Dear Steve & Radsafers,
Some more info on this topic from Larry Kellogg at NASA
(note especially the highlighted section near the end -- do you buy that ?)
:
From: Larry Kellogg [mailto:lkellogg@mail.arc.nasa.gov]
Sent: Tuesday April 03, 2001 4:42 PM
To: KMC739@aol.com; Franta,
Jaroslav
Subject: Fwd: SUN UNLEASHES RECORD SUPERFLARE,EARTH DODGES SOLAR
BULLET
FYI as this kind of activity is part of what fuels the Van
Allen
radiation belt.
See the NOAA site for some definitions of
intensity.
http://www.sel.noaa.gov/NOAAscales/index.html
http://www.sel.noaa.gov/index.html
http://www.sel.noaa.gov/Data/
Larry
>X-Authentication-Warning: spinoza.public.hq.nasa.gov:
majordom set
>sender to owner-press-release using -f
>Date: Tue, 3
Apr 2001 15:50:27 -0400 (EDT)
>From: NASANews@hq.nasa.gov
>Subject:
SUN UNLEASHES RECORD SUPERFLARE,EARTH DODGES SOLAR BULLET
>Sender:
owner-press-release@lists.hq.nasa.gov
>To:
undisclosed-recipients:;
>
>Dolores Beasley
>Headquarters,
Washington, DC April 3, 2001
>(Phone: 202/358-1753)
>
>Bill
Steigerwald
>Goddard Space Flight Center, Greenbelt, MD
>(Phone:
301/286-5017)
>
>RELEASE: 01-66
>
>SUN UNLEASHES RECORD
SUPERFLARE,
>EARTH DODGES SOLAR BULLET
>
> The Sun blasted one
of its largest flares in 25 years
>from the same region harboring the
largest sunspot of the
>current solar cycle Monday
evening.
>
>The region, designated active region 9393, has continued
to
>rotate with the Sun and is no longer in line with the Earth,
>so
most of the flare's energy was directed away from our
>planet. However,
radiation from the flare temporarily
>disrupted radio communications, and
flare-related events
>generated a storm of high-velocity particles that,
in greater
>numbers and energies, can affect sensitive
electronic
>equipment in space.
>
>"This explosion was
estimated as an X-20 flare, and was as
>strong as the record X-20 flare on
August 16, 1989, " said Dr.
>Paal Brekke, the European Space Agency Deputy
Project
>Scientist for the Solar and Heliospheric Observatory
(SOHO),
>one of a fleet of spacecraft monitoring solar activity and
its
>effects on the Earth. "It was more powerful that the
famous
>March 6, 1989 flare which was related to the disruption of
the
>power grids in Canada."
>
>Monday's flare and the August
1989 flare are the most powerful
>recorded since regular X-ray data became
available in 1976.
>
>Solar flares, among the solar system's
mightiest eruptions,
>are tremendous explosions in the atmosphere of the
Sun capable
>of releasing as much energy as a billion megatons of
TNT.
>Caused by the sudden release of magnetic energy, in just a
few
>seconds flares can accelerate solar particles to very
high
>velocities, almost to the speed of light, and heat
solar
>material to tens of millions of degrees.
>
>The flare
erupted at 4:51 p.m. EDT Monday, and produced an R4
>radio blackout on the
sunlit side of the Earth. An R4
>blackout, rated by the NOAA SEC, is
second to the most severe
>R5 classification. The classification measures
the disruption
>in radio communications. X-ray and ultraviolet light from
the
>flare changed the structure of the Earth's
electrically
>charged upper atmosphere (ionosphere). This affected
radio
>communication frequencies that either pass through
the
>ionosphere to satellites or are reflected by it to
traverse
>the globe.
>
>The explosion, near the Sun's
northwest limb (the upper right
>in SOHO images), was associated with an
eruption of a cloud of
>electrified gas, called a coronal mass ejection,
or CME, into
>space, but apparently not directed towards
Earth.
>
>"We are perhaps lucky that this event didn't occur over
the
>weekend, when the resulting CME would almost certainly
have
>been aimed towards Earth," said Brekke. "A smaller
flare-
>related CME event in March 1989 caused major power failures
in
>Canada, and subsequent smaller events have
disrupted
>communication and navigation satellites."
>
>Solar
ejections are often associated with flares and sometimes
>occur shortly
after the flare explosion. CMEs are clouds of
>electrified, magnetic gas
weighing billions of tons ejected
>from the Sun and hurled into space with
speeds ranging from 12
>to 1,250 miles per second. Depending on the
orientation of the
>magnetic fields carried by the ejection cloud,
Earth-directed
>CMEs cause magnetic storms by interacting with the
Earth's
>magnetic field, distorting its shape and
accelerating
>electrically charged particles (electrons and atomic
nuclei)
>trapped within.
>
>Severe solar weather is often
heralded by dramatic auroral
>displays, northern and southern lights, and
magnetic storms
>that occasionally affect satellites, radio communications
and
>power systems. The flare and solar ejection has
also generated
>a storm of high-velocity particles, and the number
of
>particles with ten million electron-volts of energy in
the
>space near Earth is now 10,000 times greater than normal.
The
>increase of particles at this energy level still poses
no
>appreciable hazard to air travelers, astronauts or
satellites,
>and the NOAA SEC rates this radiation storm as a
moderate S2
>to S3, on a scale that goes to S5.
>
>The
SOHO project is an international cooperative program
>between NASA and the
European Space Agency for the
>International Solar Terrestrial Science
Program.
>
>For additional information and images regarding the
flare,
>space weather and the giant sunspot, see:
> http://sohowww.nascom.nasa.gov/hotshots/X17/
> http://www.spaceweather.com/
> http://www.sel.noaa.gov/NOAAscales/index.html
> http://www.noao.edu/outreach/press/pr01/img0101.html
> -end-
>
>
> * * *
>
>NASA press
releases and other information are available automatically
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>In the body of the
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--
Larry R.
Kellogg
lkellogg@mail.arc.nasa.gov
http://lunar.arc.nasa.gov
-----Original
Message-----
From: Frey, Steven R. [mailto:sfreyohp@SLAC.STANFORD.EDU]
Sent:
Monday April 02, 2001 3:14 PM
To: RADSAFE (E-mail)
Subject: Solar activity
dose to ISS astronaut
Fellow Radsafers -
What was the dose a
crewmember aboard the
International Space Station (ISS) likely received
from
last week's sunspot/solar flare event? Curious here.
Thanks in
advance for any
response.
Steve
***********************************************************************
Steven
R. Frey,
Radiological Control Manager
Stanford Linear Accelerator Center
(SLAC)
Room 266, Building 24, Mail Stop 84
2575 Sand Hill Road
Menlo
Park, CA 94025
Phone: (650) 926-3839
email address:
sfreyohp@SLAC.Stanford.EDU
Any opinion expressed here is the opinion of
the writer
alone and is not meant to speak on behalf of
SLAC
***********************************************************************