The activity and mass distribution of the summer daytime Taurid meteor complex streams Zeta Perseids and Beta Taurids in 1997-2004 is analysed and discussed. The results are based on radio observations obtained by the BLM

forward-scatter system (Italy-Slovakia) and by the Ondrejov backscatter meteor radar (Czech Republic). The observed positions of maxima of the streams are in a general agreement with previous analysis. The observations indicate a filamentary structure of the streams, the existence of which is supported also by the mass exponent values

Bortolotti, G.

Cevolani, G.

Franceschi, C.

Pecina, P.

Pecinová, D.

Porubčan, V.

Pupillo, G.

Trivellone, G.

Zigo, P.

English

Scientific Open-access Literature Archive and Repository

NOTE BREVIDOI 10.1393/ncc/i2005-10204-4IL NUOVO CIMENTO Vol. 28 C, N. 6 Novembre-Dicembre 2005The daytime Taurid complex meteor streams: Activity and massdistributionG. Pupillo(1)(2), V. Porubcˇan(3)(4), P. Pecina(5), D. Pecinova´(5)G. Cevolani(1), G. Bortolotti(1), C. Franceschi(1), G. Trivellone(1)and P. Zigo(3)(1) CNR-ISAC - via Gobetti 101, 40129 Bologna, Italy(2) Osservatorio di Campi Salentina - 73012 Campi Salentina (Lecce), Italy(3) Department of Astronomy, Physics of the Earth and MeteorologyFMPI Comenius University - 842 48 Bratislava, Slovak Republic(4) Astronomical Institute of the Slovak Academy of Sciences, 845 05 BratislavaSlovak Republic(5) Astronomical Institute of the Academy of Sciences of the Czech Republic251 65 Ondrˇejov, Czech Republic(ricevuto l’11 Novembre 2005; approvato il 29 Dicembre 2005; pubblicato onlineil 18 Gennaio 2006)Summary. — The activity and mass distribution of the summer daytime Tauridmeteor complex streams Zeta Perseids and Beta Taurids in 1997-2004 is analysedand discussed. The results are based on radio observations obtained by the BLMforward-scatter system (Italy-Slovakia) and by the Ondrˇejov backscatter meteorradar (Czech Republic). The observed positions of maxima of the streams are ina general agreement with previous analysis. The observations indicate a filamen-tary structure of the streams, the existence of which is supported also by the massexponent values.PACS 96.50.Kr – Meteors and meteoroids.PACS 95.85.Bh – Asteroids.1. – IntroductionThe spring/summer daytime meteor streams Zeta Perseids and Beta Taurids arepostperihelion continuation of the autumn Taurid stream and were first recorded byradio observations at Jodrell Bank in 1947 [1]. From continuing observations in 1949and 1950 the activity period of the Zeta Perseids was found to be June 1-16 with theshower radiant at right ascension α = 62◦ and declination δ = +24◦ and the Beta Tauridswere observed on June 26-July 4, 1950 with the radiant at α = 86◦, δ = +19◦ [2]. In1960’s the streams were observed by several radio equipments, however, most compactdata were obtained from the Harvard-Smithsonian Radio Meteor Project in 1961-1965 [3]c© Societa` Italiana di Fisica 941942 G. PUPILLO, V. PORUBCˇAN, P. PECINA ETC.and in 1969 [4]. A suggestion that the Beta Taurids are closely related to the Tauridsof October and November was first made in 1951 by Almond and later supported byNilsson, Sekanina and others [5], but already in 1940 Whipple [6] noted that the Tauridsmight produce a stream observable during daylight hours in summer. Based on resultsobtained from the Southern Hemisphere in 1969 (radio equipment of the University ofAdelaide) Gartrell and Elford showed that the Zeta Perseids are probably the twin ofthe Southern Taurids [7]. The annual activity of both streams is low and Sekanina [3]based on Radio Meteor Project has derived the period of activity and maximum of theZeta Perseids, May 20-June 21, June 8 and for the Beta Taurids, June 12-July 6, June26. Cook [8] gives the activity periods