A new method of discovering new meteor showers from the IMO single-station video meteor database

It has been found that unknown meteor showers could be efficiently discovered from the single station video meteor database of the International Meteor Organization (IMO) by assuming the geocentric velocity and adjusting it within the dynamically permitted range. The mean geocentric velocities of new meteor showers can be obtained, as well as the coordinates of the radiants. The activity period and maximum time can also be obtained if there are sufficient shower meteors. All single station video meteor observations between February 13 and 17 (from 2000 to 2005) in IMO’s database are processed with this method. As a result, two new meteor showers, one near RA=245.10°, Dec=41.82° in Hercules and the other near RA=233.03°, Dec=17.04° in Serpenids, are discovered. Some dynamical characteristics of the new meteor showers are also determined. Considering the random nature on the selection of period in this work, it is expected that there are some more potential new meteor showers in IMO’s video database. Supported by the National Natural Science Foundation of China (Grant No. 10373004)     

Radio Geminid meteor shower of 1994

Summary The geminid meteor shower observed by a radio forward-scatter system on the baseline Bologna-Lecce (Italy) in 1994 is discussed. The 1994 Geminid shower exhibited a distinct maximum for overdense echoes of duration >1 s, with the peak rate on December 13, 21–22 UT at solar longitude 261.0° (equinox 1950.0). The maxima of echoes of longer duration (>8 s and >32 s) are shifted to solar longitude 261.3°.     

Computer model of a meteor radio channel

A computer model of a meteor radio channel is presented. The model is based on the Monte-Carlo method. The possibility of effective choice of the model parameters is proved. The simulation results agree well with the experimental data obtained in meteor radio lines with lengths of 240, 700, and 1100 km.State University, Kazan. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 11, pp. 1177–1186, November, 1995.     

On the initial expansion of meteor trails

The asymptotic solution of the equation governing the number density n(r,t) of evaporated meteoric atons behind a steadily moving meteor is obtained which is suitable to depict the initial expansion of a meteor trail. Some unusual results of meteor observations are elucidated.     

Radiowave propagation on short meteor radio links

We present experimental results obtained on meteor radio links with lengths of 100 and 250 km. The advantage of the “lateral propagation” is demonstrated. Using the “KAMET” computer model, we simulated the propagation of radiowaves along radio links, of up to 600 km. An effective version is proposed for working on radio links of up to 300 km, which is called “tracking the meteor activity maximum.” State University, Kazan’, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 6, pp. 693–703, June, 1997.     

Experimental study of nonreciprocity of a meteor radio channel

Kazan State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 35, No. 1, pp. 94–96, January, 1992.     

Radar observations of the Lyrid meteor shower at Budrio

Summary Radar meteor observations carried out at Budrio (Italy) during the Lyrid meteor shower period in 1983–1985 are analysed and discussed. Lyrid activity is obtained applying to the observations a range distribution method. The maximum of activity is found at solar longitude 31.3° (epoch 1950), the duration of the shower between quartermaximum points is about 2 days and the overall Lyrid activity approximately 6 days.

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Riassunto Si analizzano e si discutono i risultati delle osservazioni radar di meteore effettuate negli anni 1983–1985 a Budrio (Italia) nel periodo dello sciame delle Liridi. L'attività delle Liridi è ottenuta da un metodo che fa ricorso alla distribuzione delle distanze, dei radioechi. Il massimo dell'attività è identificato alla longitudine solare di 31.3° la durata dello sciame valutata tra punti ad un quarto del massimo è di circa 2 giorni, e l'attività complessiva delle Liridi risulta essere approssimativamente di 6 giorni.

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Резюме Изучаются радиолокационные наблюдения метеорного потока Лирид проведенные в Будрио (Италия) в 1983–1985 гг. Активнссть потока получена методом распределения дальностей радиоэхо. Максимум активности наблюдалось на долготе Солнца 31.3° (равноденствие 1950), длительность повышенной активности между пунктами с 1/4 максимальной численности получилась около 2 дней; Лириды можно выделуть из спорадического фона в течение приблизительно 6 дней.

