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Dual Spacecraft Observations of Lobe Magnetic Field Perturbations Before, During and after Plasmoid ReleaseThis study examines a unique data set returned by IMP8 and Geotail on January 29, 1995 during a substorm which resulted in the ejection of a plasmoid. The two spacecraft (s/c) were situated in the north lobe of the tail and both observed a traveling compression region (TCR). From single s/c observations only the length of the plasmoid in X and an estimate of its height in Z can be determined. However, we show that dual s/c measurements of TCRs can be used to model all three dimensions of the underlying plasmoid and to estimate of its rate of expansion or contraction. For this event plasmoid dimensions of Delta(X) approximates 18, Delta(Y) approximates 30, and Delta(Z) approximates 10 R(sub e) are inferred from the IMP8 and Geotail lobe magnetic field measurements. The earthward end of the plasmoid was inferred to be near the mean location of the near-earth neutral line, X approximates -26 R(sub e). Its center was underneath IMP 8 at X approximates -34 R(sub e) and its tailward end appeared to be near X approximates -44 R(sub e). Furthermore, a factor of approximately 2 increase in the amplitude of the TCR occurred in the 1.5 min it took to move from IMP 8 to Geotail. Modeled using conservation of the magnetic flux, this increase in lobe compression implies that the underlying plasmoid was expanding at a rate of approximately 140 km/s. Such an expansion is comparable to recently reported V(sub y) speeds in "young" plasmoids in this region of the tail. Finally, the Geotail measurements indicate that a reconfiguration of the lobe magnetic field closely followed the ejection of the plasmoid which moved magnetic flux tubes into the wake behind the plasmoid where they would convect into the near-earth neutral line and reconnect.
Document ID
19990064618
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Slavin, J. A.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Hesse, M.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Owen, C. J.
(Queen Mary and Westfield Coll. London, United Kingdom)
Taguchi, S.
(University of Electro-Communications Chofu, Japan)
Fairfield, D. H.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Lepping, R. P.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Kokubun, S.
(Nagoya Univ. Toyokawa, Japan)
Mukai, T.
(Tokyo Univ. Sagamihara, Japan)
Lui, A. T. Y.
(Johns Hopkins Univ. Laurel, MD United States)
Anderson, R. R.
(Iowa Univ. Iowa City, IA United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Subject Category
Geophysics
Distribution Limits
Public
Copyright
Other

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