Cusp Proton Signatures and the Interplanetary Magnetic Field

Journal Article · Sat Nov 01 00:00:00 EST 1980 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA085iA11p05997· OSTI ID:7094367

Reiff, P H; Burch, J L; Spiro, R W

The variation of proton average energy with latitude in the cusp has been suggested as an indicator of the means of particle energy. If magnetic merging is the principal means of particle entry, the proton average energy should fall with increasing invariant latitude; if diffusion is the principal means of particle entry, the average energy should first fall and then briefly rise as a function of latitude, showing a 'V' signature. In addition, the cusp protons should occur on open field lines in the former and closed field lines in the latter case. Four hundred passes of the AE-D satellite were scanned for appropriate cusp passes during periods when IMP-J interplanetary or magnetosheath magnetic field data were available. Sixty passes fulfilled all criteria. Of these, roughly a third showed clear or likely merging-type energy dispersions; a third showed clear or likely V-type energy dispersions, and a third showed unclear or no energy dispersions. The results are strongly correlated with the IMF: the merging signatures were associated with southward IMF, and the V signatures were associated with northward IMF. Unclear or no dispersion cases were associated with unsteady or weakly northward IMF or with orbits unfavorable to observe the dispersion (perpendicular to the convection direction). If one accepts the electron anisotropy boundary as an (imperfect) indicator of the last closed field line, then the cusp protons are typically on open field lines for southwest IMF and on closed field lines for northward IMF. In addition, the presence of > or =3-keV electrons in the cusp is strongly correlated with V dispersions and therefore with northward IMF.

• Research Organization: Department of Space Physics and Astronomy, Rice University, Houston, Texas 77001
• OSTI ID: 7094367
• Journal Information: J. Geophys. Res.; (United States), Vol. 85:A11
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
INTERPLANETARY MAGNETIC FIELDS
TRAPPED PROTONS
CHARGED-PARTICLE TRANSPORT
DIFFUSION
LATITUDE EFFECT
MAGNETIC FIELD CONFIGURATIONS
MAGNETOSHEATH
MAGNETOSPHERE
BARYONS
EARTH ATMOSPHERE
ELEMENTARY PARTICLES
FERMIONS
GEOGRAPHICAL VARIATIONS
HADRONS
MAGNETIC FIELDS
NUCLEONS
PROTONS
RADIATION TRANSPORT
VARIATIONS
640203* - Atmospheric Physics- Magnetospheric Phenomena- (-1987)