The scaling of the energy of ion beams (beamlets) W N ∼ N A in the N resonant regions of the current sheet in data from the SC-1 and SC-4 CLUSTER satellites has been analyzed. The case on February 5, 2003, for energy dispersive small-scale substructures, which are signatures of 1–20 keV beamlets in the auroral magnetosphere at geocentric distances (4.5–5.3) R E , where R E is the radius of the Earth, has been studied. This case is anomalous, since the energies of beamlets in the resonant regions (seven regions N = 1−7 with resonances R = 1−7 are identified and the region with R = 7 is located in the highest latitude auroral region) do not obey a single scaling law. The exponents A are 0.04 and 0.40 for the regions with resonances R = 1−4 and are 0.83 and 1.14 for the regions with R = 5−7 according to the SC-1 and SC-4 data, respectively. The exponents obtained from the CLUSTER satellite data differ from the theoretically predicted value A = 1.33 [L.M. Zeleny et al., JETP Lett. 85 , 187 (2007)]. The beamlet energy scales for the regions with R = 5−7 can be explained by taking into account the electric field E z perpendicular to the plane of the current sheet. The observed exponents A in the regions N = 1−4 can occur because the spatial decrease in the normal component B z of the magnetic field, which controls the increment of the energy of ion beams in the current sheet, in these resonant regions is smaller than that in the regions N = 5−7.

The Interhelioprobe mission aims to investigate the inner heliosphere and the Sun from close distances (up to 0.3 AU) and from out of the ecliptic plane (up to 30°). In this paper we present the relevance of the mission and its main scientific objectives, describe the scientific payload, ballistic scenario and orbits of the spacecraft. Possibilities of scientific cooperation with other solar and heliospheric space missions are also mentioned.

Multiple energy dispersion structures of H+ ions that were observed at the passage of the INTERBALL-Auroral satellite through the plasma sheet at a geocentric distance of about 3R E, where R E is the radius of the Earth, on November 3, 1996, have been analyzed. The structure in the plasma sheet boundary layer, which has direct dispersion in energy and invariant latitude, in the range of 0.5–10.0 keV (velocity-dispersed ion structure) is an “autograph” of accelerated ion beams (primary beamlets) generated in the current sheet along the geomagnetic tail. The central plasma sheet contains five dispersion structures c1–c5 with the average energy ranging from 2.80 to 7.36 keV. The average energy of the structures increases with a decrease in the latitude. The event under consideration is a case of the regime of formation of the central plasma sheet by echo beamlets of the accelerated ion beam in the absence of a diffusion thermalized population of ions. This phenomenon is possibly explained by the fact that a magnetically quite period was observed three days before the passage of the satellite, when the regime of long-term diffusion of particles from the central plasma sheet occurred.

The scaling of the energy of ion beams (beamlets) in resonance regions of the low-altitude plasma sheet boundary layer has been analyzed using the measurements made on the Interball-2 and Cluster satellites at distances of 3.0 to 6.0 Earth’s radii and numerical simulations of the acceleration of ions in the current sheet of the Earth’s magnetotail. The experimental test of the previously theoretically predicted scaling W N ∼ N A (where W N is the energy at the N th resonance and A ∼ 1.33) shows that the real scaling of resonance energies varies in a wide range A ∈ [0.61, 1.75] and is independent of the geomagnetic indices K p and AE . Model calculations with allowance for an electric field E z perpendicular to the current sheet are in good agreement with the experimental data. They indicate that the scaling increases in the case of the dominance of the ion current and decreases in the case of the dominance of the electron current ( A > 1.33 and A < 1.33, respectively).

An analysis of energy-dispersed structures of protons and populations of electrons has been made using the Interball-2 satellite data for the apogee parts of 1579 (September 13, 1997) and 1276 (July 2, 1997) orbits. At each orbit, the satellite crossed the auroral zone twice at altitudes of 13500–19000 km moving first poleward (the first crossing) and then equatorward (the second crossing). A transformation of the types of energy-dispersed structures near the outer boundary of the auroral zone was observed at the first and second crossings: VDIS into TDIS (orbit 1579) and TDIS into VDIS (orbit 1276). The VDIS represent solitary structures of 0.3–10 keV consisting of several small-scale structures 2–5 min long, while the TDIS are repeating injections of 1–14 keV 1–3 min long with the repetition period of 2–4 min. It is shown that the VDIS-to-TDIS and TDIS-to-VDIS transformations are distinctly related to the phase of a substorm. The VDIS were observed under magnetically quiet conditions before a substorm or at the recovery phase of a substorm, while TDIS were observed during the main phase of a substorm.

