Magnetospheric line radiation: 6.5 years of observations by the DEMETER spacecraft

Bezděková, B.; Němec, F.; Parrot, M.; Santolı́k, O.; Krupařová, O.

doi:10.1002/2015ja021246

Cited by 9 publications

(21 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There is, however, a noticeable interval at geomagnetic longitudes between about 0° and 100°, where both the background wave intensities and QP occurrence rate during the northern winter remain low. The low QP occurrence rate obtained by DEMETER in this longitudinal interval (Hayosh et al, ) as well as apparently analogous low occurrence rate of MLR events at these longitudes (Němec et al, ) was formerly attributed to the precipitation of energetic particles in the drift loss cone and its possible negative effects on the event generation (Bezděková et al, ). However, if this was indeed the case, the QP occurrence rate at these longitudes would be lower also on the Van Allen Probes, which is not observed.…”

Section: Discussionmentioning

confidence: 69%

Whistler Mode Quasiperiodic Emissions: Contrasting Van Allen Probes and DEMETER Occurrence Rates

et al. 2020

Self Cite

View full text Add to dashboard Cite

Quasiperiodic emissions are magnetospheric whistler mode waves at frequencies between about 0.5 and 4 kHz which exhibit a nearly periodic time modulation of the wave intensity. We use large data sets of events observed by the Van Allen Probes in the equatorial region at larger radial distances and by the low-altitude DEMETER spacecraft. While Van Allen Probes observe the events at all local times and longitudes, DEMETER observations are limited nearly exclusively to the daytime and significantly less frequent at the longitudes of the South Atlantic Anomaly. Further, while the events observed by Van Allen Probes are smoothly distributed over seasons with only mild maxima in spring/autumn, DEMETER occurrence rate has a single pronounced minimum in July. The apparent inconsistency is explained by considering a nondipolar Earth's magnetic field and significant background wave intensities which in these cases prevent the quasiperiodic events from being identified in DEMETER data.While according to both ground-based (Engebretson et al., 2004;Morrison et al., 1994;Smith et al., 1998) and low-altitude satellite (Hayosh et al., 2014) surveys the emissions appear to be primarily daytime phenomenon, satellite surveys at larger radial distances revealed the emissions at principally all local times, with a slight preference for the dusk sector. In the present study, we contrast the occurrence rates of QP emissions as observed by the Van Allen Probes at large radial distances and the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) spacecraft at low radial distances, and we attempt to explain the obtained discrepancies. The data set is introduced in section 2. The obtained results are presented in section 3. They are discussed and briefly summarized in section 4. We thank the engineers from CNES and scientific laboratories (CBK, IRAP, LPC2E, LPP, and SSD of ESTEC) who largely contributed to the success of the DEMETER mission. DEMETER data are accessible from the https:// sipad-cdpp.cnes.fr website. Van Allen

show abstract

Section: Discussionmentioning

confidence: 69%

Whistler Mode Quasiperiodic Emissions: Contrasting Van Allen Probes and DEMETER Occurrence Rates

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…Additionally, although the events are at times observed simultaneously or at least during the same half‐orbits, this rather appears to be a coincidence than a systematic feature. Also, while DEMETER observes QP emissions nearly exclusively during the daytime (Hayosh et al, ), daytime observations of MLR are only by a factor of about 1.7 more frequent than nighttime MLR observations (Bezděková et al, ). All these results suggest that although a possible relation between MLR and QP events would be tempting, they are most likely not related in any identifiable way.…”

Section: Discussionmentioning

confidence: 99%

“…Altogether, 1,230 MLR events were identified in the DEMETER data set (Bezděková et al, ). These events were detected in 1054 half orbits (out of 57,574 half orbits in total).…”

