOI
TL;DR: In this article, a slitless spectrograph with objective grating was deployed on FISTA during the 1999 Leonid Multi-Instrument Aircraft Campaign to measure the strong B → X emission band of the radical CN in Leonid meteor spectra at 387 nm.
Abstract: Near-ultraviolet 300–410 nm spectra of Leonid meteoroids were obtained in an effort to measure the strong B → X emission band of the radical CN in Leonid meteor spectra at 387 nm. CN is an expected product of ablation of nitrogen containing organic carbon in the meteoroids as well as a possible product of the aerothermochemistry induced by the kinetic energy of the meteor. A slit-less spectrograph with objective grating was deployed on FISTA during the 1999 Leonid Multi-Instrument Aircraft Campaign. Fifteen first-order UV spectra were captured near the 02:00 UT meteor storm peak on November 18. It is found that neutral iron lines dominate the spectrum, with no clear sign of the CN band. The meteor plasma contains less than one CN molecule per 3 Fe atoms at the observed altitude of about 100 km.

Book ChapterDOI
TL;DR: In this paper, a hybrid technique of visual and video meteor observations was developed to provide high precision near real-time flux measurements for satellite operators from airborne platforms, which revealed that the activity profile of the Leonid storm is a Lorentz profile.
Abstract: A new hybrid technique of visual and video meteor observations was developed to provide high precision near real-time flux measurements for satellite operators from airborne platforms. A total of 33,000 Leonids, recorded on video during the 1999 Leonid storm, were watched by a team of visual observers using a video head display and an automatic counting tool. The counts reveal that the activity profile of the Leonid storm is a Lorentz profile. By assuming a radial profile for the dust trail that is also a Lorentzian, we make predictions for future encounters. If that assumption is correct, we passed 0.0003 AU deeper into the 1899 trailet than expected during the storm of 1999 and future encounters with the 1866 trailet will be less intense than predicted elsewhere.

Book ChapterDOI
TL;DR: A wide-angle, visible wavelength, camera near the limb of the Earth in a 48-minute interval, and three meteors by a narrow field camera were detected by the Midcourse Space Experiment satellite (MSX).
Abstract: In November 1997, the Midcourse Space Experiment satellite (MSX) was deployed to observe the Leonid shower from space. The shower lived up to expectations, with abundant bright fireballs. Twenty-nine meteors were detected by a wide-angle, visible wavelength, camera near the limb of the Earth in a 48-minute interval, and three meteors by the narrow field camera. This amounts to a meteoroid influx of 5.5 ± 0.6 10 kin−2 hr−1 for masses > 0.3 gram. The limiting magnitude for limb observations of Leonid meteors was measured at Mv = −1.5 magn. The Leonid shower magnitude population index was 1.6 ± 0.2 down to Mv = −7 magn., with no sign of an upper mass cut-off.

Book ChapterDOI
TL;DR: A total of 18 image intensified CCD detectors were deployed at 6 locations (two in Negev Desert, Israel, and one in each of the Canary Islands, Long Key in Florida, Haleakala in Hawaii, and the Kwajalein Atoll) to provide a real-time reporting system, as well as data for subsequent detailed analysis, for the 1999 Leonid shower as discussed by the authors.
Abstract: A total of 18 image intensified CCD detectors were deployed at 6 locations (two in Negev Desert, Israel, and one in each of the Canary Islands, Long Key in Florida, Haleakala in Hawaii, and the Kwajalein Atoll) to provide a real-time reporting system, as well as data for subsequent detailed analysis, for the 1999 Leonid shower. Fields of view ranged from 9 to 34 degrees, with apparent limiting stellar magnitudes from about +7 to +9. In addition, a dual frequency (29.850 and 38.15 MHz) automated meteor radar with directional determination capability was located in the Canadian Arctic at Alert, Nunavut and provided continuous monitoring of the shower from a location where the radiant was constantly above the horizon. Both the radar and electro-optical systems successfully recorded the activity of the shower in real time, and typical real-time activity plots are presented. Post-event analysis has concentrated on the Israel electro-optical wide field cameras and the time interval centered around the peak of the storm. About 2700 meteors have been digitized, with 680 measured for this analysis. Of these 371 were well enough determined to permit a single-station technique to yield approximate heights. Light curves and photometric masses were computed for these 371 Leonids which form the basis of the preliminary results reported in this paper. These cameras recorded Leonid meteors with peak luminosity in the magnitude range −3 to +5, corresponding to the photometric mass range 10−4 to 10−7 kg. A regression plot of photometric mass with magnitude did not indicate any change in light curve shape over the interval studied here. The peak flux as determined by the electro-optical observations was 1.6 ± 0.1 Leonid meteors of magnitude +6.5 or brighter falling on a one square kilometer area (oriented perpendicular to the Leonid radiant) per hour. This peak flux occurred at approximately 2:07 ±: 06 UT on Nov 18 1999, corresponding to solar longitudeλo= 235.248 (epoch 2000.0). The radar results were consistent with this maximum flux rate and time. There was not a strong change in mass distribution over the few hours around maximum, although there is some indication that the peak interval was stronger in fainter meteors. Height histograms are provided for beginning, maximum luminosity and ending heights. It was found that maximum luminosity and ending heights were completely independent of mass, consistent with a dustball model in which the meteoroids are fragmented into constituent grains prior to ablation of the grains. However, the beginning height increases sharply (9.1 km per decade of photometric mass change) with increasing mass. This is possibly indicative of a volatile component which ablates early in the atmospheric trajectory.

