Anomalies in Ionosonde Records Due to Travelling Ionospheric Disturbances

Heisler, L.H.

doi:10.1071/ph580079

Cited by 94 publications

(32 citation statements)

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“…For clarity and brevity, this study of the e ects of AGWs and TIDs at equatorial latitudes will henceforth ignore the initially poleward-travelling waves, and refer to the equatorially-travelling waves as`northward-travelling' (originating in the Southern Hemisphere) and southward-travelling' (originating in the Northern Hemisphere) respectively. The waves interfere at the magnetic equator and pass through to the opposite hemispheres with unchanged velocity; this is consistent with observations (Heisler, 1958). Figure 1 shows the signature of the AGWs at a ®xed pressure surface denoted as H14 (13 scale heights above an imposed¯at lower boundary of 1 Pa at 80 km), corresponding to an approximate altitude of 380 km, just below the F2 peak.…”

Section: The Signature Of the Agw In The Thermospheresupporting

confidence: 85%

A study of atmospheric gravity waves and travelling ionospheric disturbances at equatorial latitudes

Moffett

1997

Ann Geophysicae

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Abstract.A global coupled thermosphere-ionosphereplasmasphere model is used to simulate a family of large-scale imperfectly ducted atmospheric gravity waves (AGWs) and associated travelling ionospheric disturbances (TIDs) originating at conjugate magnetic latitudes in the north and south auroral zones and subsequently propagating meridionally to equatorial latitudes. A`fast' dominant mode and two slower modes are identi®ed. We ®nd that, at the magnetic equator, all the clearly identi®ed modes of AGW interfere constructively and pass through to the opposite hemisphere with unchanged velocity. At F-region altitudes the`fast' AGW has the largest amplitude, and when northward propagating and southward propagating modes interfere at the equator, the TID (as parameterised by the fractional change in the electron density at the F2 peak) increases in magnitude at the equator. The amplitude of the TID at the magnetic equator is increased compared to mid-latitudes in both upper and lower F-regions with a larger increase in the upper F-region. The ionospheric disturbance at the equator persists in the upper F-region for about 1 hour and in the lower F-region for 2.5 hours after the AGWs ®rst interfere, and it is suggested that this is due to enhancements of the TID by slower AGW modes arriving later at the magnetic equator. The complex e ects of the interplays of the TIDs generated in the equatorial plasmasphere are analysed by examining neutral and ion winds predicted by the model, and are demonstrated to be consequences of the forcing of the plasmasphere along the magnetic ®eld lines by the neutral air pressure wave.

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Section: The Signature Of the Agw In The Thermospheresupporting

confidence: 85%

A study of atmospheric gravity waves and travelling ionospheric disturbances at equatorial latitudes

Moffett

1997

Ann Geophysicae

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“…It would appear, therefore, that in these cases the factors controlling direction of travel mentioned in connexion with Figure 5 are not significant and, since the particular phenomenon is observed only during sunspot maximum, some form of solar control is indicated. V. HEIGHT AND SPEED OF DISTURBANCES As previously described (Heisler 1958), large ionospheric disturbances extend over a range of ionospheric heights and travel long distances with no apparent change in form or amplitude. Moreover, observations Heisler 1956a, 1956b) indicate that a travelling disturbance always has an apparent vertical component of progression which is assumed to be the result of a forward tilt in the wavefront of the disturbance.…”

Section: Height and Direction Of Disturbancesmentioning

confidence: 74%

“…Large disturbances are more readily observed and their nature studied from sequences of ionosonde records made with a panoramic type recorder . .Anomalies in such records due to travelling ionosonde disturbances have already been described (Heisler 1958). One particular type described therein as a 0 type anomaly occurs as a cusp-shaped trace at the top of F 1 forming a double peak, and gradually travels down the FI trace.…”

Section: (B) Variable-frequency Observationsmentioning

confidence: 89%

“…Heisler (1956a, 1956b) have described large disturbances which occur in variable-frequency ionosonde records, and Heisler (1958), comparing records from Australian ionosonde stations, has shown that these disturbances travel distances of at least 3000 km, with fronts possibly broader than 1000 km. The existence of similar disturbances in the northern hemisphere, first mentioned by Munro (1957), has recently been confirmed by Valverde (1958), using backscatter techniques.…”

Section: Introductionmentioning

confidence: 99%

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Vertical Characteristics of Travelling Ionospheric Disturbances

Heisler¹

1960

Aust. J. Phys.

