PLEASE NOTE:
*
CCNet DIGEST, 21 April 1999
---------------------------
QUOTE OF THE DAY
"Dr Peiser says that he finds the
lack of public notice
disturbing. But astronomers seem happy
with the way it was done"
(The Times, 21 April 1999)
(1) A SPACE CHARGE MODEL FOR ELECTROPHONIC BURSTERS
Luigi Foschini <L.Foschini@isao.bo.cnr.it>
(2) ON PREDICTING THE TIME OF LEONID STORMS
http://www.demon.co.uk/astronomer/leonid_maxima.html
(3) SPOT THE ASTEROID
THE TIMES, 21 April 1999
(4) VIEWER'S GUIDE TO THIS WEEK'S LYRID METEOR SHOWER
EXPLOREZONE, 20 April 1999
(5) KECK PHOTOS OF VESTA, TITAN
Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
(6) NEANDERTHALS MATED WITH MODERN HUMANS
BBC Online Network, 20 April 1999
(7) TSUNAMI SYMPOSIUM
Michael Paine <mpaine@tpgi.com.au>
==============
(1) A SPACE CHARGE MODEL FOR ELECTROPHONIC BURSTERS
From Luigi Foschini <L.Foschini@isao.bo.cnr.it>
Dear Benny,
I would like to inform you about a new theory on electrophonic
sounds,
that was published yesterday.
"A space charge model for electrophonic bursters"
by Martin Beech and Luigi Foschini
ASTRONOMY AND ASTROPHYSICS 345, (1999), L27-L31.
ABSTRACT: The sounds accompanying electrophonic burster meteors
are
characteristically described as being akin to short duration
"pops"
and staccato-like "clicks". As a phenomenon distinct
from the enduring
electrophonic sounds that occasionally accompany the passage and
ablation of large meteoroids in the Earth's lower atmosphere, the
bursters have proved stubbornly difficult to explain. A
straightforward
calculation demonstrates that in contradistinction to the
enduring
electrophonic sounds, the electrophonic bursters are not
generated as a
consequence of interactions between the meteoroid ablation plasma
and
the Earth's geomagnetic field. Here we present a novel and
hitherto
unrecorded model for the generation of short-duration pulses in
an
observer's local electrostatic field. Our model is developed
according
to the generation of a strong electric field across a shock wave
propagating in a plasma. In this sense, the electrophonic
bursters are
associated with the catastrophic disruption of large meteoroids
in the
Earth's atmosphere. We develop an equation for the description of
the
electric field strength in terms of the electron temperature and
the
electron volume density. Also, by linking the electron line
density to
a meteor's absolute visual magnitude, we obtain a lower limit to
the
visual magnitude of electrophonic burster meteors of M_{v}~ -6.6,
in
good agreement with the available observations.
Greetings,
Luigi
Dr. Luigi Foschini
CNR - ISAO (formerly FISBAT and IMGA)
Via Gobetti 101, I-40129 Bologna (Italy)
Tel. +39 0516399620; Fax +39 0516399654
E-mail: L.Foschini@isao.bo.cnr.it
URL: http://www.isao.bo.cnr.it/~dinamica/
============
(2) ON PREDICTING THE TIME OF LEONID STORMS
From http://www.demon.co.uk/astronomer/leonid_maxima.html
On Predicting the Time of Leonid Storms
R. H. McNaught.
First published in The Astronomer, 1999 March.
The use of the orbit of 55P/Tempel-Tuttle in predicting Leonid
storms
is discussed and rejected in favour of dust trail calculations.
Asher
(1999) has calculated the perturbations to the individual dust
trails
from ejection from the comet for three revolutions or more prior
to any
potential encounter. These calculations confirm the encounter
circumstances given by Kondrat'eva et al. (1997), but with ten
times
better resolution in the node of the dust trails. All observed
storms
correlate closely with the Earth's passage within about 0.001 AU
from a
dust trail. It is shown that the time of encounter with Asher's
dust
trails very closely represent the observed times of maxima given
in
Brown (1999) for all six storms (ZHR>1000) of the last 200
years.
Asher's dust trails indicate that the Leonid maxima in the next
two
years will occur at:
1999 Nov. 18 02:08 UT
2000 Nov. 18 07:50 UT
with an uncertainty of +/- 90 minutes and possibly as small as
+/- 10
minutes. The uncertainty is based on the close correspondence
between
the time of encounter of the dust trails and the time of
observed storms in the last 200 years.
