[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.

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.

Abstract. The advanced energetic particle spectrometer RAPID on board Cluster can provide a complete description of the relevant particle parameters velocity, V , and atomic mass, A, over an energy range from 30 keV up to 1.5 MeV. We present the first measurements taken by RAPID during the commissioning and the early operating phases. The orbit on 14 January 2001, when Cluster was travelling from a perigee near dawn northward across the pole towards an apogee in the solar wind, is used to demonstrate the capabilities of RAPID in investigating a wide variety of particle populations. RAPID, with its unique capability of measuring the complete angular distribution of energetic particles, allows for the simultaneous measurements of local density gradients, as reflected in the anisotropies of 90 • particles and the remote sensing of changes in the distant field line topology, as manifested in the variations of loss cone properties. A detailed discussion of angle-angle plots shows considerable differences in the structure of the boundaries between the open and closed field lines on the nightside fraction of the pass and the magnetopause crossing. The 3 March 2001 encounter of Cluster with an FTE just outside the magnetosphere is used to show the first structural plasma investigations of an FTE by energetic multi-spacecraft observations.Correspondence to: U. Mall (mall@linmpi.mpg.de) Key words. Magnetospheric physics (energetic particles, trapped; magnetopause, cusp and boundary layers; magnetosheath) The instrumentThe RAPID spectrometer (Research with Adaptive Particle Imaging Detectors), described in detail by Wilken et al. (1995), is an advanced particle detector for the analysis of suprathermal plasma distributions in the energy range from 20-400 keV for electrons, 30 keV-1500 keV for hydrogen, and 10 keV/nucleon-1500 keV for heavier ions. Innovative detector concepts, in combination with pinhole acceptance, allow for the measurement of angular distributions over a range of 180 • in the polar angle for electrons and ions. Identification of the ion species is based on a two-dimensional analysis of the particle's velocity and energy. Electrons are identified by the well-known energy-range relationship. Table 1 list the main parameters of the RAPID instrument.The energy signals in RAPID are analyzed in 8 bit ADCs. With a mapping process the 256 channels are reduced to 8 channels in the case of the ion sensor and into 9 channels in the case of the electron sensor. The resulting energy channel limits are listed in Table 2.

We have used a unique constellation of Earth‐orbiting spacecraft and ground‐based measurements in order to study a relatively isolated magnetospheric substorm event on August 27, 2001. Global ultraviolet images of the northern auroral region established the substorm expansion phase onset at 0408:19 (±1 min) UT. Concurrent measurements from the GOES‐8, POLAR, LANL, and CLUSTER spacecraft allow us to construct a timeline which is consistent with magnetic reconnection on the closed field lines of the central plasma sheet near XGSM ∼ −18 RE some 7 minutes prior to the near‐earth and auroral region times of substorm expansion phase onset. This suggests that magnetic reconnection (i.e., the substorm neutral line) in this case formed in the mid‐tail region substantially before current disruption, field dipolarization near geostationary orbit, or auroral substorm onsets occurred. Thus, the magnetic reconnection process is interpreted as the causative driver of dissipation in this well‐observed case.

At 0027 UT on July 29, 1977 an interplanetary shock wave arrived at the front side magnetosphere and triggered substantial geomagnetic activity throughout the day. The propagation of the resulting MHD wave within the magnetosphere has been studied with measurements from a total of six satellites in (or near) the geostationary orbit and the interplanetary space and groundbased magnetometers. At the time of the SSC the European spacecraft GEOS 1 was located at R --6.7 RE and 1300 LT providing accurate reference measurements for the hydromagnetic impulse spreading out in the magnetosphere. The signal transmission from the front side magnetopause down to the equatorial ionosphere corresponded to an average wave speed of v = 600 km/s. A propagation speed of v = 910 km/s was found for the signal transmission in the outer magnetosphere in and beyond the geostationary altitude.The results compared reasonably well with model calculations.sphere was strongly compressed. The sudden increase in solar wind pressure pushed the subsolar point from an estimated preshock location at R0 = 7.8 RE [Knott et al., 1982] down to R0 = 6.3 RE and triggered substantial magnetic activity with repeated occurrences of major substorms. The SSC event occurred after a quiet period of several days in which Kp was equal to or smaller than 1 +.The focus of this paper is on the immediate effects of the shock arrival on the state of the magnetosphere as observed by energetic particle distributions and magnetic field signatures. The propagation of these effects throughout the magnetosphere is determined from ground-based magnetograms, particles, and field data from five satellites in and near the geostationary altitude and one spacecraft in the interplanetary region. INSTRUMENTATIONThe present analysis is based mainly on energetic particle measurements obtained from a set of similar instruments flown on the synchronous satellites ATS 6, 1976-059, 1977-007, and on the elliptical ESA spacecraft GEOS 1. Instrumental details of the various particle spectrometers are given by Fritz and Cessna [1975] for ATS 6, Higbie et al. [1978], and Baker et al. [1979a, b] for the satellites 1976-059 and 1977-007 and by Wilken et al. [1977] for GEOS 1. In addition, magnetic field and solar wind data are used from GEOS 1 and IMP 8. The instrumentation available for this study, the energy coverage for ions and electrons, and the local time positions of the various satellites at the time of the SCC are summarized in Table 1.The different particle spectrometers employed on the various satellites use essentially the same detection techniques. Electron/ion discrimination is achieved by combining simple broom magnets or more sophisticated magnetic spectrometers with solid state detectors. Significant differences, however, exist in the overall measuring geometry resulting from the principle used for the spacecraft attitude 5901