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Just what do the Sunspot and Geomagnetic and Solar Indices numbers mean?
While increasing SFI may be good for HF propagation, it also tends to correspond with high
Ap and K indices, which cause D-Layer absorption and noisy band condition. Solar flux is measured in solar flux units (SFUs).
It is the amount of radio noise or flux emitted at a frequency of 2800 MHz (10.7 cm, hence is it also called the 10.7 cm flux
While increasing SFI may be good for
HF propagation, it also tends to correspond with high Ap and K indices, which cause D-Layer absorption and noisy band condition.
Solar flux is measured in solar flux units (SFUs). It is the amount of radio noise or flux emitted at a frequency of 2800
MHz (10.7 cm, hence is it also called the 10.7 cm flux index).
Just what is the Planetary A index?
It is a measure of how disturbed the Earth's magnetic field is. It varies in
value from 0 to about 400, in linear steps. It is computed from the actual
deviations (non-quiet-time deviations) measured at a number of geomagnetic
observatories (mostly mid-latitude ones) around the world. A value of 30
represents minor storm conditions. Values of 50 represent major storm
conditions and values greater than 100 represent severe storm conditions. It
is derived from the planetary K indices (Kp). The A index is a planetary
daily value, while the Kp index is a planetary measurement derived every 3
hours. The Kp index is a semi-logarithmic index that varies from 0 to 9,
where a 5 represents minor storm conditions, a 6 represents major storm
conditions, and a value of 7 or greater represents severe storm conditions.
The K-index is a code that is related to the maximum fluctuations of horizontal components observed on a magnetometer relative
to a quiet day, during a three-hour interval. The conversion table from maximum fluctuation (nT) to K-index, varies from observatory
to observatory in such a way that the historical rate of occurrence of certain levels of K are about the same at all observatories.
In practice this means that observatories at higher geomagnetic latitude require higher levels of fluctuation for a given
K-index. The maximum positive and negative deviations during the 3-hour period are added together to determine the total maximum
fluctuation. These maximum deviations may occur anytime during the 3-hour period.
The higher the K-index, the more
unstable propagation becomes, the effect is stronger at high latitudes, but weaker near low latitudes.
When storm level is reached, propagation strongly degrades, possibly fade out at high latitudes.
Classification of K-indices are as follows:
K8=Very severe storm
K9=Extremely severe storm
As with the K-index, the higher the A-index, the more unstable propagation becomes.
Classification of A-indices are as follows:
A0 - A7 = quiet
A8 - A15 = unsettled
A16 - A29 = active
A30 - A49 = minor storm
A50 - A99 = major storm
A100 - A400 = severe storm
The solar cycle, or the solar magnetic activity cycle, is
a periodic change in the amount of irradiation from the Sun that is experienced on Earth. It has
a period of about 11 years, and is one component of solar variation, the other being aperiodic fluctuations.
Solar variation causes changes in space weather and to some degree weather and climate on Earth. The cycle is observed by
counting the frequency and placement of sunspots visible on the Sun. Powered by a hydromagnetic
dynamo process, driven by the inductive action of internal solar flows, the solar cycle:
For the current Auroral Activity click the links below:
http://spaceweather.com/, and http://www.solarham.net/
Weak Solar Activity Puzzles Scientists:
At almost regular intervals,
our sun displays phenomena benignly called sunspots. Actually, they are violent storms.
scientists closely observe this activity, because it may have adverse effects on communications, navigation and even power
grids. But the diminishing intensity of the last two solar cycles leaves them puzzled.
gigantic electromagnetic storms occur on the sun, we see them eight minutes later, which is how long it takes the light to
It takes the first charged particles ejected by the storms 20 to 30 minutes to arrive.
They are dangerous to humans, so if the storm is intense, astronauts aboard the International Space Station are advised to
move into specially protected areas.
After a day or two comes the biggest part of the storm, the
coronal mass ejection.
“That is billions of tons of solar material that’s blown away
from the sun," said Alex Young of NASA's Heliophysics Science Division. "It’s traveling millions of kilometers an hour,
but that is relatively slow.”
What are radio blackouts?
blackouts are caused by bursts of X-ray and Extreme Ultra Violet radiation
which are emitted during solar flares and affect the sunlit side of the Earth.
Radio blackouts primarily affect High Frequency (HF) (3-30 MHz) communication,
although fading and diminished reception may spill over to Very High Frequency
(VHF) (30-300 MHz) and higher frequencies. These effects occur on the sunlit
side of the Earth and are most intense at locations where the Sun is directly
overhead. These blackouts are a consequence of enhanced electron densities
caused by solar flare emissions. These emissions ionize the sunlit side of
Earth, which increases the amount of energy lost as radio waves pass through
the upper atmosphere. Radio blackouts are the most common space weather events
to affect Earth. Minor events occur about 2000 times each solar cycle. Radio
blackouts are by far the fastest space weather event to impact our planet. The
electromagnetic emission produced during flares travels at the speed of light
taking just over 8 minutes to travel from the Sun to Earth. Radio blackouts can
last from several minutes to several hours depending on the duration of the
solar flare. How severe a radio blackout is depends on the strength of the
Frequency (HAF) during a
Highest Affected Frequency (HAF) during an X-ray radio blackout during local
noon is based on the current X-ray flux value between the 1-8 Ångström. The
Highest Affected Frequency (HAF) can be derived by a formula. Below you will
find a table where you can see what the Highest Affected Frequency (HAF) is
during a specific X-ray flux.
|GOES X-ray class &
Highest Affected Frequency
uses a five-level system called the R-scale, to indicate the severity of a
X-ray related radio blackout. This scale ranges from R1 for a minor radio
blackout event to R5 for a extreme radio blackout event, with R1 being the
lowest level and R5 being the highest level. Every R-level has a certain X-ray
brightness associated with it. This ranges from R1 for a X-ray flux of M1 to R5
for a X-ray flux of X20. On Twitter we provide alerts as soon as a certain
radio blackout threshold has been reached. Because each blackout level
represents a certain GOES X-ray brightness, you can associate these alerts
directly with a solar flare that is occurring at that moment. We can define the
following radio blackout classes:
GOES X-ray threshold by
class & flux
per cycle (950 days per cycle)
per cycle (300 days per cycle)
per cycle (140 days per cycle)
per cycle (8 days per cycle)
than 1 per cycle
image below shows the effects of an X1 (R3-strong) solar flare on the sunlit
side of the Earth. We can see that the Highest Affected Frequency (HAF) is
about 25 MHz there where the Sun is directly overhead. Radio frequencies lower
than the HAF suffer an even greater loss. Image: NOAA SWPC - D Region
blackouts also occur at Arctic latitudes during space radiation storms. These
are known as Polar Cap Absorption Events and can last for days. These events
are indicated by the S-scale which is used for space radiation storms. Polar
Cap Absorption Events are not to be confused with radio blackouts that are
caused by bursts of X-ray and Extreme Ultra Violet radiation which are emitted
during solar flares. Polar Cap Absorption Events are caused by protons that
enter Earth's atmosphere above the polar regions during space radiation storms.
Asked Questions about Aurora and Answers
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