PLEASE NOTE:


*

CCNet, 24 AUGUST 1999: CLIMATIC & SOCIAL CATASTROPHES AROUND 4000 BP
--------------------------------------------------------------------


(1) 4000 BP CLIMATIC UPHEAVAL
    Doug Keenan <doug.keenan@virgin.net>

(2) LATE HOLOCENE ENVIRONMENTAL AND SOCIAL UPHEAVAL: SEARCH FOR CLUES
    STILL WIDE OPEN
    Benny J Peiser <b.j.peiser@livjm.ac.uk>

(3) SHOCK, HORROR: EARTH'S OCEANS WILL DRY UP - IN A BILLION YEARS
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(4) SDSS DISCOVERS ITS FIRST COMET
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(5) PERSEIDS 1999
    Rainer Arlt <rarlt@aip.de>

===========
4000 BP CLIMATIC UPHEAVAL

From Doug Keenan <doug.keenan@virgin.net>

Hi Benny,
 
At the Cambridge conference of 1997 and at the NATO conference of 1994,
the main question was this: was there a major climatic upheaval four
millennia ago, and if so, what was the cause? The conferences, and
several papers in the scientific literature, have led to much
discussion. The general view seems to be that something 
happened--though it has been unclear what. The most popularly-suggested
cause has been a comet.
 
Below is the abstract of a paper that I presented at the 1999 meeting
of the IUGG (the main international conference for Earth scientists). 
I believe that the paper effectively answers the main question posed
above. The case for a climatic upheaval now appears conclusive--and the
upheaval was likely the largest climatic event since the ice ages. 
There is, however, only inconclusive/questionable evidence for a comet
being the cause; rather, the upheaval appears to have been triggered by
a colossal volcanic eruption.
 
The work also strongly supports proposals from Barbara Bell (Harvard),
Harvey Weiss (Yale), and others, for a major climatic influence on
civilisations.  In each of the world's three regions of civilisation,
the influence of the upheaval appears to have been dramatic:

*  In the Ancient Near East, drought led to the collapse of the
   earliest civilisations--including the millennium-old Kingdom of
   Egypt.
*  In the Indus Valley, the upheaval coincided with the transition of
   the civilisation to its depopulated Post Urban phase.
*  In ancient China, the upheaval induced flooding, and the organisation to
   deal with this likely led to the founding of the first Chinese
   dynasty.
 
The upheaval was thus probably the biggest natural event to happen to
humanity since the ice ages.
___________________________________________________________
 
THE THREE-CENTURY CLIMATIC UPHEAVAL OF C. 2000 BC, AND REGIONAL
RADIOCARBON DISPARITIES
 
Douglas J. KEENAN (The Limehouse Cut, London E14 6N, U.K.)
 
Several researchers have previously identified a severe climatic
upheaval in tropical North Africa that began just over 4000 years ago
and lasted for about three centuries. The upheaval is known to have
occurred shortly after a volcanic eruption, and companion work proposes
that this eruption was colossal. Here, we suggest how the eruption
acted as a trigger for the upheaval: by forcing changes in ocean
circulation; although the initial (atmospheric) forcing lasted only a
few years, the ocean required three centuries to regain equilibrium. 
The suggested triggering mechanism is supported by palaeoceanographic,
palaeoecological, and archaeo-historical data and by related
experiments with a (coupled general-circulation) climate model. We
argue that the changes in ocean circulation forced changes in
sea-surface temperatures that led to a weakening of the south-west North
African monsoon.
 
The upheaval has been proposed to have also encompassed south-western
Asia. We argue that it encompassed most of the Northern Hemisphere: we
present a variety of palaeoecological and palaeoceanographic evidence
and describe the principal underlying climatology.  In some areas the
upheaval was the most severe since the ice ages.
 