Section: Data Setmentioning

confidence: 99%

“…The frequency drift of the events was shown to be usually positive and neither the frequency drift nor the frequency spacing were related to the L‐shell where the events were observed. The analysis of MLR events observed during the entire DEMETER mission including 1,230 MLR events was reported by Bezděková et al (). This study shows that the events are observed more likely between November and April, their occurrence is statistically related to specific variations of solar wind parameters, and it is significantly lower at geomagnetic longitudes corresponding to the South Atlantic Anomaly, which indicates the importance of drift loss cone electrons for the wave occurrence.…”

Section: Introductionmentioning

confidence: 96%

See 1 more Smart Citation

Dependence of Properties of Magnetospheric Line Radiation and Quasiperiodic Emissions on Solar Wind Parameters and Geomagnetic Activity

et al. 2019

Self Cite

View full text Add to dashboard Cite

Very low frequency electromagnetic waves in the inner magnetosphere sometimes exhibit either frequency or time modulation. These phenomena are called, respectively, magnetospheric line radiation (MLR) and quasiperiodic (QP) emissions. Data from Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions spacecraft were used to analyze their properties, such as MLR frequency spacing, QP modulation period, and QP intensity as functions of geomagnetic activity and solar wind parameters. Altogether, 1,152 MLR events and 2,172 QP emissions were analyzed. It is shown that the influence of the analyzed parameters on QP emissions is different for QP events with modulation periods shorter/longer than 20 s. While the properties of QP events with long modulation periods are significantly related to the geomagnetic activity and solar wind parameters, no such dependences are observed for events with short modulation periods. This suggests that there might be two types of QP emissions generated by two different mechanisms. It is further shown that there seems to be no relation between the properties of QP and MLR events observed at the same times. Finally, the event properties do not seem to be related to the whistler occurrence rate.

show abstract

“…The remaining events, whose frequency spacing does not correspond to the base frequency of electric power systems, are usually called magnetospheric line radiation (MLR). Although their basic properties are rather well known [ Němec et al , , ; Bezděková et al , ], their generation mechanism remains unclear. Such emissions were, nevertheless, observed also on the ground [ Rodger et al , , ], and their origin is likely natural [ Rodger et al , ].…”

Section: Introductionmentioning

confidence: 99%

Line radiation events induced by very low frequency transmitters observed by the DEMETER spacecraft

et al. 2017

Self Cite

View full text Add to dashboard Cite

Electromagnetic wave data measured by the low‐altitude Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) spacecraft sometimes exhibit intense emissions at discrete, harmonically spaced frequencies. We present a comprehensive analysis of this type of phenomenon, and we demonstrate that it is caused by very low frequency (VLF) transmitters in Europe. All available data were investigated for a possible presence of the events. Altogether, 87 events were identified, occurring exclusively during the nighttime. The occurrence of the events does not show any clear relation to the AE and Dst geomagnetic activity indices. The events are clearly localized, occurring either close to Great Britain or in the vicinity of its geomagnetically conjugated region. The frequency spectra of the events typically consist of up to four spectral peaks at multiples of about 1.3 kHz. Additional weaker spectral peaks at frequencies of about 1.9 kHz and 3.2 kHz are occasionally present. The events observed in the Northern Hemisphere tend to have larger‐frequency bandwidths than the events observed in the Southern Hemisphere. The occurrence of these events is correlated with the simultaneous detection of signals from VLF transmitters. A bicoherence analysis is employed to demonstrate that wave‐wave coupling takes place. Finally, it is shown that the occurrence of the events is associated with a significantly increased precipitation of energetic electrons in a wide range of energies.

show abstract

Magnetospheric line radiation: 6.5 years of observations by the DEMETER spacecraft

Cited by 9 publications

References 38 publications

Whistler Mode Quasiperiodic Emissions: Contrasting Van Allen Probes and DEMETER Occurrence Rates

Whistler Mode Quasiperiodic Emissions: Contrasting Van Allen Probes and DEMETER Occurrence Rates

Dependence of Properties of Magnetospheric Line Radiation and Quasiperiodic Emissions on Solar Wind Parameters and Geomagnetic Activity

Line radiation events induced by very low frequency transmitters observed by the DEMETER spacecraft

Contact Info

Product

Resources

About