News from ISTP on Coordinated Studies
December 1999: On the Day the Solar Wind Disappeared,
- December 1999: On the Day the Solar Wind Disappeared,
Scientists Sample Particles Directly from the Sun
- May 1999: Polar, Wind, Interball Verify Dungey
Theories of Reconnection
- April 1999: Outreach Successes in 1998-1999
- March 1999: ISTP, ACE Assist Sounding Rocket Launch
- December 1998: Earth's Own Magnetosphere,
Not Solar Wind, Accelerates the Particles
of the Radiation Belts
- September 1998: ISTP on the Road: Workshops
- June 1998: ISTP Observes Effects of New
- May 1998: Succession of Flares, CMEs Upsets Spacecraft,
Presages Solar Maximum
- April 1998: ISTP Conducts Successful Workshop
- April 1998: New Poster Conveys Excitement, Relevance
of Sun-Earth Connection
- January 1998: Scientists Tracking Ejection from Sun that
Reached Earth January 6
- December 1997: Space Physicists Find the Energy that
Powers Explosive Coronal Mass Ejections and Discover
Their Origins and Impact
- October 1997: Wind, Ulysses Triangulate, Pinpoint Radio Burst
- October 1997: September Space Weather Events
Scientists Sample Particles Directly from the Sun
>From May 10-12, 1999, the solar wind that blows constantly from the Sun virtually disappeared in the most
drastic and longest-lasting decrease ever observed. Dropping to a fraction of its normal density and to half its
normal speed, the solar wind died down enough to allow physicists to observe particles flowing directly from
the Sun's corona to Earth. This severe change in the solar wind also drastically changed the shape of Earth's
magnetic field and produced a rare auroral display at the North Pole.
Starting late on May 10 and continuing through the early hours of May 12, the density of the solar wind
dropped by more than 98%. Because of the drop-off of the wind, energetic electrons from the Sun arrived at
the Earth in narrow beams, known as the strahl. Under normal conditions, electrons from the Sun are diluted,
mixed, and redirected in interplanetary space and by Earth's magnetic field (the magnetosphere). But in May
1999, several satellites detected electrons arriving at Earth with properties similar to those of electrons in the
Sun's corona, suggesting that they were a direct sample of particles from the Sun.
"This event provides a window to see the Sun's corona directly," said Dr. Keith Ogilvie, project scientist for
NASA's Wind spacecraft and a space physicist at Goddard Space Flight Center. "The beams from the corona do
not get broken up or scattered as they do under normal circumstances, and the temperature of the electrons
is very similar to their original state on the Sun."
"Normally, our view of the corona from Earth is like seeing the Sun on an overcast, cloudy day," said Dr. Jack
Scudder, space physicist from the University of Iowa and principal investigator for the Hot Plasma Analyzer
(HYDRA) on NASA's Polar spacecraft. "On May 11, the clouds broke and we could see clearly."
Scudder, Ogilvie, and other scientists affiliated with the International Solar-Terrestrial Physics program (ISTP)
presented their findings at the Fall Meeting of the American Geophysical Union in San Francisco's Moscone
Center. Researchers working with more than a dozen spacecraft observed various facets of this event.
Fourteen years ago, Scudder and Dr. Don Fairfield of NASA Goddard predicted the details of an event such as
occurred on May 11, saying that it would produce an intense "polar rain" of electrons over one of the polar
caps of Earth. The polar caps typically do not receive enough energetic electrons to produce visible aurora
because those electrons are slowed and depleted by too many collisions in interplanetary space. But in an
intense polar rain event, Scudder and Fairfield theorized, the "strahl" electrons would flow unimpeded along
the Sun's magnetic field lines to Earth and should precipitate directly into the polar caps, inside the normal
Such a polar rain event was observed as a steady glow in X ray images and confirmed for the first time in May
1999. Aurora were observed at the North Pole, which can only happen if these energetic electrons are coming
directly from the solar wind.
"While we saw weak aurora in the south, in the north we saw the effects of intense, energetic electrons on the
upper atmosphere in the form of X rays," said Dr. Dave Chenette, a space physicist at Lockheed Martin and
principal investigator of the Polar Ionospheric X-Ray Imaging Experiment (PIXIE) on NASA's Polar spacecraft.
