Skip to main content

Ionospheric measurements during the total solar eclipse of 11 August 1999

Abstract

A number of radio experiments were conducted at Ahmedabad (23°N, 73°E) with the aim of studying the ionospheric effects of the total solar eclipse of 11 August 1999. Rapid radio soundings from the ionosonde were made on the eclipse day and on control days. A riometer was operating at 30 MHz, and field strength measurements along the three oblique incidence paths of Colombo-Ahmedabad (11905 kHz), Bombay-Ahmedabad (558 kHz) and Rajkot-Ahmedabad (810 kHz) were also made. A reduction of about 20% was observed in the minimum frequency of reflection from the ionosonde (fmin), which indicates a reduction in D-region ionization. The critical frequency of the E-layer was not measurable beyond 1600 h IST on eclipse day due to the strong blanketing sporadic-E, but there is a 20% decrease in the critical frequency of the F1-layer. Although there was no change in the minimum virtual height of the F-layer on eclipse day, there appears to have been a decrease in the height of maximum ionization (hpF2) during the eclipse, indicating a reduction in the thickness of the F-layer. The signal strength of the Colombo-Ahmedabad path shows an initial rapid increase with the start of the eclipse (indication of a decrease in ionization in the D- and lower E-regions), but subsequently decreases until the maximum of the eclipse (excessive deviative absorption because of the wave penetrating to the E-region). The field strength measurements of the Bombay-Ahmedabad path show a large fading after sunset as the sky wave also appeared. On eclipse day the fading started about an hour earlier. Riometer recordings also show a higher signal during eclipse day, which again indicates an eclipse-associated decrease in ionization.

References

  • Abraham, S., S. K. Dhaka, N. Nath, and K. L. Baluja, Ionospheric absorption on October 24, 1995 solar eclipse, Geophy. Res. Lett., 25, 2945–2947, 1998.

    Article  Google Scholar 

  • Altadill, D., J. G. Sole, and E. M. Apostolov, Vertical structure of a gravity wave like oscillation in the ionosphere generated by the solar eclipse of August 11, 199, J. Geophys. Res., 106, 21419–21428, 2001.

    Article  Google Scholar 

  • Chandra, H., G. Sethia, G. D. Vyas, M. R. Deshpande, and H. O. Vats, Ionospheric effects of the total solar eclipse of 16 February 1980 observed over Ahmedabad, Indian J. Radio Space Phys., 10, 45–48, 1981.

    Google Scholar 

  • Chandra, H., G. D. Vyas, and S. Sharma, Ionospheric effects of the total solar eclipse of 24 October 1995 over Ahmedabad, Indian J. Radio Space Phys., 26, 30–35, 1997.

    Google Scholar 

  • Davis, C. J., M. Lockwood, S. A. Bell, J. A. Smith, and E. M. Clarke, Ionospheric measurements of relative coronal brightness during the total solar eclipses of 11 August, 1999 and 9 July, 1945, Ann. Geophys., 18, 182–190, 2000.

    Article  Google Scholar 

  • Dixit, P. S., P. K. Rao, R. V. Bhonsle, G. Sethia, M. R. Deshpande, and H. Chandra, Phase and field measurements at VLF, LF and HF during the solar eclipse of February 16, 1980—Preliminary results, Bull. Astron. Soc. India, 8, 145–148, 1980.

    Google Scholar 

  • Farges, T., J. C. Jadogne, R. Bamford, Y. Le Roux, F. Gauthier, P. M. Vila, D. Altadill, J. G. Sole, and G. Miro, Disturbances of the western European ionosphere during the total solar eclipse of 11 August 1999 measured by a wide ionosonde and radar network, J. Atmos. Solar- Terrest. Phys., 63, 915–924, 2001.

    Article  Google Scholar 

  • Jani, K. G., G. Datta, D. B. Patel, and K. M. Kotadia, Ionospheric radio effects of the solar eclipse on 16 February 1980, Proc. Ind. Natn. Acad. Sci., 48A, 316–324, 1982.

    Google Scholar 

  • Lele, P. D., K. G. Jani, and A. P. Patel, Multifrequency vertical incidence (A-1 method) absorption measurements at Ahmedabad during total solar eclipse of October 1995, Kodaikanal Obs. Bull., 13, 209–212, 1997a.

    Google Scholar 

  • Lele, P. D., K. G. Jani, and A. P. Patel, Field strength measurements A-3 method (Oblique incidence) absorption at Ahmedabad during total solar eclipse of October 1995, Kodaikanal Obs. Bull., 13, 213–216, 1997b.

    Google Scholar 

  • Muller-Wodarg, I. C. F., A. D. Aylward, and M. Lockwood, Effects of a mid-latitude solar eclipse on the thermosphere and ionosphere—A modelling study, Geophys. Res. Lett., 25, 3787–3790, 1998.

    Article  Google Scholar 

  • Patel, D. B., K. M. Kotadia, P. D. Lele, and K. G. Jani, Absorption of radio waves during a solar eclipse, Proc. Indian Acad. Sci., 95, 193–200, 1986.

    Google Scholar 

  • Rastogi, R. G. and R. M. Sheriff, A note on radio field strength observations made at Ahnmedabad during the total solar eclipse on 30 June 1954, J. Sci. Indust. Res., 14A, 159–161, 1955.

    Google Scholar 

  • Rishbeth, H., Solar eclipses and ionospheric theory, Space Sci. Rev, 8, 543–554, 1968.

    Article  Google Scholar 

  • Sridharan, R., C. V. Devasia, N. Jyoti, D. Tiwari, K. S. Viswanathan, and K. S. V. Subbarao, Ann. Geophys., 20, 1977–1985, 2002.

    Article  Google Scholar 

Download references

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to H. Chandra.

Rights and permissions

Open Access  This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.

The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/.

Reprints and Permissions

About this article

Cite this article

Chandra, H., Sharma, S., Lele, P.D. et al. Ionospheric measurements during the total solar eclipse of 11 August 1999. Earth Planet Sp 59, 59–64 (2007). https://doi.org/10.1186/BF03352023

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1186/BF03352023

Key words

  • Solar eclipse
  • ionosphere