- Open Access
Nighttime D-region equivalent electron density determined from tweek sferics observed in the South Pacific Region
Earth, Planets and Space volume 61, pages905–911(2009)
Atmospherics or sferics that originate from lightning discharges on propagating large distances in the Earthionosphere waveguide, particularly at the night, form dispersed sferics called tweeks. Tweeks are novel diagnostic tool to monitor the nighttime D-region ionosphere. Mean equivalent electron density nem at mean tweek reflection heights hm and electron density profile have been estimated using the higher harmonic tweeks recorded in the time between 21–03 hrs LT at Suva (18.2°S, 178.3°E), Fiji, during a period March–December 2006. The values of nem vary from 29–170 cm−3 in the altitude range of about 3.5 km at hm of about 83 km. In terms of usually used exponential electron density profile, the ionospheric reference height and the exponential sharpness factor are calculated to be 83.1 km and 0.64 km−1, respectively. The scale height is calculated to be 1.9 km. Equivalent electron density profile of the nighttime lower ionosphere, using tweek method, shows lower values of electron density by about 20–45% than those obtained from the IRI-2001 model.
Budden, K. G., Radio Waves in the ionosphere, Cambridge University Press, New York, 1961.
Cummer, S. A. and U. S. Inan, Ionospheric E region remote sensing with ELF radio atmospherics, Radio Sci., 35, 1437–1444, 2000.
Cummer, S. A., U. S. Inan, and T. F. Bell, Ionospheric D region remote sensing using VLF radio atmospherics, Radio Sci., 33, 1781–1792, 1998.
Danilov, A. D., Solar cycle variations of the D-region ionosphere, Ann. Geophys., 25, 1527–1533, 1998.
Dowden, R. L., J. B. Bruendell, and C. J. Rodger, VLF lightning location by time of group arrival (TOGA) at multiple sites, J. Atmos. Sol.-Terr. Phys., 64, 817–830, 2002.
Ferencz, O. E., Cs. Ferencz, P. Steinbach, J. Lichtenberger, D. Hamar, M. Parrot, F. Lefeuvre, and J. J. Berthelier, The effects of subionospheric propagation on whistlers recorded by the DEMETER satellite—observation and modeling, Ann. Geophys., 25, 1103–1112, 2007.
Hayakawa, M., K. Ohta, and K. Baba, Wave characteristics of tweek atmospherics deduced from the direction-finding measurement and theoretical interpretation, J. Geophys. Res., 99, 10,733–10,743, 1994.
Hughes, H. G., R. J. Gallenburger, and R. A. Pappert, Evaluation of nighttime exponential ionospheric models using VLF atmospherics, Radio Sci., 9, 1109–1116, 1974.
Kumar, S., A. Kishore, and V. Ramachandran, Higher harmonic tweek sferics observed at low latitude: Estimation of VLF reflection heights and tweeks propagation distance, Ann. Geophys., 25, 1451–1459, 2008.
McRae, W. M. and N. R. Thomson, Solar flare induced ionospheric Dregion enhancements from VLF phase and amplitude observations, J. Atmos. Sol.-Terr. Phys., 66, 77–87, 2004.
Ohya, H., M. Nishino, Y. Murayama, and K. Igarashi, Equivalent electron densities at reflection heights of tweek atmospherics in the low-middle latitude D-region ionosphere, Earth Planets Space, 55, 627–635, 2003.
Ohya, H., M. Nishino, Y. Murayama, K. Igarashi, and A. Saito, Using tweek atmospherics to measure the response of the low-middle latitude D-region ionosphere to a magnetic storm, J. Atmos. Sol.-Terr. Phys., 68, 697–709, 2006.
Ohya, H., K. Shiokawa, and Y. Miyoshi, Development of an automatic procedure to estimate the reflection height of tweek atmospherics, Earth Planets Space, 60, 837–843, 2008.
Ratcliffe, J. A., The magneto-ionic theory and its applications to the ionosphere, Cambridge University Press, Cambridge, 1959.
Rodger, C. J., S. W. Werner, J. B. Brundell, N. R. Thomson, E. H. Lay, R. H. Holzworth, and R. L. Dowden, Detection efficiency of the VLF World-Wide Lightning Location Network (WWLLN): Initial case study, Ann. Geophys., 24, 3197–3214, 2006.
Shvets, A. V. and M. Hayakawa, Polarization effects for tweek propagation, J. Atmos. Sol.-Terr. Phys., 60, 461–469, 1998.
Thomson, N. R., M. A. Clilverd, and W. M. McRae, Nighttime D region parameters from VLF amplitude and Phase, J. Geophys. Res., 112, A07304, doi:10.1029/2007JA01227, 2007.
Wait, J. R. and K. P. Spies, Characteristics of the Earth-ionosphere waveguide for VLF radio waves, NBS Tech. Not., 300 pp., 1964.
Yamashita, M., Propagation of tweek atmospherics, J. Atmos. Terr. Phys., 40, 151–156, 1978.
About this article
Cite this article
Kumar, S., Deo, A. & Ramachandran, V. Nighttime D-region equivalent electron density determined from tweek sferics observed in the South Pacific Region. Earth Planet Sp 61, 905–911 (2009). https://doi.org/10.1186/BF03353201
- Earth-ionosphere waveguide
- tweek atmospherics
- reflection heights
- equivalent electron densities