"These X-ray emissions are the most intense that we have ever seen at the north magnetic pole since Polar
was launched in 1996."
According to Chenette and Scudder, the fact that the aurora appeared only at one pole in May 1999 suggests
that the North Pole is connected to the end of the magnetic field from the Sun, while the South Pole is
connected to the end of the Sun's magnetic field that extends to the outer reaches of the solar system.
"The May event provides unique conditions to test ideas about solar-terrestrial interactions," Ogilvie noted. "It
also strengthens our belief that we understand how the Sun-Earth connection works."
Under typical conditions, the Sun emits a tenuous gas of protons, helium, and electrons - the solar wind -- in
all directions across the solar system. Carrying energy and magnetic fields from the Sun, the solar wind
varies but usually stays within 5 to 10 particles per cubic centimeter (cc) and between 400-600 kilometers
per second. The pressure from this solar wind buffets and confines Earth's magnetic field, ramming it up
against the planet on the day side and stretching a long magnetic tail on the night side.
But on May 11, the drop in the density of the solar wind (to less than 0.2 particles per cc) allowed Earth's
magnetosphere to swell unimpeded to five to six times its normal size. According to observations from the ACE
spacecraft, the density of helium in the solar wind dropped to less than 0.1% of its normal value, and heavier
ions, held back by gravity, apparently could not escape from the Sun at all. NASA's Wind, IMP-8, and Lunar
Prospector spacecraft and the Japanese Geotail satellite observed Earth's bow shock - the region where the
solar wind slams into the sunward edge of the magnetosphere - moving out to 238,000 miles from Earth
(380,000 kilometers). The event produced the most distant bow shock ever recorded by satellites; the norm is
41,500 miles (67,000 km) from Earth toward the Sun.
In addition, the Earth's magnetic field took on a more dipolar shape - similar to the shape of iron filings spread
around a magnet - as Earth's field would appear if there was no solar wind. And data from NASA's SAMPEX
spacecraft reveal that in the wake of this event, Earth's radiation belts dissipated and nearly disappeared for
several days afterward.
Nearly a dozen spacecraft observed this unusual event, including NASA's Polar, Wind, ACE, IMP-8, SAMPEX,
FAST, and Lunar Prospector satellites. Contributions also were made by Interball (Russian Space Agency),
Geotail (Japan's Institute for Space and Astronautical Science), and by satellites operated by the National
Oceanic and Atmospheric Administration and the U.S. Department of Defense.
A NASA Video File relating to this story will air on December 13 at Noon EDT. NASA Television is available on
GE-2, transponder 9C at 85 degrees West longitude, with vertical polarization. Frequency is on 3880.0
megahertz, with audio on 6.8 megahertz. Video File Advisories can be found at
May 1999: Polar, Wind, Interball
Dungey Theories of Reconnection
J. W. Dungey predictions, before satellites were: IMF south,
reconnection on dayside, low latitude (previously verified by ISEE);
IMF north (reconnection on nightside of cusp, had not been
verified); tests of strong north IMF (quantified in simulation by
Fedder and Lyon, 1995). Reconnection now verified, observed by
Reconnection is one of the most important plasma processes
in the universe, a key method of energy exchange.
- Measures strong northward IMF -- Dungey's condition -- on May
- Solar wind pressure 4 times normal squeezes magnetosphere so
much that Polar approached magnetopause
- Magnetic field shows major variations from models
- New MHD simulation including nightside reconnection explains
- Plasma measurements shows trapped magnetosheath plasma on
closed field lines on day side -- which simulation predicts
April 1999: Example Successes -- ISTP, ACE, SOHO
Live From the Sun
Images and Animations
- "Electronic field trip" combines broadcast TV and videotape, Web chats, e-mail Q&A, hands-on activities, and printed materials
- Covers 35% of science standards
- Video/live shows aired March 16 and April 13, 1999, broadcast by 250 PBS stations and NASA-TV.
- Estimated reach: 1.5 to 2 million teachers and students.
