Reply [to “Comment on ‘Propagation characteristics of low‐latitude whistlers’ by T. Ondoh, M. Kotaki, T. Murakami, S. Watanabe, and Y. Nakamura”]

Ondoh, T.; Kotaki, M.; Aikyo, K.; Nakamura, Y.

doi:10.1029/ja085ia04p01801

Cited by 2 publications

(2 citation statements)

References 5 publications

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“…ACE and Wind observations of the solar wind speed at the time of the observations reveal a flow of the order of approximately 600 km/s (Fig. 17): typical solar wind speeds are of the order of a few hundred km/s (Asai et al, 1998;Ondoh & Marubashi, 2001).…”

Section: Discussionmentioning

confidence: 99%

Towards the possibility to combine LOFAR and GNSS measurements to sense ionospheric irregularities

Flisek,

Forte,

Fallows

et al. 2023

J. Space Weather Space Clim.

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Inhomogeneities within the ionospheric plasma density affect trans-ionospheric radio signals, causing radio wave scintillation in the amplitude and phase of the signals. The amount of scintillation induced by ionospheric irregularities typically decreases with the radio wave frequency. As the ionosphere affects a variety of technological systems (e.g., civil aviation, financial operations) as well as low-frequency radio astronomy observations, it is important to detect and monitor ionospheric effects with higher accuracy than currently available. Here, a novel methodology for the detection and characterization of ionospheric irregularities is established on the basis of LOFAR (Low-Frequency Array) scintillation measurements at Very High Frequency (VHF) that take into account the lack of ergodicity in the intensity fluctuations induced by scintillation. The methodology estimates the S4 scintillation index originating from irregularities with spatial scales in the inertial sub-range of electron density fluctuations in the ionosphere. The methodology is illustrated by means of observations that were collected through the Polish LOFAR stations located in Bałdy, Borowiec and Łazy: its validation was carried out by comparing LOFAR VHF scintillation observations with independent Global Navigation Satellite Systems (GNSS) observations that were collected through a high-rate receiver located near the LOFAR station in Bałdy as well as through geodetic receivers from the Polish ASG-EUPOS network. Two case studies are presented: 31 March 2017 and 28 September 2017. The comparison between LOFAR S4 observations and independent ionospheric measurements of both scintillation and rate of change of Total Electron Content (TEC) from GNSS reveals that the sensitivity of LOFAR and GNSS to ionospheric structures is different as a consequence of the frequency dependency of radio wave scintillation. Furthermore, it can be noticed that observations of LOFAR VHF scintillation can be utilised to detect plasma structures forming in the mid-latitude ionosphere, including electron density gradients occurring over spatial scales that are not necessarily detected through traditional GNSS measurements: the detection of all spatial scales is important for correct monitoring and modelling of ionospheric processes. Hence, the different sensitivity of LOFAR to ionospheric structures, in addition to traditional GNSS ionospheric measurements, allows us to expand the knowledge of ionospheric processes.

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Section: Discussionmentioning

confidence: 99%

Towards the possibility to combine LOFAR and GNSS measurements to sense ionospheric irregularities

Flisek,

Forte,

Fallows

et al. 2023

J. Space Weather Space Clim.

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“…However, their separate consideration sometimes results in considerable simplification of the problem, which is necessary for a better understanding of the physical background of the process. A number of generation mechanism both incoherent (Cerenkov radiation, cyclotron radiation, Doppler-shifted cyclotron radiation) and coherent (Cerenkov instability, cyclotron instability, traveling wave-tube mechanism) have been proposed from time to time to explain the observed hiss emission intensity at ground stations as well as on-board rockets and satellites [13][14][15][16][17][18][19][20][21][22]. In all the theoretical treatments of instability mechanism it was assumed that all the waves are amplified around the magnetic equator while propagating back and forth along the geomagnetic field lines, till their intensity reaches the observed intensity [4,[23][24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

Hiss emissions during quiet and disturbed periods

Singh

2002

Pramana - J Phys

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The characteristic features of VLF hiss emissions during quiet and disturbed conditions observed at ground stations and on-board satellites are summarized. The increased intensity of the hiss emissions during magnetic storm period is explained by considering the enhanced flux of energetic electrons during magnetic storm period. The generation and propagation mechanism of VLF hiss are also briefly discussed.

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Reply [to “Comment on ‘Propagation characteristics of low‐latitude whistlers’ by T. Ondoh, M. Kotaki, T. Murakami, S. Watanabe, and Y. Nakamura”]

Cited by 2 publications

References 5 publications

Towards the possibility to combine LOFAR and GNSS measurements to sense ionospheric irregularities

Towards the possibility to combine LOFAR and GNSS measurements to sense ionospheric irregularities

Hiss emissions during quiet and disturbed periods

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