PLEASE NOTE:
*
CCNet 115/2001 - 7 November 2001
================================
"It is true that there are reports that a dip in ozone
levels is
associated with the Tunguska impact. What is not mentioned in
association with these reports is that at the time there was no
global
ozone monitoring network and that what measurements there were,
were
highly unreliable. The measurements in question were made using
experimental
data from stellar spectroscopy. Early versions of the technique
have
errors of 50% or more, even when designed to measure ozone and
little
real credence can be placed on the claims from 1908. Claims that
an ozone
hole existed in the 1950s are based on a similar technique that
was used
to measure ozone at the French Dumont D'Urville station in
Antarctica.
Unfortunately when compared to measurements made with the Dobson
ozone
spectrophotometer the evidence disappears. This is not to say
that the
Tunguska event didn't affect the ozone layer, just that there is
no
conclusive evidence that it did."
-- Jonathan Shanklin, British Antarctic Survey, Cambridge,
England
(1) LEONID METEOR STORM: WHEN, WHERE AND HOW TO WATCH
Space.com, 6 November 2001
(2) SOHO REVEALS HOW SUNSPOTS TAKE A STANGLEHOLD ON THE SUN
ESA Media Relations <ContactESA@esa.int>
(3) ARTHUR C CLARKE TO STAY IN SRI LANKA
MSNBC, 6 November 2001
(4) TUNGUSKA & OZONE DEPLETION
Jonathan Shanklin <jdsh@bas.ac.uk>
(5) NEO OBSERVATION STRATEGY
Syuzo Isobe <isobesz@cc.nao.ac.jp>
(6) MODERATE IMPACTS AND THE VULNERABILITY OF CIVILISATION
Mike Darancette <mhdaran@pop.mindspring.com>
(7) SMOKE FROM BRONZE AGE GUN?
Hermann Burchard <burchar@mail.math.okstate.edu>
================
(1) LEONID METEOR STORM: WHEN, WHERE AND HOW TO WATCH
>From Space.com, 6 November 2001
http://www.space.com/scienceastronomy/astronomy/leonid_watching_011106-1.html
By Heather Sparks
The Leonid meteor shower will flicker and flash above North
America late on
Saturday, Nov. 17 through early Nov. 18. All you need to see it
are your
eyes, a dark location, and a little weather luck. This and a few
other
simple tips will assure a good view of the event, which experts
say should
be spectacular this year.
The Leonid meteor shower is brought to us by comet Tempel-Tuttle,
a ball of
ice and rock that orbits the Sun every 33 years, jettisoning tiny
fragments
of itself. Each pass lays down a new trail of bits and pieces, or
meteoroids, which burn from the friction of the Earth's
atmosphere as we
cross the Tempel-Tuttle trails every November.
The resulting meteors are popularly called shooting stars.
Tempel-Tuttle's path is slightly different each orbit, and the
individual
debris streams spread out and drift through space. So each year
the number
of shooting stars varies depending on which trails Earth passes
through.
Forecasters say 2001 should provide the most spectacular show
since 1966.
Several peaks of activity are expected in various parts of the
world.
For North American skywatchers, Earth will enter the heavier
parts of the
stream at about 11 p.m. EST on Saturday, Nov. 17. Activity will
peak around
5 a.m. Sunday morning, when as many as 13 meteors per minute
could be
visible, likely for a stretch of time that lasts less than 1
hour. The peak
corresponds to 4 a.m. CST, 3 a.m. MST and 2 a.m. PST.
Because this peak occurs near dawn on the East Coast, West Coast
watchers
will have a longer period following the peak to look for meteors,
said Bill
Cooke, a meteor forecaster at NASA's Marshall Space Flight
Center.
The nights and early mornings surrounding the peak -- from Nov.
14-21 --
should also offer up a handful of meteors and possibly some
meteor outbursts
as Earth potentially passes through various old debris streams.
Residents around the Pacific Rim may see a more intense storm.
The heaviest
part of the debris stream is expected to slam into the atmosphere
over the
western Pacific Ocean. Top viewing in Australia, Japan, eastern
China and
the Philippines is expected to occur between 1:30 and 4:30 a.m.,
local time,
on Nov. 19. Rates during these peaks could approach two shooting
stars every
second.
While Europeans will likely miss the strongest bursts, the
Leonids should
still offer a decent shower there.
What you'll see
"The Leonids have a reoccurrence of heavy activity every
thirty years or
so," said Dreyfuss Planetarium Astronomer Kevin Conod.
