dI/I
) are required to study mechanisms of generation of
ionospheric irregularities and to evaluate transionospheric radio
signal distortions.
[28] Statistical characteristics of the relative amplitude of
TEC variations: first, probability distributions
P( dI/I ) are required to study mechanisms of generation of
ionospheric irregularities and to evaluate transionospheric radio
signal distortions.
|
| Figure 8 |
|
| Figure 9 |
dI/I ) of the relative amplitude TEC variations in quiet
(thin line, index 1) and disturbed (thick line, index 2)
conditions. MS and IS ionospheric irregularities are shown on the
left and on the right in Figure 8: Figures 8a and 8d, 8b and 8e,
and 8c and 8f correspond to high and middle latitudes and to the
equatorial zone, respectively. The total amounts of 2-hour
averaged series over the entire area of the North America were 288
and 936 for quiet and disturbed periods, respectively. The
approximation of the total normalized distributions
P( dI/I )
for the same conditions is shown in Figure 9. The
most probable values of
dI/I in quiet
(X1) and disturbed
(X2 ) conditions are shown.
[30] One can see from Figures 8 and 9 that at high latitudes in quiet periods the relative amplitude of MS disturbances does not exceed 4-5%, whereas in disturbed periods it may reach 10-12%. Similar dependence is also observed for IS variations of TEC with the only difference that the general disturbance level is by a factor of 4-5 less than for MS.
[31] At middle latitudes,
dI/I dependence on
the geomagnetic disturbance level is similar to that at high
latitudes. However, on the whole, the amplitude of the MS and IS
disturbances decreases by a factor of 2-3 and 5, respectively. At
the equator, on the average, the amplitudes of MS and IS
variations in quiet and disturbed periods almost do not differ.
|
| Figure 10 |
dI/I averaged over 3-hour-long intervals, and
the thick line shows the approximating lines: MS TID are given in
Figures 10a-10c, IS TID in Figures 10d-10f; Figures 10a and 10d,
10b and 10e, and 10c and 10f correspond to high, middle, and
equatorial latitudes, respectively.
[33] On the average, the relative amplitude of TEC variations is proportional to the value of the geomagnetic Kp index. This dependence is most pronounced at high latitudes (the proportionality coefficient k=0.37 ), it is weaker at middle latitudes ( k=0.2 ) and weakest at the equator ( k<0.1 ).
|
| Figure 11 |
dI/I averaged over
3-hour-long intervals. The thick line is an approximating line: MS
TID are given in Figures 11a-11c and IS TID are given in
Figures 11d-11f; Figures 11a and 11d, 11b and 11e, and 11c and 11f
correspond to high, middle, and equatorial latitudes,
respectively. One can see that the amplitude of TEC variations
almost does not depend on solar activity.
Powered by TeXWeb (Win32, v.2.0).