Our results are in good agreement with earlier measurements and theoretical estimates. The key feature of our data is a higher reliability of determining the main parameters of the response to eclipse which is due to high space-time resolution and to the increased sensitivity of detection of ionospheric disturbances inherent in the GPS-array method which we are using.
The main parameters of the ionospheric response include the value
of the delay τ with respect to the eclipse totality phase,
as well as its amplitude A and duration ΔT. Almost all
publications devoted to the study of the ionospheric response to
solar eclipses make estimates of these parameters. A knowledge of
these values makes it possible to refine, in terms of the
respective aeronomic ionospheric models, the time constants of
ionization, and the recombination processes at different heights
in the ionosphere.
The statistic of measurements of these parameters of the total solar eclipses
March 9, 1997 (Table 1); August 11, 1999 (Table 2); June 21, 2001 (Table 3):
Table 1
PRN
A, TECU
τ, min.
1
-
34
2
3
10
3
2
10
4
2
9
A - amplitude; τ -
the value of the delay with respect to the eclipse totality phase.
Table 2
|
N |
The number of subionospheric points |
A, TECU |
ΔT, min. |
τ, min. |
|
1 |
98 |
0,298/0,197 |
62/32 |
16,4/14 |
|
2 |
19 |
0,193/0,081 |
61/36 |
8/4 |
The first line of Table 2 presents the results of a statistical
processing for the entire set of GPS stations. The second line
includes only those stations which lie in the immediate vicinity
of the eclipse path, within +/- 50 with respect to the
centre line (near zone). In Table 2, the values before the bar
are mean values, and those after the bar correspond to the
standard deviation.
Table 3
|
PRN |
The sunionosphric point |
À, TECU |
ΔT, min. |
τ, min. |
|
|
Latitude, deg. |
Longitude, deg. |
||||
|
HRAO (25,890 S; 27, 690 E) |
|||||
|
1 |
-20,30 |
24,47 |
0,815 |
53 |
28 |
|
3 |
-28,47 |
29,55 |
0,723 |
30 |
13 |
|
13 |
-25,73 |
22,90 |
0,879 |
60 |
9 |
|
22 |
-27,27 |
34,03 |
0,682 |
49 |
13 |
|
27 |
-28,81 |
24,78 |
0,503 |
41 |
34 |
|
31 |
-26,49 |
27,03 |
0,850 |
47 |
14 |
|
SUTH (32,380 S; 20, 810 E) |
|||||
|
27 |
-35,04 |
17,79 |
0,523 |
39 |
37 |
|
31 |
-32,99 |
20,97 |
0,693 |
59 |
21 |
|
MALI (2,990 S; 40, 190 E) |
|||||
|
31 |
-7,05 |
38.88 |
0,640 |
67 |
10 |
The values of the parameters τ, A and ΔT, obtained by analyzing the ionospheric response to the total solar eclipses of August 11, 1999 and June 21, 2001, differ by no more than 5-21 min, 0.4-0.6 TECU, and 2-5 min, respectively. The difference of the parameters τ, A and ΔT; can be explained by the difference of the geometry of the eclipses as well as by the difference of the latitude and longitude ranges.