I M O   S h o w e r   C i r c u l a r

       Activity profile of the 1998 LEONIDS

--OVERVIEW

A first population index and ZHR profile of the 1998 return
of the Leonids is given below. The population index r represents
the increase of meteor numbers towards fainter magnitudes. A
small value means a high proportion of bright meteors. The
profile shows low r-values between solar longitudes 233.9
and 235.5 (Nov 16, 11h and Nov 18, 01h UT), except for a short
period of high r-value at 235.26 (Nov 17, 19h15m UT; all long-
itudes refer to eq. J2000).

The low population index is typical for the background component
of the Leonid meteoroid stream being rich in bright meteors.
Predictions were given for the storm component of the stream.
The strength of this component, which is formed by freshly ejected
material from the parent comet 55P/Tempel-Tuttle, can hardly be
estimated in advance. A young meteoroid stream component is rich
in faint meteors. The increase of r at the time of storm pre-
diction hints on the presence of this component.

The ZHR profile shows a broad maximum centred at solar longitude
234.5 (Nov 17, 01h30m UT) with an average ZHR of 260. The full
width at half maximum is about 16 hours. The 'storm component'
exhibits an enhancement at the declining part of the background
activity. The peak time of this component lies between 235.3 and
235.4 (Nov 17, 20h20m and 22h30m UT).

The maximum ZHR is lower than what one might have expected after
the excited reports about the fireball night Nov 16-17. However,
there is actually no report giving 500 _recorded_ meteors in an 
hour. Rates of 1000 or 2000 are obviously based on extrapolations
or sums of several observers.

The strong background component before the 'storm component'
resembles the appearance of the 1965 Leonids, one year before
the 1966 storm. The prospects for 1999 may be evaluated
comparing the 1998 Leonid data with previous Leonid outbursts
and their 'year before'.

--DATA SECTION

The population index and ZHR profiles given below are based on
the following observers:

Ghazalaha Al-Abed (ABEGH), Iyad Ahmad (AHMIY), Ahmad Al-Niamat (ALNAH),
Rainer Arlt (ARLRA), Joseph D. Assmus (ASSJO), Zaid Ata (ATAZA),
Jlia Babina (BABJL), Ana Bankovic (BANAN), Rony Barry (BARRO),
Luis R. Bellot (BELLU), Felix Bettonvil (BETFE), Neil Bone (BONNE),
Mark Borg (BORMR), Michael Boschat (BOSMI), Joana M. Brunet (BRUJO),
Marija Cajetinac (CAJMA), Arturo Carvajal R. (CARAR), Tal Carmon (CARTA),
Andrew Casely (CASAN), Matthew Collier (COLMA), Tim Cooper (COOTI),
Uros Cotar (COTUR), Stefano Crivello (CRIST), Hani Dalee (DALHA),
Luigi d'Argliano (DARLU), Mark Davis (DAVMA), Benoit Dejust (DEJBE),
Vincent Desmarais (DESVI), Peter Detterline (DETPE), Elena Dimovski
(DIMEL), John Drummond (DRUJO), Tonis Eenmae (EENTO), Maurizio Eltri
(ELTMA), Frank Enzlein (ENZFR), Tamas Fodor (FODTA), Keiiti Fukui
(FUKKE), Nobuyuki Fukuda (FUKNO), Ofer Gabzo (GABOF), George W. Gliba
(GLIGE), Orly Gnat (GNAOR), Shelagh Godwin (GODSH), Amit Gokhale (GOKAM),
Sagar Gokhale (GOKSA), Yeshodhan Gokhle (GOKYE), Alexandra Golova (GOLAL),
Prerana Gore (GORPA), Roberto Gorelli (GORRO), Michal Haltuf (HALMI), 
Takema Hashimoto (HASTA), Roberto Haver (HAVRO), Kim Hay (HAYKI), 
Amera Hemsy (HEMAM), Kamil Hornoch (HORKM), Daiyu Ito (ITODA), 
Kiyoshi Izumi (IZUKI), Helle Jaaniste (JAAHE), Vibor Jelic (JELVI), 
Carl Johannink (JOHCA), Ivan Jokic (JOKIV), Kevin Jones (JONKE), 
Javor Kac (KACJA), Primoz Kajdic (KAJPR), D. Kalayda (KALDU), 
Dmitrij Karkach (KARDM), Niladri Kar (KARNI), Kenya Kawabata (KAWKE), 
Srdjan Keca (KECSR), Akos Kereszturi (KERAK), Noor Al-Khateeb (KHANO), 
Mark Kidger (KIDMA), Kevin Kilkenny (KILKE), Khalil Konsul (KONKH), 
Marija Kotur (KOTMA), Jakub Koukal (KOUJA), Nikola Kresojevic (KRENI),
Tom Kucharski (KUCTO), Brigitte Kuneth (KUNBR), Werfried Kuneth (KUNWE),
Zsolt Lantos (LANZS), Anna S. Levina (LEVAN), Mihir Limaye (LIMMH), 
Vladimir Lukic (LUKVL), Robert Lunsford (LUNRO), Mirjana Malaric (MALMR),
Katuhiko Mameta (MAMKA), David Martinez Delgado (MARDA), Pierre Martin
(MARPI), Takuya Maruyama (MARTA), Antonio Martinez (MARTI),
Yukihisa Matumoto (MATYU), Alastair McBeath (MCBAL), Stephen McCann
(MCCST), Lukas Mecir (MECLU), Mark Mikutis (MIKMR), Ana Milovanovic
(MILAA), Dragan Milisavljevic (MILDR), Iris Miljacki (MILIR), 
Hidekatu Mizoguchi (MIZHI), Amruta Modani (MODAM), Sirko Molau (MOLSI), 
William Morgan (MORWI), Darshan Mundada (MUNDA), Sin Nakayama (NAKSI),
Koji Naniwada (NANKO), Sven Nather (NATSV), Dalibor Nikolic (NIKDA),
Prakash Nitsure (NITPR), Mohammad Odeh (ODEMO), Ibrahim Odwan (ODWIB),
Eran Ofek (OFEER), Hiroyuki Okayasu (OKAHI), Masayuki Oka (OKAMA), 
Dragana Okolic (OKODR), Kazuhiro Osada (OSAKA), Ketan Pendse (PENKE), 
Alfredo Pereira (PERAF), Dusan Perovic (PERDU), Suyin Perret-Gentil
(PERSU), Furio Pieri (PIEFU), Mila Popovic (POPMI), Dubravko Potkrajac
(POTDU), Tushar Purohit (PURTU), Ina Rendtel (RENIN), Jurgen Rendtel
(RENJU), Francisco Rodriguez Ramirez (RODFR), Juan Rodriguez (RODJU), 
Victor Ruiz Ruiz (RUIVI), K.V. Sankaranarayanan (SANKV), Shashank
Shalgar (SHASH), Brian Shulist (SHUBR), Hiroyuki Sioi (SIOHI), 
Vesna Slavkovic (SLAVE), James N. Smith (SMIJN), Manuel Solano Ruiz
(SOLMA), George Spalding (SPAGE), Ulrich Sperberg (SPEUL), Mark
Stafford (STAMA), Enrico Stomeo (STOEN), Niko Stritof (STRNI), David
Swann (SWADA), Eva Szabados (SZAEV), Richard Taibi (TAIRI), Masaaki
Takanasi (TAKMA), Mika Takanasi (TAKMI), Khaled Tell (TELKH), Istvan
Tepliczky (TEPIS), Kazumi Terakubo (TERKA), Neelima Thatte (THANE),
Danilo Tomic (TOMDA), Yasuhiro Tonomura (TONYA), Michael Toomey (TOOMI), 
Gabrijela Triglav (TRIGA), Josep M. Trigo Rodriguez (TRIJO), Mihaela
Triglav (TRIMI), Anne van Weerden (VANAE), Erwin van Ballegoy (VANER),
Miquel A. Villalonga Vidal (VILMQ), Catarina Vitorino (VITCA), 
Marija Vlajic (VLAMA), Maja Vuckovic (VUCMJ), Barbara Wilson (WILBA),
George Zay (ZAYGE).