     

Multiple reflections from meteor trails and small-scale wind structure

Summary A new observational method for determining winds on extremely small scales in the upper mesosphere has been developed by radar observations of relatively rare, but long enduring trails of bright meteors, known as fireballs. The radar meteor system near Bologna enables to determine wind velocities at the points on the fireball trail, separated from each other in a time scale of 1 s and in a distance scale by 0.1 km. Results of investigation of the fireballs observed in Bologna during the EBC (Energy Budget Campaign) in November 1980, based on the analysis of multiple or double reflections from meteor trails show the variation of the wind velocity in very small areas. Fireball trains can provide several independent echoes, connected with the position, orientation, total duration of the trail and with the efficiency of the radar equipment used. More complex information on the atmospheric irregularities and on their occurrence can be derived during the observations of meteor showers, analysing simultaneously the motion of the effective reflection point on the trail from the range drift of echoes, and the Doppler shift wind measurements.

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Riassunto è stato sviluppato un nuovo metodo per determinare i venti nell'alta mesosfera su scale estremamente piccole, dall'osservazione radar di tracce di meteore luminose, relativamente rare e durevoli, conosciute come ?fireballs?. Il sistema radar di Budrio, nei pressi di Bologna, consente di determinare velocità del vento in punti sulla scia del fireball, separati nel tempo e nella distanza, rispettivamente di 1 secondo e di 0.1 km. I risultati di un'indagine sui fireballs osservati durante l'EBC (Energy Budget Campaign) nel novembre 1980, basata sull'analisi di riflessioni multiple da tracce di meteore, mostra che la velocità del vento varia su aree molto piccole. Le scie di fireballs possono fornire parecchi echi indipendenti associati, da una parte, alla posizione, orientazione e durata totale della traccia, e dall'altra, all'efficienza dell'apparato radar utilizzato. Informazioni più complesse su alcune irregolarità atmosferiche e sulla loro incidenza, possono essere desunte nel corso delle osservazioni di sciami di meteore, analizzando simultaneamente il moto del punto effettivo di riflessione sulla traccia (dalle deviazioni nelle distanze degli echi), nonché le misure Doppler di vento.

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Резюме Развивается новый метод для определения ветров с очень малыми масштабами в верхней мезосфере, используя радарные наблюдения относительно редких, но продолжительных хвостов ярких метеоров, известных как файерболы. Радарная система в Будрио, недалеко от Болоньи, позволяет определить скорости ветра в точках в кильваторе файербола, которые разделены друг от друга по времени в 1 секунду, а по расстоянию в 0.1 км. Результаты исследования файерболов, наблюденных в течение ЕВС, в ноябре 1980, основанные на анализе многократных отражений от метеорных хвостов, обнаруживают изменения скорости ветра в очень малых областях. Кильваторы файерболов могут образовывать несколько независимых эхо-сигналов, связанных, с одной стороны, с положением, ориентацией и полной длительностью хвоста, а, с другой стороны, с эффективностью используемого радарного оборудования. Более полную информацию об атмосферных нерегулярностях и их возникновении можно получить во время наблюдений метеорных ливней, анализируя одновременно движение эффективной точки отражения в хвосте (из дрейфа расстояния для эхо) и измерения ветра по доплеровскому сдвигу.

     

Reflection properties of meteor trails in a forward-scatter radar experiment

Summary The distribution of the energy reflected by a meteor trail is strongly connected to the ionization density distribution across and along a meteor trail. Recent forward-scatter observations over the Bologna-Lecce baseline in Italy carried out in 1991–92, show that the number of underdense meteor trails (with electron line densityq≤2.10¹⁴ electrons/mvs. peak signal amplitudes decreases more rapidly with the increasing signal level than what predicted. An exponential (simple and/or log-normal) model is proposed, by taking into account different signal-to-noise ratio thresholds and the Kolmogorov-Smirnov (K-S) procedure is used to test the overall goodness of fit between the set of observations and specified theoretical distributions. It is shown that this model provides a better fit to data mainly for middle-high levels of received power and for values ofq≥10¹³ electrons/m.     