The full scope of the upheaval has previously been missed in part
because radiocarbon dates from some areas are centuries too early:
palaeoclimatic events in different areas thus appeared asynchronous. 
(The erroneous radiocarbon dates also misled searches seeking ice-core
and tree-ring evidence of the eruption.) The cause of the
radiocarbon-dating disparities is identified as a regional deficiency
in 14C, and we locate the region's source of 14C-deficient carbon.
 
___________________________________________________________
 
The paper is available from  http://freespace.virgin.net/doug.keenan
Following are some brief technical remarks.
 
The initial (atmospheric) forcing was a cooling over the Labrador Sea
and a warming over the Norwegian Sea.  Such cooling/warming is caused
by the intensification of the polar vortex that is induced by
volcanogenic aerosols. The cooling/warming in the Labrador/Norwegian
Sea increased/decreased deepwater production there. This, in turn,
forced an extremely high phase of the North Atlantic Oscillation.  The
high NAO explains why, for example, some areas of Europe were cool/dry
while others were warm/wet and still others experienced little change. 
Once disequilibrated, the oceans took centuries to recover: so did the
climate.
 
The mechanism underlying the radiocarbon dating errors has been largely
developed by others. Briefly, it is as follows. During the last ice
age, the Black Sea was actually a freshwater lake. As the ice age
ended, this freshwater flowed out of the Black Sea into the
Mediterranean, which greatly altered Mediterranean circulation. In
particular, Mediterranean subsurface waters stagnated for at least six
millennia. During the stagnation, 14C in subsurface waters
radioactively decayed and was not replenished. Later, as the
Mediterranean circulation was restored--a process that took more
millennia--the 14C-deficient subsurface waters circulated back to the
surface. The 14C-deficient carbon was then degassed to the atmosphere:
similar processes have been observed today off Ecuador, in the Arabian
Sea, and possibly in the Weddell Sea.  Thus many radiocarbon dates from
samples that grew in or downwind from the Mediterranean are some
centuries too old.
 
Cheers,
Doug Keenan

==============
(2) LATE HOLOCENE ENVIRONMENTAL AND SOCIAL UPHEAVAL: SEARCH FOR CLUES
    STILL WIDE OPEN

From Benny J Peiser <b.j.peiser@livjm.ac.uk>

No discussion of late 3rd millennium BC environmental change and
civilisation collapse is complete without a survey of those Early
Bronze Age settlements which fell into ruin due to seismic activity.
Earthquake damage has been a frequent explanation for settlement
destruction, destruction layers or abandonment of sites. Despite the
often fragmentary and sometimes inconclusive character of
archaeological findings, it is feasible to recognise specific
features of earthquake effects in archaeological works and thereby to
distinguish these peculiarities and those from other natural or
anthropogenic effects of site damage and destruction (Stiros 1996).

Interestingly, of all the various factors and data scrutinised for
clues related to the environmental and social upheavals at the end of
the Early Bronze Age, seismic and tectonic activity is the subject
matter most neglected by scholars. Yet most archaeologists are only
too aware that Claude Schaeffer’s voluminous 'Stratigraphie Comparée
et Chronologie de l’Asie Occidentale' is teeming with archaeological
evidence for extensive earthquake damage detected in Bronze Age
settlements throughout the Near and Middle East (Schaeffer 1948).

Claude Schaeffer, the 20th century’s most eminent French
archaeologist, was the first researcher to present evidence for
widespread seismic catastrophes in large parts of Asia minor and the
Levant at around 2300 BC. Based on a comparative study of destruction
layers in more than 40 sites, he ordered and classified earthquake
horizons as synchronous and interrelated benchmarks in archaeological
stratigraphy and chronology. Evidence for major earthquake damage in
Early Bronze Age strata had been detected in many Anatolian and Near
Eastern settlements, such as Troy, Alaca Hüyük, Boghazköy, Alishar,
Tarsos, Ugarit, Byblos, Qalaat, Hama, Megiddo, Tell Hesi, Beit
Mirsim, Beth Shan, Tell Brak and Chagar Bazar (Gammon 1980; 1982).