and maxima for both streams June 1-17, June 7and June 24-July 6, June 29, respectively.In the present paper the radio observations of both stream by the BLM forward-scatter system (Italy-Slovakia) and by the Ondrˇejov backscatter meteor radar (CzechRepublic) in the period 1997-2004 are presented and discussed.2. – Equipments and observationsThe BLM (Budrio-Lecce-Modra) forward-scatter system for meteor observations hasbeen transmitting a radio signal along two mutually almost rectangular baselines. Thetransmitter is located at Budrio near Bologna (44.6◦N; 11.5◦E, Italy) and receivers arelocated at Lecce (40.3◦N; 18.2◦E, Italy) and Modra (48.4◦N; 17.3oE, Slovakia). Theequipment utilizes a continuous wave transmitting frequency at 42.7 MHz, a fixed mod-ulating tone at 1 kHz and 0.25 kW mean power transmitted in the direction of bothreceiving stations. The baseline distances between the transmitter and receivers are:Bologna-Lecce of 700 km (azimuth 307◦) and Bologna-Modra of 590 km (azimuth 224◦).Details about the equipment published Cevolani et al. [9].The Ondrˇejov radar operates at 37.5 MHz, with a peak power of 10 kW, a pulserepetition frequency of 500 Hz. The equipment utilizes a steerable antenna in azimuthbut fixed in elevation at 45◦. Detailed description of the radar and its operation can befound elsewhere [10].The BLM equipment is operating in the frame of coordinated observations duringselected periods of the year, which cover partially also the periods of activity of thesummer Taurid complex streams, Zeta Perseids and Beta Taurids. Therefore, each yearanother of the streams was observed. In this campaign, the Zeta Perseids were observedin 2000, 2001 and 2002, and Beta Taurids in 1997, 1999 and 2004. Due to reconstructionof the equipment there are missing observations of the streams in 2003.The Ondrˇejov meteor radar started regular observations of the Zeta Perseids andBeta Taurids in 2003 and the first results concerning the activity and mass distributionof particles in the streams in 2003 have already been analysed and published [11].3. – AnalysisFrom the studies of echo counts obtained by the BLM forward-scatter system it is evi-dent that shower echoes can be clearly recognized from sporadic background echo countsonly for long duration echoes [12]. Therefore, the activity curves from the BLM forwardscatter were derived only for long duration echoes of ≥ 8 s. Shower activity was obtainedby subtracting sporadic background counts from all echo counts in corresponding hours.The activity curves represented by the hourly shower echo counts were derived, wherepossible, by combining the data from both receiving stations (Lecce and Modra).THE DAYTIME TAURID COMPLEX METEOR STREAMS: ACTIVITY AND ETC. 943Fig. 1. – Counts of Zeta Perseid meteor shower echoes of duration ≥ 8 s in one hour intervalsobserved by the BLM forward-scatter radio system in 2000, 2001 and 2002. The curves representthe mean values of the data from Lecce and Modra. The counts are normalized to 100 echoesfor the peak activity.The activities of the Zeta Perseids and Beta Taurids for overdense echoes of duration≥ 8 s in individual years, in three days around the maximum, acquired by the BLMsystem are shown in fig. 1 and fig. 2, respectively. The observed counts of echoes forwhich the radiant elevation h was lower than 20◦ were eliminated from the analysis andall echo counts were corrected for the radiant elevation (reduced to the zenithal hourlyrates).The 2004 Ondrˇejov observations were carried out on May 30-31 together with June18 in order to detect the sporadic background of the Zeta Perseids and June 6-12 toestablish the core of the shower. The corresponding periods concerning the Beta Tauridswere respectively June 19 and July 7-8 and June 25-July 1. The