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Statistical studies of impulsive events at high latitudesA statistical study has been made of the high-latitude impulsive events that were observed during the 1985-1986 South Pole Balloon Campaign. The events were selected by searching for unipolar pulses greater than or equal to 10 nT above background in the vertical component of the magnetic field on the ground and/or pedestal or 'W' shaped horizontal electric field perturbations greater than or equal to 10 mV/m in amplitude and accompanied by perturbations in the vertical electric field at balloon altitude. A main event list comprising 112 events was compiled from the 468 hours of data available. Three aspects of the events were examined: the solar wind conditions prior to the event, local time of observation, and intrinsic properties of the events. The local time distribution was obtained from the 112 entry main event list and was found to be nearly uniform across the dayside, with no midday gap. The event rate found using our low-amplitude selection criteria was 0.7 event/hr, comparable to expectations based on in situ studies of the magnetopause. A total of 42 events were found for which data were available from Interplanetary Monitoring Platform (IMP) 8. Of these events, 12 occurred when the Z(sub GSM) component (B(sub Z)) of the interplanetary magnetic field (IMF) was northward and 30 occurred when B(sub Z) was southward or fluctuating. Only three of the B(sub Z) northward cases and only five of the B(sub Z) southward cases were preceded by pressure pulses greater than 0.4 nPa in amplitude. Ten of the events were studied in detail by means of a model-fitting method discussed elsewhere. This method infers values of several parameters, including the total current flowing in a coaxial or monopole system and a two-dimensional dipole system. The intrinsic properties of the events showed that only approximately 10% of the total current contributed to momentum transfer to the high-latitude ionosphere, that the direction of the motion depended more on local time of observation than IMF B(sub y), and that events were usually several hundred kilometers in size. The observed B(sub z) control found in the 42 event list and the prevalence of coaxial current dominated events are inconsistent with the predictions of the pressure pulse model.
Document ID
19950058889
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Lin, Z. M.
(University of Houston, Houston, TX United States)
Bering, E. A.
(University of Houston, Houston, TX United States)
Benbrook, J. R.
(University of Houston, Houston, TX United States)
Liao, B.
(University of Houston, Houston, TX United States)
Lanzerotti, L. J.
(AT&T Bell Laboratories, Murray Hill, NJ United States)
Maclennan, C. G.
(AT&T Bell Laboratories, Murray Hill, NJ United States)
Wolfe, A. N.
(AT&T Bell Laboratories, Murray Hill, NJ United States)
Friis-Christensen, E.
(Danish Meteorological Institute Copenhagen, Denmark)
Date Acquired
August 16, 2013
Publication Date
May 1, 1995
Publication Information
Publication: Journal of Geophysical Research
Volume: 100
Issue: A5
ISSN: 0148-0227
Subject Category
Geophysics
Accession Number
95A90488
Funding Number(s)
CONTRACT_GRANT: NSF DPP-84-15203
CONTRACT_GRANT: NSF DPP-86-18974
CONTRACT_GRANT: NSF DPP-90-19567
CONTRACT_GRANT: NAG5-584
CONTRACT_GRANT: NSF DPP-89-21094
CONTRACT_GRANT: NSF DPP-83-18013
CONTRACT_GRANT: NSF DPP-86-14091
Distribution Limits
Public
Copyright
Other

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