Equatorial spread F and plasma bubbles

by Quirino Sugon Jr.

I need some literature survey for the equatorial Spread F and plasma bubbles to see if what we are doing has been done before.

D. L. Hysell, M. F. Larsen, C. M. Swenson, A. Barjatya, T. F. Wheeler, T. W. Bullet, M. F. Sarango, R. F. Woodman, J. L. Chau, D. Sponseller, Onset conditions for equatorial spread F determined during EQUIS II. This is the result of rocket investigations of the equatorial spread F in Kwajalein Atoll on August 7 and 15, 2004. The electron density that they found is not a smooth function of height but jagged.

There another paper by the same authors: Rocket and radar investigation of background electrodynamics
and bottom-type scattering layers at the onset of equatorial

J. Krall, J. D. Huba, G. Joyce, and T. Yokoyama, Density enhancements associated with equatorial spread F, Ann. Geophys., 28, 327–337 (2010). The paper uses the following definition:”equatorial spread F as diffuse echoes in the ionosphere received continuously at night in equatorial regions over a wide range of frequencies (Booker and Wells, 1938). They use an ionosphere model SAMI3/ES, which uses certain ion diffusion equations. The electron density obtained in from rocket measurements is also jagged as shown in Fig. 8. But I still have to see its corresponding ionogram.

I need a paper that shows a jagged ionosphere from rocket measurements and its corresponding ionogram.

K. L. Bowles, Radio Wave Scattering in the Ionosphere, in Advances in Electronics and Electron Physics by L. L. Marton, vol. 19, pp. 55-176 (1964). This is an excellent monograph. Here are some notes:

Bowles said in p. 56 that “the scattering of radio waves arises from fluctuations or irregularities in the otherwise smoothly varying distribution of ionization density in the ionosphere…. The term ‘backscattering’ or simply ‘scattering’ will be used to refer to propagation effects in which a small fraction of the signal intensity reaches the observer because its path has been deviated through a relatively large angle by irregular structures of small scale, usually a few tens of meters.” (p. 56)

Bowles has an excellent treatment of scintillation.

p. 142: “At HF frequencies in the vicinity of the F region plasma frequencies, the phenomenon of spread F is frequently observed in conventional sweep-frequency ionograms. Spread F appears in a number of forms which are relatively distinct, at least as viewed in the ionograms, and one such form has been positively identified with field-aligned irregularities. The difficulties associated with the theory of spread-F for frequencies close to the plasma frequency are great, and the association of spread-F in general with field-aligned irregularities is still mainly conjectural.”

p. 145: The South America observations suggested that the range spread F is associated with a relatively thin layer located near the bottom of the profile of F layer ionization density. The thickness of this layer was often 50 im or less, although much thicker regions were sometimes observed. VHF scatter was not associated with frequency spreading, and when ionogram showed only frequency spreading, no VHF F layer scatter was observed.

p. 146: “The mechanism of frequency spread F is considerably more difficult to understand, because the propagation effects apparently occur in the heigh and frequency region where the radio freqquency approaches the local plasma frequency.” Bowden computed the ionograms for ionospheric holes.


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Physics News and Features from Ateneo de Manila University

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