We study two main types of ion energy dispersions observed in the energy range ∼1 to 14 keV on board the Interball‐Auroral (IA) satellite at altitudes 2–3 RE at the poleward boundary of the plasma sheet. The first type of structure is named velocity dispersed ion structures (VDIS). It is known that VDIS represent a global proton structure with a latitudinal width of ∼0.7–2.5°, where the ion overall energy increases with latitude. IA data allow to show that VDIS are made of substructures lasting for ∼1–3 min. Inside each substructure, high‐energy protons arrive first, regardless of the direction of the plasma sheet boundary crossing. A near‐continuous rise of the maximal and minimal energies of consecutive substructures with invariant latitude characterizes VDIS. The second type of dispersed structure is named time‐of‐flight dispersed ion structures (TDIS). TDIS are recurrent sporadic structures in H+ (and also O+) with a quasi‐period of ∼3 min and a duration of ∼1–3 min. The maximal energy of TDIS is rather constant and reaches ≥14 keV. During both poleward and equatorward crossings of the plasma sheet boundary, inside each TDIS, high‐energy ions arrive first. These structures are accompanied by large fluxes of upflowing H+ and O+ ions with maximal energies up to 5–10 keV. In association with TDIS, bouncing H+ clusters are observed in quasi‐dipolar magnetic field tubes, i.e., equatorward from TDIS. The electron populations generally have different properties during observations of VDIS and TDIS. The electron flux accompanying VDIS first increases smoothly and then decreases after Interball‐Auroral has passed through the proton structure. The average electron energy in the range ∼0.5–2 keV is typical for electrons from the plasma sheet boundary layer (PSBL). The electron fluxes associated with TDIS increases suddenly at the polar boundary of the auroral zone. Their average energy, reaching ∼5–8 keV, is typical for CPS. A statistical analysis shows that VDIS are observed mainly during magnetically quiet times and during the recovery phase of substorms, while sporadic and recurrent TDIS are observed during the onset and main phases of substorms and magnetic storms and, although less frequently, during substorm recovery phases. From the slope of the (velocity)−1 versus time dispersions of TDIS, we conclude that they have a sporadic source located at the outer boundary of the central plasma sheet, at distances from 8 to 40 RE in the equatorial plane. The disappearance of the PSBL associated with TDIS can be tentatively linked to a reconfiguration of the magnetotail, which disconnects from the Earth the field lines forming the “quiet” PSBL. We show that VDIS consist of ion beams ejected from an extended current sheet at different distances. These ion beams could be formed in the neutral sheet at distance ranging from ∼30 RE to ∼100 RE from the Earth. Inside each substructure the time‐of‐flight dispersion of ions generally dominate over any latitudinal dispersion induced by a dawn‐dusk electric field. These two main types of energy‐dispersed ion structures reflect probably two main states of the magnetotail, quiet and active. Finally, it must be stressed that only ∼49% (246 over 501) of the Interball‐Auroral auroral zone‐polar cap boundary crossings can be described as VDIS or TDIS. On the other 51% of the crossings of the plasma sheet boundary, no well‐defined ion dispersed structures were observed.

The azimuthal distribution of magnetospheric plasma pressure was studied using the precipitating particle fluxes observed by the low-altitude polar-orbiting Aureol-3 satellite. The data from the 18 March 1982 event was used to calculate the pressure along the satellite trajectory during quiet geomagnetic conditions. The magnetic flux tube volumes for the field-lines, corresponding to the points of measurement at the satellite trajectory, were calculated by using Tsyganenko 96 magnetic-field model. The gradients of the plasma pressure along the isosurfaces of the volume of the magnetic flux tube per unit flux were estimated, and the field-aligned currents were calculated assuming that the condition of the magnetostatic equilibrium is valid. The results obtained were compared with the [J. Geophys. Res. 81 (13) (1976) 2165] field-aligned current distribution.

Nose structures are objects formed by H + particles penetrating into the inner magnetosphere [1, 2]. We present the results of experimental studies and numerical modeling of the nose structures. Statistical processing of the observations of nose structures in 1997 by the ION instrument onboard the Interball-2 satellite at heights of 10 000–15 000 km demonstrates that the probability of formation of the nose structures under quiet magnetic conditions (with current values K p = 0–1) in the nighttime sector of the magnetosphere is ∼90%. The probability of observation of the nose structures in the daytime sector equals ∼ 50% at the current value K p = 0–1, and the correlation between the observations of nose structures and K p can be improved (up to ∼ 75%) if the K p index is taken 6 h before the observed events. It is shown that nose structures are a characteristic feature not only of the substorm processes but also of quasi-stationary phenomena in the quiet magnetosphere. The nose structures observed in magnetically quiet periods are called stationary nose structures in this work. By modeling drift trajectories for protons, it is shown that the stationary nose structures are formed in all sectors of the MLT. The stationary nose structures observed by the ION instrument are modeled in the night, morning, and daytime sectors of the MLT. The relation between the stationary nose structures and ion spectral gaps is considered.