- Produced by Passport to Knowledge, supported by OSS, ISTP, SOHO, ACE, other agencies
- Created and produced new animations of:
- Coronal Mass Ejection and shock wave
- Radiation belts
- Ionospheric outflow into magnetosphere
- Deep di-electric charging of spacecraft
- Earth's Magnetosphere
- Produced 3-minute video intro to ISTP
- Produced 9-minute and 3-minute montages of Sun-Earth Connections movies/images to spark student, public interest in SEC
- Maryland Science Center will use ISTP videos in its new "SpaceLink" exhibit
- Footage distributed to more than 50 science centers and planetaria nationwide
- Developed themed backdrop to promote awareness of solar maximum at science fairs, education meetings, civic events
March 1999: ISTP, ACE Assist Sounding
The Polar and ACE missions, and ISTP ground stations in Canada,
were instrumental in achieving maximum return from the recent launch
of the Enstrophy sounding rocket.
Launched Feb. 11 from Poker Flat,
the rocket studied the fine structure of auroral electric currents.
The launch sent four magnetometers through the poleward edge of the
ACE solar wind data told researchers that conditions
were right for loading Earth's magnetic tail. UVI and VIS images
from Polar showed the auroral structure through which the rocket was
launched. CANOPUS ground magnetometer data indicated approaching
auroral activity, so the rocket could be launched as the auroral arc
reached the site.
December 1998: Earth's Own Magnetosphere,
Not Solar Wind, Accelerates the Particles
of the Radiation Belts
EMABARGOED FOR RELEASE ON DECEMBER 7 AT 8:30 A.M. PST
Forty years after James Van Allen discovered the radiation belts, scientists have found that Earth's space
environment is a massive particle accelerator, boosting electrons to near light speed in a matter of
minutes. By using the coordinated measurements from two dozen spacecraft together with sophisticated
computer models, scientists should soon be able to make "weather maps" of this acceleration, allowing
predictions of the intensity of the radiation belts and the location of the most active regions. The
acceleration of particles inside the radiation belts can affect the operation of satellites.
The Van Allen radiation belts are a pair of doughnut shaped rings of ionized gas (or plasma) trapped in
orbit around Earth. The outer belt stretches from 19,000 km (11,500 miles) in altitude to 41,000 km
(25,000 miles); the inner belt lies between 13,000 km (7600 miles) and 7,600 km (4,500 miles) in
For decades, space physicists theorized that the Sun and its solar wind provided most of the high-energy
particles found in Earth's radiation belts. But new observations from the International Solar-Terrestrial
Physics (ISTP) program and other missions suggest that Earth's own magnetic shell in space, or
magnetosphere, is a more effective and efficient accelerator of particles.
According to Dr. Geoffrey Reeves of Los Alamos National Laboratory and an investigator for ISTP, the
solar wind and Sun are insufficient sources for the radiation belts. "There are just not enough
high-energy electrons in the solar wind to explain how many we observe near Earth," said Reeves, who
discussed the findings on December 7 in San Francisco during the Fall Meeting of the American
Data from NASA's Polar and SAMPEX spacecraft, as well National Oceanic and Atmospheric
Administration (NOAA) and the Department of Defense satellites, show that the radiation belts change in
response to a variety of solar events. High-speed streams of solar wind, coronal mass ejections, and
shock waves from the Sun all can compress and excite the magnetosphere. But it is the pressure and
energy of these events, not the particles buried in them, that energizes the particles trapped inside the
"It is amazing that the system can take the chaotic energy of the solar wind and utilize it so quickly and
coherently," said Dr. Daniel Baker of the University of Colorado, an investigator for ISTP and SAMPEX.
"We had thought the radiation belts were a slow, lumbering feature of Earth, but in fact they can change
on a knife's edge."
Discovered in 1958, the radiation belts have long been treated as a relatively stable and predictable
phenomenon. But in studying recent space weather events, space physicists have found that the
intensity of the belts can vary by 10, 100, or even 1000 times in a matter of seconds to minutes. "The
radiation belts are almost never in equilibrium," said Reeves. "We don't really understand the process,
but we do know that things are changing constantly."
For instance, in early May 1998, a series of solar events provoked the most powerful storm in the
radiation belts of the current solar cycle. Following a succession of coronal mass ejections and flares on
the Sun, several major magnetic storms brought auroras to Boston and Chicago, and ISTP ground
observatories in Canada and Antarctica measured electric currents in the ionosphere about 3-4 times
the norm. The leading edge of the magnetosphere, which usually sits at 76,000 km (45,000 miles) from
Earth toward the Sun, was pushed in to 25,000 km (15,300 miles).
