Millions of amps surge through our atmosphere . . .

. . . And make bright Northern lights.
A close-up of the Sun (shown in ultraviolet light)

reveals a mottled surface, bright flares,

 and tongues of hot gas leaping into space.

Though they look like burns in the face of the Sun, sunspots

are actually much cooler than the rest of the surface.

Bubble, Bubble, Toil and Trouble

Looking at the sky with the naked eye, the Sun seems static,

placid, constant. From the ground, the only noticeable variations in

the Sun are its location (where will it rise and set today?) and its color

(will clouds cover it or will the atmosphere make it turn pink or

orange?) But our Sun gives us more than just a steady stream of

warmth and light. The Sun is turbulent and dynamic, provoking the

cosmic equivalent of winds, clouds, waves, precipitation, and storms

which bathe us in energy and star dust.

The Sun is a huge thermonuclear reactor, fusing hydrogen atoms

into helium and producing million degree temperatures and intense

magnetic fields. Near its surface, the Sun is like a pot of boiling

water, with bubbles of hot, electrified gas—actually electrons and

protons in a fourth state of matter known as plasma—circulating up

from the interior, rising to the surface, and bursting out into space.

The steady stream of particles blowing away

from the Sun is known as the solar wind.

Blustering at 800,000 to 5 million miles per hour, the solar wind carries a million tons

of matter into space every second (that’s the mass of Utah’s Great Salt Lake). It’s not the

mass or speed, however, that makes the solar wind potent. In

fact, the solar wind would not even ruffle the hair on your head

because there are too few particles in the breeze (our air is

millions of times denser than the solar wind). Instead, it is the

energy and the magnetic fields associated with that plasma that

buffet Earth’s protective magnetic shield in space (the magnetosphere). Though less than 1% of the solar wind penetrates the

magnetosphere, that’s enough to generate millions of amps of

electric current in our atmosphere and to cause occasional

magnetic storms in the space around Earth.

If the character of the solar wind is like the everyday winds

on Earth—mild, steady, and global—then sunspots and solar

flares are like lightning and tornadoes—potent, but localized.

Sunspots are dark splotches on the Sun caused by the appearance

of cooler (3000

degrees Celsius)

areas amidst the roiling gases on the surface (6000 degrees C). These

areas are cooler because much of their energy is tied up in intense

magnetic fields 1000 times stronger than the magnetic field of Earth.

On the other hand, solar flares appear as explosive bright spots on

the surface of the Sun. Flares occur when magnetic energy built up in

the solar atmosphere near a sunspot is suddenly released in a burst

equivalent to ten million volcanic eruptions. Radiation—including

radio waves, X rays, and gamma rays—and electrically charged

particles emanate from the Sun following a solar flare (though most of

it is blocked by Earth’s atmosphere and magnetic field). The strongest

flares occur just several times per

 year, while weaker flares are relatively common, with as many as

a dozen a day during the Sun’s most active periods.

The use of an occulting disk—the orange and white

circle in the center of the photo—allows scientists to see

the solar wind streaming away from the Sun
The bubble of plasma in a CME expands and grows more potent until it escapes

from the magnetic and gravitational energy of the Sun.

Hurricane Sol

One of the most important solar events from Earth’s perspective is the coronal mass ejection (CME), the solar

equivalent of a hurricane. A CME is the eruption of a huge bubble of plasma from the Sun’s outer atmosphere, or

corona. The corona is the gaseous region above the surface that extends millions of miles into space. Thin and

faint compared to the Sun’s surface, the corona is only visible to the naked eye during a total solar eclipse. Temperatures in this region exceed one million degrees Celsius, 200 times hotter than the surface of the Sun.

How the corona can be so much hotter than the surface remains a mystery to scientists, but most suspect that it

has to do with the complicated magnetic fields that burst from the interior and extend above the surface in great

arches and loops. The buildup and interaction of these magnetic loops—which can stretch over, under, and around

each other—seems to supply the energy to heat the corona and produce the violent explosion of a CME.