Most scholars, however, have refrained from taking Schaeffer’s main
research-findings into consideration. The recent and most
comprehensive textbook on 3rd millennium BC civilisation collapse
fails to mention his research altogether (Dalfes et al. 1997). One
looks in vain for any reference to his theory of Early Bronze Age
collapse. This reticence is even more remarkable in view of the fact
that Schaeffer was also, to my knowledge, the first archaeologist to
claim that a distinct shift in climate was synchronous with
civilisation collapse. “Au Caucase et dans certains régions de
l’Europe protohistorique, des changements de climat semblent, ŕ cette
période, avoir amené des transformations dans l’occupation et
l’économie du pays” (Schaffer 1948, 555/556). 

There is, of course, a plausible reason for the selective perception
of the available evidence by most scholars. Of all the proxy data
available in the vast literature on late 3rd millennium environmental
change, the evidence for seismic and tectonic activity appears to be
the most inconclusive. Moreover, it seems impossible to integrate
widespread seismic activity into any scenario of abrupt climate
change. Indeed, most researchers would agree that there seems to be
no natural phenomenon capable of triggering abrupt climate change
*and* extensive seismic activity at the same time. Yet almost 35
years ago, René Gallant (1964) focused on this apparent anomaly in
Schaeffer’s work and suggested that cosmic impacts would easily
account for the synchronicity of climate change and seismic activity.

“C.F.A. Schaeffer”, Gallant wrote, “presumes that the catastrophes
which caused the end of civilisations in Eurasia originated in
devastating earthquakes which shook the world. He mentions that many
sites show that the destructions have been contemporary with
‘climatic changes, which seem to have brought about transformations
in the occupation and the economy of the country’. Schaeffer does not
seem to have been struck by the connection between those two
important contemporaneous events: earthquakes and climatic changes.
As we have previously seen, those two events are closely connected
with cosmic catastrophism: both are inevitable results of huge
meteoric impacts” (Gallant 1964, 214/15).

Some twenty years later, Mandelkehr (1988) published further evidence
which confirmed a pattern of geological perturbations at c. 2300 BC.
According to his findings, “the most significant aspect of the
geological evidence is the crustal movements that apparently began at
about the same time around 2300 BC at many regions of the Earth”
(Mandelkehr 1988, 11). In this section, I will present the most
important palaeo-seismic data collated by Mandelkehr and will add to
that more recent research findings.

During the 1950s and 60s, a number of geological investigations along
the east coast of North America found that the Atlantic coast
experienced differential warping at c. 2300 BC (Mandelkehr 1988).
While the regional uplifts in question appear to be a gradual
geological upward movement, the onset of these discontinuities at
this particular time is certainly conspicuous.

Strong earthquakes leave geological evidence in form of surface
faulting, folding or (in the case of earthquakes in urban areas) in
form of site destruction. These features are often preserved in the
archaeological record and can therefore be detected by
archaeo-seismological research (Stiros and Jones 1996). The presence
of historical seismicity and tectonic features are recognised as the
most reliable criteria for identifying earthquake damage. However,
lack of such unambiguous characteristics cannot be considered
conclusive evidence for a lack of earthquake destruction (Vittori et
al. 1991).

Geological evidence for ancient earthquakes may be preserved in the
archaeological record and, therefore, palaeo-seismological studies
may detect and date them. Historical seismicity and the presence of
well-developed tectonic geomorphic features are often recognised as
reliable criteria for identifying active faulting. However,
extra-terrestrial impacts are capable of triggering seismic activity
in geological areas which are normally not prone to tectonic
activity.

Crustal deformation at around the same time has also been detected
along the Gulf of Mexico. At Vera Cruz, Mexico, the so-called Palo
Hueco Culture which had existed here since c. 4000 BC “was found to
be sealed throughout its extent by a culturally sterile sand cap
after 2400 BC, apparently corresponding to a major inundation shortly
after that time […]. The conclusion reached by the investigator was
that the Mexican coast experienced a long term subsidence at the same
time that the Florida region apparently underwent uplift” (Mandelkehr
1988, 12).

