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The ionosphere is a region of electrically charged particles in the earth's atmosphere, which extends upward from approximately 50 km to 600 km. This ionized part of earth's
atmosphere acts as a mirror for HF (3-30 MHz) radio waves so that long range communication becomes possible. A constant watch / tab of the ionosphere is essential for reliable HF communication.
For this purpose SUPARCO had started ionospheric sounding in Pakistan as early as 1973. |
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Vertical Ionospheric Soundings: |
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The most widely used instrument for monitoring the ionosphere is ionosonde / ionospheric sounder. An ionospheric sounder uses basic radar techniques to detect
the electron density of ionosphere as a function of height. It is a high frequency radar, which sends very short pulses of radio waves vertically into the ionosphere and measures the
time, which elapses before its echoes are received. SUPARCO presently operates three Vertical Ionospheric Stations, one each at Islamabad, Multan and Karachi, for monitoring local
ionosphere round the clock at 15-minute intervals. At Karachi and Islamabad, Digisonde (DGS-256) are being operated whereas at Multan an analogue PIR-9 sounder is in operation. |
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Digital Ionospheric Sounder DGS-256
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Theoretical Studies |
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Total Electron Contents (TEC) are computed during the solar eclipse, meteorites and comets to study the effect on radio wave communication during these phenomena. The ionospheric/
geomagnetic data acquired by means of ionospheric sounder and geomagnetic observatory are used to study the effects on ionosphere and geomagnetic field during various phenomena associated with
sunspots activity. For regional models of critical frequencies of ionospheric E & F2 layers over Pakistan, the techniques of expansion in empirical orthogonal functions (EOFs) are used.
Levels of solar activity specified by Smoothed Sunspot Number (R) from 10 to 200 at a difference of 1 is taken into account, whereas the modified dips (Im) ranging from 300 to 600 at a difference
of 10 are used. |
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Daytime Ionogram
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Night-Time Ionogram
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Effects of Traveling Ionospheric Disturbances, Spread-F & Bite-outs on HF Communication |
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Events like Traveling Ionospheric Disturbances, Spread-F & Bite-outs disturb HF communication. These events are regularly studied for finding out their possible causes and
remedial measures. |
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Solar Flare & its effects on HF Communications |
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Sometimes HF communication is completely cut off for a period of 15 to 60 minutes due to excited state of the Sun termed as Solar Flare. During a Solar Flare,
a burst of enhanced ultraviolet radiation and X-rays enters the Earth's atmosphere in about 8 minutes. If solar flare is mild, only lower range of frequencies is curtailed so that the
range of usable frequencies is narrowed. |
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Erupting Solar Flare |
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Geomagnetic Field Monitoring |
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Geomagnetic field variations are monitored at Karachi round the clock by means of Automatic Magnetic Observatory System-III (AMOS-III). Monthly bulletins of
Karachi Geomagnetic Data are prepared and provided to national and international users. Information on the 'sfe' (solar flare effects) and severe magnetic storms monitored by AMOS-III
is passed on, as alert / warning regarding the bad conditions for HF communications, to national users. The geomagnetic data are also used for research by the scientists of SUPARCO.
Information on Principal Magnetic Storms monitored at Karachi by AMOS-III are regularly published in the monthly Solar Geophysical Data prompt reports of NOAA, Boulder, Colorado, USA. |
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AMOS-III
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Magnetic Storms |
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If the magnetic storm is unusually severe, High Frequencies become unusable. However, during a mild storm, communication may be possible by using a lower frequency. Currents flowing
in the ionosphere pose a hazard to artificial satellites, during magnetic storm, when build-up of charge on electrical components can cause damage. |
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Magnetogram showing the severe magnetic storm recorded at Karachi
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Move mouse over above
image to view larger version |
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New Moon Prediction |
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SUPARCO regularly provides predictions (on monthly basis) for the visibility of new moon to relevant agencies in Pakistan. Moon's parameters for
sighting the new moon are predicted for various cities of Pakistan. |
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Phases of the Moon |
New Moon |
Waxing Crescent |
First Quarter |
Waxing Gibbous |
Full Moon |
Waning Gibbous |
Last Quarter |
Waning Crescent |
New Moon |
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Ionosphere