============
(3) SPOT THE ASTEROID
From THE TIMES, 21 April 1999
http://www.sunday-times.co.uk:80/news/pages/Times/frontpage.html?999
By Science Editor, Nigel Hawkes
IT IS remarkable what you find once you start looking. Since a
systematic search of the sky for near-Earth asteroids began, the
numbers are piling up at a remarkable rate. Fifty-five new
asteroids
with the potential to collide with the Earth were found during
1998 -
more than in the previous six years. None of the asteroids poses
a
threat, but there are plenty more to find. The American space
agency
Nasa, which says there are 2,000 such objects, set a target of
identifying most of them within ten years. So far, 163 have been
found.
A new telescope, due to go on line soon, will speed up the
search, but
the target looks optimistic.
Dr Brian Marsden, of the Minor Planets Centre in Cambridge,
Massachusetts, expects 90 per cent of the potentially dangerous
asteroids to be found within 17 years.
A few years is hardly likely to make any difference, says Don
Yeomans,
of Nasa's Near Earth Orbit programme. He expects that if there is
an
asteroid with the Earth's name on it, we will get ten, 20 or 30
years'
warning, enough time to devise a way of shifting the asteroid's
orbit,
perhaps by explosives, to ensure that it misses.
One recent discovery, called 1999 AN10, has caused controversy
not
because of any risk of an impact but because of the way its
discovery
was handled.
A year ago, some astronomers were embarrassed after Dr Marsden
gave
warning that an asteroid might be on course for a 2028 impact.
More
refined calculations, when further details of its orbit were
known,
showed the fears to be unfounded. The low-key announcement of
AN10 is
seen by some, including Benny Peiser, an anthropologist at John
Moores University in Liverpool, as an overreaction to that
embarrassment. The news slipped out on a website in the form of a
paper
from three Italian astronomers. The interest in AN10 is that its
orbit
is tilted at an angle of 70 degrees and intersects that of the
Earth
twice a year in February and August. It is thought to be about a
mile
in diameter, quite large enough to do continent-wide damage if it
hit.
Dr Andrea Milani and Dr Steven Chesley, of the University of
Pisa, and
Dr Giovanni Valsecchi, of the Planetary Institute in Rome, say
that it
will remain close for the next 600 years.
There is, they say, a one-in-a-billion chance that it could
strike the
Earth in August 2039, but that is smaller than being struck by an
unknown asteroid any day without warning, and not something to
worry
about. The long-term potential needs careful watching, though, as
the
orbit of AN10 may be disturbed by its constant close approaches
to the
Earth, possibly increasing the chances of impact.
Dr Peiser says that he finds the lack of public notice
disturbing. But
astronomers seem happy with the way it was done. "I commend
them for
the process of being careful," Richard Binzel, of
Massachusetts
Institute of Technology, told the Boston Globe. "On a scale
of zero
to five," he said, "this thing is a zero."
Copyright 1999, The Times Newspapers Ltd.
===============
(4) VIEWER'S GUIDE TO THIS WEEK'S LYRID METEOR SHOWER
From EXPLOREZONE, 20 April 1999
http://explorezone.com/archives/99_04/20_lyrid_meteors.htm
By Robert Roy Britt, explorezone.com
04/20/99: Though the Lyrids are not high-profile as far as meteor
showers go, the annual event should still provide a good
opportunity to
see ancient cosmic dust stream through Earth's atmosphere this
week.
The Lyrids are named for Lyra, the constellation from which the
meteors, often called "shooting stars," seem to come.
Provided skies
are clear, viewers may be treated to 15-20 meteors an hour late
Wednesday night and early Thursday morning, astronomers said.
How to see them
The best viewing will be in the wee hours of Thursday after the
Moon,
now in its first quarter, has set.
"Lyra doesn't get very high in the sky until after midnight,
so the
best time to look will be the early morning hours of Thursday,
April
22," said Kevin Conod, astronomer at the Newark Museum's
Dreyfuss
Planetarium in New Jersey.
Conod told explorezone.com that unlike some meteor showers, no
hunting
is required to find the Lyrids.
"Although Lyra will be rising in the East, you don't
necessarily have
to face in that direction," Conod said. "Meteors will
appear all over
the sky. It is more important to find a spot where there are no
lights
shining in your eyes and you can face the darkest, clearest part
of the
sky."