According to some of the newest observations and

theories, the larger and higher magnetic loops of the Sun’s

field are believed to hold down the newer fields emerging

from below the surface. They also tie down the hot plasma

carried by those fields. Much like a net holding down a hotair balloon, this network of magnetic loops restrains the

plasma and magnetic fields trying to rise into the corona. This

causes tremendous upward pressure to build. Eventually,

some of the overlying magnetic loops merge and cancel each

other, cutting a hole in the magnetic net and allowing the

CME to escape at high speed.

Researchers compare this process to filling a balloon with

helium. If you inflate it without holding it down, the balloon

will slowly drift upward. But if you hold the balloon down

with a string, you generate increasing force as you fill it,

causing it to push upward. Once you let go of the string, the

balloon shoots skyward.

Once it escapes the Sun’s gravity, a CME speeds across

the gulf of space at velocities approaching one million miles per hour (400 km/sec), with the fastest CMEs accelerating to 5 million mph. A typical CME can carry more than 10 billion tons of plasma into the solar system, a mass

equal to that of 100,000 battleships. The energy in the bubble of solar plasma packs a punch comparable to that of a

hundred hurricanes combined.

Just hours after blowing into space,

a CME cloud can grow to dimensions

exceeding those of the Sun itself, often

as wide as 30 million miles across. As it

plows into the solar wind, a CME can

create a shock wave that accelerates

particles to dangerously high energies

and speeds. Behind that shock wave,

the CME cloud flies through the solar

system bombarding planets, asteroids,

and other objects with radiation and

plasma. If a CME erupts on the side of

the Sun facing Earth, and if our orbit

intersects the path of that cloud, the

results can be spectacular and sometimes hazardous.

When scientists see a faint halo around the Sun

(expanding around the disk), they know a coronal mass

ejection is headed for Earth.
STORMS fr

A computer simulation of the magnetosphere

shows how a CME cloud can compress our

magnetic field and increase its intensity.

Photo Credit: Jan Curtis

Storm Front

Coronal mass ejections occur at a rate of a few times a week to several times per day, depending on how

active the Sun may be. And because of the size of the plasma clouds they produce, the odds say Earth is going to

get hit by a CME from time to time. Fortunately, our

planet is protected from the most harmful effects of the

radiation and hot plasma by our atmosphere and by an

invisible magnetic shell known as the magnetosphere.

Produced by Earth’s internal magnetic field, the magnetosphere shields us from 99% of the Sun’s plasma by deflecting it into space.

But some energetic particles do enter the magnetosphere from time to time, migrating in through Earth’s

magnetic tail or funneling in near the North and South

Poles, where the magnetic field is weakest and the magnetosphere is partially open to space. The flow of plasma

into our magnetosphere can induce magnetic storms, alter

Earth’s magnetic field as measured on the ground, and

produce the phenomena known as auroras.

Many things can happen in the magnetosphere during

a magnetic storm

because a lot of energy is being dumped into the system. When stimulated

by plasma from the Sun or from the far reaches of the magnetosphere, the

electrons, protons, and oxygen ions of surrounding Earth become denser,

hotter, and faster. Due to their motion, these particles produce as much as a

million amperes of electrical current, a jolt of power that can decrease the

relative strength of Earth’s magnetic field. Some of the current flows along

Earth’s magnetic field lines and into the upper atmosphere. The passage of

electric current through the upper atmosphere and the loss of electrons and

protons from the upper magnetosphere can cause the atmosphere to warm,

expand, or become more dense.

Also, excited particles inside the magnetosphere can plunge into the

upper atmosphere, where they collide with oxygen and nitrogen. These

collisions—which usually occur between 40 and 200 miles above ground—

cause the oxygen and nitrogen

to become electrically excited

and to emit light (fluorescent

lights and televisions work in

much the same way). The

result is a dazzling dance of

green, blue, white, and red

light in the night sky, also

known as aurora borealis and

aurora australis (“Northern and Southern lights”). Auroras can appear

as colorful, wispy curtains of light ruffling in the night sky, or sometimes as diffuse, flickering bands. Either way, they tell us that something electric is happening in the space around Earth.

Though they grow more intense when a CME

hits Earth, auroras are present every day.