Conditions are right,
he said, for Earth to pass through a dense stream this year.
Conod predicts the shower will flourish with 100 to 1,000 streaks
and
flashes from different meteors throughout the night in North
America. A
similar display should occur in Central America.
But like most meteor showers, the Leonids are notoriously
difficult to
forecast.
"It's almost impossible to predict the exact number that
will be seen at
this point," Conod said, comparing the challenge to another
difficult
prognostication effort: "Weather forecasts don't tell you
how many raindrops
are going to fall."
What you'll need
No serious equipment is needed for optimal viewing. Binoculars
and
telescopes are of no use, because the shooting stars move across
the sky too
fast. Your eyes are the only instruments you'll need.
The Leonids get their name from a point in the sky, called the
radiant, from
which the shooting stars appear to emanate. The radiant is in the
constellation Leo, which rises in the eastern sky at night,
getting higher
toward morning. But astronomers suggest looking almost anywhere
but directly
at the radiant. Shooting stars will streak all across the sky.
The shower will be best in the early morning hours, so
astronomers advise
getting up early rather than staying up late. It is in the early
morning
that the radiant is high in your local sky, so more meteors are
visible all
across the sky.
A cozy lawn chair or blanket to recline on will also prove
helpful; without
one, all that looking up could put a strain on the neck. Warm
clothing and
something hot to drink could prove wise, also.
Beyond that, the smartest planning involves getting away from
bright lights
and cities. Light pollution has rendered much of the night sky
void of stars
and can obscure much of the shower as well.
On the bright side, there will be no bright moonlight to drown
out this
year's Leonids.
Where to go
Robert Lunsford, the Visual Program Coordinator of the American
Meteor
Society, recommends getting as far into the country as possible.
This will
help everyone, from astronomers to first-time viewers, watch and
even
photograph the event. If you can't see many stars where you live,
you won't
see many meteors, either.
If you live in a dense city, or a perennially foggy place, you
might
consider planning ahead and booking a room at a remote bed and
breakfast.
High mountainous areas will also provide better viewing because
there's less
atmosphere up there to scatter light; more of the fainter meteors
are
visible from high altitudes.
To get the full effect, find a dark location outside that's clear
of trees.
Lunsford recommends allowing a half-hour for your eyes to adjust
to the
darkness. Gradually you'll be able to see more and more stars as
well as
meteors.
"The more stars you can see before the shower," said
Lunsford, "the better
level of activity you'll see as well."
Earth will encounter another dense ribbon of the debris next
November.
Europe and Africa are the favored locations for another predicted
storm. But
a full Moon will dampen the 2002 show. After that, scientists say
it will
likely be nearly a century before the Leonids storm again.
"It's now or never," said Robert Naeye, editor of
Mercury, the magazine of
the Astronomical Society of the Pacific. "People should take
advantage of
this year's Leonid storm, because astronomers don't think we'll
see another
storm like this one until the year 2099. We will probably never
see a better
meteor shower in our lifetimes."
Copyright 2001, Space.com
=============
(2) SOHO REVEALS HOW SUNSPOTS TAKE A STANGLEHOLD ON THE SUN
>From ESA Media Relations <ContactESA@esa.int>
Paris, 6 November 2001
Information Note
N° 09-2001
SOHO reveals how sunspots take a stranglehold on the Sun
A sunspot turns out to be a kind of whirlpool, where hot gas near
the Sun's
surface converges and dives into the interior at speeds of up to
4000
kilometres per hour. This is the latest discovery by the ESA-NASA
SOHO
spacecraft. Solar physicists have long known that intense
magnetic fields in
sunspots strangle the normal upflow of energy from the interior,
leaving the
sunspot cooler and therefore darker than its surroundings. The
converging
flows of gas around a spot, found by SOHO, explain why the
magnetic fields
become concentrated, and how a sunspot can persist for days or
weeks.
Bernhard Fleck, ESA's project scientist for SOHO, comments,
"The origin and
stability of sunspots has been one of the long-standing mysteries
in solar
physics. I am delighted to see that with SOHO we are beginning to
crack this
problem."
The gas flows around and beneath a sunspot have been detected by
a team of
scientists in the USA, using the Michelsen Doppler Imager (MDI)
on SOHO. The
instrument explores the solar interior by detecting natural sound
waves at a
million points on the Sun's surface.