Journal ArticleDOI
TL;DR: In this paper, the correlation of sporadic meteor rates from radar observations in January, August, and December non-show-er periods in 1958-2000, and relevant solar activity represented by the solar relative number, R, is investigated.
Abstract: The correlation of sporadic meteor rates from radar observations in January, August, and December non-show-er periods in 1958–2000, and relevant solar activity represented by the solar relative number, R, is investigated. Similar analysis of the December sporadic period was already presented by Simek 1999, and Pecina. Complete analysis indicates high correlation of both phenomena with sporadic meteor counts curve following that of solar activity after 1.5–2 years in the mean eleven year solar cycle with the correlation index exceeding 70%. This result supports the large volume of observing material of the Ondřejov meteor radar in the above mentioned span covering almost four solar cycles.

Book ChapterDOI
TL;DR: In this article, the atmospheric trajectory of a particularly well studied fireball and train during the 1999 Leonid Multi-Instrument Aircraft Campaign is calculated, and the train curves into a 2-shape, which persisted until at least 13 minutes after the fireball.
Abstract: The atmospheric trajectory is calculated of a particularly well studied fireball and train during the 1999 Leonid Multi-Instrument Aircraft Campaign. Less than a minute after the meteor’s first appearance, the train curves into a “2”-shape, which persisted until at least 13 minutes after the fireball. We conclude that the shape results because of horizontal winds from gravity waves with a scale height of 8.3 km at 79–91 km altitude, as well as a westerly wind gradient with altitude. In addition, there is downward drift that affects the formation of loops in the train early on.

Journal ArticleDOI
TL;DR: In this paper, the dielectric tensor, modified plasma dispersion function and dispersion relation for Whistler mode instability in an infinite magnetoplasma are obtained in the case of cold plasma injection to background hot anisotropic generalized bi-Lorentzian (κ) plasma in the presence of external perpendicular a.c. electric field.
Abstract: The dielectric tensor, modified plasma dispersion function and dispersion relation for Whistler mode instability in an infinite magnetoplasma are obtained in the case of cold plasma injection to background hot anisotropic generalized bi-Lorentzian (κ) plasma in the presence of external perpendicular a.c. electric field. The method of characteristics solutions using perturbed and unperturbed particle trajectories have been used to determine the perturbed distribution function. Integrals and modified plasma dispersion function Zκ *(ξ ) are reduced in power series expansion form. Numerical methods using computer technique have been used to obtained temporal growth rate for magnetospheric plasma at geostationary height. The bi-Lorentzian (κ) plasma is reducible to various forms of distribution function by changing the spectral index κ. The results of bi-Lorentzian (κ) plasma are compared with those of bi-Maxwellian plasma. It has been found that the addition of cold plasma injection gives different frequency spectra. The a.c. frequency of moderate amplitude increases the growth rate and instability in K space to lower range. Growth rate maximum is not affected by a.c. frequencies. However, it shifts the maximum to lower K space in both cases, rather than on the variation of the magnitude. Thus a physical situation like this may explain emission of various high frequency whistler emissions by cold plasma injection. The potential application of controlled plasma experiments in the laboratory and for planetary atmosphere are indicated.