Nunn’s research (1995) has established that the islands of the
south-central Lau Ridge of the South Pacific experienced a number of
seismic events, one of which appears to coincide with the mid/late
Holocene transition. On the island of Lekeba, four coseismic-uplift
events during the Holocene were identified, the latest of which
occurred c. 3800 BP.

Research by Worsley et al. (1995) on the Holocene vegetational
evolution around Lake Hendry in northern Quebec, Canada, shows that
the development of a thin peat cover coincided with the emergence of
land around 4300 BP, following an episode of isostatic uplift.
Analysis of stratigraphic sections of the Montague Harbour in British
Columbia has documented a distinct episode of sea-level transgression
caused by tectonic subsidence of the area c 3600 BP (Reinhardt et al.
1996). At about the same time, tectonic sea-level changes have also
occurred in other parts of western British Columbia. Evidence for
tectonically-induced events at c. 3600 BP in southern areas of
Vancouver Island, Canada, have recently been reported by Matthews and
Clague (1994). These punctuations are thought to have caused coastal
subsidence and are consistent with large-scale (magnitude M>8)
earthquakes (Reinhardt et al. 1996).

A particularly manifest episode of seismic activity at the mid/late
Holocene boundary has been detected by Forman et al. (1991) in
sediment cores of the Wasatch fault zone, in north central Utah. The
stratigraphy in two trenches excavated across fault scarps is
characterised by a distinct earthquake stratum which buried a soil
developed on a middle Holocene layer. The researchers have dated this
palaeo-earthquake at the mid/late Holocene transition tentatively to
c. 4300 BP.

Other evidence for extensive tectonic activity during the late 3rd
millennium BC comes from the Oquirrh fault zone, a normal fault that
bounds the east side of Tooele Valley in central Utha. A recent study
by Olig et al. (1994) on scarp morphology suggests that the most
recent surface-faulting earthquake in this region occurred during the
3rd millennium BC, an event tentatively dated to c. 4400 BP. The
researchers also found that, at two sites at the Big Canyon and Pole
Canyon, trenches exposed faulted Lake Bonneville sediments and thick
wedges of fault-scarp derived colluvium associated with this event.
Since a bulk sediment sample from fluvial deposits which buried the
fault scarp of the last major earthquake yielded a radiocarbon age
estimate of c. 4340 ± 60 BP, it is highly probable that this massive
earthquake coincided with similarly high levels of seismic activity
in other parts of the world.

Conclusions

At some time around 2300 BC, a large number of major civilisations
collapsed. At the same time, there is widespread evidence for abrupt
and widespread environmental catastrophes. Sudden sea-level changes,
catastrophic inundations, widespread seismic activity and earthquake
damage, changes in glacial features and a signal for an abrupt
climatic downturn have been detected at c. 2350. A survey of some 500
excavation reports, research papers and scientific abstract on late
3rd millennium BC civilisation collapse and environmental change show
a distinct pattern of environmental and social upheaval at this time.

A large number of sites and cities of the first uraban civilisations
in Asia, Africa and Europe appear to have collapsed at around the
same time. The proxy data detected in the marine, terrestrial,
biological, climatological and archaeological records point to sudden
environmental, climatic and social upheavals which appear to coincide
with simultaneous sea- and lake-level changes, increased levels of
seismic activity and widespread flood disasters. The main problem in
interconnecting this vast amount of data is the application of
incoherent and imprecise dating methods in different areas of
geological and climatological research. It is hypothesised that the
globally detected evidence for the sudden environmental and social
upheavals at the start of the late Holocene are interconnected and
that chronological deviations are primarily due to imprecise dating
methods. Neither a seismic nor a climatic explanation for these
significant natural and social punctuations appear capable to account
for these events since it is evidenced by a great diversity of
ecological alterations and an enormous variety of damage features. The
punctuation of extra-terrestrial debris, on the other hand, can have
catastrophic effects on the ecological system in a variety of
patterns which match the main features documented in this comparative
analysis.

