Dayside cleft aurora and its ionospheric effects

Journal Article · Thu Nov 01 04:00:00 EST 1979 · Rev. Geophys. Space Phys.; (United States)

DOI:https://doi.org/10.1029/RG017i008p02017· OSTI ID:5730188

Shepherd, G G

The existence of an opening on the dayside of the earth's magnetic field through which solar plasma could penetrate was noted by Chapman and Ferraro in 1931, and although observational evidence of its auroral and ionospheric effects accumulated steadily over the years, the dayside cleft (or cups) was not accepted as a real magnetospheric feature until 1971. The history of this development is described, and some reasons for the long delay in recognizing this profound ionispheric influence are given. The entry of magnetosheath plasma to ionospheric levels provides an essentially permanent dayside energy source for the F region that generates a rather constant 1--2 KR of 6300-A atomic oxygen emission, a weak hydrogen emission, and some other emissions. It also produces ionospheric irregularities and enhanced electron temperatures that can be detected by a variety of methods, all of this in a region normally centered at noon and 78/sup 0/ in invariant coordinates, with a latitude extent of a few degrees and a longitude extent of a few hours. The cleft ionization is an important source for the polar cap ionisphere, and the detailed nature of its effect depends upon the interplanetary field and on magnetospheric influences on the polar cap convection pattern. Some questions for further study are given in conclusion.

• Research Organization: Department of Plasma Physics, Royal Institute of Technology, S-100 44 Stockholm, Sweden
• OSTI ID: 5730188
• Journal Information: Rev. Geophys. Space Phys.; (United States), Journal Name: Rev. Geophys. Space Phys.; (United States) Vol. 17:8; ISSN RGPSB
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAE
CHARGED-PARTICLE PRECIPITATION
DAILY VARIATIONS
EARTH ATMOSPHERE
ELECTRON TEMPERATURE
INTERPLANETARY MAGNETIC FIELDS
IONIZATION
IONOSPHERE
MAGNETIC FIELDS
MAGNETOSHEATH
PLANETARY IONOSPHERES
PLASMA DRIFT
VARIATIONS