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SummaryThe vertical dimensions of travelling disturbance phenomena have been investigated by derivation of the associated true height distributions of ion density. The height at which they appear often has an upper limit which may fluctuate in height from day to day.It appears that direction of travel is related mainly to season, with the possibility of some additional form of solar control only evident at times of sunspot maximum.During a particular season, there is no obvious change of direction of travel with height in the height range under observation.No definite variation of speed with height is evident in the ionospheric region considered, which extends from 160 to 230 km.

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“…It is commonly accepted that both AGW-TIDs and solitary waves propagate over large distances without essential modification of their form and amplitude. A solitary-like TID behavior was once recorded when one TID transited through another, and both remained unchanged (Heisler 1958). Therefore, we suppose that the theory of AGW-TID origin and propagation may be based on the soliton theory.…”

Section: Introductionmentioning

confidence: 89%

Model of traveling ionospheric disturbances

Fedorenko

Tyrnov

Fedorenko

et al. 2013

J. Space Weather Space Clim.

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A multiscale semi-empirical model of traveling ionospheric disturbances (TIDs) is developed. The model is based on the following assumptions: (1) TIDs are generated by acoustic-gravity waves (AGWs) and propagate as pressure waves; (2) time intervals between adjacent extrema of atmospheric pressure oscillations in a disturbance source are constant; (3) the pressure extrema propagate from the source up to~14 000 km at a constant horizontal velocity; (4) the velocity of each extremum is determined only by its number in a TID train. The model was validated using literature data on disturbances generated by about 20 surface and highaltitude nuclear explosions, two volcano explosions, one earthquake and by energetic proton precipitation events in the magnetospheric cusp of the northern hemisphere. Model tests using literature data show that the spatial and temporal TID periods may be predicted with an accuracy of 12%. Adequacy of the model was also confirmed by our observations collected using transionospheric sounding. The following TID parameters: amplitudes, horizontal spatial periods, and a TID front inclination angle in a vertical plane are increasing as the distance between an AGW and the excitation source is increasing. Diurnal and seasonal variability of the TID occurrence, defined as ratio of TID events to the total number of observations for the corresponding period, is not observed. However, the TID occurrence was growing from~50% in 1987 to~98% in 2010. The results of other studies asserting that the TID occurrence does not depend on the number of sunspots and magnetic activity are confirmed. The TID occurrence has doubled over the period from 1987 to 2010 indicating increasing solar activity which is not associated with sunspot numbers. The dynamics of spatial horizontal periods was studied in a range of 150-35 000 km.Key words. semi-empirical model -multiscale traveling ionospheric disturbances -horizontal velocity of extremum -nuclear explosion -volcano explosive eruption -energetic proton precipitation -magnetospheric cusp -transionospheric soundingdisturbance occurrence -sunspot number -magnetic activity

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Anomalies in Ionosonde Records Due to Travelling Ionospheric Disturbances

Abstract: Anomalies which frequently appear on ionosonde records of the F region during the passage of travelling disturbances are classified into four main types; and the diurnal and seasonal distribution of their occurrence is discussed.

Cited by 94 publications

References 2 publications

A study of atmospheric gravity waves and travelling ionospheric disturbances at equatorial latitudes

A study of atmospheric gravity waves and travelling ionospheric disturbances at equatorial latitudes

Vertical Characteristics of Travelling Ionospheric Disturbances

Model of traveling ionospheric disturbances

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