---------------
Excerpt from Benny J Peiser: "Comparative Analysis of Late Holocene
Environmental and Social Upheaval: Evidence for a global disaster
around 4000 BP", in: NATURAL CATASTROPHES DURING BRONZE AGE
CIVILIZATIONS: ARCHAEOLOGICAL, GEOLOGICAL, ASTRONOMICAL AND CULTURAL
PERSPECTIVES, Benny J Peiser, Trevor Pamer, Mark E Bailey, eds.
British Archaeological Report [BAS S728], Oxford 1998, pp. 117-139

===================
(3) SHOCK, HORROR: EARTH'S OCEANS WILL DRY UP - IN A BILLION YEARS

From Andrew Yee <ayee@nova.astro.utoronto.ca>

[http://asia.yahoo.com/headlines/230899/news/935399580-90823091301.newsasia.html]

Monday, August 23, 1999, 5:13 AM EDT

Japanese team says Earth's oceans will dry up in a billion years

TOKYO (AFP) -- Earth's oceans will dry up in one billion years,
following in the footsteps of Mars and extinguishing all life on the
planet, according to Japanese research released here Monday.

"Considering the accelerating speed of the water's disappearance, it
will take about one billion years for the last waters to disappear from
the Earth's surface," said the research chief, professor Shigenori
Murayama.

The oceans were sinking into the mantlerock -- the interior of the
Earth above the central core -- along with the tectonic plates, said
the paper by the Tokyo Institute of Technology.

"It is an historical necessity (sic!) for life forms on all 
water-bearing planets to follow a path to extinction after the complete
dissapearance of water from the surface," he told AFP.

The disappearance of water from Earth "happened on Mars as well," said
Murayama, professor of earth and natural sciences at the institute.

The report was based on experiments measuring Earth's sub-surface
temperatures and 2,000 academic works aimed at calculating the
formative period for sedimentary rocks, he said.

The cooling of the Earth's magma led to falling temperatures 100
kilometers (62 miles) below the surface, which in turn dragged water
beneath the crust, the professor told AFP after the report's release.

While about 1.12 billion tonnes of ocean waters sank into the crust
annually, only 230 million tonnes were being released, according to the
research.

The report estimated that sea water started to return to the mantlerock
about 750 million years ago, leading to an expansion in the
subcontinental mantle and the emergence of continents above water.

"This is a new interpretation to answer why most continents had been
under seawater before 750 million years ago," said the report.

If shown to be true, it would also explain a rapid increase in the
level of oxygen in the atmosphere at the time, he said.

Oxygen-rich plankton which formed rocks beneath the oceans would have
been exposed to the air by the receding waters, unlocking the gas, the
professor explained.

In turn, the increased oxygen levels in the atmosphere may have led to
"the emergence of large life bodies" which defined the start of the
Phanerozoic time.

The Earth passed an "irreversible" point 750 million years ago, before
which seawater volumes had been stable.

"The volume of seawater has decreased with time since then -- the Earth
will lose seawater in future, which would be the time of ending life on
this planet."

Scientists already believe that water once flowed freely on Mars, but
do not understand why it may have disappeared.

Copyright © 1999 Agence France-Presses. All rights reserved.

======================
(4) SDSS DISCOVERS ITS FIRST COMET

From Andrew Yee <ayee@nova.astro.utoronto.ca>

Sloan Digital Sky Survey (SDSS)
 
August 13, 1999
 
SDSS Discovers its First Comet
 
The Sloan Digital Sky Survey has found its first new comet, the latest
in a series of interesting treasures mined from the Survey's test-year
data.
 
