The Solar Irradiance
is a measure of the energy of the electromagnetic radiation
emitted by the Sun at all wavelengths. The Solar
is found strongest when the solar activity is at a
maximum, which is a result of two competing processes.
The presence of Sun Spots on the solar surface blocks
out radiation and causes a decrease of the Irradiance.
This is compensated by the fact that other magnetic
regions known as plagues and faculae emit excess radiation.
Overall, the effect is that more radiation is emitted
at a solar maximum.
The energy we receive from the sun is one of the most
important factors for life and the climate on earth.
However, the observed changes in the total solar irradiance
during the last solar cycles are so small that they
are not expected to have any significant influence
on our climate. Long term variation of the solar irradiance
could on the other hand play an important role in climate
The data used here are daily averages
of the solar irradiance measured by a variety of spacecrafts.
To be more precise, it is the version d25_07_0310a of
a datapack obtained from PMOD/WRC, Davos, Switzerland
and uses unpublished data from the VIRGO Experiment
on the cooperative ESA/NASA Mission SoHO. For more details
C.Fröhlich and J. Lean, 1998, "The Suns Total
Irradiance: Cycles, Trends and Related Climate Change
Uncertainties since 1978", Geophys.Res.Let., 25,
pp. 4377-4380, 1998
The size of the inner circle as well as the colour correspond
to the Irradiance and are smoothly changed from one
measurement to the next. Interpolated values can be
identified by the thin line surrounding the inner circle.
The colour of the outer circle jumps from one measurement
to the next.
The value of the Irradiance measurement changes the
sound of a cello and a violin, the higher the value
of the Irradiance, the more the original sound of the
strings are altered.