Some Experimental Studies of the Arctic D-Region

Holt, O.; Landmark, B.

doi:10.1016/b978-0-08-010828-5.50005-9

Cited by 6 publications

(6 citation statements)

References 14 publications

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“…The SC-max extreme cases almost without exception are the same as the slow onset events in Hakura's system. The relationships between the three classification systems are illustrated by Table 1 (after HOLT, 1963b). It was observed early in the PCA research by the Alaska group and has also been found in a recent detailed study (LEINBACH et al, 1965) that the polar cap absorption at Thule, close to the geomagnetic pole, consistently is less than twice the absorption value at College.…”

Section: B Classification Of Pca Eventsmentioning

confidence: 91%

“…LEINBACH et al (1965) have estimated the cutoff at College for a number of PCA events to 35 MeV or less. HOLT (1963b) has studied the latitude dependence of the intensity of the PCA by means of a dozen of Norwegian riometers distributed from Spitzbergen (geomagnetic latitude 74 ~ N) down to Oslo (geomagnetic latitude 60 ~ N). His results are illustrated by Figure 8 for two hard and two soft events (see previous paragraph).…”

Section: B Classification Of Pca Eventsmentioning

confidence: 99%

“…LEINBACH (1962), AXEORO and REID (1962) and HOLT (1963b). A typical example of such a pre-SC absorption increase is shown in Fig.…”

Section: Nonperiodic Variations Of Pca Associated With Magnetic Stormsmentioning

confidence: 99%

“…It is, therefore, of great interest that several studies have been made of the twilight changes of auroral absorption since (I) was written, also for different classes of AA. HOLT (1963b) has made a study without dividing up in categories or classes of AA. He has found a value of the ratio between posttwilight and pretwJlight values at sunrise and between pretwilight and posttwilight at sunset to be about 2.…”

Section: Diurnal Variationsmentioning

confidence: 99%

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Ionospheric absorption of cosmic radio noise

Hultqvist¹

1966

Space Sci Rev

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The development of the field of study of ionospheric absorption of cosmic radio noise since 1962 is reviewed. Contributions to the basic theory and methods of analysis are first dealt with. News concerning measuring technique are then briefly treated. In the main part of the paper the development of our knowledge of sudden cosmic noise absorption, polar cap absorption, and auroral absorption is reviewed. The emphasis is on the ionospheric effects. The solar disturbances associated with the absorption effects, the propagation of particles from the Sun to the Earth, and other extraterrestrial sides of the story are not treated.

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Section: B Classification Of Pca Eventsmentioning

confidence: 91%

Section: B Classification Of Pca Eventsmentioning

confidence: 99%

“…LEINBACH (1962), AXEORO and REID (1962) and HOLT (1963b). A typical example of such a pre-SC absorption increase is shown in Fig.…”

Section: Nonperiodic Variations Of Pca Associated With Magnetic Stormsmentioning

confidence: 99%

Section: Diurnal Variationsmentioning

confidence: 99%

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Ionospheric absorption of cosmic radio noise

Hultqvist¹

1966

Space Sci Rev

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“…One of these, the ionospheric wave interaction experiment [Fejer, 1955; Barrington and Thrane, 1962] has given useful results, but there are major difficulties, both in the experimental technique and in the interpretation of the data. Another method utilizes the partial reflection of ordinary and extraordinary component waves from scatterers within the D region [Gardner and Pawsey, 1953;Fejer and Vice, 1959;Holt, 1963]. This experiment, in this paper referred to as the partial reflection experiment, has proved most fruitful in that observations can be made more easily and more frequently than by the cross modulation experiment.Since the spring of 1961 the partial reflection method has been extensively used to explore the daytime D region at Ottawa.…”

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confidence: 99%

Study of the lower ionosphere using partial reflection: 1. Experimental technique and method of analysis