Where the debris comes from
The Lyrid meteors are caused when Earth passes through a trail of
debris left behind by Comet Thatcher, which was discovered in
1861,
Conod said.
Comets are thought to be ancient storehouses of relatively
pristine
cosmic material leftover from the early days of our solar
system's
formation, 4 to 6 billion years ago. As a comet nears the Sun
during
its often lengthy orbit, gas and dust burn off and are left
behind.
When these grains of dust, which scientists then call meteoroids,
hit
the atmosphere, they're name changes to meteors. They rub against
air
particles and create friction, heating up to more than 3000
degrees
Fahrenheit. The heat vaporizes most meteors, creating what we
call
shooting stars (most become visible at around 60 miles up).
Comet Thatcher takes 415 years to make its elongated trip around
the
Sun, Conod said, and it won't pass through the inner solar system
again
until the year 2276. The annual Lyrids, therefore, are created by
the
debris left back in 1861.
What to expect this year
Though some scientists have noted a periodic increase in the
Lyrids,
they haven't figured out why the activity fluctuates. Conod said
this
year will probably be a typical year.
"It is very hard, if not impossible, to predict how many
meteors we
will see in a shower," he said. "The Lyrids have
occasionally produced
a very nice shower; in 1982 about 100 per hour were seen in the
U.S."
Conod said that while the Perseids and Geminids are stronger, the
Lyrids are still worth a look, probably even for city dwellers.
"Given that it usually produces 15-20 meteors per hour, I'd
give it "8"
or "9" on a Top-10 list of best showers," he said.
ez
Copyright 1999, Explorezone
============
(5) KECK PHOTOS OF VESTA, TITAN
From Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
The Keck Telescope II, the world's largest telescope, has started
to
take images with its Adaptive Optics (AO) system in
February. On only
its second night of operation, the best photos ever of Asteroid
Vesta
were taken. Images of Titan were also taken in February along
with some
galaxy images:
http://www2.keck.hawaii.edu:3636/realpublic/ao/aolight.html
Ron Baalke
===========
(6) NEANDERTHALS MATED WITH MODERN HUMANS
From the BBC Online Network, 20 April 1999
http://news.bbc.co.uk/hi/english/sci/tech/newsid_323000/323657.stm
A hybrid skeleton showing features of both Neanderthal and early
modern
humans has been discovered, destroying theories that our
ancestors
drove Neanderthals to extinction.
The skeleton of a young boy was found in Portugal. Scientists say
it
shows for the first time that Neanderthals, who became extinct
tens of
thousands of years ago, mated with early members of our own
species.
FULL STORY at
http://news.bbc.co.uk/hi/english/sci/tech/newsid_323000/323657.stm
============
(7) TSUNAMI SYMPOSIUM
From Michael Paine <mpaine@tpgi.com.au>
Dear Benny,
Here is the program for the Tsunami Symposium.
PROGRAM TSUNAMI SYMPOSIUM
May 25-27, 1999
Honolulu, Hawaii, USA
Sponsored by The Tsunami Society
8:30 - OPENING CEREMONIES - George Curtis, President
The Tsunami
Society
ASTEROID MEGA-TSUNAMIS - 5/25/99 Morning
9:00 - Comet and Asteroid Hazards: - Threat and Mitigation:
- J.
Solem, LANL
9:30 - Asteroid Tsunami Project at Los Alamos - J.
Hills, and P.
Goda LANL
10:30 - High Fidelity Computational Simulations of Asteroid
and
Comet Impacts -
D. Crawford, SNL
11:00 - Impact Tsunami: A Hazard
Assessment - S. Ward, E.
Asphaug, UC SC
11:30 - Animations of Asteroid Tsunami Inundations -
C. Mader, MCC
OTHER MEGA-TSUNAMIS - 5/25/99 Afternoon
1:00 - The 1958 Lituya Bay Mega-Tsunami - C. Mader,
LANL
1:30 - Analysis of Mechanism of
Lituya Bay Tsunami - G.
Pararas-Carayannis
2:00 - Did a ``Giant Wave''
Strike Lanai? - B. Keating, A.
Felton, HIGP
RECENT TSUNAMI DISASTERS - 5/25/99 Afternoon - G. Fryer,
Chairman
3:00 - The 1998 New Guinea Tsunami - C. Synolakis,
USC
3:30 - 1994 Skagway Landslide
Tsunami - B. Campbell, D.