"After many years of contradictory theories about sunspots,
MDI on SOHO is
at last telling us what really happens," comments Junwei
Zhao of Stanford
University, California, lead author of a report published in the
Astrophysical Journal. Inflows and downflows similar to those now
detected
with SOHO were envisaged in 1974 by Friedrich Meyer of Germany's
Max-Planck-Institut für Physik und Astrophysik, and his
colleagues. A
similar expectation figured in a theory of sunspots advanced in
1979 by
Eugene Parker of Chicago. "Our observation seems to provide
strong evidence
for both predictions," Zhao says.
Sunspots have fascinated scientists since Galileo's time, 400
years ago,
when they shattered a belief that the Sun was divinely free of
any blemish.
As symptoms of intense magnetic activity, sunspots are often
associated with
solar flares and mass ejections that affect space weather and the
Earth
itself. The Sun's activity peaks roughly every 11 years, and the
latest
maximum in the sunspot count occurred in 2000.
Even with huge advances in helioseismology, which deduces layers
and flows
inside the Sun by analysis of sound waves that travel through it
and agitate
the surface, seeing behind the scenes in sunspots was never going
to be
easy. The MDI team refined a method of measuring the travel time
of sound
waves, invented in 1993 by Thomas Duvall of NASA Goddard, called
solar
tomography. It is like deducing what obstacles cross-country
runners have
faced, just by seeing in what order the contestants arrive at the
finish.
Here the runners are packets of sound waves, and the obstacles
are local
variations in temperature, magnetic fields and gas flows beneath
the Sun's
surface.
"We needed better mathematical tricks," comments
Duvall. "So we put together
ideas from classical and quantum physics, and also from a recent
advance in
seismology on the Earth."
In an earlier application of solar tomography, the team examined
in detail
the ante-natal events for an important group of sunspots born on
12 January
1998. They found sound waves beginning to travel faster and
faster through
the region where sunspots were about to form. Less than half a
day elapsed
between signs of unusual magnetic activity in the Sun's interior
and the
appearance of the dark spots on a previously unblemished surface.
"Sunspots form when intense magnetic fields break through
the visible
surface," says Alexander Kosovichev of Stanford. "We
could see the magnetic
field shooting upwards like a fountain, faster than we
expected."
Even late on the previous day there was little hint of anything
afoot,
either at the surface or in the interior. By midnight (Universal
Time) a
region of strong magnetic field had risen from a depth of 18 000
kilometres
and was already half way to the surface, travelling at 4500
km/hr. Sound
speeds were increasing above the perturbed zone. By 8:00 a.m. an
intense,
rope-like magnetic field was in possession of a column of gas 20
000
kilometres wide and reaching almost to the visible surface. In
the uppermost
layer beneath the surface, the magnetic rope divided itself into
strands
that made the individual sunspots of the group.
Under a large, well-established sunspot, in June 1998, the sound
waves
revealed a persistent column of hot, magnetised gas rising from
deep in the
interior. At a depth of 4000 kilometres it spread fingers towards
neighbouring parts of the surface where it sustained some smaller
sunspots.
The magnetic column was not connected to another nearby spot
where the
magnetic field went in the opposite direction. Immediately below
the large
spot was a cushion of cooler, less intensely magnetised gas.
A closer look at the gas flows, during the development of that
June 1998
sunspot, led to the further findings now reported. The inflows
and downflows
in the immediate vicinity of the sunspot reach downwards for only
a few
thousand kilometres from the surface, which means less than one
per cent of
the distance to the Sun's centre. The discovery therefore
depended on MDI's
unique ability to explore just below the surface.
The whirlpool of gas is responsible for the persistence of a
sunspot. The
cooling due to the magnetic field of the sunspot provokes the
down-flow, and
the gas disappearing downwards is replaced by more gas flowing
inwards
towards the spot. It brings with it its own associated magnetic
field and
prevents the strong magnetic field of the sunspot from
dissipating. So the
cooling and downflow continue, and the process is
self-sustaining.
The downflow of gas may also help to explain the puzzling fact
that the Sun
is actually brighter when it is freckled with dark spots. The
VIRGO
instrument on SOHO, operated by a Swiss-led team, confirmed the
observations
of earlier solar spacecraft, showing that sunshine is slightly
more intense
at sunspot maximum. Douglas Gough of Cambridge University, a
leading solar
theorist, notes that the downflow of gas seen by MDI on SOHO can
redistribute energy bottled up by a sunspot.
