Magnetospheric ducting of low-latitude whistlers as deduced from the rocket measurement of their wave normal directions

Hayakawa, Masashi; Iwai, Akira

doi:10.1016/0021-9169(75)90192-0

Cited by 26 publications

(9 citation statements)

References 11 publications

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“…Consequently, there has remained some doubt that low‐latitude whistlers even can exist. Some researchers have proposed a nonducted mode of propagation for low‐latitude whistlers [ James , ; Ceisier , ; Singh and Tantry , ; Hayakawa and Iwai , ; Tanaka and Cairo , ; Kumar et al , ], while others have suggested ducted propagation based on ground data and direction‐finding measurements [ Somayajulu and Tantry , ; Hayakawa et al , , ; Ohta et al , ; Singh et al , ].…”

Section: Introductionmentioning

confidence: 99%

Very low latitude (L = 1.08) whistlers and correlation with lightning activity

Gokani

Singh²,

Cohen

et al. 2015

JGR Space Physics

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We present analysis of more than 2000 lightning‐generated whistlers recorded at a low‐latitude station, located at Allahabad (geographic latitude, 25.40°N; geographic longitude, 81.93°E; L = 1.081), India, during December 2010 to November 2011. The main focus of this work is on the correlation between observed low‐latitude whistlers and lightning activity detected by the World‐Wide Lightning Location Network near the conjugate point (geography 9.87°S, 83.59°E) of Allahabad. Whistler occurrence is higher in the postmidnight period as compared to the premidnight period. Whistlers were observed in the daytime only on 2 days that too before 8:30 LT (morning). Seasonally, occurrence is maximum during winter months, which is due to more lightning activity in the conjugate region and favorable ionospheric conditions. About 63% of whistlers were correlated with lightning strokes in the vicinity of the conjugate point within spatial extent of 1000 km (conjugate area). Most (about 53%) whistlers were found to be associated with lightning strokes that were offset to the southeast of the conjugate point. The results indicate that an energy range of 7.5–17.5 kJ of lightning strokes generate most of whistlers at this station. The L shell calculations show that propagation paths of the observed whistlers were embedded in the topside ionosphere. Based on these results we suggest a possibility of ducted mode of propagation even for such very low latitude whistlers.

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Section: Introductionmentioning

confidence: 99%

Very low latitude (L = 1.08) whistlers and correlation with lightning activity

Gokani

Singh²,

Cohen

et al. 2015

JGR Space Physics

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“…For example, we can notice two bands of emission frequency for LT 0500 and 0600; one is 1-3 kHz in the ELF range, and the other is in the VLF range between 3 and 5 kHz. The latter VLF emissions have been discussed in detail by Hayakawa et al [1975] and Tanaka et al [1974]. It does not seem from Figure 5 that the emission frequency of the ELF hiss observed exhibits an apparent dependence either on Kp index or on LT.…”

Section: Emission Frequencymentioning

confidence: 78%

“…To our knowledge, ground-based measurements have not been reported for plasmaspheric ELF hiss, and the measurements at low-latitude ground stations would provide invaluable additional information on the hiss generation which is complementary to the previous satellite measurements. The observations are made at our Moshiri Observatory (geomagnetic latitude 35øN; L--1.59) [Hayakawa et al, 1975], and the morphological features of ELF hiss are derived from synoptic magnetic tape recordings made during four years; also a recent measurement of the polarization of ELF hiss at Moshiri is presented. These morphological properties as deduced in the present paper are compared with the previous ionospheric and magnetospheric in-situ measure- ments and are used to discuss the generation and propagation mechanism of plasmaspheric ELF hiss.…”

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confidence: 99%

Morphological characteristics and the polarization of plasmaspheric ELF hiss observed at Moshiri (L ∼ 1.6)

