[1] The wave-particle interaction is a possible candidate for the energy coupling between the ring current and plasmaspheric plumes. In this paper, we present wave and particle observations made by the Cluster C1 satellite in a plasmaspheric plume in the recovery phase of the geomagnetic storm on 18 July 2005. Cluster C1 simultaneously observed Pc1-2 waves and extremely low frequency (ELF) hiss in the plasmaspheric plume. Through an analysis of power spectral density and polarization of the perturbed magnetic field, we identify that the observed Pc1-2 waves are linearly polarized electromagnetic ion cyclotron (EMIC) waves and show that the ELF hiss propagates in the direction of the ambient magnetic field in whistler mode. In the region where the EMIC waves were observed, the pitch angle distribution of ions becomes more isotropic, likely because of the pitch angle scattering by the EMIC waves. It is shown that the ELF hiss and EMIC waves are spatially separated: The ELF hiss is located in the vicinity of the electron density peak within the plume while the EMIC waves are detected in the outer boundary of the plume because of the different propagation characteristics of the ELF hiss and EMIC waves.

Dayside modulated relativistic electron's butterfly pitch angle distributions (PADs) from ∼200 keV to 2.6 MeV were observed by Van Allen Probe B at L = 5.3 on 15 November 2013. They were associated with localized magnetic dip driven by hot ring current ion (60–100 keV proton and 60–200 keV helium and oxygen) injections. We reproduce the electron's butterfly PADs at satellite's location using test particle simulation. The simulation results illustrate that a negative radial flux gradient contributes primarily to the formation of the modulated electron's butterfly PADs through inward transport due to the inductive electric field, while deceleration due to the inductive electric field and pitch angle change also makes in part contribution. We suggest that localized magnetic field perturbation, which is a frequent phenomenon in the magnetosphere during magnetic disturbances, is of great importance for creating electron's butterfly PADs in the Earth's radiation belts.

[1] In this paper, we present characteristics of precipitating energetic ions/electrons associated with the wave-particle interaction in the plasmaspheric plume during the geomagnetic storm on July 18, 2005 with observations of the NOAA15 NOAA16, IMAGE satellites and Finnish network of search coil magnetometers. Conjugate observations of the NOAA15 satellite and the Finnish network of search coil magnetometers have demonstrated that a sharp enhancement of the precipitating ion flux is a result of ring current (RC) ions scattered into the loss cone by EMIC waves. Those precipitating RC ions lead to a detached subauroral proton arc observed by the IMAGE FUV. In addition, with observations of NOAA15 and NOAA16, the peak of precipitating electron flux was equatorward to that of precipitating proton flux, which is in agreement with the region separation of ELF hiss and EMIC waves observed by the Cluster C1 in the Yuan et al. (2012) companion paper. In combination with the result of the companion paper, we demonstrate the link between the wave activities (ELF hiss, EMIC waves) in plasmaspheric plumes and energetic ion/electron precipitation at ionospheric altitudes. Therefore, it is an important characteristic of the plasmaspheric plumes-RC-ionosphere interaction during a geomagnetic storm that the precipitation of energetic protons is latitudinally separated from that of energetic electrons.Citation: Yuan, Z., Y. Xiong, D. Wang, M. Li, X. Deng, A. G. Yahnin, T. Raita, and J. Wang (2012), Characteristics of precipitating energetic ions/electrons associated with the wave-particle interaction in the plasmaspheric plume, J. Geophys.

We present a multiple‐satellite observation of the magnetic dip event during the substorm on 10 October 2013. The observation illustrates the temporal and spatial evolution of the magnetic dip and gives a compelling evidence that ring current ions induce the magnetic dip by enhanced plasma beta. The dip moves with the energetic ions in a comparable drift velocity and affects the dynamics of relativistic electrons in the radiation belt. In addition, the magnetic dip provides a favorable condition for the electromagnetic ion cyclotron (EMIC) wave generation based on the linear theory analysis. The calculated proton diffusion coefficients show that the observed EMIC wave can lead to the pitch angle scattering losses of the ring current ions, which in turn partially relax the magnetic dip in the observations. This study enriches our understanding of magnetic dip evolution and demonstrates the important role of the magnetic dip for the coupling of radiation belt and ring current.