In the wake of this disturbance, the natural gap (or "slot" region) between the two radiation belts was
filled by a new radiation belt, as energized particles were trapped where they wouldn't naturally settle.
The new belt lasted for nearly six weeks.
"The May 1998 event was a harbinger of what may come during the approaching solar maximum," said
Baker. At the height or maximum of the 11-year solar cycle -- predicted for 2000-2001 -- coronal mass
ejections and other solar events that disturb the radiation belts are likely to be much more common.
Observations from the May event are prompting researchers and space weather forecasters to reconsider
the radiation belt models relied upon by the engineers who design and operate satellites. "We now have
a fleet of satellites that gives us a more complete picture of what's going on in the radiation belts," said
Reeves. "We are using this data to construct pictures, essentially 'weather maps' of what's going on in
the radiation belts."
"Within the research community, there has been continuous progress in modeling the space
environment, but very little of that research has made it into the space weather operations community,"
said Dr. Terrance Onsager of NOAA's Space Environment Center. "Most of the models in use today do a
reasonable job of predicting average conditions, but few of them take into account the dynamics and
how quickly the system can change."
"Some of the new models that we are developing will allow us to visualize the radiation environment
over vast regions of space and then specify and predict the conditions at any location," Onsager added.
"We are beginning to synthesize mature models with the new stream of real-time measurements from
space in order to give industry and the government the information it needs to work in space."
September 1998: ISTP on the Road:
Workshops Foster Collaboration
In September, ISTP conducted its first workshop in Europe
(Rutherford Appleton Labs) to foster collaboration with Equator-S,
Over 150 scientists from a dozen countries participated. Russian,
Japanese, and Czech labs were well-represented. Highlights
included: first review of May 1998 solar-terrestrial events;
discussion of first simultaneous observations of reconnection in the
magnetopause. By coincidence, a CME lifted off the Sun, the fourth
time a CME coincided with an ISTP workshop.
Also in September, ISTP project scientists participated in a NATO
workshop in Kosice, Slovakia. Much of the meeting focused on
greater participation of Russian spacecraft in ISTP.
June 1998: ISTP Observes Effects of New
Observations made by ISTP scientists suggest that a new radiation
belt was formed in May, an unusual phenomenon not observed
Following 7 coronal mass ejections and 2 X-class flares in early
May, the population of relativistic electrons in Earth's radiation
belts achieved "killer" energy levels, according to investigators
Dan Baker and Geoff Reeves. The boost in radiation lasted longer
and achieved higher energy than any event since the last solar
During one magnetic storm in May, the disturbance storm-time
(or Dst) index reached -218 on the scale of 0 to -220---the largest
storm of the current solar cycle. An ISTP ground station
(CANOPUS) measured electric currents in the ionosphere well
above 4000 nanotesla, about 6-8 times the norm for solar
As a result of the consecutive doses of radiation, the Polar
spacecraft was upset to the point of being shut down for several
hours. ISTP investigators also have found compelling evidence
that several other satellite failures may have been related to
radiation belt activity.
May 1998: Succession of Flares, CMEs Upsets Spacecraft,
Presages Solar Maximum
>From April 27 through May 6, ISTP spacecraft and observatories got
of what is to come during the maximum of the solar cycle. In the
10 days, the Sun produced seven coronal mass ejections, two X-class
(the most energetic type), and at least two energetic particle
Earth, several major magnetic storms upset several spacecraft,
auroras to lower-than-normal latitudes, and forced power companies
reconfigure the grid in New England.
On April 29, a "halo" CME left the Sun and its shock arrived at the
spacecraft within 53 hours. The shock arrived faster than any
detected so far by SOHO. A magnetic storm followed on May 2.
rumors and anecdotal reports, the failure of the Equator-S
not necessarily a result of CME or magnetic storm.
ISTP observers have noted that sunspots are becoming more
moving with a clockwise rotation--telltale properties of proton
On May 1-2, ISTP observed two halo CMEs, as well as an X-class
High-energy protons from the flare arrived at SOHO within 30
a major magnetic storm developed on May 4.
