[1] Strong interplanetary shock interactions with the Earth's magnetosphere have great impacts on energetic particle dynamics in the magnetosphere. An interplanetary shock on 7 November 2004 (with the maximum solar wind dynamic pressure of $70 nPa) was observed by the Cluster constellation to induce significant ULF waves in the plasmasphere boundary, and energetic electrons (up to 2 MeV) were almost simultaneously accelerated when the interplanetary shock impinged upon the magnetosphere. In this paper, the relationship between the energetic electron bursts and the large shock-induced ULF waves is studied. It is shown that the energetic electrons could be accelerated and decelerated by the observed ULF wave electric fields, and the distinct wave number of the poloidal and toroidal waves at different locations also indicates the different energy ranges of electrons resonating with these waves. For comparison, a rather weak interplanetary shock on 30 August 2001 (dynamic pressure $2.7 nPa) is also investigated. It is found that interplanetary shocks or solar wind pressure pulses with even small dynamic pressure change can have a nonnegligible role in the radiation belt dynamics.

A new method is described to analyze the dimensional character of observed structures using multipoint magnetic field measurements of four or more spacecraft. The technique can provide three directions along which the magnetic field has the minimum, intermediate, and maximum derivatives if the magnetic gradient tensor G = ∇ at every moment has been estimated by multipoint measurements. It follows that the structure's dimensionality and the variation direction can be directly determined. Both Cluster observations and simulations have shown that it is feasible to obtain the invariant axis orientation for two‐dimensional structures such as flux tubes, and to find the normal directions for one‐dimensional structures such as discontinuities. One advantage of this method is that these directions can be determined instantaneously, point by point in the time series, and so can be tracked through each observed structure. The analysis tool provides us a new perspective of the observed structures in the space.

Energetic electron and ion (electrons: 30 keV to 500 keV, protons: 30 keV to 1.5 MeV) flux variations associated with ultralow frequency (ULF) waves in the dayside magnetosphere were observed during the CLUSTER's perigee pass near 0900 MLT on Oct. 31, 2003. The ULF modulation terminated where higher frequency fluctuations appeared, as the CLUSTER spacecraft entered the plasmasphere boundary layer (PBL) where the plasma ion density was elevated. In the region from L ∼ 5.0 to 10, the periods of the ion flux modulation and the electron flux modulation are same but out‐of‐phase. The observed magnetic ULF pulsations are dominated by the toroidal mode, along with a relatively weaker poloidal wave. A 90° phase shift between the radial electric field and the azimuthal magnetic field indicates that dominating toroidal standing waves observed at the southern hemisphere are a fundamental harmonic. This study shows that the modulation of the electron flux is dominated by the toroidal mode in the region of L > 7.5. The observations made in this analysis suggest the excitation of the energetic electron drift resonance at around 127 keV.

No abstract

One of the most important issues in space physics is to identify the dominant processes that transfer energy from the solar wind to energetic particle populations in Earth's inner magnetosphere. Ultra-low-frequency (ULF) waves are an important consideration as they propagate electromagnetic energy over vast distances with little dissipation and interact with charged particles via drift resonance and drift-bounce resonance. ULF waves also take part in magnetosphereionosphere coupling and thus play an essential role in regulating energy flow throughout the entire system. This review summarizes recent advances in the characterization of ULF Pc3-5 waves in different regions of the magnetosphere, including ion and electron acceleration associated with these waves.

[1] The energetic electrons and ions embedded in Earthward-moving plasmoid structures have been observed. These plasmoids are associated with a rotational local B z component (bi-polar) signature. Energetic electrons are found to be confined in a smaller spatial region than ions inside the plasmoid. Energetic ions and electrons seem to be a good indicator for the structure boundary. The fleet of Cluster spacecraft cross the plasmoid structure in a ''first entry, last out'' order (Note: when spacecraft cross a planar discontinuity, e.g. magnetopause, they will be in ''first entry, first out'' order). This documents the fact that the plasmoid has a non-planar nested structure. The large separation distance (around 1 R E ) of the Cluster satellites in October 2002 is an advantage to provide constraints on the size and shape of the plasmoid structure of interest. In addition, the plasmoid (with closed field lines) should preserve the ion composition information where it is formed. The ion composition observed in the plasmoid shows significantly lower O and He than in the ambient plasma. This implies few heavy ions are involved in the reconnection process where the plasmoid is formed. Multiple flux ropes/plasmoids observation presented in this paper can be interpreted as strong evidence for multiple X-lines.