Julianne Dalcanton, an SDSS astronomer from the University of
Washington, was sifting through test run data from March 20. She was
using a "fuzzy blob" search algorithm to find faint galaxies for her
research. But in addition to many fuzzy-looking galaxies, the algorithm
also yielded an elongated fuzzy blob with a bright splotch at one end.
In other words, Dalcanton had found a comet in the SDSS data. Along
with SDSS astronomers Steve Kent and Sadanori Okamura, Dalcanton
reported the discovery to the Central Bureau for Astronomical Telegrams.
 
It turns out that Dalcanton's sighting wasn't actually the first
detection of this particular heavenly body. Near Earth Object (NEO)
surveys had observed the object several times, up to a year earlier.
Based on Dalcanton's report of the comet's position and motion, Gareth
Williams of the IAU Minor Planet Center located the object in the
LINEAR project database, and Gene Magnier of the University of
Washington produced another observation from the LONEOS survey.
However, the NEO surveys had merely classified the object as
"apparently asteroidal," not as an actual comet. Comet C/1999 F2 was
therefore officially named Comet Dalcanton, in recognition of her
correct identification.
 
The Sky Survey seems to be acquiring a reputation for finding unusual
and interesting objects during its ongoing test phase. The SDSS is
first and foremost a survey of distant galaxies and quasars in an
effort to map the large-scale structure of the universe, and it has
already distinguished itself in this arena by finding some of the most
distant quasars known. But in the process of surveying one-quarter of
the sky, the 2.5-meter SDSS telescope will also image millions of
objects in our own Milky Way galaxy. Many of these objects, such as the
recently discovered methane dwarfs, are interesting in their own right.
 
Comet Dalcanton is no exception to this trend of interesting finds. It
is one of only a few known comets that are thought to come from the
inner Oort Cloud, a collection of billions of cometary bodies around
our solar system that are thousands of times further from the sun than
Earth is. Comet Dalcanton also didn't make it especially far into our
solar system, compared to comets that we can see with the unaided eye.
It reached its perihelion (distance of closest approach to the sun)
just inside the orbit of Jupiter in August 1998, and is now on its way
back to the Oort Cloud. It will travel further away than almost all
other known periodic comets.
 
Despite not having come very close to the sun, Comet Dalcanton has an
especially prominent tail. Such comets beyond the inner solar system
often escape detection because they lack visible tails. Comet tails
form as the icy outer layers of the comet are vaporized by the sun and
then blown in the direction away from the sun by radiation pressure and
the solar wind. Each time a periodic comet comes back to perihelion,
the tail becomes weaker as less material is available to evaporate. So,
on the basis of Comet Dalcanton's significant tail, astronomers suspect
this is the comet's first foray near the sun.
 
This won't be Comet Dalcanton's last visit to our part of the solar
system, according to the SDSS and NEO surveys' data. But don't hold
your breath; the comet's round trip will take 186,000 years.
 
Images
 
Larger image containing comet
http://www.sdss.org/news/features/19990813.comet.img1.html
 
Graph showing motion of comet
http://www.sdss.org/news/features/19990813.comet.img2.html
 
Graph of known comet apohelia
http://www.sdss.org/news/features/19990813.comet.img3.html
 
Related links

IAU Circular for Comet Dalcanton (with orbital elements)
http://cfa-www.harvard.edu/iauc/07100/07194.html
 
The Kuiper Belt and the Oort Cloud
http://seds.lpl.arizona.edu/nineplanets/nineplanets/kboc.html
 
Near Earth Object Program
http://neo.jpl.nasa.gov/
 
The NEO Page
http://cfa-www.harvard.edu/iau/NEO/TheNEOPage.html

================
(5) PERSEIDS 1999

From Rainer Arlt <rarlt@aip.de>
 
I M O   S h o w e r   C i r c u l a r
 
PERSEIDS 1999
 
The perfect coincidence with the total solar eclipse on August 11
let many amateurs be on holidays and at a place good for meteor
observing too. The new Moon served with dark nights, and particularly
south-eastern Europe was lucky with widely clear skies, and, as
usual, Near Eastern observers enjoyed good weather as well. This
allowed for a good coverage of the 'new' Perseid peak, expected for
near 23h UT, which has been noticed since 1988 and seems to be
declining in activity. The traditional Perseid maximum should fall
near 4h UT on August 13, but poor weather has limited the efforts
of many east-coast observers in the US. Other American observers
were fortunately more lucky.
 
