Detection of ultralow‐frequency cavity modes using spacecraft data

Waters, C. L.; Takahashi, Kazue; Lee, Dong Hun; Anderson, B. J.

doi:10.1029/2001ja000224

Cited by 55 publications

(98 citation statements)

References 81 publications

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“…We should note, however, that observational evidence for global fast mode cavity resonance or waveguide mode is still very limited (Samson and Rankin, 1994;Waters et al, 2002).…”

Section: Discussionmentioning

confidence: 99%

Empirically modelled Pc3 activity based on solar wind parameters

et al. 2010

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Abstract. It is known that under certain solar wind (SW)/interplanetary magnetic field (IMF) conditions (e.g. high SW speed, low cone angle) the occurrence of groundlevel Pc3-4 pulsations is more likely. In this paper we demonstrate that in the event of anomalously low SW particle density, Pc3 activity is extremely low regardless of otherwise favourable SW speed and cone angle. We re-investigate the SW control of Pc3 pulsation activity through a statistical analysis and two empirical models with emphasis on the influence of SW density on Pc3 activity. We utilise SW and IMF measurements from the OMNI project and groundbased magnetometer measurements from the MM100 array to relate SW and IMF measurements to the occurrence of Pc3 activity. Multiple linear regression and artificial neural network models are used in iterative processes in order to identify sets of SW-based input parameters, which optimally reproduce a set of Pc3 activity data. The inclusion of SW density in the parameter set significantly improves the models. Not only the density itself, but other density related parameters, such as the dynamic pressure of the SW, or the standoff distance of the magnetopause work equally well in the model. The disappearance of Pc3s during lowdensity events can have at least four reasons according to the existing upstream wave theory: 1. Pausing the ion-cyclotron resonance that generates the upstream ultra low frequency waves in the absence of protons, 2. Weakening of the bow shock that implies less efficient reflection, 3. The SW becomes sub-Alfvénic and hence it is not able to sweep back the waves propagating upstream with the Alfvén-speed, and 4. The increase of the standoff distance of the magnetopause (and of the bow shock). Although the models cannot account Correspondence to: B. Heilig (heilig@elgi.hu) for the lack of Pc3s during intervals when the SW density is extremely low, the resulting sets of optimal model inputs support the generation of mid latitude Pc3 activity predominantly through upstream waves.

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“…We should note, however, that observational evidence for global fast mode cavity resonance or waveguide mode is still very limited (Samson and Rankin, 1994;Waters et al, 2002).…”

Section: Discussionmentioning

confidence: 99%

Empirically modelled Pc3 activity based on solar wind parameters

et al. 2010

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“…Russel and Hoppe, 1981;Yumoto et al, 1984;Takahashi et al, 1984;Engebretson et al, 1986Engebretson et al, , 1987. Contrarily, a number of investigations using numerical modelling have suggested that cavity or waveguide modes in the magnetosphere are the drivers of the FLRs (Allan et al, 1985;Samson et al, 1995;Waters et al, 2000). A few studies have also presented results in support of the observation of these fast mode resonances (FMRs) in ground-based data (Samson et al, 1995;Menk et al, 2000).…”

Section: Introductionmentioning

confidence: 60%

“…A few studies have also presented results in support of the observation of these fast mode resonances (FMRs) in ground-based data (Samson et al, 1995;Menk et al, 2000). However, direct observational evidence for FMRs in satellite data is sparse (Waters et al, 2002). Verõ et al (1998) investigated the relationship between FLRs and UWs but alluded to the possible presence of signals from another unidentified source.…”

Section: Introductionmentioning

confidence: 97%

“…It is also commonly suggested that the energy source which drives the FLRs are upstream waves (UWs) generated in the Earth's foreshock (e.g. Russel and Hoppe, 1981;Yumoto et al, 1984;Takahashi et al, 1984;Engebretson et al, 1986Engebretson et al, , 1987. Contrarily, a number of investigations using numerical modelling have suggested that cavity or waveguide modes in the magnetosphere are the drivers of the FLRs (Allan et al, 1985;Samson et al, 1995;Waters et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

“…Waters et al, 1991Waters et al, , 1994Verõ et al, 1998;Vellante et al, 2004;Ndiitwani and Sutcliffe, 2009). It is also commonly suggested that the energy source which drives the FLRs are upstream waves (UWs) generated in the Earth's foreshock (e.g.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Spectral structure of Pc3–4 pulsations: possible signatures of cavity modes

Sutcliffe

Heilig²,

Lotz³

2013

Ann. Geophys.

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In this study we investigate the spectral structure of Pc3–4 pulsations observed at low and midlatitudes. For this purpose, ground-based magnetometer data recorded at the MM100 stations in Europe and at two low latitude stations in South Africa were used. In addition, fluxgate magnetometer data from the CHAMP (CHAllenging Minisatellite Payload) low Earth orbit satellite were used. The results of our analysis suggest that at least three mechanisms contribute to the spectral content of Pc3–4 pulsations typically observed at these latitudes. We confirm that a typical Pc3–4 pulsation contains a field line resonance (FLR) contribution, with latitude dependent frequency, and an upstream wave (UW) contribution, with frequency proportional to the IMF (interplanetary magnetic field) magnitude B_IMF. Besides the FLR and UW contributions, the Pc3–4 pulsations consistently contain signals at other frequencies that are independent of latitude and B_IMF. We suggest that the most likely explanation for these additional frequency contributions is that they are fast mode resonances (FMRs) related to cavity, waveguide, or virtual modes. Although the above contributions to the pulsation spectral structure have been reported previously, we believe that this is the first time where evidence is presented showing that they are all present simultaneously in both ground-based and satellite data

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Enhancement of ultralow frequency wave amplitudes at the plasmapause

Clausen

Glaßmeier

2014

JGR Space Physics

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We present measurements of ultralow frequency (ULF) wave amplitudes measured by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes while crossing the plasmapause. During one crossing on 24 June 2007 which we study in detail, all three probes of which data that were obtained show an increase in the ULF compressional wave amplitude between 10 and 50 mHz by about 30%. These results are confirmed by a statistical study that examines the ULF compressional wave amplitude in the same frequency range averaged over 132 sharp plasmapause crossings between June 2007 and December 2007 made by THEMIS C, D, and E. Sharp plasmapause crossings are defined as those where the density increases by more than a factor of 50 over a spatial scale of 500 km. We find that assuming that the plasmapause can be approximated by a tangential MHD discontinuity, a ULF wave amplitude enhancement of 30% is in good agreement with theoretical transmission coefficient calculations if the plasma density increases from about 4 cm −3 on the magnetospheric trough side to about 540 cm −3 on the plasmaspheric side while simultaneously the magnetic field magnitude increases from 250 nT to 350 nT. These results might have important implications for the detection of global fast modes by satellites as their amplitude is hence expected to be higher inside the plasmasphere than outside.

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Detection of ultralow‐frequency cavity modes using spacecraft data

Cited by 55 publications

References 81 publications

Empirically modelled Pc3 activity based on solar wind parameters

Empirically modelled Pc3 activity based on solar wind parameters

Spectral structure of Pc3–4 pulsations: possible signatures of cavity modes

Enhancement of ultralow frequency wave amplitudes at the plasmapause

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