Is the plasmapause a preferred source region of electromagnetic ion cyclotron waves in the magnetosphere?

Fraser, B. J.; Nguyen, Tien Son

doi:10.1016/s1364-6826(00)00225-x

Cited by 218 publications

(364 citation statements)

References 99 publications

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“…The waves occurred in the preferred EMIC wave excitation region, i.e., near the plasmapause [e.g., Fraser and Nguyen, 2001], and the waves are driven by energetic H + in so-called nose-like spectral structures. This H + population resides near the ion injection boundary on the nightside, specifically,~1-2 h before the local midnight.…”

Section: Discussionmentioning

confidence: 99%

Excitation of EMIC waves detected by the Van Allen Probes on 28 April 2013

Zhang

Saikin

Kistler

et al. 2014

Geophysical Research Letters

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We report the wave observations, associated plasma measurements, and linear theory testing of electromagnetic ion cyclotron (EMIC) wave events observed by the Van Allen Probes on 28 April 2013. The wave events are detected in their generation regions as three individual events in two consecutive orbits of Van Allen Probe-A, while the other spacecraft, B, does not detect any significant EMIC wave activity during this period. Three overlapping H + populations are observed around the plasmapause when the waves are excited. The difference between the observational EMIC wave growth parameter (Σ h ) and the theoretical EMIC instability parameter (S h ) is significantly raised, on average, to 0.10 ± 0.01, 0.15 ± 0.02, and 0.07 ± 0.02 during the three wave events, respectively. On Van Allen Probe-B, this difference never exceeds 0. Compared to linear theory (Σ h > S h ), the waves are only excited for elevated thresholds.

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Section: Discussionmentioning

confidence: 99%

Excitation of EMIC waves detected by the Van Allen Probes on 28 April 2013

Zhang

Saikin

Kistler

et al. 2014

Geophysical Research Letters

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“…Propagating at frequencies below the proton gyrofrequency (f cp ), electromagnetic ion cyclotron (EMIC) waves have been extensively observed in the inner magnetosphere in the frequency range 0.1-5.0 Hz, i.e., the ultralow frequency Pc1-2 band [e.g., Anderson et al, 1992aAnderson et al, , 1992bFraser et al, 1992Fraser et al, , 1996Fraser and Nguyen, 2001;Meredith et al, 2003Meredith et al, , 2014Zhang et al, 2014]. Partially controlled by the ion composition and anisotropy [e.g., Kozyra et al, 1984;Horne and Thorne, 1994] and by the location with respect to the plasmapause [Fraser and Nguyen, 2001], EMIC waves can be generated in three distinct frequency bands below the hydrogen (H + ), helium (He + ), and oxygen (O + ) ion gyrofrequencies.…”

Section: Introductionmentioning

confidence: 99%

“…Partially controlled by the ion composition and anisotropy [e.g., Kozyra et al, 1984;Horne and Thorne, 1994] and by the location with respect to the plasmapause [Fraser and Nguyen, 2001], EMIC waves can be generated in three distinct frequency bands below the hydrogen (H + ), helium (He + ), and oxygen (O + ) ion gyrofrequencies. Compared to the frequently measured H + -band and He + -band EMIC waves, O + -band EMIC waves are rarely observed but were recently reported in the outer plasmasphere at L = 2-5 from the Van Allen Probes Electric and Magnetic Field Instrument Suite and Integrated Science and Electric Fields and Waves data [Yu et al, 2015].…”

Section: Introductionmentioning

confidence: 99%

Resonant scattering of outer zone relativistic electrons by multiband EMIC waves and resultant electron loss time scales

