References

ANGEO

Annales Geophysicae

ANGEO

1432-0576

Copernicus GmbH

Göttingen, Germany

10.5194/angeo-25-1827-2007

Maps of foF2, hmF2, and plasma frequency above F2-layer peak in the night-time low-latitude ionosphere derived from Intercosmos-19 satellite topside sounding data

Deminova

G. F.

Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences (IZMIRAN), 142190 Troitsk, Moscow region, Russia

29 08 2007

25 8 1827 1835

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Maps of foF2, hmF2, and plasma frequency, fp, in the topside ionosphere at low latitudes, derived from Intercosmos-19 satellite topside sounding data, obtained from March 1979 to January 1981 and covering all longitudes, are presented for quiet geomagnetic conditions in June and December solstices at solar maximum for several local time intervals during the night. Based on these maps, features of the equatorial anomaly (EA) at different longitudes and their change during the night are considered. The maps show that averaged foF2, hmF2, and fp longitudinal variations are rather complicated, their structure looks wave-like with quasi-periods in longitude of about 75–100°, similar to that on individual days revealed previously at low latitudes using Intercosmos-19 data. Positions of the structure extrema in certain longitude intervals are stable enough so that they are clearly seen in the maps after averaging over a large number of measurements made on different days and even in different years. Such structure seems to need at least five harmonics for its description. The maps derived from Intercosmos-19 data were compared with the maps given by the IRI model. Along with general resemblance, essential distinctions between them were found. Intercosmos-19 maps show more complicated and pronounced longitudinal structure than IRI maps. They also show that at solar maximum, in general, at night, EA is stronger and persists for a longer time (on average, until 04:00 LT) than that presented in IRI model. Besides, much stronger asymmetry between the characteristics of the EA northern and southern crests in certain longitude intervals was revealed, most evident in hmF2 maps.

References 1

Akasofu, S.-I. and Chapman, S.: Solar-Terrestrial Physics, Clarendon Press, Oxford, 1972.

Anderson, D. and Roble, R. G.: Neutral wind effects on the equatorial F-region ionosphere, J. Atmos. Terr. Phys., 43, 835–843, 1981.

Benkova, N. P., Deminov, M. G., Karpachev, A. T., Kochenova, N. A., Kushnerevsky, Yu. V., Migulin, V. V., Pulinets, S. A., and Fligel, M. D.: Longitude features shown by topside sounder data and their importance in ionospheric mapping, Adv. Space Res., 10, 57–66, 1990.

Bilitza, D.: International Reference Ionosphere 2000, Radio Sci., 36, 261–275, 2001.

Bilitza, D., Koblinsky, C., Zia, S., Williamson, R., and Beckley, B.: The equator anomaly region as seen by the TOPEX/Poseidon satellite, Adv. Space Res., 18, 23–32, 1996.

Bradley, P. A.: Mapping the critical frequency of the F2-Layer: Part 1 – Requirements and developments to around 1980, Adv. Space Res., 10, 47–56, 1990.

Bradley, P. A., Stanislawska, I., and Juchnikowski, G.: Perspectives on updated \textitfoF2 maps for IRI, Adv. Space Res., 34, 2067–2074, 2004.

Challinor, R. A. and Eccles, D.: Longitudinal variations of the mid-latitude ionosphere produced by neutral-air winds – 1. Neutral air winds and ionospheric drifts in the northern and southern hemispheres, J. Atmos. Terr. Phys., 33, 363–369, 1971.

Deminov, M. G. and Karpachev, A. T.: Longitudinal effect in the night-time mid-latitude ionosphere as given by the "Intercosmos-19" data, Geomagn. Aeronomy (in Russian), 28, 76–80, 1988.

Deminov, M. G., Kochenova, N. A., and Sitnov, Yu. S.: Longitudinal variations of electric field in the equatorial ionosphere, Geomagn. Aeronomy (in Russian), 28, 71–75, 1988.

Deminova, G. F.: Wave-like structure of longitudinal variations of the night-time equatorial ionosphere, Geomagn. Aeronomy (in Russian), 33, 167–169, 1993.

Deminova, G. F.: Wave-like structure of longitudinal variations of the night-time equatorial anomaly, Geomagn. Aeronomy (in Russian), 35, 169–173, 1995.

Deminova, G. F.: One type of the low-latitude trough of the ionization in the Southern hemisphere, Adv. Space Res., 24, 1503–1506, 1999.

Deminova, G. F.: Asymmetry of the longitudinal effect in the low-latitude ionosphere, Adv. Space Res., 29, 911–915, 2002a.

Deminova, G. F.: Variations of the altitude-longitudinal characteristics of the equator anomaly during night, Geomagn. Aeronomy (in Russian), 42, 771–779, 2002b.

Deminova, G. F.: Fine structure of \textitfoF2 longitudinal distribution in the night-time low-latitude ionosphere derived from Intercosmos-19 topside sounding data, Adv. Space Res., 31, 531–536, 2003a.

Deminova, G. F.: Comparison of the \textitfoF2 longitude distribution in the night-time low-latitude ionosphere inferred from Intercosmos-19 data with IRI and ground-based data, Geomagn. Aeronomy (in Russian), 43, 377–381, 2003b.