During the storm, the disturbance storm-time index (Dst) reached
the scale of 0 to -220. It is the largest storm of the current
An ISTP ground station (CANOPUS) measured electric currents in the
ionosphere well above 2000 nanotesla, about 3-4 times the norm for
minimum. The January 1997 event that knocked out Telstar 401 had
of 1800 nT.
In response to the magnetic storm, power companies in New England
their power sharing capacity with Canadian utilities. Auroras were
reported as far south as Boston and Chicago.
May 6 also was an extremely active day: ISTP observatories detected
CME, a moderate-speed halo CME, and a fast CME, though none led to
storms. However, an X-class flare burst from the Sun, raining
protons toward Earth. The protons upset the Polar spacecraft,
controllers to shut it down for several hours. All of the
electronics have since been restored.
April 1998: ISTP Conducts Successful Workshop
Latest ISTP workshop -- held April 7-9 at GSFC -- attracted 187
participants from at least 15 countries.
Included interactive panels on the highlights of ISTP and the future
of the mission. Science team suggested that time has come for an
Workshop included a preview of some of the 200+ ISTP-related papers
to be presented next month at AGU.
Highlights included evidence for reconnection in Earth's magnetic
tail and plans for Wind's exploration of high-latitude magnetosphere.
Outreach session showcased a dozen efforts being made to share
space physics with students and the public.
April 1998: New Poster Conveys Excitement,
of Sun-Earth Connection
ISTP has created a new 22" by 34" poster for high school students and adult
science buffs. The poster highlights the dynamic, electric connection
between Sun and Earth by using more than two dozen images (front &
back), a magazine-length article on space weather, and a CME tracking
exercise. 28,000 copies of "Storms from the Sun" are now being produced
for distribution at the April meeting of the National Science Teachers
Association and other meetings. It will also be available through NASA
Educator Resource Centers. A Spanish-language version of the poster will
be produced later this year.
January 1998: Scientists Tracking Ejection
from Sun that
Reached Earth January 6
Researchers from the International Solar-Terrestrial Physics (ISTP)
program are currently
tracking a coronal mass ejection (CME) that left the Sun late on
January 2 and began
arriving at Earth around 10 a.m. Eastern Time on January 6. CMEs
charged gas from the Sun that can trigger magnetic storms around
eruptions--which are becoming more frequent as the Sun builds up
toward the maximum
of its 11-year cycle--occasionally disturb spacecraft, navigation
systems, and electric power grids.
The Wind, Polar, and Geotail spacecraft, as well as a network of
smaller satellites and
ground-based observatories are now monitoring the interplanetary
storm as it crosses
paths with Earth. Scientists are observing changes in the strength
of Earth's magnetic
field and radiation belts, while gathering images of Earth's
Forecasters at the Space Environment Center of the National Oceanic
Administration predicted the CME would begin arriving during the
latter half of January
6 and would continue through January 7. The disturbance to Earth's
magnetic field and
space environment is not expected to be particularly strong;
however, observers at high
latitudes (Canada, Scandinavia, etc.) are likely to see aurora
tonight and tomorrow.
On January 2, scientists operating the Solar and Heliospheric
spacecraft detected a "halo" type coronal mass ejection erupting
from the Sun at
approximately 500 km/s (more than 1 million miles per hour). The
SOHO team alerted
the rest of ISTP to the possibility of an Earthbound storm. In
research presented at the
December meeting of the American Geophysical Union, ISTP
researchers announced that
"halo" CMEs almost always result in magnetic activity at Earth.
Halo CMEs are so
named because they appear as expanding halos around the Sun when
seen from Earth.
ISTP is a joint, comprehensive effort to observe and understand our
star, the Sun, and its
effects on Earth's environment in space. The primary participating
NASA, the European Space Agency (ESA), the Japanese Institute of
Astronautical Sciences (ISAS), the Russian Space Research Institute
To view the same data and images as ISTP scientists, visit the
Event web page here.
information about ISTP and the physics of the Sun and Earth, go
For the official U.S. space weather forecast, visit
An image to accompany this story is available here.