Seen here over Alaska, auroras are native to the far northern

and southern lands. The most powerful magnetic storms can

bring auroras all the way to Texas.
Sondrestromfjord radar

Seeing the Invisible

Auroras are a visible sign of the magnetic mayhem in our atmosphere, but beyond that, the human eye can’t

detect much of what we call space weather. That’s because most of the material flowing from Sun to Earth is too

diffuse or too dim—when

measured against the background of space or the

brightness of the Sun—to be seen by most telescopes or

cameras.

For instance, since the corona is only visible to the

naked eye during an eclipse, scientists must use an

occulting disk—which blocks the light from the solar

surface to create an artificial eclipse—to detect what the

Sun is spitting into space. Some of the most important

recent advances in understanding and tracking coronal

mass ejections have come from cameras that can resolve

the faint light of the corona and detect the CMEs as they

head toward Earth.

In order to “see the invisible,” space physicists rely on

telescopes

that detect visible light, ultraviolet light, gamma rays, and X rays.

They use receivers and transmitters that detect the radio shock waves

created when a CME crashes into the solar wind (the equivalent of a

sonic boom in space). They employ particle detectors to count ions

and electrons, magnetometers to record changes in magnetic fields,

and cameras to observe auroral patterns above the Earth.

All of these instruments and many others are the tools of the

hundreds of scientists participating in the International Solar-Terrestrial Physics (ISTP) program, a global effort to observe and understand

our star and its effects on our environment. An armada of more than

25 satellites carry those instruments into space, and together with ground-based

observatories, they allow scientists to study the Sun, the Earth, and the space

between them. Individually, the spacecraft contributing to ISTP act as microscopes, studying the fine detail of the Sun, the solar wind, and the boundaries and

internal workings of Earth’s magnetic shell. When linked together with each other

and the resources on the ground, they act as a wide-field telescope that sees the

entire Sun-Earth environment.

The spacecraft of ISTP—

principally, Wind, Polar,

Geotail, and the Solar and Heliospheric Observatory (SOHO)—

allow physicists to observe all the key regions of Earth’s space.

They study the interior of the Sun, its surface and corona, the

solar wind, and Earth’s magnetosphere, including the auroral

regions and Van Allen radiation belts. Orbiting as far as one

million miles and as close as two hundred miles above Earth, the

spacecraft of ISTP make coordinated, simultaneous observations

of the Sun and of activity in the magnetosphere. Working together with ground observatories, these spacecraft can—for the

first time in history—track CMEs and other space weather events

from origin to arrival. Someday, they might even be able to

predict when such storms will happen.

The orbits of Sun-Earth Connection satellites

allow scientists to see the entire system from many angles

ISTP includes spacecraft from NASA, the European Space

Agency, Japan’s Institute of Space and Astronautical

Science, and Russia’s Space Research Institute.

Polar

SOHO
rom the SUN

The effects of magnetic storms—what scientists call space weather—extend

from the ground to geostationary orbit and beyond.

Magnetic storms, like this one seen in

ultraviolet light, can wreak havoc on radio

communications and electric power stations.

Blackouts, Burnouts, and Bummers

Aside from bright auroras, there are less benevolent effects of the connection between Sun and Earth. In fact,

bright auroras are merely a visible sign that the balance of electrical and magnetic energy in Earth’s magnetosphere

has been upset. With the average CME dumping about 1500 Gigawatts of electricity into the atmosphere (double

the power generating capacity of the entire

United States), big changes can occur in

space. Those changes can wreak havoc on

a world that has come to depend on satellites, electrical power, and radio communication—all of which are affected by electric

and magnetic forces.

For the satellites dancing in and out of

the radiation belts and the solar wind,

CMEs and magnetic storms can be perilous.

For instance, a series of flares and coronal

mass ejections in March 1989 produced a

potent magnetic storm. After the particles

and energy from the Sun bombarded the

Earth, more than 1500 satellites slowed

down or dropped several miles of altitude in

their orbits due to increased drag.

But atmospheric drag isn’t the only

effect CMEs can have on satellites. When

excited and accelerated by a storm, highenergy electrons can degrade the solar

panels used to power satellites and can upset and even shut off computers on a spacecraft. The increased flow of

electricity in Earth’s space also can cause electrical charge to build up on the surface of a spacecraft. That charge

can eventually be released as a damaging spark (a spark like the one you get when you touch a friend after dragging

your feet on a carpet). In 1994, two Canadian satellites were shut

down when each was electrically shocked during magnetic storms; as

a result, telephone service across Canada was disrupted for months.

