Anomalous Scaling of the Ion Beam Energy in the Current Sheet

Abstract

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.