Sun, a roiling ball of plasma, occupies its place in space
approximately 93 million miles from Earth. Though it seems simple to
inhabitants of this planet -- the Sun shines, giving light and heat --
the processes occurring in the Sun are so complex that many scientists
devote their careers to just one aspect of solar activity.
Changes in the activity of the Sun particularly engage solar scientists.
Whether fluctuations in the
solar magnetic field, expulsions of plasma called
coronal mass ejections, emissions of high-energy
flares, or changes in the
sunspot number, variations in solar activity can be dramatic and
therefore highly interesting.
Through careful study of solar activity (particularly sunspots, visible
from Earth through telescopes) over hundreds of years, scientists
have found a consistent cycle of activity: every eleven years,
activity rises to a maximum, then falls to a minimum. To track the
solar cycle, scientists plot the average of Wolf numbers (values from a
method of counting sunspots devised by Johann Rudolf Wolf in 1848)
from various observatories daily to get a
sunspot number graph.
The sunspot or solar cycle does not have the same magnitude every
eleven years, however. Entire cycles can have lower activity levels
than usual, as during the
Maunder Minimum from 1645 to 1700, or the upcoming maximum might
have more activity than ever. A look at the sunspot plot for
the last two centuries will show the fluctuation in minima and
Solar maximum, the peak of solar activity, occurs,
according to the latest
predictions, in the year 2000. Scientists expect to see
increased activity from sunspots to flares, and the public can expect
to see more solar effects at Earth (like magnetic storms and aurora)
and more news pieces on the subject over the next few years.
For more details about the Sun and its cycle, follow the links below.
More about the Solar Cycle
The Changing Solar Wind
Windows to the Universe compares fluctuations in different types of solar activity to the solar cycle.
Dr. SOHO's FAQ: Questions about Sunspots
Another of Dr. SOHO's detailed question pages, this page gives good information and links
relating to sunspots and the solar maximum.
Solar Cycle (Oulu)
A Finnish textbook defines the characteristics of the solar cycle.
The Solar Cycle (Scibernet)
This site contains multiple pages on the solar cycle, with equations and graphics.
Solar Cycle (WtU)
An explanation of the solar cycle from Windows to the Universe.
This site, all about sunspots, discusses them and gives history, related research,
activities, and a glossary.
Sunspots and the Solar Cycle
Maintained by the National Solar Observatory at Sacramento Peak, this page contains
detailed information on nearly every aspect of the solar cycle.
This student-oriented page has brief descriptions of the solar cycle and its effects
on Earth, but its real value is in its links to other good resources.
A page of links to information and images about the 2000
What is the Sunspot Number?
Gives a brief description of how scientists calculate the sunspot number every day.
More about the Solar Cycle's Effects
More about the Last Solar Maximum
Blackout -- Massive Power Grid Failure
This Windows to the Universe page discusses the HydroQuebec power failure during
a storm of the last solar maximum.
Damage from Space Weather
Gives statistics on the effects of the March 1989 (solar maximum) magnetic storm.
The image on this page shows the effect of the March 1989 magnetic storm on the aurora,
as observed by the Dynamics Explorer spacecraft.
How Much Does a Solar Storm Cost?
The huge cost of blackouts shown on this page to companies and customers makes
prediction of solar maximum conditions important.
3 Problems in Restoring Power
As if a blackout alone were not bad enough -- this page details how getting power back
to customers after a solar maximum power failure can be even worse.
More about the Sun
Dr. SOHO's FAQ: Questions about the Sun
If you have any question at all about the Sun, from the missing-neutrino mystery to the
date of the next solar eclipse, Dr. SOHO probably has the answer or knows someone who does.
Our Changing Sun
Explains the various parts and features of the Sun, such as prominences, flares,
and the corona.
Space Weather Center: Questions and Answers
This page deals with space weather and solar cycle questions, too, but it contains
basic information about the Sun in its first half.
The Sun: A Pictorial Introduction
This slide set has very detailed information about the Sun -- slides 17, 18, 10, and the
conclusion deal specifically with the solar maximum.
Brought to you by the
International Solar-Terrestrial Physics Program and
Web Design and Development: Theresa Valentine
Last Modified: 8/3/00