Investigation of geomagnetic duct propagation of high-frequency radio signals

Gassmann, G. J.; Barrett, T.B.; Pratt, B.

doi:10.1029/jz070i003p00613

Cited by 2 publications

(1 citation statement)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Stepped-frequency sounders and CW transmission were used by Gassmann, Barrett, and Pratt [1965] in a search for geomagnetic duct propagation of HF signals. Spectral analysis of the CW data S. A.…”

Section: Propagation Measurementsmentioning

confidence: 99%

U.S.A. National Committee Report, Fifteenth URSI General Assembly, Munich, September 1966: Commission 3, Ionospheric Radio; Progress in Ionospheric Radio

Bowhill¹,

Bibl²,

Calvert³

et al. 1966

Radio Science

View full text Add to dashboard Cite

Auroral absorption measured in the auroral zone with riometers is on the average more pronounced in the winter months for both hemispheres. Also, in winter it has a pronounced diurnal variation with a maximum a few hours before noon. The average absorption in winter is twice that in summer, but sunlight has no influence in its value [Leinbach and Basler, 1963; Basler, 1963]. Individual events at night are characterized by a quiet phase of relatively small absorption, a sharp increase of absorption associated with the breakup phase of the visible aurora, and a fast recovery with irregular fluctuation of absorption. Detailed correlation of areas of absorption and luminosity exists for such events [Ansari, 1964]. The structure is less than 200 km in the north‐south direction and 700 km in the east‐west direction [Parthasarathy and Berkey, 1965]. An event seen only after midnight consists of a relatively slow increase and recovery of extremely high absorption with no de~ailed correlation of light emission and absorption. It is associated with a harder electron spectrum [Ansari, 1964]. A peculiar type of absorption event frequently observed during midmorning usually increases very smoothly, reaches a high value of absorption, and is not accompanied by appreciable magnetic activity [Ansari, 1965]. Absorption associated either with negative bays or with breakup events shows no difference in intensity between day and night [Brown and Barcus, 1963; Brown, 1964]. There is a limited correlation between the high‐energy part of the electron spectrum, as measured by X‐rays in balloons, and the absorption [Barcus, 1965].

show abstract

Section: Propagation Measurementsmentioning

confidence: 99%

U.S.A. National Committee Report, Fifteenth URSI General Assembly, Munich, September 1966: Commission 3, Ionospheric Radio; Progress in Ionospheric Radio

Bowhill¹,

Bibl²,

Calvert³

et al. 1966

Radio Science

View full text Add to dashboard Cite

show abstract

Ground-based radio sounding of the Earth magnetosphere

Grossi¹,

Padula-Pintos²

1971

J. Geophys. Res.

View full text Add to dashboard Cite

A sounding link at I-IF established between tightly synchronized ground-based terminals located at shell conjugate sites (Jupiter, Florida, and Ushuaia, Argentina) has obtained echoes with 62 millisec delay. The echoes can be interpreted as being due to propagation along an enhancement of electron density aligned with the L ----1.8 shell. The echoes are characterized by path losses 80 db worse than free space and were received at 7.46, 9.04, and 12.00 MI-Iz for 7.6% of the over-all observing time, during night hours. Typically their strength was 15 db below noise and they were recovered with an integration time of 1 hour (3600 pulse repetition periods).We report that a sounding link at HF established between shell conjugate ground-based terminals has obtained long-delay echoes that can be interpreted as being due to propagation guided along a field-aligned enhancement of electron density. Enhancements of this type were detected by the electron probe of the Ariel 1 satellite [Sayers et al., 1963]. Early observations of man-made long-delay 'cosmic echoes' were reported by Stormer [1928] and Van der Pol [1928]. These experimenters worked with radio links that operated at 9.55 MHz and observed echoes with delay up to 15 sec. Although the. mechanism that was active in these observations must have been different [Villard et al., 1969] from wave guidance along field-aligned structures, it is of interest to note that these early researchers interpreted the observed echoes as signals penetrating through the ionosphere and reflected by a toroidal surface formed around the earth by a stream of charged particles emitted from the sun [Alperr, 1963]. Similar observations were made at 6.7 and 9.5 MHz by Appleton [1934]. However, tests carried out at 13 and 20 MHz by Budden and Yates [1952] failed to provide evidence of longdelay echoes at these frequencies, and airborne listenings at 13.7 MHz by Gassman et al. [1965] were also inconclusive. Manczarski [1964] performed experiments with links opera-Copyright ¸ 1971 by the American Geophysical Union. ting between 6.075 and 17.180 MHz. He reported the reception of long-delay echoes for several per cent of the observation time at frequencies near the lower end of his tuning range and also saw some rare occurrence of these echoes near the upper end. Booker [1962] has shown that if magnetospheric wave guidance is involved in cosmic echo events the probability of their occurrence decreases sizeably above approximately 10 MHz. From experimentation conducted with HF radars, echoes with delays up to a few hundred milliseconds have been observed and interpreted in terms of wave guidance in the laminar structure of the magnetosphere [Obayashi, 1959; Gallet and Utlaut, 1961; DuCastel, 1963]. However, an interpretation in terms of transmission below the ionosphere has not been eliminated [Booker, 1962]. Rumi [1968], working with a 13.866-MHz radar, obtained lunar echoes with the antenna beam aimed in the direction of the geomagnetic field and concluded that the em waves were strongly guided i...

show abstract

Investigation of geomagnetic duct propagation of high-frequency radio signals

Cited by 2 publications

References 9 publications

U.S.A. National Committee Report, Fifteenth URSI General Assembly, Munich, September 1966: Commission 3, Ionospheric Radio; Progress in Ionospheric Radio

U.S.A. National Committee Report, Fifteenth URSI General Assembly, Munich, September 1966: Commission 3, Ionospheric Radio; Progress in Ionospheric Radio

Ground-based radio sounding of the Earth magnetosphere

Contact Info

Product

Resources

About