Results.

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

, 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.

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