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.

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 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)