Contribution of Solar and Auroral Ionization of the Atmosphere to the E-Layer Critical Frequency of the Nighttime Auroral Region
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The contribution of the solar fsol and auroral favr components of foE to the critical frequency of the E layer foE are estimated based on an analysis of the medians of the E-layer critical frequency foE in the nighttime (2200–0200 LT) auroral region with allowance for the noncoincidence in the heights of maxima of these components. This noncoincidence is taken into account with a correction coefficient that manifests the relation of fsol to the critical frequency of the E layer due to solar radiation foEsol. The analytical dependence of this coefficient on the solar zenith angle for χ < 85° is derived. It is shown that one can usually disregard the contribution of fsol in foE in the nighttime auroral region for χ > 85° and approximately foE = foEavr for these conditions in which foEavr is the critical frequency of the E layer due to precipitation of auroral electrons. It is obtained that the allowance for the noncoincidence of the heights of maxima in the solar and auroral components of foE with estimation of the annual changes in foEavr based on the foE measurements leads to an increase in foEavr in summer and thus provides a decrease in the amplitude of the winter anomaly in foEavr. Nevertheless, even in this case, the amplitude of the winter anomaly in foEavr is higher than the winter anomaly in foE, and that demonstrates the important role of accelerated auroral electrons in formation of this anomaly.
The foE medians of ionospheric stations and the solar and geomagnetic activity indices were taken from the sites of Space Physics Interactive Data Resource (SPIDR, http://spidr.ngdc.noaa.gov/), World Data Center for Solar–Terrestrial Physics, Chilton (http:// www.ukssdc.ac.uk/wdcc1/), World Data Center for Geomagnetism, Kyoto (http://wdc.kugi.kyoto-u.ac.jp/). The work was partly supported by the Russian Foundation for Basic Research (project no. 17-05-00427) and by Program 28 of the Presidium of RAS.
- 1.Badin, V.I., Deminov, M.G., Deminov, R.G., and Shubin, V.N., E-layer critical frequency median model for auroral region, Soln.-Zemnaya Fiz., 2013, no. 22, pp. 24–26.Google Scholar
- 4.Bryunelli, B.E. and Namgaladze, A.A., Fizika ionosfery (Ionospheric Physics), Moscow: Nauka, 1988.Google Scholar
- 6.Deminov, M.G. and Deminova, G.F., Winter anomaly of the E-layer critical frequency in the nighttime auroral zone, Geomagn. Aeron. (Engl. Transl.), 2017, vol. 57, no. 5, pp. 584–590.Google Scholar
- 7.Deminov, M.G. and Deminova, G.F., Winter anomaly in the critical frequency of the E-layer in the nighttime polar cap, Geomagn. Aeron. (Engl. Transl.), 2018, vol. 58, no. 1, pp. 62–69.Google Scholar
- 8.Johnson, M.T. and Wygant, J.R., The correlation of plasma density distributions over 5000 km with solar illumination of the ionosphere: Solar cycle and zenith angle observations, Geophys. Res. Lett., 2003, vol. 30, no. 24, 2260. doi 10.1029/2003GL018175Google Scholar
- 9.Kashirin, A.I., Photoionization in the nocturnal ionosphere, Geomagn. Aeron., 1986, vol. 26, no. 4, pp. 563–568.Google Scholar
- 13.Newell, P.T., Sotirelis, T., and Wing, S., Seasonal variations in diffuse, monoenergetic, and broadband aurora, J. Geophys. Res., 2010, vol. 115, A03216. doi 10.1029/2009JA014805Google Scholar
- 15.Picone, J.M., Hedin, A.E., Drob, D.P., and Aikin, A.C., NRLMSISE-00 empirical model of the atmosphere: Statistical comparisons and scientific issues, J. Geophys. Res., 2002, vol. 107A, pp. 1468–1483.Google Scholar
- 19.Titheridge, J.E., Re-modeling the ionospheric E region, Kleinheubacher Ber., 1996a, vol. 39, pp. 687–696.Google Scholar