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อภิธานศัพท์: อภิธานศัพท์ฟิสิกส์ (อวกาศ)
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SOLAR CYCLE The approximately 11-year quasi-periodic variation in frequency
or number of solar active events.
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SOLAR MAXIMUM The month(s) during the SOLAR CYCLE when the 12-month mean
of monthly average SUNSPOT NUMBERS reaches a maximum. The most
recent solar maximum occurred in July 1989.
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SOLAR MINIMUM The month(s) during the SOLAR CYCLE when the 12-month mean
of monthly average SUNSPOT NUMBERS reaches a minimum.
the most recent minimum occurred in September 1986.
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SOLAR SECTOR BOUNDARY (SSB) The apparent solar origin, or base, of the
interplanetary SECTOR BOUNDARY marked by the larger-scale polarity
inversion lines.
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SOLAR WIND The outward flux of solar particles and magnetic fields from the
sun. Typically, solar wind velocities are near 350 km/s.
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SPORADIC E A phenomenon occurring in the E REGION of the
IONOSPHERE, which significantly affects HF radiowave
propagation. Sporadic E can occur during daytime or nighttime
and it varies markedly with latitude.
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SPOTNIL Spotless disk
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SUDDEN COMMENCEMENT(SC, or SSC for Storm Sudden Commencement) An abrupt
increase or decrease in the northward component of the geomagnetic
field, which marks the beginning of a GEOMAGNETIC STORM.
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SUDDEN IMPULSE (SI+ or SI-) A sudden perturbation of several gammas
in the northward component of the low-latitude geomagnetic field,
not associated with a following GEOMAGNETIC STORM. (An SI becomes
an SC if a storm follows.)
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SUDDEN IONOSPHERIC DISTURBANCE (SID) HF propagation anomalies due to
ionospheric changes resulting from solar FLAREs, PROTON EVENTs
and GEOMAGNETIC STORMs.
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SUNSPOT An area seen as a dark spot on the PHOTOSPHERE of the sun. Sunspots
are concentrations of magnetic flux, typically occurring in bipolar
clusters or groups. They appear dark because they are cooler than
the surrounding photosphere.
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SUNSPOT GROUP CLASSIFICATION (Modified Zurich Sunspot Classification)
A - A small single unipolar SUNSPOT or very small group of
spots without PENUMBRA.
B - Bipolar sunspot group with no penumbra.
C - An elongated bipolar sunspot group. One sunspot must have
penumbra.
D - An elongated bipolar sunspot group with penumbra on both ends
of the group.
E - An elongated bipolar sunspot group with penumbra on both
ends. Longitudinal extent of penumbra exceeds 10 deg. but
not 15 deg.
F - An elongated bipolar sunspot group with penumbra on both
ends. Longitudinal extent of penumbra exceeds 15 deg.
H - A unipolar sunspot group with penumbra.
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SUNSPOT NUMBER A daily index of SUNSPOT activity (R), defined as
R = k (10 g + s) where S = number of individual spots, g =
number of sunspot groups, and k is an observatory factor.
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SURGE A jet of material from ACTIVE REGIONs that reaches coronal heights
and then either fades or returns into the CHROMOSPHERE along the
trajectory of ascent.
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TWO-RIBBON FLARE A FLARE that has developed as a pair of bright strands
(ribbons) on both sides of the main inversion ("neutral") line
of the magnetic field of the ACTIVE REGION.
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