method of observationswas the same as in 2003 [11].From the observed data also the mass distribution exponent showing information onsize distribution of particles in the streams could be derived. The mass distribution ex-ponent s was found from the cumulative numbers of echo duration considering ambipolardiffusion for dominant process of an echo decay in the form [13]logNc = − (3/4) (s− 1) log TD + const,(1)where Nc is the cumulative number of echoes with the duration in excess of TD.944 G. PUPILLO, V. PORUBCˇAN, P. PECINA ETC.Fig. 2. – Counts of Beta Taurid meteor shower echoes of duration ≥ 8 s in one hour intervalsobserved by the BLM forward-scatter radio system in 1997, 1999 and 2004. The curves representthe mean values of the data from Lecce and Modra. The 1997 curve is from Modra only. Thecounts are normalized to 100 echoes for the peak activity.The values of s in individual years were obtained as the mean values from the periodof the shower maximum (approximately 8 h) and corresponding sporadic background.The exponent values are together with the positions of activity maxima listed in table I.3.1. Zeta Perseids. – The stream is active in the first half of June with the radiantabove horizon in the Northern mid-latitude sites for about 17 hours and culminates at11 LT. The peak activity according to Cook [8] corresponds to solar longitude of 76.7◦(eq. 2000). The BLM forward-scatter monitored the stream activity in 2000, 2001 and2002, the Ondrˇejov radar in 2003 and 2004.In 2000, the observations were carried out in June 9-16 and probably covered onlythe descending branch of activity. Thus the peak observed at solar longitude of 79.1o isprobably not the main peak. Due to a high level of noise in Lecce, the mass exponentcould be derived from the Modra data only and for the shower (June 9) and sporadicbackground (June 15) s is 1.98 and 2.48, respectively. The value of 1.98 indicates thatthe stream was at the peak relatively rich in larger particles.In 2001 observations (June 5-15) the peak was observed at solar longitude of 76.5◦and was well defined at both stations (Lecce and Modra). The mass exponent derivedfor the shower meteors (June 7) s = 2.24 and for the background meteors (June 12)s = 2.38, which indicates that in 2001 return of the stream both populations were verysimilar.The 2002 Zeta Perseids were observed over the period June 4-10. The peak activityappeared at 76.5◦ and the mass exponents for the shower (June 8) and sporadic (June4) were 2.25 and 2.80, respectively.The 2003 and 2004 Zeta Perseids were observed only at Ondrˇejov. The 2003 resultsTHE DAYTIME TAURID COMPLEX METEOR STREAMS: ACTIVITY AND ETC. 945Table I. – The maxima of activity and mass distribution exponent s derived for the Zeta Perseidsand Beta Taurids observed by the BLM radio system in 1997-2004 and Ondrˇejov meteor radarin 2003-2004.Year Maximum s-sh s-sp Observation(eq. 2000.0) (shower) (sporadic) (receiver)Zeta Perseids2000 79.1◦ 1.98 2.48 combined2001 76.5◦ 2.24 2.38 combined2002 77.2◦ 2.25 2.80 combined2003 78.8◦ 2.12 2.24 Ondrˇejov [11]2004 81.5◦ 2.28 2.50 OndrˇejovBeta Taurids1997 95.7◦ 2.37 2.23 Modra1999 96.1◦ 2.14 2.38 combined2003 94.1◦ 2.23 2.37 Ondrˇejov [11]2004 95.9◦ 2.10 2.38 Lecce(95.8◦) - 2.40 Ondrˇejovwere analysed elsewhere [11]. The 2003 peak of overdense echoes was recorded for solarlongitude of 78.8◦ with the mass exponent of shower meteors s = 2.12. The 2004 peakwas recorded for 81.5◦. This value is exhibiting that the peak activity of the stream canchange from one shower return to another also for a few degrees indicating a filamentarystructure of the stream.3.2. Beta Taurids. – The Beta Taurids are active in the second half of June andbeginning of July [8]. The shower radiant culminates at 11:15 LT and is above horizonfor