Similarly, in January 1997, an American satellite went dead just

hours after a CME struck the magnetosphere. The loss of that satellite disrupted television signals, telephone calls, and part of a U.S.

earthquake monitoring network.

Magnetic storms also play havoc with radio signals, which are

bounced off Earth’s ionosphere (the outermost layer of our atmosphere, made up mostly of plasma) as a sort of natural relay station.

In March 1989, listeners in Minnesota reported that they could not

hear their local radio stations, but they could hear the broadcasts of

the California Highway Patrol. In the extreme, magnetic storms can

completely wipe out radio communication around Earth’s North and

South Poles for hours to days.

Ohdiff
These images from SOHO (left) and Polar (right) show particles from the

Sun bombarding the satellites. SOHO sees the solar wind in the first

image, then a snow of protons accelerated by a CME. Polar looks down on

the aurora and Earth’s dayglow before the protons smack the camera.

On the ground, magnetic storms can affect

the strength of Earth’s magnetic fields.

Changes in magnetic fields can produce surges

in power lines and strong electrical currents in

gas and oil pipelines. The extra current can

cause pipelines to corrode and deteriorate faster

than they would naturally; in power lines, the

extra electricity can burn out transformers and

cause brownouts and blackouts. During the

March 1989 storm, a transformer burned up at a

power plant in New Jersey, and a whole system

was blown out at a power station in Quebec,

leaving 6 million people without electricity for

hours, some for days.

Since so much modern information is

relayed by satellites and other advanced technology—from automated teller machines and

television broadcast signals to the Global

Positioning System and disaster warning

networks—CMEs pose a natural and technological hazard to life on Earth.

Make Your Own Sun-Earth Connections

Thanks to the Internet, it is easy for you to keep up with the latest observations and breakthroughs in the study

of Sun and Earth. In fact, anyone who can access the World Wide Web can study the Sun, Earth’s magnetosphere,

and interplanetary space, because that is where ISTP scientists receive and share their

data. You can see this poster come to life with video clips or read it in Spanish at

http://www-istp.gsfc.nasa.gov/istp/outreach/cmeposter/index.html.

Many of the observations made by ISTP are available within hours to days after

they are made, allowing you to witness science in action. In particular, every time a

CME lifts off the Sun and heads toward Earth, you can watch the storm develop by

viewing some of the same images and data sets that space physicists are using. So

don’t wait for science to show up in your textbooks or magazines—look over a

scientist’s shoulder and watch it happen.

Mission to Geospace

To learn more about how and why physicists study the space around Earth, go to

http://www-istp.gsfc.nasa.gov/istp/outreach. The site includes easy-to-read articles and

primers; a place to question and read about real scientists; activities, images and movies;

and an extensive library of news items and articles about the latest and greatest discoveries from our neighborhood in space.

SOHO Explore

To learn more about the Sun as seen through the keen eyes of the Solar and Heliospheric

Observatory, go to http://sohowww.nascom.nasa.gov/explore/. The site includes exercises, a paper

model, image sets, posters, and a place to get all your Sun questions answered.

Getting the Latest on Space Weather

Whether it’s the chances for auroras or the number of sunspots, a good

site to get up-to-date information is http://www.spaceweather.com/

International Solar Terrestrial Physics Program

To see the same raw, unedited data and images that ISTP scientists

view, visit http://www-istp.gsfc.nasa.gov/istp/. These pages can be quite

technical, but they are the real deal.
Credit: This activity is based on “Sun Centered Physics,”

 a set of lesson plans developed by Linda Knisely.

Universal Time Time Interval Avg. Acceleration Position Avg. Velocity

8:05

8:36

9:27

10:25

11:23

Measure the Motion

of a Coronal Mass Ejection

Activity: Calculate the velocity and acceleration of a coronal mass ejection

(CME) based on its position in a series of images from the Large-Angle

Spectrometric Coronograph (LASCO) instrument on SOHO.

