Page 97 - Intro to Space Sciences Spacecraft Applications

Introduction to Space Sciences and Spacecraft Applications
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Example Problem:

The sun’s actual average “surface” temperature is about 5,750 OK.
Based on this temperature, determine the blackbody power output of
the surface of the sun, the expected solar constant in the vicinity of
the earth, and the wavelength and associated frequency of maximum
solar energy output.

Solutions:

From equation 4-2: E, = 62.96 x lo6 W/m2

Using equation 4-4: E, = 1,364.7 W/m2

From equation 4-5: A,, = 0.50 pm

Finally equation 4- 1 : f,, = 6 x 1014 Hz

Solar Magnetic Field. The dynamic nature of the sun, causing motions of
the solar plasma, generates strong magnetic fields. Magnetic field strength
is commonly measured in units of Gauss or gamma (1 G = lo5 y) The
strength and direction of the magnetic fields change over time and with
changing processes on the surface, which will be described shortly. How-
ever, on average, the sun’s surface magnetic field strength is about 15 G,
approximately 30 times the surface magnetic field strength of the earth
(0.5 G at mid-latitudes).

Particle Radiation. In addition to the electromagnetic energy released, there
is a significant amount of particulate matter emitted into space by the sun of
which there are basically two major sources: solar wind and solar flares.

Solar Wind. The solar wind, actually the extension of the corona, is a
steady stream of plasma particles given sufficient energy to escape the
sun’s gravitational attraction and propagate into space in all directions.
Through a process which implies that the product of the density and
velocity of these particles remains constant with increasing distance from