On the activity and structure of the Quadrantid meteor stream

Summary The activity of the Quadrantid meteor stream is analysed on the basis of radar observations at Budrio (44.5°N, 11.6°E), Italy, in 1983, 1984 and 1987. The Quadrantids have appeared as a prominent meteor stream and the compound activity curve is symmetrical with the maximum at solar longitude 282.69°±0.06° (equinox 1950.0). The maxima in individual years vary and are consistent with visual observations in corresponding years. Mean orbit of the stream as well as the radiant area were derived from 54 photographic Quadrantid orbits compiled from Meteor Data Centre and Nippon Meteor Society. The mean radiant was found at α=230.8°, δ=49.5° and the radiant area is elongated covering an area of 8°×4°. The photographic orbital elements obtained over a period of almost 40 years follow the trend of orbital evolution of the stream proposed by Hugheset al. (1979).     

On the 1986 Ursids meteor shower observed at Budrio

Summary Outburst in activity of the 1986 Ursids reported from visual observations was observed also by the Budrio meteor radar. The radar maximum consisting mainly of long-duration echoes preceded the visual one by about half an hour. The peak appeared on December 22, 20∶49 UT (solar longitude 270°.202). The mean photographic orbit of the Ursids shower was derived and compared with that of the parent comet Tuttle.     

Detection of the height of maximum ionization in a meteor trail

Summary Reflection of radio waves from a meteor trail is mainly due to the first Fresnel zone, that is the section of the trail which lies across the foot of the perpendicular from the observer to the trail itself. In general, a radar eche does not give any evidence to the tract of maximum ionization along the same trail. This can be considered as a shortcoming of the radar technique for the exploration of the meteors, which otherwise is so fruitful. This paper shows that, under some specific conditions, even the reflection from the tract of maximum ionization can show up in a meteor echo. This possibility is quite significant, since the knowledge of the height at which the maximum ionization is located leads to the determination of β, the coefficient of meteoric ionization in the upper atmosphere.

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Riassunto La riflessione delle radioonde da una scia meteorica è dovuta preminentemente alla prima zone di Fresnel, cioè al tratto di scia che sta a cavallo del piede di perpendicolare dall'osservatore alla scia medesima. In generale, un eco radar non fornisce indicazioni dell tratto di massima ionizzazione che si trova lungo la scia. è questa una limitazione della tecnica radar per l'esplorazione delle meteore, che peraltro permette di ottenere tante utili informazioni. Il presente articolo mostra che, quando si verifichino alcune specifiche condizioni, anche la rifflessione dal tratto di massima ionizzazione può comparire in un eco meteorico. Questa possibilità è assai rilevante, poichè la conoscenza dell'altezza a cui si ha la massima ionizzazione conduce alla determinazione di β, il coefficiente di ionizzazione delle meteore nell'alta atmosfera.

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Резюме Отражение радиоволн от хвоста метеора в основном обусловлено первой зоной Френеля, что является сечением хвоста, которое лежит поперек основания перпендикуляра от наблюдателя к хвосту. Вообще говоря, радарное эхо не дает каких-либо подтверждений полосы с максимальной ионизацией вдоль хвоста. Это можно рассматривать как недостаток радарной техники для исследования метеоров, которая в остальном является плодотворной. В этой статье показывается, что при некоторых специальных условиях отражение от полосы с максимумом ионизации может быть выделено в метеорном эхо. Эта возможность является очень вазной, т.к. знание высоты, где расположен максимум ионизации, приводит к определению β, козффициента ионизации метеорита в верхних слоях атмосферы.

     

Baseline effect on the forward-scatter radar reflections from meteor trains

Summary The influence of the baseline orientation on the rate of recorded meteor echoes has been shown from the observations carried out during the Lyrid meteor shower periods in 1992 and 1993 with receivers rectangularly displaced from the transmitting station in Bologna with a baseline length of about 700 km. It is shown that the maximum echo rate precedes or occurs later than the shower radiant culminates (at heights of 80°), favouring the 45° radiant elevation and similar angle between the radiant and the beam axis. The consequences of the measured effect on the meteor flux within the shower and sporadic radiant distribution is discussed.