Hayakawa¹,

Tanaka²,

Okada³

1985

J. Geophys. Res.

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Morphological characteristics (local time and Kp dependences and emission frequency) of ground‐based plasmaspheric ELF hiss have been examined on the basis of the magnetic tape records observed at Moshiri (geomagnetic latitude 35°N; L = 1.6) during the four‐year period from January 1973 to December 1976. About 160 hiss events have been identified during the relevant period, and they are found to be observed during severely disturbed periods (Kp = 4–7) and during daytime. The ground‐based morphological properties including the above results are shown to support the previous in‐situ observational results. The most important contribution of the present paper is the information on the relative location of the ionospheric exit region of the hiss with respect to the observing station. About one fifth of the ELF hiss events are found to be cut off at the low frequency coincident with the cut off frequency of the first‐order mode of the earth‐ionosphere waveguide mode propagation, indicating that the ionospheric exit point of the hiss is located far away from the observing station and that the hiss has propagated over a considerable distance in the waveguide. One third of the emission events did not exhibit any effect of the waveguide propagation, suggesting that they have penetrated the ionosphere close to the station, and this is confirmed by the polarization measurement for such an event. The present observational results from a low‐latitude ground station are clearly complementary to the in‐situ observations and are used to elucidate the generation mechanism of plasmaspheric ELF hiss and its subseuequent propagation in the magnetosphere and ionosphere.

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“…Hayakawa and Ohtsu [1973] have succeeded in interpreting the results for both time intervals obtained with simultaneous measurement of a multistation network (Kagoshima, Sakushima, and Moshiri (35øN)) in terms of ducted propagation and a suitable horizontal ionospheric gradient at the duct exit. Later rocket measurement of wave normal direction for daytime whistlers [Iwai et al, 1974] has yielded that the wave normal direction is distributed around the magnetic field with an upper cutoff indicative of the trapping cone for ducted propagati6n [Hayakawa and Iwai, 1975]. Hayakawa and Tanaka [1973] have found hybrid and echo train whistlers at Sakushima and implied that they are attributable to ducted propagation.…”

Section: Introductionmentioning

confidence: 99%

Goniometric direction finding for low‐latitude whistlers and their propagation mechanism

Hayakawa¹,

Tanaka²,

Okada³

et al. 1981

J. Geophys. Res.

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In order to study the propagation mechanism of low-latitude whistlers, their ionospheric exit points have been determined by a triangulation of the goniometer-polarimeter systems at the two stations of Kagoshima (geomagnetic coordinates 20ø24'N, 197ø53'E; L --1.22) and Ohgata (22ø06'N, 199ø5 I'E; L --1.25), supplemented by the routine observation at Sakushima (24ø08'N, 203ø19'E; L --1.28). Detailed analyses were made for January 23, 1978, when the whistler activity was most enhanced during one month's measurement. The difference in temporal variations of the occurrence rate at the three stations and the temporal variation of the single-valued dispersion enabled us to subdivide the daytime whistlers into three characteristic time intervals and the nighttime ones into two intervals. The characteristics during the whole intervals were found to be satisfactorily accounted for in terms of ducted propagation. The azimuth measurements have indicated that there is present a discontinuity in the characteristics between each two intervals, indicative of the different duct group for different time intervals; in other words, indicative of the identity and persistency of ducts for each period. Then we obtained the 'apparent lifetime' of ducts of 1-2 hours. During the last interval for the daytime whistlers, a few ducts were found to be aligned on a certain latitude, which showed a temporal movement, or first increased and then decreased. The simultaneous presence of a few ducts at the same latitude is also seen at night.A.

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Magnetospheric ducting of low-latitude whistlers as deduced from the rocket measurement of their wave normal directions

Cited by 26 publications

References 11 publications

Very low latitude (L = 1.08) whistlers and correlation with lightning activity

Very low latitude (L = 1.08) whistlers and correlation with lightning activity

Morphological characteristics and the polarization of plasmaspheric ELF hiss observed at Moshiri (L ∼ 1.6)

Goniometric direction finding for low‐latitude whistlers and their propagation mechanism

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