TY - JOUR

T1 - FEATURES OF STEADY MAGNETOSPHERIC CONVECTION

AU - YAHNIN, A

AU - MALKOV, MV

AU - Sergeev, V.A.

AU - PELLINEN, RJ

AU - AULAMO, O

AU - VENNERSTROM, S

AU - FRIISCHRISTENSEN, E

AU - LASSEN, K

AU - DANIELSEN, C

AU - CRAVEN, JD

AU - DEEHR, C

AU - FRANK, LA

PY - 1994/3/1

Y1 - 1994/3/1

N2 - The large-scale patterns of ionospheric convection and particle precipitation are described during two intervals of steady magnetospheric convection (SMC) on November 24, 1981. The unique data set used in the analysis includes recordings from the worldwide network of magnetometers and all-sky cameras, global auroral images from the DE 1 spacecraft, and particle precipitation data from low-altitude NOAA 6 and NOAA 7 spacecraft. The data show that intense magnetospheric convection continued during more than 10 hours under the steady southward interplanetary magnetic field without any distinct substorm signatures. All data sets available confirmed the stable character of the large-scale magnetospheric configuration during this period. In particular, the magnetic flux threading the polar cap was stable (within 10%) during 3.5 hours of continued DE 1 observations. The dayside cusp was located at an unusually low latitude (70-degrees CGL). The nightside auroral pattern consisted of two distinct regions. The diffuse aurora in the equatorward half of the expanded (10-degrees wide) auroral oval was well-separated from the bright, active auroral forms found in the vicinity of the poleward boundary of the oval. The twin-vortex convection pattern had no signature of the Harang discontinuity; its nightside ''convection throat'' was spatially coincident with the poleward active auroras. This region of the auroral oval was identified as the primary site of the short-lived transient activations during the SMC intervals. The energetic particle observations show that the auroral precipitation up to its high-latitude limit is on closed field lines and that particle acceleration up to > 30-keV energy starts close to this limit. The isotropic boundaries of the > 30-keV protons and electrons were found close to each other, separating regions of discrete and diffuse precipitation. This suggests that these precipitation types originate on the very taillike and very dipolelike field lines, respectively.

AB - The large-scale patterns of ionospheric convection and particle precipitation are described during two intervals of steady magnetospheric convection (SMC) on November 24, 1981. The unique data set used in the analysis includes recordings from the worldwide network of magnetometers and all-sky cameras, global auroral images from the DE 1 spacecraft, and particle precipitation data from low-altitude NOAA 6 and NOAA 7 spacecraft. The data show that intense magnetospheric convection continued during more than 10 hours under the steady southward interplanetary magnetic field without any distinct substorm signatures. All data sets available confirmed the stable character of the large-scale magnetospheric configuration during this period. In particular, the magnetic flux threading the polar cap was stable (within 10%) during 3.5 hours of continued DE 1 observations. The dayside cusp was located at an unusually low latitude (70-degrees CGL). The nightside auroral pattern consisted of two distinct regions. The diffuse aurora in the equatorward half of the expanded (10-degrees wide) auroral oval was well-separated from the bright, active auroral forms found in the vicinity of the poleward boundary of the oval. The twin-vortex convection pattern had no signature of the Harang discontinuity; its nightside ''convection throat'' was spatially coincident with the poleward active auroras. This region of the auroral oval was identified as the primary site of the short-lived transient activations during the SMC intervals. The energetic particle observations show that the auroral precipitation up to its high-latitude limit is on closed field lines and that particle acceleration up to > 30-keV energy starts close to this limit. The isotropic boundaries of the > 30-keV protons and electrons were found close to each other, separating regions of discrete and diffuse precipitation. This suggests that these precipitation types originate on the very taillike and very dipolelike field lines, respectively.

KW - INTERPLANETARY MAGNETIC-FIELD

KW - ION PRECIPITATION

KW - TRAPPING BOUNDARY

KW - ELECTRIC-FIELDS

KW - CURRENT SYSTEMS

KW - HIGH-LATITUDE

KW - CURRENT SHEET

KW - PLASMA SHEET

KW - MAGNETOTAIL

KW - MIDNIGHT

U2 - 10.1029/93JA02868

DO - 10.1029/93JA02868

M3 - статья

VL - 99

SP - 4039

EP - 4051

JO - Journal of Geophysical Research: Biogeosciences

JF - Journal of Geophysical Research: Biogeosciences

SN - 0148-0227

IS - A3

ER -