"What is interesting from the physical point of view is
that, being cool,
the descending flow is readily able to extract the heat that
accumulates
beneath the spot," Gough says. "It then spreads the
heat away from the
sunspot and eventually brings it to the surface of the Sun far
from the
spot, from where it is radiated into space."
Note to editors
The SOHO project is an international cooperation between ESA and
NASA. The
spacecraft was built in Europe for ESA and equipped with
instruments by
teams of scientists in Europe and the USA. NASA launched SOHO in
December
1995, and in 1998 ESA and NASA decided to extend its highly
successful
operations until 2003.
For more information please contact:
ESA - Communication Department, Media Relations Office
Tel: +33(0)1.53.69.7155
Fax: +33(0)1.53.69.7690
Dr. Bernhard Fleck, ESA - SOHO Project Scientist
ESA Space Science Dept, c/o NASA- GSFC, Greenbelt (Maryland USA)
Tel: +1 301 286 4098
Fax: +1 301 286 0264
Email: bfleck@esa.nascom.nasa.gov
Note on scientific papers
'Investigation of Mass Flows Beneath a Sunspot by Time-Distance
Helioseismology' by Junwei Zhao and Alexander G. Kosovichev
(Stanford) and
Thomas L. Duvall Jr (NASA Goddard) is published in Astrophysical
Journal,
vol. 557, p. 384, 2001. A related paper, 'Time-Distance Inversion
Methods
and Results' by Kosovichev, Duvall and Philip H. Scherrer
(Stanford)
appeared in Solar Physics, vol. 192, p. 159, 2000.
For more material about this story (images) and information
about the SOHO
mission and the ESA Science Programme, visit the ESA Science
Website at
http://sci.esa.int
Other useful links
· SOHO Home page http://soho.estec.esa.nl
· MDI home page: http://soi.stanford.edu/
· MDI Sunspot results page: http://soi.Stanford.EDU/press/ssu09-01/
· NASA press release: http://www.gsfc.nasa.gov/topstory/20010919sunspot.html
=============
(3) ARTHUR C CLARKE TO STAY IN SRI LANKA
>From MSNBC, 6 November 2001
http://www.msnbc.com/news/586894.asp?0dm=T24BT
Nov. 6 - Science-fiction sage Arthur C. Clarke said Tuesday
that he planned
to spend the rest of his days in Sri Lanka, his adopted home,
because he no
longer had the energy for overseas travel.
CLARKE, 83, WIDELY acclaimed as a prophet of the space age, said
the
crippling post-polio syndrome had forced him to decline an
invitation for a
gala dinner in his honor at the Playboy Mansion in Los Angeles.
"I can no longer face overseas travel, and in fact, hope
never to leave Sri
Lanka again," Clarke said in videotaped message to the Nov.
15 gala. "I am
now completely wheelchaired owing to post-polio syndrome and am
very limited
in time and energy."
The celebrity guest list for the dinner, hosted by the Space
Frontier
Foundation, includes actor Tom Hanks, director James Cameron,
Playboy
founder Hugh Hefner, moonwalker Buzz Aldrin and Dennis Tito, the
first space
tourist.
British-born Clarke, whose books including "2001: A Space
Odyssey" have made
him one of the most celebrated science-fiction writers of all
time, has
lived in Sri Lanka for more than 30 years.
He has seen many of his predictions come true, including a
then-controversial 1945 theory of a world linked by geostationary
satellites.
Copyright 2001, MSNBC
============================
* LETTERS TO THE MODERATOR *
============================
(4) TUNGUSKA & OZONE DEPLETION
>From Jonathan Shanklin <jdsh@bas.ac.uk>
It is true that there are reports that a dip in ozone levels is
associated
with the Tunguska impact. What is not mentioned in association
with these
reports is that at the time there was no global ozone monitoring
network and
that what measurements there were, were highly unreliable.
The measurements
in question were made using experimental data from stellar
spectroscopy.
Early versions of the technique have errors of 50% or more, even
when
designed to measure ozone and little real credence can be placed
on the
claims from 1908. Claims that an ozone hole existed in the
1950s are based
on a similar technique that was used to measure ozone at the
French Dumont
D'Urville station in Antarctica. Unfortunately when
compared to
measurements made with the Dobson ozone spectrophotometer the
evidence
disappears.
This is not to say that the Tunguska event didn't affect the
ozone layer,
just that there is no conclusive evidence that it did.