Nottingham, PN and D
4:00 - 1983-2000 Global Tsunami
Catalogue - J. Lander, K.
O'Loughlin, L.
Whiteside, CIRES
TSUNAMI WARNING CENTERS - 5/26/99 Morning - R. Hagermeyer,
Chairman
8:30 - Pacific Tsunami Warning Center - C. McCreery
9:00 - The U.S. West Coast and Alaska Tsunami Warning
Center - T.
Sokolowski
9:30 - Japanese Tsunami Warning
System - A. Furumoto, H.
Tatehata, A.
Morioka
10:20 - Caribbean Tsunami and Warning System Status -
J. Lander, K.
O'Loughlin, L.
Whiteside, CIRES
10:45 - Tsunami Risk for Australia - J. Rynn and
J. Davidson, CERA
11:10 - Landslide Tsunami: Generation, Detection and Warning
- S.I.
Iwasaki, S.
Sakata, Tsukuba, Japan
11:35 - Tsunami Warning in Central
America - M. Fernandez ,
CIGEFI, Costa Rica
J. Havskov, K. Atakan,
University of
Bergen, Norway
TSUNAMI CIVIL DEFENSE PROJECTS -5/27/99 Morning
- D. Cox, Chairman
8:30 - Hawaii CD Local Tsunami Problem - D. Walker,
UH
9:00 - Tsunami Warning Systems in
U.S.A. - A. Furumoto,
Honolulu, HI
9:30 - Finite Element Modeling of Potential
Cascadia Subduction
Zone Tsunamis E.
Myers, A. Baptista, G. Priest, OGI
10:30 - Cascadia Paleotsunamis - I. Hutchinson, P.
Bobrowsky, J.
Clague and R.
Mathewes, SFU Canada
11:00 - Tsunami Mitigation for the City of Suva, Fiji -
J. Rynn, G.
Prasad, A.
Kaloumaira, CERA
11:30 - Pacific Tsunami Museum - W. Dudley, UH
HISTORICAL TSUNAMIS - 5/27/99 Afternoon - M. Blackford,
Chairman
1:00 - Tsunamis on the Coast Lines of India - T.
S. Murty, lBA
Canada
1:30 - Paleotsunami Evidence from the Australian
Continent - J.
Nott, JCU
2:00 - Tsunamis in Greece - D. Domeny Howes -
Coventry Univ.
2:30 - Methods of Calculation of Tsunami Risk -
G. Curtis, E.
Pelinovsky, UH
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*
BRIEF NOTE BY THE IAU GENERAL SECRETARY
From Johannes Andersen, IAU General Secretary <ja@iap.fr>
Without wishing to interfere in a scientific debate on CCNet in
a field outside my own, and without being the 'eminent official'
referred to yesterday by B. Peiser, I should like to add the
following brief comment to the discussion on 1999 AN10:
1: I have followed with considerable interest the vigorous debate
in the community on the methods for and interpretation of the
predicted orbits of 1999 AN10 and, by implication, future NEOs
with possible close approaches to Earth sometime in the future.
The fact that this has been going on for three weeks in a wide
community including most of the prominent NEO researchers known
to at least this outsider, and without the kind of media hysteria
seen earlier in the cases of 1997 FX11 or Pluto seems to me to
be experimental proof that the matter has basically been handled
professionally and responsibly by the authors and other
colleagues
taking part in this debate.
2. While I can agree for the need to give the public free access
to scientific information on NEOs, I strongly disagree that there
should be a need to actively alert 'Joe Public' each time a
possible
detection has been made of an NEO that might conceivably pass
uncomfortably close to Earth several decades hence. If that
philosophy were applied to all conceivable sources of potentially
dangerous events over the next half-century, however unlikely,
I have no doubt that attention would quickly wane. Certainly it
should be possible to debate and refine the data and computations
for particularly interesting cases in the community for some time
without involving the media, when an object is certified to be
safe for the next few decades.
3. After the 1997 FX11 affair, the IAU made its policy on NEO
research clear (see official statement on the IAU Web page). The
Torino Workshop has been organised in part to develop practical
procedures for its implementation. The discovery and discussion
of 1999 AN10 has speeded up that process and provided a good
starting approximation. There are certainly matters that can
still be considered for improvement, such as the precise review
procedures and the presentation and labelling of discovery papers
on the web or elsewhere, which we trust will be debated in a
constructive spirit in Torino.
April 21,
1999
J. Andersen