The structure of the polar ionosphere during exceptionally quiet periods

Wagner, R. A.; Snyder, Arnold; Akasofu, S.‐I.

doi:10.1016/0032-0633(73)90120-7

Cited by 15 publications

(6 citation statements)

References 13 publications

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“…Another indication of this larger significance is the consistency of the auroral states in periods I, III, and VI with the auroral patterns described by Wagner et al [1973] during extremely quiet periods: the nonmerging of oval and continuous auroras because the discrete oval aurora is absent or poleward of the continuous aurora. The occurrence of polar cap aurora in periods III and VI is also consistent with quiet conditions [Dat)is, 1963].…”

Section: Auroral Statesmentioning

confidence: 75%

“…The identification of the band as continuous aurora is confirmed by the occurrence of the associated auroral E layer detected by the Narssarssuaq sounder throughout the entire period. A narrow band of continuous aurora, discrete aurora being either absent or extremely faint, is characteristic of the aurora during extremely quite periods[Wagner et al, 1973].Another DMSP picture at 0235 UT (not shown) detected no auroral phenomena. However, since the Narssarssuaq sounder detected the continued presence of the auroral E layer at about the same foE, the disappearance of the band of continuous aurora was not due to a change in the aurora.…”

mentioning

confidence: 83%

“…This spatial uncertainty, coupled with the super-Copyright ¸ 1977 by the American Geophysical Union. position of the phenomena and the rapid changes which can occur in all of the observables, presents a confusing pattern in all but the most quiet conditions [Wagner et al, 1973].…”

Section: Introductionmentioning

confidence: 99%

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A 12-hour case study of auroral phenomena in the midnight sector: Oval, polar cap, and continuous auroras

Whalen¹,

Wagner²,

Büchau³

1977

J. Geophys. Res.

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This paper and two companion papers describe a case study of multiple auroral phenomena in the midnight sector. The duration of the study was 12 hours on December 9, 1971. For 9 of the 12 hours the Air Force Geophysics Laboratory airborne ionospheric observatory flew near local midnight across North America so as to intersect many successive passes of Defense Meteorological Satellite Program (DMSP) and Isis 2 satellites which were also in the midnight sector. The large‐scale DMSP auroral photographs have been combined with the temporally continuous aircraft‐ and ground‐based measurements to provide extensive observations of long duration compared to the lifetimes of the two substorms observed. All the types of observations (satellite pictures, aircraft ionospheric soundings, all‐sky camera photographs, photometer recordings, as well as particle and other satellite‐ and ground‐based measurements) have been combined to describe the temporal histories of a large number of phenomena and of their interrelations. The phenomena are the discrete auroras in the oval and polar cap, the continuous (E layer) aurora, auroral absorption (nearly absent on this day), and (in the companion papers) the F layer irregularity zone and 6300‐Å emission, particle precipitation, the electrojet, and interplanetary magnetic field and magnetospheric phenomena. DMSP photographs are found to detect both discrete and continuous auroras; uses and limitations of the data are described. In terms of the overall perspective of this study the phenomena are found to fall into six periods of 1–3 hours each. Two of these periods contain substorms of differing characteristics; the remaining four periods are relatively quiet but also differ from one another. Throughout each of the periods the polar cap, oval, and continuous auroras as a whole retain the same configuration as described, in terms of whether each of the auroras is present or absent and whether adjacent auroras are joined or separated. These configurations are described as phenomenological states of the aurora, and the periods are regarded as the lifetimes of these states. The large‐scale, long‐term features of the auroral states suggest that they reflect individual states of the magnetosphere.

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Section: Auroral Statesmentioning

confidence: 75%

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confidence: 83%

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A 12-hour case study of auroral phenomena in the midnight sector: Oval, polar cap, and continuous auroras

Whalen¹,

Wagner²,

Büchau³

1977

J. Geophys. Res.

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“…The high latitude E s layers are generally considered to be due to particle precipitation (Buchau et al, 1972;Whitehead, 1970;Whalen et al, 1971;Wagner et al, 1973). Naridner et al (1980) found that electron precipitation usually is the major cause for the formation of the high latitude Sporadic-E layer and that the modified wind shear mechanism, which takes into account the effect of electric fields, is important under low electron precipitation conditions only.…”

Section: Discussionmentioning

confidence: 98%

Observations on the variability and screening effect of Sporadic-E

Ritchie

Honary

2009

Journal of Atmospheric and Solar-Terrestrial Physics

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a b s t r a c tSporadic-E is a problem in high latitude HF communications because of its irregular and as yet unpredictable behaviour. This paper characterises the change in E-layer critical frequency (f o E) that occurs in the four hours following a storm sudden commencement (SSC) event which is a precursor to magnetospheric storms which adversely affect ionospheric communications.Following checks for any seasonal or solar activity dependency in the data, further analysis determines the occurrence of full blanketing (screening) Sporadic-E layer formation at high latitudes as seen on vertical ionosondes in Northern Finland (671 Latitude). An appropriate threshold value of f o E is proposed that could be used following the commencement of ionospheric storms, indicating that there is a high probability that F-layer screening will occur. As far as the authors are aware this is the first statistical analysis of the onset of Sporadic-E following SSC.

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“…E s has different characteristics in different latitudinal zones and there may be several mechanisms governing the behaviour of these layers. The high latitude E s layers are generally considered to be due to particle precipitation [20,21,22,23]. It has been found that electron precipitation usually is the major cause for the formation of the high latitude sporadic E-layer and that the modified wind shear mechanism, which takes into account the effect of electric fields, is important under low electron precipitation conditions only, i.e.…”

Section: Modelling Of Scamentioning

confidence: 99%

Advances in ionospheric propagation modelling at high-latitudes

Ritchie

Honary

2009

IET 11th International Conference on Ionospheric Radio Systems and Techniques (IRST 2009)

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Many services rely on the output of propagation planning tools to predict the future state of the ionosphere and the availability of suitable communications channels. While this approach is adequate for services operating at high-latitudes during quiet ionospheric conditions it is insufficient to deal with a disturbed ionosphere. This paper presents the results of empirical modelling of the changes that occur in the D-and E-regions of the ionosphere following the onset of disturbed conditions as defined by the occurrence of a storm sudden commencement.

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The structure of the polar ionosphere during exceptionally quiet periods

Cited by 15 publications

References 13 publications

A 12-hour case study of auroral phenomena in the midnight sector: Oval, polar cap, and continuous auroras

A 12-hour case study of auroral phenomena in the midnight sector: Oval, polar cap, and continuous auroras

Observations on the variability and screening effect of Sporadic-E

Advances in ionospheric propagation modelling at high-latitudes

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