Open AccessField‐aligned beam observations at the quasi‐perpendicular bow shock: Generation and shock angle dependence
Author(s) -
Oka M.,
Terasawa T.,
Saito Y.,
Mukai T.
Publication year - 2005
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2004ja010688
Subject(s) - magnetosheath , bow shock (aerodynamics) , solar wind , physics , shock (circulatory) , bow wave , mach number , ion , foreshock , flux (metallurgy) , shock wave , geophysics , atomic physics , plasma , magnetopause , mechanics , materials science , geology , nuclear physics , seismology , aftershock , medicine , quantum mechanics , metallurgy
On 19 October 1995 the Geotail satellite skimmed along the quasi‐perpendicular bow shock for more than 3 hours, and field‐aligned ion beams (FABs) were continuously observed in the foreshock region. Also observed were 11 crossings with the bow shock where these FABs are thought to be generated. The upstream condition of the bow shock was in the state of low Mach number (M A ∼ 2.9) and low beta (β ∼ 0.02). By a detailed study of the evolution of the ion distribution across one of the crossings, we have found that leakage as origin of these ions from the magnetosheath is unlikely. Comparison of the observations with simulations suggests that FAB ions are generated by multiple interaction of incoming solar wind ions with the bow shock. We have then compared the FAB flux normalized by the solar wind flux, , with the shock angle θ Bn and have found that falls off rapidly just above θ Bn > 60°, but it maintains significant level ( ∼ 0.01%) up to ∼75°.