Journal ArticleDOI
TL;DR: In this paper, a comprehensive analysis of the dynamics of Veritas family members located in a chaotic strip centered at 3.174 AU is presented, where a total of 600 chaotic members of the family and their clones were integrated for 100 Myr, and the variation of the distance with respect to the barycenter of family have been computed for all of them.
Abstract: We present a comprehensive analysis of the dynamics of Veritas family members located in a chaotic strip centeredat 3.174 AU. A total of 600 chaotic members of the family and their clones were integrated for 100 Myr, and the variation of the distance with respect to the barycenter of the family have been computed forall of them. A simple classification of the prevailing behaviors hasbeen introduced to help identify typical dynamical patterns and states that could affect an estimate of the upper bound to the age of the family. We pointed out the importance of the temporary captures in thequasi-stable states, which occur often enough to affect the statistical analysis of the exits. The results are compatible with the young age (<100 Myr) for the family of Veritas, but we cannot say precisely how young it really is.

Book ChapterDOI
TL;DR: In this article, the authors examined the dynamical evolution of the train of a bright Leonid meteor for evidence of the source of the luminosity and the physical conditions in the meteor path.
Abstract: The dynamical evolution of the persistent train of a bright Leonid meteor was examined for evidence of the source of the luminosity and the physical conditions in the meteor path. The train consisted of two parallel somewhat diffuse luminous tracks, interpreted as the walls of a tube. A general lack of wind shear along the trail allowed these structures to remain intact for nearly 200 s, from which it was possible to determine that the tubular structure expanded at a near constant 10.5 ms−1, independent of altitude between 86 and 97 km. An initial fast decrease of train intensity below 90 km was followed by an increase in intensity and then a gradual decrease at longer times, whereas at high altitudes the integrated intensity was nearly constant with time. These results are compared to a model that describes the dynamical evolution of the train by diffusion, following an initial rapid expansion of the hot gaseous trail behind the meteoroid. The train luminosity is produced by O (1S) emission at 557 nm, driven by elevated atomic O levels produced by the meteor impact, as well as chemiluminescent reactions of the ablated metals Na and Fe with O3. Ozone is rapidly removed within the train, both by thermal decomposition and catalytic destruction by the metallic species. Hence, the brightest emission occurs at the edge of the train between outwardly diffusing metallic species and inwardly diffusing O3. Although the model is able to account plausibly for a number of characteristic features of the train evolution, significant discrepancies remain that cannot easily be resolved.


Journal ArticleDOI
Mirel Birlan1
TL;DR: In this paper, the authors present a synthesis of these results in terms of the asteroid density, taking into account several techniques, and the possible correlation of the density through the taxonomic system.
Abstract: High quality new data on the asteroid mass and volume were produced in the last years from both extra-atmospheric instruments and the groundbased high-performance telescopes This paper presents a synthesis of these resultsin terms of the asteroid density, taking into account several techniques, and the possible correlation of the density through the taxonomic system The important conclusion is that M-type asteroids seems to have an unexpected low density, which cannot be explained by the present mineralogy assumed by the comparative mineralogy

Book ChapterDOI
TL;DR: In this article, the formation of several dust layers and their subsequent descent and dissipation were observed during these periods and the particle number density at 117 km altitude was estimated to be ~30 p cm−3.
Abstract: November twilight sounding experiments carried out in the Abastumani Astrophysical Observatory including the Leonid showers of 1998 and 1999 provided an opportunity to obtain height distributions of dust of meteoric origin between 20 km to 140 km altitudes The formation of several dust layers and their subsequent descent and dissipation were observed during these periods The layers at 117 km and 54 km were estimated to consist of particles of 001 pm and 21–23 μm radii respectively, according to settling velocities of these layers The particle number density at 117 km altitude was estimated to be ~30 p cm−3

Journal ArticleDOI
TL;DR: In this article, the authors analyzed the nature of the transient phenomena as it could be the result of explosive venting on the surface of the Jovian satellite, and they also considered other alternative mechanisms able to produce bright events.
Abstract: Europa's low crater density suggests that geological activity has continued to the present epoch, leading to the possibility that current resurfacing events might be detectable. CCD observations were carried out with a ST-6 camera at the 0.5 m Mons Cassegrain telescope (Izana Observatory, Tenerife,Canary Islands, Spain) during the night between 2–3 October 1999. Our images show a transient bright feature on the Galilean satellite. These images are analyzed here with the purpose of understanding the nature of the transient phenomena as it could be the result of explosive venting on the surface of the Jovian satellite. By comparison, we use NASA Infrared Telescope Facility images of two Io hot spots taken on12 October 1990. Although we mainly restrict our discussion on apossible eruptive nature of the observed spots, we also consider other alternative mechanisms able to produce bright events. In particular, an interaction between charged material being ejected from Europa and the Jovian magnetosphere cannot be entirely ruled out. If confirmed, this result would lend support for the existence of active resurfacing in Europa.