Materials: ruler, calculator, and a set of CME images from the LASCO

instrument on SOHO. You can use the ones here or gather another set from

http://sohowww.nascom.nasa.gov/gallery/LASCO/las001.gif

Background: An important part of space weather research is to measure the

velocity of CMEs and their acceleration as they leave the Sun. This is done

by tracing features in the CME and measuring their positions at different

times. In the sequence of images shown on the right, you can see a CME

erupting from the Sun on the right side of the coronagraph disk. The white

circle shows the size and location of the Sun. The black disk is the occulting

disk that blocks the surface of the Sun and the inner corona. The lines along

the bottom of the image mark off units of the Sun’s diameter.

Procedure: Select a feature of the CME that you can see in all five images—

for instance, the outermost extent of the cloud, or the inner edge. Measure its

position in each image. Your measurements can be converted to kilometers

using a simple ratio:

 actual distance of feature from Sun position of feature as measured on image

 diameter of the Sun (1.4 million km) diameter of Sun as measured on image

Using the distance from the Sun and the time (listed on each image), you can

calculate the average velocity. Velocity is defined as the rate of change of

position. Using the changes in position and time, the velocity for the period

can be calculated using the following equation: v = (s2 - s1) / (t2 - t1), where s2

is the position at time, t2; s1 is the position at time, t1. The acceleration equals

the change in velocity over time; that is, a = (v2 - v1) / (t2 - t1), where v2 is the

velocity at time t2; v1 is the velocity at time t1. You can record your results in

a table.

Further Questions and Activities

• Select another feature, trace it, and calculate the velocity and acceleration.

Is it different from the velocity and acceleration of the other feature you

measured? Scientists often look at a number of points in the CME to get an

overall idea of what is happening.

• How does the size of the CME change with time? What kind of forces

might be acting on the CME? How would these account for your data?

=

8:05 UT

8:36 UT

10:25 UT

9:27 UT

11:23 UT
NASA Resources for Educators 8:05

NASA’s Central Operation of Resources for Educators

(CORE) was established for the national and international

distribution of NASA-produced educational materials in

multimedia format. Educators can obtain a catalogue and an

order form by one of the following methods:

NASA CORE

Lorain County Joint Vocational School

15181 Route 58 South. Oberlin, OH 44074-9799

Phone: (440) 775-1400, FAX: (440) 775-1460

E-mail nasaco@leeca.org

Home Page: http://core.nasa.gov

Educator Resource Center Network (ERCN)

To make additional information available to the education

community, NASA has created the NASA Educator Resource

Center (ERC) network. Educators may preview, copy, or

receive NASA materials at these sites. Phone calls are

welcome if you are unable to visit the ERC that serves your

geographic area. A list of the centers and the regions they

serve includes:

AK, Northern CA, HI, ID, MT, NV, OR, UT, WA, WY

NASA Educator Resource Center

NASA Ames Research Center

Mail Stop 253-2

Moffett Field, CA 94035-1000

Phone: (650) 604-3574

http://amesnews.arc.nasa.gov/erc/erchome.html

IL, IN, MI, MN, OH, WI

NASA Educator Resource Center

NASA Glenn Research Center

Mail Stop 8-1

21000 Brookpark Road

Cleveland, OH 44135

Phone: (216) 433-2017

http://www.grc.nasa.gov/WWW/PAO/html/edteachr.htm

CT, DE, DC, ME, MD, MA, NH, NJ, NY, PA, RI, VT

NASA Educator Resource Laboratory

NASA Goddard Space Flight Center

Mail Code 130.3

Greenbelt, MD 20771-0001

Phone: (301) 286-8570

http://www.gsfc.nasa.gov/vc/erc.htm

CO, KS, NE, NM, ND, OK, SD, TX

Space Center Houston

NASA Educator Resource Center for

NASA Johnson Space Center

1601 NASA Road One

Houston, TX 77058

Phone: (281) 244-2129

http://www.spacecenter.org/educator_resource.html

FL, GA, PR, VI

NASA Educator Resource Center

NASA Kennedy Space Center

Mail Code ERC

Kennedy Space Center, FL 32899

Phone: (321) 867-4090

http://www-pao.ksc.nasa.gov/kscpao/educate/edu.htm

KY, NC, SC, VA, WV

Virginia Air & Space Center

NASA Educator Resource Center for

NASA Langley Research Center

600 Settlers Landing Road

Hampton, VA 23669-4033

Phone: (757) 727-0900 x 757

http://www.vasc.org/erc/

AL, AR, IA, LA, MO, TN

U.S. Space and Rocket Center

NASA Educator Resource Center for

NASA Marshall Space Flight Center

One Tranquility Base

Huntsville, AL 35807

Phone: (256) 544-5812

http://erc.msfc.nasa.gov

MS

NASA Educator Resource Center

NASA Stennis Space Center

Mail Stop 1200

Stennis Space Center, MS 39529-6000

Phone: (228) 688-3338

http://education.ssc.nasa.gov/erc/erc.htm

CA

NASA Educator Resource Center for

NASA Jet Propulsion Laboratory

Village at Indian Hill

1460 East Holt Avenue, Suite 20

Pomona, CA 91767

Phone: (909) 397-4420

http://learn.jpl.nasa.gov/resources/

resources_index.html

AZ and Southern CA

NASA Educator Resource Center

NASA Dryden Flight Research Center

PO Box 273 M/S 4839

Edwards, CA 93523-0273

Phone: (661) 276-5009

http://www.dfrc.nasa.gov/trc/ERC/

VA and MD’s Eastern Shores

NASA Educator Resource Center for

GSFC/Wallops Flight Facility

Visitor Center Building J-17

Wallops Island, VA 23337

Phone: (757) 824-2298

http://www.wff.nasa.gov/~WVC/ERC.htm

NASA’s Education Home Page serves as the education

portal for information regarding educational programs and

services offered by NASA for the American education

community. This high-level directory of information

provides specific details and points of contact for all of

NASA’s educational efforts, Field Center offices, and points

of presence within each state. Visit this resource at the

following address: http://education.nasa.gov.

NASA Spacelink is one of NASA’s electronic resources

specifically developed for the educational community.

Spacelink serves as an electronic library to NASA’s educational and scientific resources, with hundreds of subject

areas arranged in a manner familiar to educators. Using

Spacelink Search, educators and students can easily find

information among NASA’s thousands of Internet resources.

Special events, missions, and intriguing NASA Web sites are

featured in Spacelink’s “Hot Topics” and “Cool Picks” areas.

Spacelink may be accessed at: http://spacelink.nasa.gov.

NASA Spacelink is the official home to electronic versions of NASA’s Educational Products. A complete listing of

NASA Educational Products can be found at the following

address: http://spacelink.nasa.gov/products.

NASA Television (NTV) features Space Station and

Shuttle mission coverage, live special events, interactive

educational live shows, electronic field trips, aviation and

space news, and historical NASA footage. Programming has

a 3-hour block—Video (News) File, NASA Gallery, and

Education File—beginning at noon Eastern and repeated

four more times throughout the day. Live feeds preempt

regularly scheduled programming.

Check the Internet for programs listings at: http://

www.nasa.gov/ntv. For more information on NTV, contact:

NASA TV

NASA Headquarters - Code P-2

Washington, DC 20546-0001

Phone (202) 358-3572

NTV Weekday Programming Schedules (Eastern Times)

Video File NASA Gallery Education File

12–1 p.m. 1–2 p.m. 2–3 p.m.

 3–4 p.m. 4–5 p.m. 5–6 p.m.

 6–7 p.m. 7–8 p.m. 8–9 p.m.

9–10 p.m. 10–11 p.m. 11–12 p.m.

12–1 a.m. 1–2 a.m. 2–3 a.m.

How to Access Information on NASA’s Education Program, Materials, and Services (EP-2002-07-345-HQ)

This brochure serves as a guide to accessing a variety of

NASA materials and services for educators. Copies are

available through the ERC network, or electronically via

NASA Spacelink. Regional Educator Resource Centers offer more educators

access to NASA educational materials. NASA has formed partnerships with universities, museums, and other educational institutions to serve as regional ERCs in many states. A complete list of

regional ERCs is available through CORE, or electronically via

NASA Spacelink at http://spacelink.nasa.gov/ercn.

Please take a moment to evaluate this product at

http://ehb2.gsfc.nasa.gov/edcats/educational_wallsheet.

Your evaluation and suggestions are vital to continually

improving NASA educational materials. Thank You.

EW-1998-03-003-GSFC (Rev. 11/02)