We report in situ observations by the Cluster spacecraft of plasmaspheric electron heating in the plasmaspheric plume. Electron heating events were accompanied by enhancements of electromagnetic ion cyclotron (EMIC) waves in the increased density ducts on the negative density gradient side for two substructures of the plasmaspheric plume. Electron heating is much stronger for the pitch angle of 0°and 180°than for the pitch angle of 90°. Theoretical calculations of the Landau resonant interaction between electrons and observed EMIC waves demonstrate that Landau damping of oblique EMIC waves is a reasonable candidate to heat cold electrons in the presence of O + ions in the outer boundary of the plasmaspheric plume. Therefore, this observation is considered in situ evidence of plasmaspheric electron heating through Landau damping of EMIC waves in plasmaspheric plumes.

[1] The wave-particle interactions and associated precipitation of energetic ions/electrons play an important role in the coupling between the inner magnetosphere and the ionosphere. In this paper, we present characteristics of precipitating ring current (RC) ions/electrons and precipitating radiation belt electrons associated with wave-particle interactions in the plasmaspheric plume in the main phase of a geomagnetic storm during 8-9 May 2001. With observations of the NOAA 16 satellite, within the anisotropic zone, the peak of precipitating RC electron flux was equatorward to that of precipitating RC proton flux in a plasmaspheric plume recognized by the IMAGE and LANL-91/94 satellites. An enhancement of precipitating flux for >3 MeV electrons was simultaneously observed by NOAA 16 with the increase of precipitating RC proton flux within the anisotropic zone. Theoretical calculations of pitch angle diffusion coefficients for RC protons and for radiation belt electrons caused by electromagnetic ion cyclotron (EMIC) waves demonstrated that precipitating flux enhancements of RC protons and >3 MeV radiation belt electrons are a result of EMIC wave-particle interactions in the plasmaspheric plume. Our result suggests that EMIC waves in the plasmaspheric plume can scatter not only RC ions but also radiation belt electrons into the loss cone, which cause the loss of the RC ions and radiation belt electrons.

Localized magnetic field depressions in the inner magnetosphere, known as magnetic dips, are produced by the diamagnetic motion of energetic ions injected via substorm activities. The magnetic dips, if deep enough, can produce a local minimum in the radial profile of the field strength to trap the injected protons. Therefore, the trapped protons would drift at the same speed as the dip propagation, which leads to the simultaneous enhancements of proton fluxes in multiple energy channels at the leading edge of the dip structure. On the trailing side, the reduction of proton fluxes shows dispersive features, which can be attributed to the energy‐dependent drift motion of the injected protons in the absence of the local field minimum. This scenario is examined based on comparisons between multi‐spacecraft observations and test‐particle simulations, and their good agreement validates the scenario to shed new light on the dynamics of the inner magnetosphere‐magnetotail coupled system.

In this paper, we have presented the influence of precipitating energetic ions caused by electromagnetic ion cyclotron (EMIC) waves on the subauroral ionospheric E region during a geomagnetic storm on 8 March 2008 with observations of the Meteorological Operational (METOP-02) of the Polar Orbiting Environmental Satellites (POES), a GPS receiver in Vaasa of Finland and Finnish network of search coil magnetometers. Conjugate observations of the POES METOP-02 satellite and Finnish network of search coil magnetometers have demonstrated that enhancements of the precipitating energetic ion flux within the proton anisotropic zone are attributed to the interaction between ring current (RC) ions and EMIC waves. With enhancements of the intensity of Pc1 waves observed by search coil magnetometers, the total electron content observed by the GPS receiver accordingly increased, meaning that the enhancement of the ionospheric electron density is attributed to the precipitation of RC ions caused by EMIC waves. The electron density profiles derived by the International Reference Ionosphere (IRI-2007) model and with precipitating energetic protons observed by the POES METOP-02 satellite show that the energetic proton precipitation can cause the E layer peak electron density to increase from 1.62 × 10 9 m À3 to 5.05 × 10 11 m À3 by 2.49 orders of magnitude. In comparison with the height-integrated conductivities derived by the IRI-2007 model, the height-integrated Pedersen and Hall conductivities derived with precipitating energetic protons increase by 2.4 and 2.34 orders of magnitude, respectively. Our result suggests that precipitating energetic ions caused by EMIC waves can lead to an obvious enhancement of the electron density and conductivities in the subauroral ionospheric E region during geomagnetic storms.