Belrose¹,

Burke²

1964

J. Geophys. Res.

137

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The amplitude of weak echoes partially reflected from ionization irregularities in the height range 50-100 km are recorded. By utilizing two frequencies, 2.66 and 627 Mc/s, and recording the amplitudes of both the ordinary and extraordinary component waves, information is obtained about electron density and electron collision frequency in this height range under both normal and abnormal conditions. The method of analysis (discussed in detail in this paper) is essentially similar to that developed by Gardner and Pawsey, except that the generalized magnetoionic formulas, which take into account the energy dependence of the collision cross section, are employed. The results being obtained are believed to be more accurate in detail than those obtained by other ground-based techniques. Introduction. Our knowledge of electron densities and electron collision frequencies in the lower ionosphere (50-100 km) is relatively meager, partly because of observational limitations and partly because of difficulties in inter-preting the observational data that have been obtained. Under normal conditions the electron number densities are so low that low frequencies are needed for reflection in this height range. Despite an abundance of experimental data, few results have emerged from these studies. Under abnormal conditions the attenuation of radio waves propagating within the region can become so great that radio reflections, other than from the base of the ionosphere, are not obtained. The dynamic range of changes, even under normal conditions, is large, since the electron density and collision frequency change by about four orders of magnitude in the height range 50-100 km.The relatively high gas densities make environmental measurements with sounding rockets difficult, and most experiments have therefore been designed to provide information about the ionosphere at heights above 100 km. A few results have been obtained for the normal D region [Aikin et al., 1963; Kransnuskin and Kox With the University of Brisbane, Queensland, Australia (work performed while on sabbatical leave to DRTE during 1961). lesnikov, 1962], but these are less reliable than those obtained at times when radio-wave absorption was great [Kane, 1961; Jespersen et al., 1963].The magnitude of the electron density and its variation with height is roughly known, but superimposed on a general increase with height are important structural features, the dynamic changes of which cannot be studied by means of rockets. There is thus a need for a reliable means of studying the lower ionosphere by ground-based experiments. In recent years two new techniques have been developed for studying the D region. One of these, the ionospheric wave interaction experiment [Fejer, 1955; Barrington and Thrane, 1962] has given useful results, but there are major difficulties, both in the experimental technique and in the interpretation of the data. Another method utilizes the partial reflection of ordinary and extraordinary component waves from scatterers within the D region [Gardner ...

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The mutual effect of precipitated auroral electrons and the auroral electrojet

Maehlum¹,

O’Brien²

1968

J. Geophys. Res.

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It has been found that the perturbation in the geomagnetic field produced by the auroral electrojet also perturbs the pitch‐angle distribution of the precipitated electrons that are the dominant contributors to the auroral ionization within which it is assumed the auroral electrojet flows. To study this interaction in detail, a computer program has been developed for model calculations. This program computes: (1) the electron concentration profile in the ionosphere from a given pitch‐angle and energy distribution of the ionizing electrons, and (2) the changes in the pitch‐angle distribution created by the geomagnetic field deformations caused by the auroral electrojet current system itself. Results from preliminary computations are discussed. It is shown that the interaction can cause significant time variations in an initially time‐stationary electron precipitation event. Thus, for the first time it is seen that naturally occurring atmospheric ‘feed‐back’ effects can account for some of the dynamic auroral variations without requiring the auroral source itself to vary in time. The variations are governed by the pitch‐angle distribution and the total flux of precipitated electrons, as well as by the normal loss parameters in the upper atmosphere. For medium‐to‐strong electron precipitation events, the calculated periodicity of the variations lies in the range 50–200 seconds, which is in agreement with some of the direct observations of auroral electron periodicities.

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Some Experimental Studies of the Arctic D-Region

Cited by 6 publications

References 14 publications

Ionospheric absorption of cosmic radio noise

Ionospheric absorption of cosmic radio noise

Study of the lower ionosphere using partial reflection: 1. Experimental technique and method of analysis

The mutual effect of precipitated auroral electrons and the auroral electrojet

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