analysis from the gps

8/7/2019 Analysis from the GPS

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1. DIURNAL VARIATION OF TOTAL ELECTRONE CONTENT

The analysis of TEC for diurnal variation can be done by considering a single GPS measurementselecting a typical quiet day ( i.e where all the heliospheric phenomena results lowest impact on the

ionosphere). This condition can be inferred from different geomagnetic index which are essential to

describe the process in the upper atmosphere. Here we can easily chose the Ap index to indicate thedisturbance level created by the sun on the earth. From the Ap index description it is commonly a

accepted that if the Ap index has value of < 4 the upper atmosphere is attains lowest disturbance from

the sun.

Based on the above idea we have so many days which are characterized by law Apindex value starting from December 2007 & December 2008.

Month Days Ap value in respective order of the give days(corresponding magnetic field change H for

some specific days)Dec 2007 1, 2, 3, 4, 5, 6, 7, 8, 9 3, 2, 1, 1, 2, 3, 1, 0, 3

H=Dec5=98nT Ap=2 , Dec24=48nT Ap=3

Jan 2008 1, 2,,3,4,10,11,22,23,

27,28,29, 30

4,2,2,2,4,3,2,4,4,4,4 ,2H=Jan10=90nT Ap=4 , Jan11=88nT Ap=3H=Jan28=128nT Ap=4 , Jan30=95nT Ap=2

Feb 2008 5,6,9,22,24,25,26 4,4,4,4,4,4,4

March 2008 5,6,7,17,22,24,25,31 3,3,2,4,4,3,3,4 H=March 4=93nT Ap=3

April 2008 1,2,3,4,14,20 4,4,1,2,2,4

H=Apr3=97nT , Apr20=53nT , Apr20=111nTMay 2008 7,8-17 1 4

H=May7=96nTAp=4 ,May16=58nT Ap=4H=May17=50nTAp=1 ,May26=55nT Ap=3H=May27=54nTAp=3

Jun 2008 3, 4, 9, 10, 12, 13, 30 4, 3,3, 2,3,2,4 ( H=52,48,50,50,46,44,55 nT )

Jul 2008 2,3,6,17 2,2,3,4 H=45,52,49,51nT

Aug 2008 7, 30, 31 4,2,4 H=48,51,107nT

Sept 2008 2, 27, 28 3,3,2 H=105,98,104nT

Nov 2008 10, 15, 23 3, 3, 4 H=46,102,38,nT

Dec 2008


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April 20, 2008 min value magnetic field figure

April 20, 2008 hourly value magnetic field


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GPS TEC data from aau and adr January 11, 2008

GPS TEC data from aau and adr January 10, 2008


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3. Geomagnetic storm effect on the TEC measured


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The year 2008 is marked by the lowest solar activity. This is b/c it the time of the end of the 23 solar

cycle and the beginning of the 24 solar cycle. This can be indicated by the number of geomagnetic

storm recoded by magnetometer. From the Dst value the there is no major storm observed. But thereare about 4 storms observed by the mid- latitude station situated in the region where there is no effect

of EEJ and auroral electrojet ( AEJ).

The date and the corresponding Dst values are;

March 2008 from 8-11 Dst = -72nTSept 2008 from 2-6 Dst= -51nTOct 2008 from 9-14 Dst= -60nT

Aug 2008 from 8-12 Dst=(b/n +40nT & -40nT)

Other dates which are available are

Nov 2007 18-23 Dst=-71nT

January 2009 from 12-15 Dst=-130

Remark for the storm recorded in January 2009 from 12-15, even if the Dst value indicates theexistence of major storm the magnetometer measuring in Addis Ababa University doesn't significantly

shows the as a major storm while the expected measurement to be very large negative value which

more than the Dst index. In addition, other interplanetary process indicators like; Solar wind speed,proton density, interplanetary magnetic field measurement form space doesn't indicate the existence of

this storm.


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4. Solar flare effect on the GPS TEC measurement

The main aim of computing solar flare effect in Bahir Dar and AAU is to detect the TEC

variation b/n EEJ region and mid low latitude station. This variation is hard to identify form the TECvalue as most of the solar flare recorded influence on the ionosphere persists for a very short time

interval/hours. But the its significant can be easily detected using the S4 index for a single satellite or a

single satellite minute value of the TEC . The other way in which the solar flare impact can be easilyobserved is to consider the logarithm values of S4 index or TEC.

During 2008 there are about five seven solar flare at C level and one solar flare occurred

on the sun surface. Out of this only two of the flares sufficiently produced significant change on themeasurement of the magnetometer at AAU. Therefore, this two time are sufficient enough to to analyze

the there effect on the ionosphere around AAU and Bahir Dar.

The two dates with the time at which the solar flare takes place are;

C-flare 2008 01 02

M-flare 2008 03 25Remark on evaluating the variation of TEC during such conditions can be done considering the TEC

mint. measurement by a single satellite and taking the time derivative (the time rate of the TEC (rTEC))

in this case it easy to observe very pronounceable effect of the solar flare.


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4. Seasonal variation analysis of TEC

Variation of TEC depends on the location of the sun (zenith angle) with respect to the earth. Thechange in position result in seasonal variation. This variation can be observed on the total electron

content measured using GPS. In order to analyze this effect at AAU and Bahir Dar the seasons

(Equinox, Summer and Winter) can be considered for a single year. The result which is obtained byanalyzing hourly TEC content for each season can be compared with the prediction made by the

International Ionospheric Reference (IRI) for both AAU and Bahir Dar. The months that corresponds

to the three season are;

Equinox months (March, April, September, October)

analysis from the gps

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