Pc1 wave generation by sudden impulses

Olson, John V.; Lee, L. C.

doi:10.1016/0032-0633(83)90079-x

Cited by 145 publications

(155 citation statements)

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“…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). Olson and Lee (1983) reviewed ground magnetometer observations which connect the occurrence of Pc 1 waves with sudden compressions of the magnetosphere (or sudden impulse SI). From double adiabatic theory, they show that compressions lead to an increase in the hot particle anisotropy A ≡ (T ⊥ − T )/T − 1, which in turn leads to the stimulation of Pc 1 waves.…”

Section: Introductionsupporting

confidence: 54%

“…In fact, Anderson et al (1996) showed that EMIC instability can be roughly predicted if Aβ 1/2 > ∼ 1, where β is the ratio of the parallel plasma pressure to the magnetic pressure. The model of Olson and Lee (1983) shows that compressions do not significantly change β , but can lead to a significant increase in A. Erlandson et al (1994) present an example of a compression-induced Pc 1 event associated with a magnetospheric substorm in which the Pc 1 waves turn on and off with the precise timing of the compression.…”

Section: Introductionmentioning

confidence: 98%

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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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Section: Introductionsupporting

confidence: 54%

Section: Introductionmentioning

confidence: 98%

Location of Pc 1–2 waves relative to the magnetopause

2002

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“…The outer zone, local noon EMIC waves reported here are consistent with a solar wind pressure pulse generation mechanism accelerating preexisting ∼10-100 keV protons in E ⟂ with consequential instability generating the waves [Olson and Lee, 1983;Anderson and Hamilton, 1993;Tsurutani et al, 2001;Engebretson et al, 2002;Usanova et al, 2012]. The waves shown in this paper lacked obvious rising tone structures.…”

Section: Final Commentssupporting

confidence: 83%

“…Another possible means of generating energetic proton and electron temperature anisotropies is by the impingement of interplanetary shocks [Olson and Lee, 1983;Kennel et al, 1985;Papadopoulos, 1985;Tsurutani et al, 1988] or other types of solar wind pressure pulses onto the magnetosphere. Fast forward shocks have density jumps comparable to their magnetosonic Mach numbers [Kennel et al, 1985;Tsurutani et al, 2011a] and thus the enhanced ram pressure leads to a rapid compression of the magnetosphere.…”

Section: 1002/2015ja021327mentioning

confidence: 99%

Electromagnetic cyclotron waves in the dayside subsolar outer magnetosphere generated by enhanced solar wind pressure: EMIC wave coherency

et al. 2015

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Electromagnetic ion (proton) cyclotron (EMIC) waves and whistler mode chorus are simultaneously detected in the Earth's dayside subsolar outer magnetosphere. The observations were made near the magnetic equator 3.1°–1.5° magnetic latitude at 1300 magnetic local time from L = 9.9 to 7.0. It is hypothesized that the solar wind external pressure caused preexisting energetic 10–100 keV protons and electrons to be energized in the T⊥ component by betatron acceleration and the resultant temperature anisotropy (T⊥>T∥) formed led to the simultaneous generation of both EMIC (ion) and chorus (electron) waves. The EMIC waves had maximum wave amplitudes of ∼6 nT in a ∼60 nT ambient field B0. The observed EMIC wave amplitudes were about ∼10 times higher than the usually observed chorus amplitudes (∼0.1–0.5 nT). The EMIC waves are found to be coherent to quasi‐coherent in nature. Calculations of relativistic ∼1–2 MeV electron pitch angle transport are made using the measured wave amplitudes and wave packet lengths. Wave coherency was assumed. Calculations show that in a ∼25–50 ms interaction with an EMIC wave packet, relativistic electron can be transported ∼27° in pitch. Assuming dipole magnetic field lines for a L = 9 case, the cyclotron resonant interaction is terminated ∼±20° away from the magnetic equator due to lack of resonance at higher latitudes. It is concluded that relativistic electron anomalous cyclotron resonant interactions with coherent EMIC waves near the equatorial plane is an excellent loss mechanism for these particles. It is also shown that E > 1 MeV electrons cyclotron resonating with coherent chorus is an unlikely mechanism for relativistic microbursts. Temporal structures of ∼30 keV precipitating protons will be ∼2–3 s which will be measurable at the top of the ionosphere.

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“…These pulsations are often referred to as "SIexcited micropulsations". Olson and Lee (1983) have shown that the increase in the temperature anisotropy of the magnetospheric plasma arising from the sudden compression of the geomagnetic field is one of the primary causes of the wave activity observed after SIs. Thus, the SI-excited micropulsations, when studied, can provide insight into the internal structure of the magnetosphere.…”

Section: Introductionmentioning

confidence: 99%

Bursts of ULF noise excited by sudden changes of solar wind dynamic pressure

Safargaleev

Kangas²,

Kozlovsky³

et al. 2002

Ann. Geophys.

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Abstract. We present the results of analysis of the dayside magnetic pulsation response to a sudden change in solar wind dynamic pressure. We concentrate on the events when a burst or a series of short-lived bursts in the Pc1 frequency range with the repetition period of 7-15 min were observed on the ground around the local noon. Not every impulse of large amplitude caused this phenomenon. We have found that the ULF bursts were excited when the spectrograms of the DMSP satellites showed a signature of 10-30 keV ions in the vicinity of the magnetic flux tube of the ground observatory, that may be related to a geomagnetic storm preceding the event. In light of this finding a possible model of the phenomenon is suggested in which the hot protons influence significantly both the generation and modulation of Pc1 activity.

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Pc1 wave generation by sudden impulses

Cited by 145 publications

References 11 publications

Location of Pc 1–2 waves relative to the magnetopause

Location of Pc 1–2 waves relative to the magnetopause

Electromagnetic cyclotron waves in the dayside subsolar outer magnetosphere generated by enhanced solar wind pressure: EMIC wave coherency

Bursts of ULF noise excited by sudden changes of solar wind dynamic pressure

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