et al. 2015

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To improve our understanding of the role of electromagnetic ion cyclotron (EMIC) waves in radiation belt electron dynamics, we perform a comprehensive analysis of EMIC wave‐induced resonant scattering of outer zone relativistic (>0.5 MeV) electrons and resultant electron loss time scales with respect to EMIC wave band, L shell, and wave normal angle model. The results demonstrate that while H+‐band EMIC waves dominate the scattering losses of ~1–4 MeV outer zone relativistic electrons, it is He+‐band and O+‐band waves that prevail over the pitch angle diffusion of ultrarelativistic electrons at higher energies. Given the wave amplitude, EMIC waves at higher L shells tend to resonantly interact with a larger population of outer zone relativistic electrons and drive their pitch angle scattering more efficiently. Obliquity of EMIC waves can reduce the efficiency of wave‐induced relativistic electron pitch angle scattering. Compared to the frequently adopted parallel or quasi‐parallel model, use of the latitudinally varying wave normal angle model produces the largest decrease in H+‐band EMIC wave scattering rates at pitch angles < ~40° for electrons > ~5 MeV. At a representative nominal amplitude of 1 nT, EMIC wave scattering produces the equilibrium state (i.e., the lowest normal mode under which electrons at the same energy but different pitch angles decay exponentially on the same time scale) of outer belt relativistic electrons within several to tens of minutes and the following exponential decay extending to higher pitch angles on time scales from <1 min to ~1 h. The electron loss cone can be either empty as a result of the weak diffusion or heavily/fully filled due to approaching the strong diffusion limit, while the trapped electron population at high pitch angles close to 90° remains intact because of no resonant scattering. In this manner, EMIC wave scattering has the potential to deepen the anisotropic distribution of outer zone relativistic electrons by reshaping their pitch angle profiles to “top‐hat.” Overall, H+‐band and He+‐band EMIC waves are most efficient in producing the pitch angle scattering loss of relativistic electrons at ~1–2 MeV. In contrast, the presence of O+‐band EMIC waves, while at a smaller occurrence rate, can dominate the scattering loss of 5–10 MeV electrons in the entire region of the outer zone, which should be considered in future modeling of the outer zone relativistic electron dynamics.

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“…As discussed by Anderson et al (1992a) and Fraser and Nguyen (2001), early theoretical considerations favored the region just inside the plasmapause as the most likely location for the production of EMIC waves. This outer region of the plasmasphere would overlap with the ring current population (which Correspondence to: R. E. Denton (richard.denton@dartmouth.edu) drives the instability), yet would have small group velocity v g ∼ V A ∼ ρ −1/2 , where V A is the Alfvén speed and ρ is the mass density.…”

Section: Introductionmentioning

confidence: 99%

“…They explain this increase with a simple magnetospheric model in which the decrease in magnetic field B (dipole model) at large L contributes significantly to a decrease in v g ∼ V A ∼ B. Fraser and Nguyen (2001) studied Pc 1 spatial occurrance using the CRRES satellite, which includes electron density measurements, allowing the plasmapause position to be identified. They found a slight enhancement of Pc 1 wave power at the plasmapause, but concluded that Pc 1 occurrence does not maximize at the plasmapause; instead it predominates in the afternoon and increases with radial distance, consistent with the results of Anderson et al (1992a).…”

Section: Introductionmentioning

confidence: 99%

Location of Pc 1–2 waves relative to the magnetopause

2002

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Abstract. Spacecraft-borne and ground-based magnetometers frequently detect magnetospheric micropulsations in the period range 0.2-10 s, termed Pc 1-2, and attributed to electromagnetic ion cyclotron waves driven by temperature anisotropy (T ⊥ > T ). Previous surveys of Pc 1 occurrence locations have been limited to L ≤ 9. We present AMPTE/IRM observations of the distribution of Pc 1 waves out to the magnetopause, for a limited region of MLT = 10-14. The probability of wave occurrence P wav is large (> 0.15) between L = 7-12, peaking at L = 8-10 (P wav ∼ 0.25). When the L-value is normalized to the magnetopause position L mp , however, the highest probabilities of Pc 1 wave occurrence are close to the magnetopause, with P wav ∼ 0.25 for L norm ≡ L/L mp = 0.8-1.0. These results are consistent with increased convective growth rate at large L and with the greater effect of magnetosphere compression close to the magnetopause. On the other hand, we only directly observe magnetic field compression for at most about 25% of the wave events.

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Is the plasmapause a preferred source region of electromagnetic ion cyclotron waves in the magnetosphere?

Cited by 218 publications

References 99 publications

Excitation of EMIC waves detected by the Van Allen Probes on 28 April 2013

Excitation of EMIC waves detected by the Van Allen Probes on 28 April 2013

Resonant scattering of outer zone relativistic electrons by multiband EMIC waves and resultant electron loss time scales

Location of Pc 1–2 waves relative to the magnetopause

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