This index is keyed to the estimated instantaneous "asymptotic
voltage" across the polar cap, the
single most important measure of electrical power delivered to the
atmosphere from the solar wind. We now use data from the
ACE real-time solar wind package.
The index is determined as follows:
GREEN if PCP < 150 kV;
YELLOW if 150 kV <= PCP < 200 kV;
RED if PCP >= 200 kV*
* The PCP status is changed to red only if the current
10-minute average exceeds 200 kV AND the previous 10-minute average
exceeds 150 kV. This is designed to reduce shifts in status due to
short-term spikes in the value of the potential.
Latest Observations from the ACE spacecraft (at the Sun-Earth L1 point) :
Interplanetary Magnetic Field
For solar wind dials without any explanatory text, see
It also has a few dials that are not shown here. A web page with more
is also available.
You can now receive e-mail notification whenever the stoplight sets to red!
(Actually, you can be notified whenever any of these conditions change.)
Just go to the
Rice University Lists and subscribe to the SPACALRT Mailing List.
To unsubscribe follow the instructions on the SPACALRT Mailing List
page, or send an e-mail to
Stoplight state changes are once again logged. There are two logs,
one for each predicted Kp
PCP (Solar Wind).
The earliest logged transition occurred on September 25, 2003.
Also, here's an index to
Space Weather Resources.
Other items of interest include
NOAA/SEC Current Conditions, the composite current Auroral Images page,
Windows on the Universe: Space Weather, and
Public Outreach Index,
Department of Physics and Astronomy, Rice University.
Patricia H. Reiff
Department of Physics & Astronomy
Static information was last revised on April 13, 2011.