[1] A series of seven hot flow anomaly (HFA) events has been observed by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) C spacecraft just upstream from the subsolar bow shock from 0100 to 1300 UT on 19 August 2008. Both young (no shocks at edges, two distinct ion populations) and mature (strong shocks at edges, a single hot ion population) HFAs have been observed. Further upstream, THEMIS B observed four proto-HFAs (density and magnetic field strength depletions, plasma heating but no flow deflections) which later developed into HFAs observed by THEMIS C. We present evidence indicating that electromagnetic right-hand resonant ion beam instabilities heat ions inside HFAs. Observations of small-amplitude perturbations (DB/B < 50%) consistent with the resonant ion beam instability in a proto-HFA, 30 s electromagnetic waves (DB/B ∼ 1) in a young HFA, and magnetic pulsations in a mature HFA (DB/B ∼ 4) indicate that they are at early, middle, and late (nonlinear) stages of the electromagnetic right-hand resonant ion beam instabilities. Both young and mature HFAs are associated with strong electromagnetic waves near the lower hybrid frequency (0.1-1 Hz). The lower hybrid waves are the likely source of the electron heating inside HFAs. THEMIS B observations of four proto-HFAs which later developed into HFAs observed by THEMIS C indicate that these four HFAs might extend beyond 14 R E upstream from the bow shock, while the other three HFAs may extend between 5 and 14 R E upstream from the bow shock. We present an example of an HFA that lies displaced toward the side of the tangential discontinuity with a quasi-parallel bow shock configuration rather than lying centered on the driving interplanetary magnetic field discontinuity.

.[1] The interaction between interplanetary shocks and the Earth's magnetosphere manifests in many important space physics phenomena including particle acceleration. We investigated the response of the inner magnetospheric hydrogen and oxygen ions to a strong interplanetary shock impinging on the Earth's magnetosphere. Both hydrogen and oxygen ions are found to be heated/accelerated significantly with their temperature enhanced by a factor of two and three immediately after $1 min and $12 min of the shock arrival respectively. Multiple energy dispersion signatures of ions were found in the parallel and anti-parallel direction to the magnetic field immediately after the interplanetary shock impact. The energy dispersions in the anti-parallel direction preceded those in the parallel direction. Multiple dispersion signatures can be explained by the flux modulations of local ions (rather than the ions from the Earth's ionosphere) by ULF waves. It is found that the energy spectrum from 10 eV to $40 keV are highly correlated with the cross product of observed ULF wave electric and magnetic field (V = (E Â B)/B2 ), which indicate that both cold plasmaspheric plasma and hot thermal ions (10 eV to $40 keV) are accelerated and decelerated with the various phases of ULF wave electric field. We then demonstrate that ion acceleration due to the interplanetary shock compression on the Earth's magnetic field is rather limited, whereas the major contribution to acceleration comes from the electric field carried by ULF waves via drift-bounce resonance for both the hydrogen and oxygen ions. The integrated hydrogen and oxygen ion flux with the poloidal mode ULF waves are highly coherent (>0.9) whereas the coherence with the toroidal mode ULF waves is negligible, implying that the poloidal mode ULF waves are much more efficient in accelerating hydrogen and oxygen ions in the inner magnetosphere than the toroidal mode ULF waves. The duration of high coherence for oxygen ions with the poloidal mode ULF wave is longer than that for hydrogen ions, indicating that oxygen ions can be heated/accelerated more efficiently by the poloidal mode ULF wave induced by the interplanetary shock.