Magnetospheric line radiation observations at Halley, Antarctica

Rodger, Craig J.; Clilverd, Mark A.; Yearby, K. H.; Smith, A. J.

doi:10.1029/1999ja900153

Cited by 21 publications

(40 citation statements)

References 11 publications

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“…It was assumed that the MLR events consist of straight lines, i.e., that their frequency drift is constant. Although there have been MLR events reported for which this approximation completely fails [ Rodger et al , 1999], it typically works well for the MLR events observed by the DEMETER spacecraft. The fact that the individual lines forming the events were identified separately for the events in the survey mode and for the 37 events for which the burst mode data are available allows us to verify the validity of the applied procedure and to estimate the corresponding errors by comparing the two data sets.…”

Section: Discussionmentioning

confidence: 99%

Detailed properties of magnetospheric line radiation events observed by the DEMETER spacecraft

Němec¹,

Parrot²,

Santolı́k³

2012

J. Geophys. Res.

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[1] Magnetospheric line radiation (MLR) events are electromagnetic waves in the frequency range of about 1-8 kHz observed in the inner magnetosphere that, when presented in a form of frequency-time spectrograms, consist of several nearly parallel and almost equidistant intense lines. Although many observations of these events have been reported using ground-based instruments and a survey of a large data set based on low-altitude satellite data has been published recently, their origin remains unclear. We use low-altitude satellite observations of MLR events to study their detailed properties, namely, the frequency spacing of individual lines and their frequency drift. Since the satellite, unlike ground observatories, is moving, it allows us to analyze the properties of the events as a function of the position, especially L-shell. We show that neither the frequency spacing of the events nor their frequency drift varies significantly with the L-shell where the event is observed. Moreover, the frequency drift is generally positive. The individual lines forming the events cannot be explained as harmonics of the base frequency equal to the frequency spacing. We suggest that a possible generation mechanism might be an interaction between a wave of a carrier frequency and an additional wave with the frequency equal to the observed frequency spacing. We cannot exclude that it comes from human activity (power lines), but a magnetospheric origin is more likely. We suggest that the emissions might be guided by the plasmasphere inner boundary before they deviate to lower L-shells at altitudes of a few thousands of kilometers.Citation: Němec, F., M. Parrot, and O. Santolík (2012), Detailed properties of magnetospheric line radiation events observed by the DEMETER spacecraft,

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Section: Discussionmentioning

confidence: 99%

Detailed properties of magnetospheric line radiation events observed by the DEMETER spacecraft

Němec¹,

Parrot²,

Santolı́k³

2012

J. Geophys. Res.

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“… Rodger et al [1995] analyzed observations of MLR events by satellites International Satellite for Ionosphere Studies (ISIS) 1 and ISIS 2, finding no correlation between 50/60 Hz multiples and the frequency of the observed lines. Concerning the ground‐based observations, they concluded the same after analyzing the data measured at Halley station [ Rodger et al , 1999, 2000a, 2000b]. Němec et al [2006b] performed a systematic analysis of events with frequency spacing of 50/100 or 60/120 Hz (PLHR) and found that the frequency spacings of all the observed events correspond well to power system frequencies in possible regions of generation.…”

Section: Introductionmentioning

confidence: 92%

Comparison of magnetospheric line radiation and power line harmonic radiation: A systematic survey using the DEMETER spacecraft

et al. 2007

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Results of a systematic search for magnetospheric line radiation (MLR) observed by the DEMETER spacecraft since the beginning of the mission are presented. DEMETER is a French microsatellite (altitude of orbit about 700 km, inclination 98°) designed to study electromagnetic phenomena connected with seismic or man‐made activity that has been launched in June 2004. An automatic identification procedure of possible MLR events has been used in order to analyze a large amount of measured data. It is shown that there are two principally different classes of events: (1) events with frequency spacing of 50/100 or 60/120 Hz (power line harmonic radiation, PLHR) and (2) events with a different frequency spacing. The first class of events is generated by power systems on the Earth's surface, with frequency spacing well corresponding to the fundamental frequency of the radiating power system. On the other hand, the second class is most probably generated in a completely natural way. All the detected events are thoroughly analyzed, and different properties of the two classes are statistically demonstrated. We have found that PLHR events occur both during low and high geomagnetic activity, with none of them significantly preferred. However, MLR events occur more frequently under disturbed conditions. Most of the PLHR events are observed at frequencies of 2 to 3 kHz. On the other hand, MLR events most frequently occur at frequencies below 2 kHz and seem to be more intense than PLHR. Additionally, PLHR events are more intense during the night than during the day, and there is about the same number of PLHR events observed during the day and during the night. On the contrary, no dependence of MLR peak intensities on magnetic local time was found, and more MLR events were observed during the day than during the night, although this difference is not statistically very significant. Finally, there is a group of MLR events with characteristics corresponding to the previous spacecraft observations of equatorial noise.

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“…In their study of ISIS2 data, Rodger et al (1995) observed MLR and did not find a frequency correlation with 50 or 60 Hz, or multiples. It was the same for observations of MLR at Halley Bay (Rodger et al, 1999(Rodger et al, , 2000a(Rodger et al, , 2000b. In a review paper concerning observations of PLHR and MLR emissions by ground-based experiments and satellites, Bullough (1995) discussed about the possibility that MLR are due to PLHR.…”

Section: Many Observations Show That the Linesmentioning

confidence: 99%

ELF magnetospheric lines observed by DEMETER

et al. 2005

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Abstract. The influence of man-made activity on the ionosphere may be very important. The effects induced by the Power Line Harmonic Radiation (PLHR) may change the natural wave activity and/or the ionospheric plasma components. One goal of the ionospheric satellite DEMETER launched in June 2004 is to study the ionospheric perturbations which could be related to this anthropogenic activity. As the first step, the paper presents Tram Lines (TL) which have been observed on board DEMETER with frequency intervals close to 50 Hz or 16 Hz 2/3 (the current frequency of the railways). When it is observable the frequency drift of these TL is very slow. It is shown that these events occur during periods of strong or moderate magnetic activity. A wave propagation analysis indicates that the TL observed below the low cutoff frequency of the hiss which is simultaneously present are coming from a region below the satellite. The conclusion is that these TL observed by DEMETER are produced by PLHR or radiation of railways lines.

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Magnetospheric line radiation observations at Halley, Antarctica

Cited by 21 publications

References 11 publications

Detailed properties of magnetospheric line radiation events observed by the DEMETER spacecraft

Detailed properties of magnetospheric line radiation events observed by the DEMETER spacecraft

Comparison of magnetospheric line radiation and power line harmonic radiation: A systematic survey using the DEMETER spacecraft

ELF magnetospheric lines observed by DEMETER

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