Current images of Earth's aurora as seen from space are available
December 1997: Space Physicists Find the Energy
Powers Explosive Coronal Mass Ejections
and Discover Signatures of
Their Origins and Impact
Using spacecraft and supercomputers, scientists from the International Solar Terrestrial Physics (ISTP)
program have developed a new theory for the explosive, high velocity coronal mass ejections (CMEs) that
will erupt from the Sun with increasing frequency during the maximum of the new solar cycle. CMEs
are eruptions of electrically charged gas from the Sun that can trigger magnetic storms around Earth.
Such storms occasionally disturb spacecraft, navigation and communications systems, and electric
Recent experimental and theoretical observations from ISTP indicate that the interaction of magnetic
fields high above the Suns surface, not low in the corona, as was previously thought, allows
tremendous energy to build up and to release CMEs at speeds approaching 2000 kilometers per second.
Scientists also have determined that halo CMEs almost always lead to geomagnetic storms, an
observation of great consequence for the prediction of space weather. Finally, ISTP researchers have
been able to create realistic visual simulations of the effects that CMEs can have on Earth's magnetic
Coronal mass ejections are the largest structures that erupt from the Sun and they one of the principal
ways that the Sun ejects material and magnetic energy into the solar system. Most CMEs travel at 400
km per second, but fast CMEs can reach speeds double or triple that. The first fast CME of the new solar
cycle was observed on November 6, 1997. Slow or fast, the eruptions produce magnetic clouds that can
cause geomagnetic storms and increase the intensity of the aurora (Northern and Southern lights). Fast
CMEs also can accelerate protons in interplanetary space to the point where they can harm spacecraft or
astronauts in space.
Inspired by images of CMEs collected by the Large Angle Spectrometric Coronograph on the SOHO
spacecraft, Dr. Spiro Antiochos of the U.S. Naval Research Laboratory in Washington, DC, has proposed a
new answer to the long-standing question of how the Sun can build up the energy to produce the
violent explosions of fast CMEs. Using supercomputers from NASA and the Department of Defense,
Antiochos has created a model that simulates the complex, interwoven magnetic structures of the Sun.
After observing how magnetic fields abut and interact, Antiochos theorizes that the Sun's magnetic
fields tend to restrain each other and force the buildup of tremendous energy.
When a stressed magnetic field low in the Sun's atmosphere pushes higher into the corona, it gets
held back by the surrounding and overlying fields. As the stressed field builds up more potential
energy, it pushes harder against these magnetic ropes and moves higher into the corona. Eventually,
through a process known as "magnetic reconnection"-- where opposing magnetic lines of force merge
and cancel--the field is released from its bonds and escapes the Sun as high speed.
Antiochos compares the process to that of filling a helium balloon. "If you fill it without anchoring it, the
balloon will slowly drift upward," he said. "But if you hold the balloon down as you fill it, you can
generate a lot of upward force, which makes the balloon take off at higher speed once you release it. Fast
CMEs are released in the same way." Antiochos added that such high-speed bursts will be more frequent
as the Sun approaches its maximum period of activity in 2000-2001.
In other research, ISTP teams headed by David Webb of Boston College and the Research Laboratory at
Hanscom Air Force Base and by Dr. Guenter Brueckner of the Naval Research Laboratory used ISTP's
SOHO and Wind spacecraft to study nine "halo" type CMEs that occurred from December 1996 to May
1997. They found that such events almost always result in magnetic activity at Earth. Halo CMEs are so
named because they appear as expanding halos around the Sun when seen from the perspective of
According to Dr. Nancy Crooker, a space physicist at Boston University, detection of halo events "will
vastly improve" methods of predicting geomagnetic storms. "If you see a halo CME, you are pretty sure
that you are going to see a storm at Earth," Crooker said. "In the past, scientists could only look at solar
flares to know if a storm was headed toward Earth. And while some flares have accompanying CMEs,
some don't. But now we have instruments sensitive enough to see the CMEs themselves."
ISTP does not predict space weather. Forecasting is the domain of the Space Environment Center of the
National Oceanic and Atmospheric Administration.
