|
Real Time Space
Weather Updates
Space weather impacts radio
communication in a number of ways. At
frequencies in the 1 to 30 mega Hertz range
(known as “High Frequency” or HF radio), the
changes in ionospheric density and structure
modify the transmission path and even block
transmission of HF radio signals completely.
These frequencies are used by amateur
(ham) radio operators and many
industries such as commercial airlines.
There are several types of space weather
that can impact HF radio communication. In a
typical sequence of space weather storms,
the first impacts are felt during the solar
flare itself. The solar x-rays from the sun
penetrate to the bottom of the ionosphere
(to around 80 km). There the x-ray photons
ionize the atmosphere and create an
enhancement of the D layer of the
ionosphere. This enhanced D-layer acts both
as a reflector of radio waves at some
frequencies and an absorber of waves at
other frequencies. The Radio Blackout
associated with solar flares occurs on the
dayside region of Earth and is most intense
when the sun is directly overhead.
Another type of space weather, the Radiation
Storm caused by energetic solar protons, can
also disrupt HF radio communication. The
protons are guided by Earth’s magnetic field
such that they collide with the upper
atmosphere near the north and south poles.
The fast-moving protons have an affect
similar to the x-ray photons and create an
enhanced D-Layer thus blocking HF radio
communication at high latitudes. During
auroral displays, the precipitating
electrons can enhance other layers of the
ionosphere and have similar disrupting and
blocking effects on radio communication.
This occurs mostly on the night side of the
polar regions of Earth where the aurora is
most intense and most frequent.
The Solar Cycle
The sun may be 93 million miles (149
million kilometers) away from Earth, but commotions on
our nearest star have consequences much closer to home,
which is why scientists have a keen interest in studying
changes in the sun's activity. The sun's temper varies
on an 11-year cycle, typically taking about 5 1/2 years
to move from the quieter period of solar minimum, to the
more turbulent solar maximum.
GOES Magnetometer:
Magnetometers provide realtime
data of the local Earth magnetic field at ground level.
Sharp deviations in the data could signal the
development of geomagnetic activity.
This data is measured by the GOES-15
satellite which does monitor Solar X-Rays. This
information is very important in tracking solar flares.
Large X-ray bursts cause short wave fades for HF
propagation paths through the sunlit hemisphere. Solar
flares can also trigger geomagnetic storms which produce
aurora and nice openings on VHF.
The K-index, and by extension the Planetary K-index, are
used to characterize the magnitude of geomagnetic
storms. Kp is an excellent indicator of disturbances in
the Earth's magnetic field and is used by SWPC to decide
whether geomagnetic alerts and warnings need to be
issued for users who are affected by these disturbances.
The principal users affected by geomagnetic storms are
the electrical power grid, spacecraft operations,
users of radio signals that reflect off of or pass
through the ionosphere, and observers of the aurora.
Solar Activity Monitor
updated every ten minutes with the
current status
Solar X-rays:
About the Solar X-ray status monitor
The X-ray Solar status monitor downloads data
periodically from the
NOAA -
Space Environment Center FTP
server. The previous 24
hours of
5 minute Long-wavelength
X-ray data
from each satellite (GOES 8 and GOES 10) is analyzed,
and an appropriate level of activity for the past 24
hours is assigned as follows:
Normal: Solar X-ray flux is quiet (<1.00e-6 W/m^2)
Active: Solar X-ray flux is active
(>=1.00e-6 W/m^2)
M Class Flare: An M Class flare has occurred (X-ray flux
>=1.00e-5 W/m^2)
X Class Flare: An X Class flare has occurred (X-ray flux
>= 1.00e-4 W/m^2)
About the Geomagnetic Field status
monitor
The Geomagnetic Field status monitor
downloads data periodically from the
NOAA
-
Space Environment Center FTP
server. The previous
24 hours
of 3 hour Planetary Kp
Index data
is analyzed and an appropriate level of activity for the
past 24 hours is assigned as follows:
Quiet: the Geomagnetic
Field is quiet (Kp < 4)
Active: the Geomagnetic Field has been
unsettled (Kp=4)
Storm: A Geomagnetic Storm has occurred (Kp>4)
Solar x-RAY
X-ray
photons travel at the speed of light and are
the first indication we receive at Earth of
solar magnetic eruptions and the associated
flares. These flare related X-rays cause
changes to the Earth’s ionosphere and can
result in significant degradation of radio
communications, including complete black
outs at some frequencies, beginning only 8
minutes (time for light to travel from the
Sun to Earth) after a flare.
GEOMAGNETIC STORMS
A geomagnetic storm is a
major disturbance of Earth's magnetosphere
that occurs when there is a very efficient
exchange of energy from the solar wind into
the space environment surrounding Earth.
These storms result from variations in the
solar wind that produces major changes in
the currents, plasmas, and fields in Earth’s
magnetosphere. The solar wind conditions
that are effective for creating geomagnetic
storms are sustained (for several to many
hours) periods of high-speed solar wind, and
most importantly, a southward directed solar
wind magnetic field (opposite the direction
of Earth’s field) at the dayside of the
magnetosphere. This condition is effective
for transferring energy from the solar wind
into Earth’s magnetosphere.
During storms, the currents in the
ionosphere, as well as the energetic
particles that precipitate into the
ionosphere add energy in the form of heat
that can increase the density and
distribution of density in the upper
atmosphere, causing extra drag on satellites
in low-earth orbit. The local heating also
creates strong horizontal variations in the
in the ionospheric density that can modify
the path of radio signals and create errors
in the positioning information provided by
GPS. While the storms create beautiful
aurora, they also can disrupt navigation
systems such as the Global Navigation
Satellite System (GNSS) and create harmful
geomagnetic induced currents (GICs) in the
power grid and pipelines.
|