the Northern mid-latitude observations for about 16 hours. The peak of activity isgenerally posed on June 29 (solar longitude 76.7◦ (eq. 2000)) [8]. The shower activitywas monitored by the BLM equipment in 1997, 1999 and 2004 and by the Ondrˇejovmeteor radar in 2003 and 2004.The 1997 Beta Taurids observation was carried out only in the direction to Modra(June 20-July 1) and due to a very low echo counts and shower activity, the curve in fig. 2for 1997 depicts all echo counts (shower and sporadic). Two peaks at 94.7◦ and 95.6◦are observed. The mass exponent derived from an interval of 8 hours about the peak at95.6◦ (period the least contaminated by background) for all echo counts, is s = 2.37 andsporadic background value from the end of observations is s = 2.23.In 1999 the transmission was made along both baselines in the period June 24-July 1and the peak was observed for 96.1◦, with mass exponent for the shower s = 2.14 andfor sporadic background s = 2.35.The 2003 shower was observed at Ondrˇejov [11] with the peak activity of overdenseechoes at 94.1◦.The observations in 2004 were performed simultaneously by both radio equipments.Very low activity of the shower was detected in 2004 at Ondrˇejov. Thus the peak pre-sented in table I (solar longitude of 95.8◦) is very uncertain. The data from Modra werecontaminated by strong interferences and spurious long duration echoes overlapping thestandard shower echo activity and therefore only data from Lecce were used and theBLM data from Lecce gives the peak for 95.9◦. The peaks obtained by both equipmentsare completely consistent.946 G. PUPILLO, V. PORUBCˇAN, P. PECINA ETC.4. – ConclusionsThe activity of the spring/summer Taurid complex streams, the Zeta Perseids andBeta Taurids over the period 1997-2004 was studied by two different radio equipmentsapplied for meteor observations: BLM forward-scatter system and Ondrˇejov backscattermeteor radar. The observed positions of maxima of the streams (table I) are in a generalagreement with previous analysis. The observations indicate a filamentary structure ofthe streams, the existence of which is supported also by the mass exponent values foundfor individual returns of the streams.∗ ∗ ∗The authors acknowledge the support of the research to the Institute ISAC-CNR,Bologna and to VEGA, the Slovak Grant Agency for Science, grant Nos. 1/0204/03,2/3024/23 and to the Grant Agency of Czech Republic, grant No. 205/03/1405.REFERENCES[1] Clegg J. A., Hughes V. A. and Lovell A. C. B., Mon. Not. R. Astron. Soc., 107(1947) 369.[2] Aspinall A. and Hawkins G. S., Mon. Not. R. Astron. Soc., 111 (1951) 18.[3] Sekanina Z., Icarus, 18 (1973) 253.[4] Sekanina Z., Icarus, 27 (1976) 265.[5] Kronk G. W., Meteor Showers: A Descriptive Catalogue (Enslow Publ., Hillside, USA)1988.[6] Whipple F. L., Proc. Am. Philos. Soc., 83 (1940) 711.[7] Gartrell G. and Elford W. G., Aust. J. Phys., 28 (1975) 591.[8] Cook A.F., Evolutionary and Physical Properties of Meteoroids, edited by Hemenway C.L., Millman P. M. and Cook A. F. (1973), p. 183.[9] Cevolani G., Bortolotti G., Franceschi C., Grassi G., Trivellone G.,Hajduk A. and Kingsley S. P., Planet. Space Sci., 43 (1995) 765[10] Plavcova´ Z. and Sˇimek M., Bull. Astron. Inst. Czechosl., 11 (1960) 228[11] Pecina P., Porubcˇan V., Pecinova´ D., To´th J., Earth, Moon and Planets, 95 (2005)in print.[12] Pupillo G., Porubcˇan V., Cevolani G., Bortolotti G., Franceschi C.,Trivellone G., Zigo P. and Hajduk A., Nuovo Cimento C, 27 (2004) 213.[13] Kaiser T. R., Meteors (Pergamon Press, London) 1955.

The daytime Taurid complex meteor streams: Activity and mass

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The daytime Taurid complex meteor streams: Activity and mass distribution

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