Abstract
Some properties of the outer ionosphere and its boundary region are discussed on the basis of recent experimental results.
The analysis of the new data has shown that the outer ionosphere, a plasma above the ionospheric main maximum, extends to a distance of 3 to 3.5 earth radii from the earth's surface, that is, up to the region of the so-called “knee”, detected and observed by means of whistlers. During periods of relatively weak magnetic storms, from time to time the electron concentration at this ionospheric boundary jumps downward by factors of 10 to 100, over a height range of only a few hundred kilometres. The inflow of charged particles into the ionosphere apparently takes place through the boundary region. Sometimes these particles are “swept” into it from the overlying regions.
There is a great number of names for the outer ionosphere. Some of these terms, for instance the “geocorona”, are not at all applicable to the outer ionosphere.
From the new experimental results it can be inferred that in a great part of the outer ionosphere there is no quasineutrality, that there are rather strong electric fields, and that the Maxwell ion distribution law of particle velocities breaks down. Therefore, to analyze the ionization balance one should know the particles' velocity distribution functions. Otherwise it would hardly be possible to solve the problem of the formation of the ionosphere.
It is shown that within the limits of uncertainty all experimental results are in good agreement and produce a single, comprehensive picture of the structure of the outer ionosphere. Only some data, deduced from measurements of particle streams by means of ion traps, are an exception. They contradict the numerous experimental results. This discrepancy is in particular due to the difficulties of determining the plasma concentration from current density measurements.
Some methods are discussed briefly. For instance, the analysis of low-frequency waves, in particular the so-called whistler and the low-frequency plasma radiation, represents a physically adequate and fruitful method for investigating the outer ionosphere.
For a theoretical analysis of the above-mentioned data, it is in some cases required to take into account the effect of kinetic “corrections” to the refraction coefficient, of cyclotron and Čerenkov attenuation and radiation, etc. Over the next few years this method will come to play a great part in the exploration of the outer ionosphere, interplanetary space, and planets.
Measurements of the energy spectra of “incoherent” back scattering of radio waves on the electron fluctuations will make another very interesting source for studying the outer ionosphere. This method is based on the interaction phenomena of radio waves with the plasma. Therefore, the scattering spectra are functions of the oscillating properties of the plasma. However, these data should be subjected to a thorough theoretical treatment on the basis of a complete theory of scattering.
Up till now a sufficiently complete probe theory has not been evolved due to essential theoretical difficulties. Often this does not allow one to interpret adequately the results of measurements and considerably limits the possibilities of these methods.
Similar content being viewed by others
References
Storey, L. R. O.: 1953, Phil Trans. Roy. Soc. A.246.
Allcok, G. Mack: 1958, J. Atmos. Terr. Phys. 14, 158.
Smith, R. L.: 1961, J. Geophys. Res. 66, 3710.
Storey, O.: 1958, Ann. de Géophysique 14, 144.
Carpenter, D. L.: 1962, J. Geophys. Res. 67, 1963; 68, 1675, 1966; 71, 693.
Angerami, J. J. and Carpenter, D.: 1965, Report on Equatorial Aeronomy, p. 311; 1966, J. Geophys. Res. 71, 711.
Liemohn, H. B. and Scarf, F. L.: 1964, J. Geophys. Res. 69, 883.
Guthart, H.: 1965, Radio Science 69D, 1417.
Gurnett, D. A., Shawhan, S. D., Brice, N. M., and Smith, R. L.: 1965, J. Geophys. Res. 70, 1966; 71, 741.
Gringauz, K. I.: 1961, Isk.Sput.Zemli [Artificial Earth Satellites] 12, 105. (See also the Patent for Discovery 27, “Bulletin of devices...” 12, 1964.)
Bowles, K. L.: 1961, J. Res. Nat. Bur-Stand. 65, D.I.
Farley, D. T. and Bowles, K. L.: 1964, NBS Report, 8489.
Evans, J. V.: 1962, J. Geophys. Res. 67, 4914.
Serbu, G. P. and Maier, K.: 1965, NBS Report, 8824; 1964, Space Research 5, 564.
Slysh, V. I.: 1965, Kosm. Issl. [Space Research] (in Russian) 3, 760.
Sagalyn, R. C. and Smiddy, M.: 1964, J. Geophys. Res. 69, 1809.
Sagalyn, R. C. and Smiddy, M.: 1965, Preprint.
Al'pert, Ja. L. and Sinel'nikov, V, M.: 1965, Geomagn. i Aeron. 5, 209; 1966. Plan. Space Sci. 14, 313.