Eccles, D., King, J. W., and Rothwell, P.: Longitudinal variations of the mid-latitude ionosphere produced by neutral-air winds – 2. Comparisons of the calculated variations of electron concentration with data obtained from the Ariel 1 and Ariel 3 satellites, J. Atmos. Terr. Phys., 33, 371–377, 1971.

Fejer, B. G.: The electrodynamics of the low latitude ionosphere: recent results and future challenges, J. Atmos. Terr. Phys., 59, 1465–1482, 1997.

Fox, M. W. and McNamara, L. F.: Improved world-wide maps of monthly median \textitfoF2, J. Atmos. Terr. Phys., 50, 1077–1086, 1988.

Hedin, A. E., Fleming, E. L., Manson, A. H., Schmidlin, F. J., Avery, S. K., Clark, R. R., Franke, S. J., Fraser, G. J., Tsuda, T., Vial, F., and Vincent, R. A.: Empirical wind model for the upper, middle and lower atmosphere, J. Atmos. Terr. Phys., 58, 1421–1447, 1996.

Herrero, F. A. and Spenser, N. W.: On the horizontal distribution of the equatorial thermosphere midnight temperature maximum and its seasonal variation, Geophys. Res. Lett., 9, 1179–1182, 1982.

Hopkins, H. D.: Longitudinal variation of the equatorial anomaly, Planet. Space Sci., 20, 2093–2098, 1972.

Jones, W. B. and Gallet, R. M.: The representation of diurnal and geographic variations of ionospheric data by numerical methods, Telecomm. J., 29, 129–149, 1962.

Jones, W. B. and Gallet, R. M.: The representation of diurnal and geographic variations of ionospheric data by numerical methods (Pt.2), Telecomm. J., 32, 18–28, 1965.

Karpachev, A. T.: Characteristics of the global longitudinal effect in the night-time equatorial anomaly, Geomagn. Aeronomy (in Russian), 28, 46–49, 1988.

Karpachev, A. T., Deminova, G. F., Depuev, V. H., and Kochenova, N. A.: Diurnal variations of the peak electron density distribution pattern at low latitudes derived from Intercosmos-19 topside sounding data, Adv. Space Res., 31, 521–530, 2003.

Kochenova, N. A.: Longitudinal variations of the equatorial ionosphere according to Intercosmos-19 data, Geomagn. Aeronomy (in Russian), 27, 142–144, 1987.

Kochenova, N. A.: Longitudinal variations of N(h) profiles at the magnetic equator, Geomagn. Aeronomy (in Russian), 28, 144–146, 1988.

Kochenova, N. A.: Longitudinal variations of the day-time equatorial ionosphere inferred from Intercosmos-19 data, Adv. Space Res., 10, 67–70, 1990.

Kohl, H., King, J. W., and Eccles, D.: An explanation of the magnetic declination effect in the ionospheric F2-Layer, J. Atmos. Terr. Phys., 31, 1011–1016, 1969.

Manson, A. H., Meek, C., Hagan, M., Zhang, X., and Luo, Y.: Global distributions of diurnal and semidiurnal tides: observations from HRDI-UARS of the MLT region and comparisons with GSWM-02 (migrating, nonmigrating components), Ann. Geophys., 22, 1529–1548, 2004.

Matuura, N. (Ed.): Atlas of ionospheric critical frequency (\textitfoF2) obtained from Ionosphere Sounding Satellite-b observation, Part 1, August to December 1978, Radio Research Lab., Ministry of Posts and Telecommunications, Japan, 1979.

Mayr, H. G., Harris, I., Spenser, N. W., Hedin, A. E., Wharton, L. E., et al.: Atmospheric tides and the midnight temperature anomaly, Geophys. Res. Lett., 6, 447–450, 1979.

Rawer, K.: Ionospheric mapping in the polar and equatorial zones, Adv. Space Res., 16, 9–12, 1995.

Rishbeth, H.: The equatorial F-layer: progress and puzzles, Ann. Geophys., 18, 730–739, 2000.

Rush, C. M., PoKempner, M., Anderson, D. N., Stewart, F. G., and Perry, J.: Improving ionospheric maps using theoretically derived values of \textitfoF2, Radio Sci., 18, 95–107, 1983.

Rush, C. M., PoKempner, M., Anderson, D. N., Perry, J., Stewart, F. G., and Reasoner, R.: Maps of \textitfoF2 derived from observations and theoretical data, Radio Sci., 19, 1083–1097. 1984.

Schirliess, I. and Fejer, B. G.: Radar and satellite global equatorial F region vertical drift model, J. Geophys. Res., 104A, 6829–6842, 1999.

Su, Y. Z., Oyama, K.-I., Bailey, G. J., Fukao, S., Takahashi, T., and Oya, H.: Longitudinal variations of the topside ionosphere at low latitudes: Satellite measurements and mathematical modeling, J. Geophys. Res., 101A, 17 191–17 205, 1996.

Thomas, L.: The F2-region equatorial anomaly during solstice periods at sunspot maximum, J. Atmos. Terr. Phys., 30, 1631–1640, 1968.

Walker, G. O.: Longitudinal structure of the F-region equatorial anomaly – a review, J. Atmos. Terr. Phys., 43, 763–774, 1981.