We are very grateful to the following observers who sent in their
results quickly and allowed the computation of the below ZHR graph:
 
Nada Abanda (ABANA, Jordan),         Rainer Arlt (ARLRA, Germany),
Emad Ashi (ASHEM, Jordan),           Jure Atanackov (ATAJU, Slovenia),
Juan A. Aveledo (AVEJU, Cuba),       Lars Bakmann (BAKLA, Denmark),
Martin Bily (BILMA, Czech R.),       Louis S. Binder (BINLO, USA),
Polona Bizjak (BIZPO, Slovenia),     Tina Bizjak (BIZTI, Slovenia),
Lukas Bolz (BOLLU, Germany),         Michael Boschat (BOSMI, Canada),
Asdai Diaz Rodriguez (DIAAS, Cuba),  Khalid Eid (EIDKH, Jordan),
George W. Gliba (GLIGE, USA),        Michal Haltuf (HALMI, Czech R.),
Takema Hashimoto (HASTA, Japan),     He Jingyang (HE JI, China),


Javor Kac (KACJA, Slovenia),         Vaclav Kalas (KALVA, Czech R.),
Kevin Kilkenny (KILKE, USA),         Andre Knofel (KNOAN, Germany),
Jakub Koukal (KOUJA, Czech R.),      Ales Kratochvil (KRAAL, Czech R.),
Ralf Kuschnik (KUSRA, Germany),      Marco Langbroek (LANMA, Netherlands),
Adrian Lelyen (LELAD, Cuba),         Robert Lunsford (LUNRO, USA),
Hartwig Luthen (LUTHA, Germany),     Pierre Martin (MARPI, Canada),
Antonio Martinez (MARTI, Venezuela), Tony Markham (MARTO, UK),
Alastair McBeath (MCBAL, UK),        Mark Mikutis (MIKMR, USA),
Koen Miskotte (MISKO, Netherlands),  Sirko Molau (MOLSI, Germany),
Francisco Munoz (MUNFR, Cuba),       Jens O. Olesen (OLEJE, Denmark),
Kazuhiro Osada (OSAKA, Japan),       Radame Perez (PERRA, Cuba),
Suyin Perret (PERSU, Venezuela),     Maciej Reszelski (RESMA, Poland),
Mileny Roche L. (ROCMI, Cuba),       Marion Rudolph (RUDMA, Germany),
Qi Rui (QI RU, China),               Ja'far Sabah (SABJA, Jordan),
Maria Shihadeh (SHIMR, Jordan),      Milos Weber (WEBMI, Czech R.),
Oliver Wusk (WUSOL, Germany),        Kim S. Youmans (YOUKI, USA),
Ilkka Yrjola (YRJIL, Finland),       Jure Zakrajsek (ZAKJU, Slovenia),
George Zay (ZAYGE, USA),             Ju Zhao (ZHAJU, China),
Xiaojin Zhu (ZHUXI, USA),            Vladimir Znojil (ZNOVL, Czech R.).
 
For this first overview, only observations near the maximum were
considered. Many more covering the activity period of the Perseids
have been received already.
 
A rough profile of the population index was computed showing the
typical climb-down from r-values near 2.5 to 2.0, a few hours
after the maximum reaching 1.8. The values were used to compute
the ZHR profile as given below. The population indices given in
the last column are interpolated values from the rough profile
which has only 0.25 degree resolution at its best.
 