Misyura, V. A., Solodovnikov, G. K., and Migunov, V. M.: 1965, Kosm. Issl. 3, 595, 604.
Istomin, V. G.: 1965, Issl. Kosm. Prostranstva [Exploration of the Outer Space]. Publishing House Nauka, Moscow, p. 192.
Taylor, H. A., Brinton, H. G., and Smith, C. R.: 1965, Preprint, Goddard Space Flight Center; 1965, J. Geophys. Res. 70, 5769.
Kurt, V. G.: 1965, Issl. Kosm. Prostranstva. Publishing House Nauka, Moscow, p. 576.
Mac Lure, J. P.: 1965, Equatorial Aeronomy, p. 170.
Pineo, V. C., Hynek, D. P., and Millman, G. H.: 1963, J. Geophys. RES. 68, 9695.
Bowles, K. L.: 1963, Space Research, p. 253.
Champion, K. C. W.: 1965, Air Force Surveys in Geophysics No. 164.
Al'pert, Ja. L.: 1960, Rasprostraneniye Radiovoln i Ionosfera [Propagation of Radio Waves and Ionosphere]. Nauka Publishing House, Moscow; 1962, Consultants Bureau, USA.
Mikhajlova, G. A.: 1962, Geomagn. i Aeron. 2, 257; 1965, 5, 183, 179.
Al'pert, Ja. L., Mikhailova, G. A., and Fligel, D. S.: 1966, J. Atmos. Terr. Phys. (in print).
Fligel, D. S.: 1962, Geomagn. i Aeron. 2, 886.
Smith, R. L. et al.: 1964, Nature 204, 274.
Shawhan, S. D.: 1966, J. Geophys. Res. 71, 29.
Shawhan, S. D. and Gurnett, D. A.: 1966, J. Geophys. Res. 71, 46.
Gurnett, D. A. and Shawhan, S. D.: 1966, J. Geophys. Res. 71, 741.
Brice, N. M. and Smith, R. L.: 1964, Nature 203, 926.
Belrose, J. S. and Barrington, R. F.: 1964, Nature 203, 926.
Gurnett, D. A. and O'Brien, B. J.: 1964, J. Geophys. Res. 69, 65.
Scarf, F. L., Crook, G. M., and Fredericks, R. W.: 1965, J. Geophys. Res. 70, 3045.
Gordon, W. E.: 1958, Proc. I.R.E., 1824.
Bowles, K. L.: 1958, Phys. Rev. Letters 1, 454.
Fejer, J. A.: 1960, Canad. J. Phys. 38, 1114; 1961, 39, 716.
Farley, D. T., Dougherty, J. D., and Barron, D. W.: 1961, Proc. Roy. Soc. A.263, 238.
Akhiezer, A. N. et al.: 1964, Kollektivnye Kolebaniya Plazmy [Collective Oscillations of Plasma]. Atomisdat, USSR. (In Russian.)
Langmuir, I. and Mott-Smith, H. M.: 1924, General Electric Review 27, 449, 538, 616, 762, 810; 1926, Phys. Rev. 28, 727.
Hok, G., Spencer, N. W., and Dow, W. G.: 1953, J. Geophys. Res. 58, 235.
Al'pert, Ja. L., Gurevich, A. V., and Pitayevsky, L. P.: 1964, Isk. Sputniki v Razrezhennoj Plazme [Artificial Satellites in Rarefield Plasma]. Nauka Publishing House, Moscow; 1965, ‘Space Physics with Artificial Satellites’, Consultants Bureau, USA.
Al'pert, Ja. L.: 1965, Geomagn. i Aeronom. 5, 3; 1965, Space Sci. Rev. 4, 373.
Gurevich, A. V., Pariyskaya, L. V., and Pitayevsky, L. P.: 1966, Sovjet Phys. JETP 22, 449.
Al'pert, Ja. L.: 1953, Usp. Fiz. Nauk [Advances of Physical Sciences] 49, No. 1; 1951, Journal of Experimental and Theoretical Physics 21, 38.
Ratcliffe, J. A.: 1957, Rep. Progr. Physics 19, 138.
Al'pert, Ja. L., Vitshas, L. N., and Sinel'nikov, V. M.: 1965, Geomagn. i Aeronom. 5, 649.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Al'pert, J.L. On the outer ionosphere (and its transition into interplanetary space). Space Sci Rev 6, 419–451 (1967). https://doi.org/10.1007/BF00173702
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00173702