Solar wind conditions for a quiet magnetosphere

Journal Article · Sat Dec 01 04:00:00 EST 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA095iA12p20867· OSTI ID:5378276

Kerns, K J; Gussenhoven, M S ^[1]

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1. Air Force Geophysics Lab., Hanscom AFB, MA (USA)

The conditions of the solar wind that lead to a quiet magnetosphere are determined under the assumption that the quiet or baseline magnetosphere can be identified by prolonged periods of low values of the am index. The authors analyzed solar wind data from 1978 to 1984 (7 years) during periods in which am {<=} 3 nT to identify those solar wind parameters that deviate significantly from average values. Parallel studies were also performed for prolonged periods of Kp = 0, 0+ and AE < 35 nT. They find that for quiet times the solar wind velocity (V), the interplanetary magnetic field magnitude (B), and the z component of the IMF (B{sub z}) show distinctive variations from average values. They independently varied these solar wind parameters and the length of time the conditions must persist to minimize am. This was done with the additional requirement that the conditions yield a reasonable number of occurrences (5% of the data set). The resulting baseline conditions are V {le} 390 km/s; 180{degree} - arctan {vert bar}B{sub y}/B{sub z}{vert bar} {le} 101{degree}, when b{sub z} {le} 0 (no restriction on B{sub z} positive); B {le} 6.5 nT; and persistence of these conditions for at least 5 hours. Minimizing the am index does not require a clear upper limit on the value of B{sub z} as might be anticipated from the work of Gussenhoven (1988) and Berthelier (1980). Apparently, this is a result of the requirement that the conditions must occur 5% of the time. When the requirement is lowered to 1% occurrence, an upper limit to B{sub z} emerges.

• OSTI ID: 5378276
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:A12; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
&amp; Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CURRENTS
DATA ANALYSIS
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ELECTRIC CURRENTS
ELECTROJETS
GEOMAGNETIC FIELD
INTERACTIONS
INTERPLANETARY MAGNETIC FIELDS
ION TEMPERATURE
LIMITING VALUES
MAGNETIC BAYS
MAGNETIC FIELDS
MAGNETIC STORMS
SOLAR ACTIVITY
SOLAR WIND
VARIATIONS
VELOCITY