Jonathan Shanklin
j.shanklin@bas.ac.uk
British Antarctic Survey, Cambridge, England
http://www.nerc-bas.ac.uk/public/icd/jds
==============
(5) NEO OBSERVATION STRATEGY
>From Syuzo Isobe <isobesz@cc.nao.ac.jp>
Dear Dr. Peiser
Recently, I saw some discussions on a topic how small NEOs should
be
detected. Alan Harris argued necessary cost depending on those
size and it
is certainly true that the cost to protect a person from NEO
hazard is high
for a small NEOs although those risk probability is nearly equal
for all the
size range of NEO. This can be an argument for an NEO community
firstly to
try to detect NEOs larger than 1 km.
When I started to work in an NEO community in 1991, NASA's
Morrison report
was published. There, it was explicitly written that an NEO
larger than 1 km
is highly probable to produce a global catastrophe. At least our
modern
civilization will be destroyed and brought back to the Stone Age.
I believe
this is the most essential reason why the NEO community try to
detect out
the NEO larger than 1 km.
Even if we will have an hazard by an NEO well smaller than 1 km,
only a local
catastrophe will happen, and some small countries may be totally
destroyed but people
in most other countries will not have any or little effects. Thus
human civilization
as such will not be affected since intervals between consecutive
NEO hazards
is well longer than 100 years.
Therefore, as the first priority, we have to protect a global
catastrophe by
the NEO larger than 1 km. This can be done with a reasonable
amount of
money. If we succeed to detect up all the NEO, our human race can
survive
continuously, and then they can consider the next level of
hazard.
Certainly, no country likes to be totally destroyed. However,
local hazards
by the NEO well smaller by 1 km happens rarely and then people
including
politicians don't realize its importance. Fortunately, now UK
politicians
have put this issue on the table and should an importance to
detect NEOs
down to 300 m with 3 m class telescope. Since efforts of NEO
observers
trying to detect the NEO larger than 1 km make a population of
this smaller
size NEOs, an idea of UK politician comes out. If in future we
have many 3m
class telescopes to detect the NEOs down to 300 m, we will have a
much clear
view of a population of NEOs smaller than 300 m and politicians
at that time
may cite an importance to detect those smaller NEOs.
This is a strategy which I proposed in a little bit different way
(S. Isobe
2000, Planetary and Space Science).
I say continuously that our NEO community does not have enough
people of
supporters in a global society. To make our future step it is not
only
important to make extensive observations, but also to make a good
public
education on the NEO topics.
Syuzo Isobe
President of the Japan Spaceguard Association
==============
(6) MODERATE IMPACTS AND THE VULNERABILITY OF CIVILISATION
>From Mike Darancette <mhdaran@pop.mindspring.com>
Regarding Your MODERATOR'S NOTE: "This is an important
point. Even a
moderate impactor some 150-200m in size would not be capable of
causing
widespread physical damage."
Given the upheaval caused by events of 9-11-2001 on today's Urban
Civilization who can say what the social fallout of an impact
event of even
moderate size would be on the earliest of Urban Civilizations.
Today's civilization has the advantage of knowing what happened
on 9-11 and
what recourse we might have to prevent it from happening again.
Whereas,
over 4,000 years ago, humans could only blame divine intervention
and strive
to appease the unknown.
Regards
Michael H. Darancette
=================
(7) SMOKE FROM BRONZE AGE GUN?
>From Hermann Burchard <burchar@mail.math.okstate.edu>
Dear Benny,
BBC has an item about a giant Reunion Island underwater landslide
causing
"the last mega-tsunami 4,000 years ago." Nothing more
specific is stated and
no reference given, unfortunately.
http://www.bbc.co.uk/science/horizon/mega_tsunami.shtml
http://www.bbc.co.uk/science/horizon/mega_tsunami_transcript.shtml
Could the exact date have been 2,200 or 2,100 BC? If so,
this may have been
triggered by an cosmic impact in the Indian Ocean ("smoke
from a smoking
gun"). The mega-tsunami also would have run up the Indus
valley and flooded
cities. The end of Mohenjo Daro is known to have come from
floods burying the city, a marvel of mathematically precise
architecture,
under mud and silt (Scientific American).
In a global meteoroid storm, we must keep in mind, 70% of
fragments will hit
in oceans. Perhaps an Indian Ocean crater was formed and can be
found, if
the impactor was large enough (which seems unlikely).
Regards,
Hermann
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