Animations of 10-11 January 1997 Geomagnetic Substorm
Prepared for the Space Weather Workshop at the
Space Environment Center in Boulder, Colorado, April 19-23,
The substorm of January 10-11, 1997, was the first
geomagnetic storm predicted using observations by the
National Aeronautics and Space Administration's Solar and
Heliospheric Observatory satellite (NASA SOHO).
Animation of the Evolution of the Magnetic Cloud
created at NCAR; courtesy of the International Solar
Terrestrial Program). An artist's illustration of an
interplanetary shock wave leaving the sun's corona and
entering the Earth's magnetosphere. The star represents the
SOHO satellite poised to detect the arrival of the magnetic
The next four animations are based on observations and a
computer model simulation of the geomagnetic storm of January
10-11, 1997. Running time for each loop averages 60 seconds.
Auroral Energy Flux and Electric Potential for 10-11 January (magnetic
polar view) 7MB MPEG.
This loop shows energetic
electrons, measured in kilo-electron volts, precipitating
from the magnetosphere into the Earth's upper atmosphere,
where they increase the ionization rate and ionospheric
conductivity. These are the particles responsible for
creating visible auroras. The contours show the electric
potential in kilovolts (kV). The higher the electric
potential gradient, the faster the ions move and the more
energy is transferred. Data are from satellite measurements
taken at about 800 kilometers (500 miles) and radars sensing
at 300-400 km (190-250 mi) altitude.
Difference in Total Electron Content for 10-11 January 1997 (geographic
polar view) 5Mb MPEG.
The Northern Hemisphere is on
the left and the Southern Hemisphere is on the right in this
animation, which shows the increase and decrease of total
electron content (TEC) with respect to the nonstorm, or
quiet-time, background. TEC is the integration of electron
density over an altitude range between 95 and 600 km (60 and
370 mi), plotted in TEC units (TECUs). TECUs are 1016
electrons per meter squared (m2); higher TECUs represent
greater electron column density.
Total Electron Content for 10-11 January 1997 (global view) 5Mb MPEG.
This loop shows the global distribution of total
electron content. The center of the frame (12 local time) is
solar noon, the most direct line between the sun and the
Earth. The Earth rotates through that noon point over a two-
day period. The unit of measure for height-integrated total
electron density is electrons per square centimeter (cm2).
Height-Integrated Joule Heating and Neutral Temperature Variation for
1011 January 1997 (satellite view) 8Mb MPEG.
illustrates the lag time between Joule heating and the
heating of the thermosphere at about 300 km (190 mi) above
the Earth's surface. Joule heating takes place when ions
collide with neutral particles, transferring the ions'
kinetic energy into thermal energy. By 07:00 Universal Time
(UT, or midnight Mountain Standard Time) on January 10 the
big substorm--and Joule heating--has begun (globe on the
left). About 20 minutes later the temperature of the neutral
particles begins rising (globe on the right). The first
increases can be seen in the aurora zone over the Northern
Hemisphere; the heating ripples outward rapidly until
temperatures have increased over the entire hemisphere by
about 8:10 UT. When the storm subsides at about 13:40 UT on
January 11, Joule heating quiets down, but elevated
temperatures persist in the thermosphere for about 24 to 30
The animation portrays the changes in temperature of neutral
particles (TN) at 300 km (190 mi) from the quiet-time
background, with no storm activity. The measure of height-
integrated Joule heating is microwatts per square meter
(mW/m2). Temperatures are shown in kelvins (K).
These animations are based on data from satellites operated
by the U.S. Air Force, the National Oceanic and Atmospheric
Administration, and NASA; high-frequency ground-based radars
operated by the Johns Hopkins University; and ground
magnetometers located around the world. The data were fitted
into a numerical simulation model created by Raymond Roble of
the National Center for Atmospheric Research, and the model
output was used to create the animations. Model results were
then compared with observations from additional sources,
including several U.S. universities.
The magnetosphere is the irregularly shaped region enveloping
the Earth from several thousand kilometers down to about
1,000 km (600 miles) above the surface. The magnetosphere is
characterized by charged particles influenced by the Earth's
magnetic field. Many Earth-orbiting satellites operate in the
The ionosphere begins within the edge of the magnetosphere,
about 1,000 km (600 mi) out from the Earth's surface, and
extends down to about 50 km (30 mi) above the Earth. Ionized
particles in this region make reflection of radio-wave
The thermosphere is the outermost layer of the Earth's
atmosphere, encompassing the main body of the ionosphere at
about 1,000 km (600 mi) and extending down to meet the next
atmospheric layer (the mesosphere) at about 90 km (56 mi).
The thermosphere is collocated with the ionosphere.
Research by Gang Lu, Arthur Richmond, Raymond Roble, Maura
Hagan, and Thomas Holzer, High Altitude Observatory, National
Center for Atmospheric Research. Video production by Benjamin
Foster and Gang Lu.
Funding for this research was provided by the National
Science Foundation and the International Solar Terrestrial