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The quasiperpendicular environment of large magnetic pulses in Earth's quasiparallel foreshock: ISEE 1&2 observations
Author(s) -
Greenstadt E. W.,
Moses S. L.,
Coroniti F. V.,
Farris M. H.,
Russell C. T.
Publication year - 1993
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/93gl00841
Subject(s) - foreshock , physics , geophysics , bow shock (aerodynamics) , magnetic field , shock (circulatory) , transverse plane , shock wave , substorm , computational physics , geology , mechanics , seismology , magnetosphere , aftershock , medicine , structural engineering , quantum mechanics , engineering
ULF waves in Earth;aposs foreshock cause the instantaneous angle ϑ Bn between the upstream magnetic field and the shock normal to deviate from its average value. Close to the quasiparallel ( Q ∥ ) shock the transverse components of the waves become so large that the orientation of the field to the normal becomes quasiperpendicular ( Q ⟂ ) during applicable phases of each wave cycle. Large upstream pulses of B were observed completely enclosed in excursions of ϑ Bn into the Q ⟂ range. A recent numerical simulation included ϑ Bn among the parameters examined in Q ∥ runs, and described a similar coincidence as intrinsic to a stage in development of the reformation process of such shocks. Thus, the natural environment of the Q ∥ section of Earth's bow shock seems to include an identifiable class of enlarged magnetic pulses for which local Q ⟂ geometry is a necessary association.