Open AccessFreja and ground‐based analysis of inverted‐V events
Author(s) -
Frey H. U.,
Haerendel G.,
Clemmons J. H.,
Boehm M. H.,
Vogt J.,
Bauer O. H.,
Wallis D. D.,
Blomberg L.,
Lühr H.
Publication year - 1998
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 - 10.1029/97ja02259
Subject(s) - physics , electron precipitation , computational physics , satellite , particle acceleration , electron , electric field , acceleration , magnetosphere , geophysics , brightness , kinetic energy , magnetic field , optics , classical mechanics , astronomy , quantum mechanics
During two campaigns, ground‐based auroral observations were performed in coordination with Freja. The high temporal and spatial resolution of the satellite instruments as well as the real‐time recording with a stereoscopic camera system from the ground enabled detailed comparison of small‐ and large‐scale optical phenomena with particle and field data measured by the satellite. Three passes of the satellite over inverted‐V auroral arcs and over precipitation regions with strong field‐aligned electron spectra are investigated. Brightness modulations within auroral arcs coincide with modulations of primary electron fluxes. The dynamics of small‐scale structures within arcs as well as the proper motion of arcs are analyzed and compared with electric fields measured by the satellite and with BARS radar measurements. Energy fluxes independently determined from the ground and from the satellite are used to calculate the field‐aligned conductance. The results agree with predictions of the kinetic theory of the mirror force, if we allow for variations of the density and thermal energy of the electrons in the source region of the magnetosphere. Detailed comparison of electron spectra and electric and magnetic field perturbations provide evidence of different acceleration mechanisms for the electrons, electrostatic acceleration inside inverted‐V's, and wave acceleration in transient regions.