We present results of a comparison of simultaneous satellite and ground-based observations of multiple auroral structures for the event of December 30, 1982. Satellite measurements of electron fluxes, field-aligned currents along with synchronous geomagnetic field variations registered by the Scandinavian chain during magnetic disturbances are considered. It is shown that the magnetospheric plasma stratification leads to the eastward electrojet splitting.

We analyse measurements of ion spectral gaps (ISGs) observed by the ION particle spectrometer on board the Interball-2 satellite. The ISG represents a sharp decrease in H+ flux at a particular narrow energy range. ISGs are practically always observed in the inner magnetosphere in a wide MLT range during quiet times. Clear examples of ISG in the morning, dayside, evening and nightside sectors of the magnetosphere are selected for detailed analysis and modeling. To obtain a model ISG, the trajectories of ions drifting in the equatorial plane from their nightside source to the observation point were computed for the energy range 0.1–15 keV. Three global convection models (McIlwain, 1972, 1986; Volland, 1973; Stern, 1975) were tested to reproduce the observed ISGs in all MLT sectors. Qualitative agreement is obtained for all three models, but the better agreement for quiet times is reached with the McIlwain (1972) convection model. It is shown that the ISGs observed by the ION spectrometer throughout the inner magnetosphere are the result of super-position of the two effects, already described in the literature (e.g. McIlwain, 1972; Shirai et al., 1997), but acting under different conditions. Also, the role of particle source location on the model gaps is investigated. It may be concluded that despite the evidence of large amplitude and directional local fluctuations of electric fields in the inner magnetosphere (Quinn et al., 1999), the existence of a stationary average convection pattern is confirmed by this modeling. This fact directly follows from observations of ISGs and from a good agreement of observations with modeled gaps calculated in the frames of adiabatic theory for a stationary (average) convection pattern.Key words. Magnetospheric physics (plasma convection; electric fields)

The latitudinal asymmetry of accelerated electron precipitations is analyzed using AUREOL‐3 satellite data. It is found that the pattern of the precipitation of auroral electrons can be very asymmetric with the most powerful structures near the equatorial boundary of the auroral oval near midnight before substorm expansion phase onset. The presence of such a feature is interpreted as the existence of maximal magnetosphere‐ionosphere decoupling in the electron precipitation structure nearest the equator. It is argued that magnetosphere‐ionosphere decoupling can play the principal role in the localization of the substorm onset. The slow evolution of plasma pressure distribution under the influence of the electrostatic disturbances is analyzed. The threshold of the marginal instability is obtained. A scenario of substorm onset is suggested, which includes the development of localized dusk‐dawn electric field and the formation of thin sheets of downward accelerated electrons producing rayed arc and upward accelerated ions on the equatorial edge of the large‐scale electron acceleration region.

We present an analysis of sporadic and recurrent injections of magnetospheric ions in the midnight auroral oval during substorms and of the associated ionospheric ion outflows. The source of plasma sheet precipitating ions is determined using a simple method, based on the measured relation between the ion inverse velocity and time (l = v × t). This method is applied here to two typical passes of the Interball-Auroral (IA) satellite at distances of ∼ 3 RE above the auroral regions. Substorm related ion injections are shown to be mainly due to time of flight effects. In contrast with particle trajectory computations (Sauvaud et al., 1999), the inverse velocity method does not require magnetic and electric field models and can thus be used systematically for the detection of time of flight dispersed ion structures (TDIS). This allowed us to build a large database of TDIS events and to perform a statistical analysis of their spatial distribution. For the cases presented here the source region of the injected ions is found at radial distances from 18 to 30 RE near the equatorial magnetosphere. At Interball altitudes (∼ 3 RE), ion injections detected at the poleward boundary of the nighside auroral oval are associated with shear Alfvén waves superimposed over large-scale quasi-static current structures. We show that the most poleward TDIS are collocated with a large outflow of ionospheric H+ and O+ displaying pitch-angle distributions peaked in the pitch-angle range 90°–120°. These ions are thus accelerated perpendicularly to the magnetic field not only in the main auroral acceleration region but also up to at least 3 RE. The expanding auroral bulge thus constitutes a significant source of H+ and O+ ions for the mid-tail magnetosphere.

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