Crooker and Webb also have identified the signature of halo CMEs on the Sun's surface. These remnants
of CMEs show up in X rays and ultraviolet light as the sudden brightening of magnetic arches, with
dimming areas on either side. These dimming areas seem to mark the roots of CMEs already launched
Downwind from those eruptions, the invisible magnetic shell (or magnetosphere) that shields Earth from
the Sun's particles and radiation is regularly shaped and shorn by CMEs. To better understand this
interaction, Dr. Charles Goodrich, of the University of Maryland, has developed a series of animations
that depict how the magnetosphere responds to the shock of a CME.
Using a Cray C-90 and other powerful computers, Goodrich and colleagues have for the first time
depicted the evolution of the magnetosphere as it is bombarded by a real CME. The simulation
reconstructs 42 hours of time centered around the arrival of a CME on January 10, 1997. The
simulation reveals the shape and orientation of Earth's magnetic field, as well as the density of plasma
in Earth's space environment.
In fact, the real January CME produced magnetic storms and spectacular auroral displays, and poured
as much as 1400 Gigawatts of electricity into the atmosphere (almost double the power generating
capacity of the United States). The magnetic cloud from the CME smacked the magnetosphere with a
burst of plasma 30 times denser than the normal solar wind. The shock compressed the leading edge of
the magnetosphere inside geosynchronous orbit, where many satellites are positioned.
"We have created a global picture of what is going on in the magnetosphere," said Goodrich. "Since we
only have a few spacecraft, and they can only make point measurements, this is the only way to look at
the whole system." Such simulations will provide researchers with insights about the conditions that
lead to--and perhaps trigger-- geomagnetic storms, Goodrich added.
In the past year, the primary spacecraft of ISTP--SOHO, Wind, Polar, and Geotail--and the program's
network of cooperating satellites, ground sensors, and theory centers have monitored approaching
interplanetary storms for the first time, from their genesis to their impact on Earth. ISTP was designed as
a joint, comprehensive effort to observe and understand our star, the Sun, and its effects on Earth's
environment in space. Participating institutions include NASA, the European Space Agency (ESA), the
Japanese Institute of Space and Astronautical Sciences (ISAS), the Russian Space Research Institute
(IKI), as well as the Max Planck Institute, the U.S. National Oceanic and Atmospheric Administration,
the Los Alamos National Laboratory, the U.S. Air Force, the Canadian Space Agency, the British
Antarctic Survey, the U.S. National Science Foundation, and the Johns Hopkins Applied Physics
(see figure). Traditionally, individual
spacecraft have been able to determine the direction of such radio
bursts, but not the true distance from the Sun. Scientists were
forced to rely on gross estimates for that. Now, through a rare
alignment of the Wind and Ulysses spacecraft--the only craft
equipped to track such radio bursts--scientists have been able to
triangulate and determine the precise location of a Type III radio
burst in three-dimensional space. If equipped to do this on a
regular basis--with a long-term, stereo alignment of
spacecraft--researchers would be able to map the interplanetary
magnetic field; track the electron streams from Sun to Earth;
measure the size, density, and intensity of radio bursts and
perhaps the events on the Sun that produce them; and track some
elements of space weather.
For reporters and editors seeking more information
about any ISTP news item, contact Mike Carlowicz, science writer
October 1997: September Space Weather Events
On September 24, a coronal mass ejection lifted off the Sun with
the classic signature of an event that should cause geomagnetic
storms. Scientists detected a Moreton wave (see
figure), several flares, and Type II radio bursts associated with the
shock fronts of a CME.
NOAA issued a press release and alerted the physics community about
a likely strong impact on Earth.
Three days later, the CME missed SOHO, Wind, Polar, and Earth,
reminding scientists that spectacular solar events don't
necessarily mean effects at Earth.
On September 28, SOHO
spied another CME (see figure) leaving the Sun.
Like the effective January 1997
event, this "halo" CME did not have the markings of a
storm-inducing event--no Moreton waves, no flares, no Type II radio
bursts, no X-ray signatures. NOAA predicted near-normal space
weather, but ISTP alerted scientists to a possible impact. On
October 1, Polar and ISTP ground stations detected bright aurora, a
geomagnetic storm, and substorms heralding the arrival of the CME
Brought to you by the International Solar-Terrestrial Physics Program and NASA.
Author: Mike Carlowicz
Official NASA Contact:ISTP-Project
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