--------------------------------------------------
Solarlong  Date      Periods  nPER  ZHR    +-   r
(eq.2000)  1999, UT
--------------------------------------------------
138.251   Aug 11 0820  10     159   29.2  2.3 2.43
138.669   Aug 11 1850  15     195   34.0  2.4 2.57
138.786   Aug 11 2140  42     510   29.3  1.3 2.55
138.899   Aug 12 0030  38     510   32.8  1.4 2.47
139.149   Aug 12 0650  19     453   46.7  2.2 2.16
139.224   Aug 12 0840   9     293   45.0  2.6 2.14
139.570   Aug 12 1720   7     417   82.4  4.3 2.08
139.719   Aug 12 2100   9     107   60.7  5.8 2.11
139.752   Aug 12 2150  19     228   69.3  4.6 2.11
--------------------------------------------------
139.778   Aug 12 2231   4      67   74.0  9.0 2.11 * resolution ~12 min.
139.783   Aug 12 2239   7      64   97.3 12.1 2.11
139.787   Aug 12 2245  11     110  100.5  9.5 2.11
139.798   Aug 12 2301   9     127  100.7  8.9 2.13
139.805   Aug 12 2312   9     125   96.9  8.6 2.14
139.814   Aug 12 2325  12     124   92.0  8.2 2.16
139.819   Aug 12 2333  15     150   87.0  7.1 2.17
139.830   Aug 12 2349  13     132   87.6  7.6 2.19
139.834   Aug 12 2355  14     134   87.5  7.5 2.20
139.840   Aug 13 0004   8     103   81.8  8.0 2.21
139.853   Aug 13 0024   5      79   93.5 10.5 2.23
139.861   Aug 13 0036   8      95   88.9  9.1 2.23
139.866   Aug 13 0043   9      98   77.6  7.8 2.23
139.878   Aug 13 0101  11     132   86.0  7.5 2.22
139.882   Aug 13 0107  10     121   86.7  7.9 2.21
139.892   Aug 13 0122   7      79   85.8  9.6 2.20
139.896   Aug 13 0128   4      53   87.0 11.8 2.20 * end high resolution
--------------------------------------------------
139.901   Aug 13 0140  10     198   76.8  5.4 2.19
140.000   Aug 13 0400   1      45   91.7 13.5 2.09 * note: only 1 obs.
140.127   Aug 13 0720  27     556   60.3  2.6 1.85
140.153   Aug 13 0750  34     831   61.4  2.1 1.84
140.287   Aug 13 1120   8     288   64.4  3.8 1.81
140.717   Aug 13 2200  23     488   48.3  2.2 2.12
140.764   Aug 13 2310  31     889   53.0  1.8 2.13
140.858   Aug 14 0130   9     414   60.9  3.0 2.15
141.236   Aug 14 1100   2      90   53.6  5.6 2.15
141.729   Aug 14 2320   4      44   24.1  3.6 2.15
--------------------------------------------------
 
The general acitivity level of the Perseids was not exciting in
1999. A clear maximum with ZHR~100 appears near 139.79 (eq. J2000.0;
August 12, 2250 UT). Please note that the averages do cover several
observers, though often only a single observer group, and systematic
effects may be present in this first analysis -- peak time and ZHR
can be easily different by 1 hour and 20 meteors/h respectively. We
dare to conclude that the 'new' peak of the Perseids is to be
vanishing next year, in two years at the latest.
 
The high value of ZHR~90 at 140.0 (August 13, 0405 UT) is supposed
to mark the traditional Perseid maximum, but is based on a single
observation due to bad weather over large areas of the eastern
United States.
 
The peak of ZHR~80 at 139.57 is based on a number of observing
periods from two high-perception observers; more observations from
Asian longitudes will be necessary to find a comprehensive average.
 
A detailed analysis will follow in one of the future issues of
WGN, the Journal of the IMO.
 
-----------------------------------------------------
Rainer Arlt, 1999 Aug 21.
Visual Commission - International Meteor Organization
visual@imo.net - http://www.imo.net

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