Space & Atmospheric Sciences  Ionosphere

 

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Ionosphere

 

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.

 

 

Vertical Ionospheric Soundings

 

Theoretical Studies

 

Effects of Traveling Ionospheric Disturbances

 

Solar Flare & its effects on HF Communications

 

Geomagnetic Field Monitoring

 

Magnetic Storms

 

New Moon Prediction

 

Vertical Ionospheric Soundings:

 

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.

 


Digital Ionospheric Sounder DGS-256

 

Theoretical Studies

 

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.

 


Daytime Ionogram


Night-Time Ionogram

 

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Effects of Traveling Ionospheric Disturbances, Spread-F & Bite-outs on HF Communication

 

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

 

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.

 

Erupting Solar Flare

 

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Geomagnetic Field Monitoring

 

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.

 


AMOS-III

 

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Magnetic Storms

 

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.

 


Magnetogram showing the severe magnetic storm recorded at Karachi

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image to view larger version
 

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New Moon Prediction

 

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.

 

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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