-----------------------------------------
Date   Time Solarlong ZHR   +-  nLEO nOBS
-----------------------------------------
Nov 14 2000  232.266  10.1  2.4   16   4
Nov 15 0830  232.789  20.8  6.6    9   1
Nov 15 2130  233.331  17.3  2.0   73  12
Nov 16 0030  233.455   8.5  0.9   90  25
Nov 16 0330  233.579   6.3  0.9   53  16
Nov 16 1030  233.887  26.9  2.4  124   6
Nov 16 1400  234.033  40.8  3.3  155   7
Nov 16 1840  234.227 121.3 11.4  113   8
Nov 16 1910  234.251 140.6  8.4  276  16
Nov 16 2050  234.315 162.0  6.1  706  25
Nov 16 2200  234.361 163.8  4.8 1188  31
Nov 16 2320  234.420 211.4  4.2 2569  57
Nov 17 0030  234.471 241.9  3.4 4992 127
Nov 17 0130  234.511 256.7  3.1 7017 176
Nov 17 0230  234.555 252.2  3.0 7190 175
Nov 17 0330  234.598 243.0  3.3 5451 129
Nov 17 0430  234.639 239.7  4.2 3222  66
Nov 17 0620  234.711 202.0  5.4 1415  35
Nov 17 0720  234.756 188.7  5.3 1265  36
Nov 17 0840  234.811 166.8  4.1 1650  41
Nov 17 0930  234.848 158.8  4.1 1470  35
Nov 17 1040  234.897 135.2  4.3  985  24
Nov 17 1130  234.931 125.0  5.7  483  11
Nov 17 1620  235.131 100.7  4.7  450  14
Nov 17 1700  235.164 101.0  3.3  924  28
Nov 17 1810  235.212 105.1  2.6 1613  47
Nov 17 1910  235.255 111.1  2.5 1996  62
Nov 17 2020  235.300 120.0  3.2 1392  51
Nov 17 2120  235.344 118.1  4.5  674  32
Nov 17 2200  235.373 127.2  7.9  260  11
Nov 18 0010  235.462  45.5  1.9  549  36
Nov 18 0110  235.505  46.7  1.3 1347  80
Nov 18 0230  235.559  44.0  1.4  983  55
Nov 18 0600  235.705  33.2  1.7  375  22
Nov 18 0800  235.791  33.3  1.9  298  19
Nov 18 0940  235.862  36.2  2.9  160   8
Nov 18 1710  236.180  32.6  6.7   23   3
Nov 18 1840  236.239  41.9  2.7  235  13
Nov 18 1940  236.281  40.1  2.5  254  13
Nov 18 2320  236.434  16.5  2.1   63   7
Nov 19 0100  236.505  13.5  1.8   53   7
Nov 19 0130  236.526  20.7  3.6   32   3
Nov 20 0800  237.809  30.1  6.3   22   2
-----------------------------------------

Solar longitudes refer to eq. J2000, 'nLEO' is the number of 
Leonids involved in the average, 'nOBS' is the number of
observing periods averaged. ZHRs were computed with the follow-
ing population index profile:

-------------------------------------
Date   Time Solarlong  r    +-   nLEO
-------------------------------------
Nov 15 1730  233.170 2.420 0.270   63
Nov 16 1130  233.919 1.307 0.073  117
Nov 16 1600  234.113 1.382 0.044  900
Nov 16 1920  234.250 1.601 0.172  833
Nov 16 2240  234.390 1.271 0.025 1873
Nov 17 0020  234.465 1.228 0.012 5947
Nov 17 0200  234.535 1.275 0.013 8378
Nov 17 0320  234.591 1.350 0.019 4702
Nov 17 0620  234.717 1.440 0.043 1779
Nov 17 0900  234.827 1.421 0.045 2076
Nov 17 1020  234.881 1.417 0.058  863
Nov 17 1620  235.130 1.940 0.283  162
Nov 17 1900  235.245 2.038 0.176  660
Nov 17 1920  235.261 1.988 0.089 1430
Nov 17 1930  235.268 1.921 0.086 1014
Nov 17 2200  235.373 1.295 0.013   45
Nov 17 2310  235.421 1.394 0.042  188
Nov 18 0020  235.467 1.534 0.042  586
Nov 18 0100  235.501 1.620 0.048  658
Nov 18 0220  235.553 1.970 0.204  315
Nov 18 0800  235.790 1.802 0.108  279
Nov 18 1720  236.184 1.982 0.186  272
Nov 18 1900  236.257 2.160 0.122  261
Nov 18 2300  236.433 2.106 0.218   65
-------------------------------------

The zenithal exponent was gamma=1.0; a re-computation with 
gamma=1.4 did not produce significantly different results.
Observations with radiant elevations lower than 20 degrees
or total corrections greater than 5.0 were excluded from the
averages.
 

More observational reports were received from

Andras Adrovicz, Farrahzadi Azzadeh, Bozorgi Behnaz, Worachate
Boonplod, Ravi Brahmavar, Diadina Cotte, Szillard Csizmadia, Marc
de Lignie, David Dickinson, Alipour Elnaz, David Farkas, Azeemlu
Fatemeh, Katalin Hidasi, Brujerdi Hoda, Peter Horvath, Hyabanyan
Hossein, Yu Ji-hong, Timo Kinnunen, Csaba Lendvai, Doug Little,
Keith Little, Paul Maley, Maleki Mania, Fred Mason, Dan McIntosh,
Karoly Mikics, Masjedi Morad, Adam Nemeth, Shigemi Numazawa, Andras
Petyus, Adam Pozsik, Rezaai Reza, Qi Rui, Khoeini Saloumeh, Moghimi
Saman, Debasis Sarkar, Lamei Sepideh, Kharrazi Sharmin, Amy Shelton,
Ghassemi Sima, Szandor Szabo, Darren Tabbot, Hezareh Talayeh,
Zoltan Tarnoki, Zoltan Toth, Zoltan Zelko, Sajjadi Zeynab Wu Zhi-wei

---
Rainer Arlt, 1998 November 26, 11h UT.
International Meteor Organization
http://www.imo.net
---
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