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Three‐dimensional currents of electrodynamic tethers obtained from laboratory models
Author(s) -
Urrutia J. M.,
Stenzel R. L.,
Rousculp C. L.
Publication year - 1994
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/94gl00002
Subject(s) - physics , whistler , plasma , superposition principle , current (fluid) , atomic physics , magnetic field , excited state , transient (computer programming) , amplitude , optics , nuclear physics , quantum mechanics , computer science , thermodynamics , operating system
Magnetic probe measurements in three dimensions (>15,000 positions) and time in a large laboratory plasma ( n e ≥10 11 cm −3 , k T e ≥1 eV, B 0 = 20 G, 1 m diam. × 2.5 m length) reveal the plasma currents J = ∇ × B /μ 0 excited by a pulsed (Δ t = 100 ns), stationary, tethered pair of electrodes (≈ 1 cm diam., 20 cm spacing ⟂ B 0 ). The plasma currents for a moving, dc‐current carrying electrodynamic tether are obtained by a superposition of delayed pulses emitted at successively displaced tether positions. The transient plasma currents are carried by low‐frequency whistlers instead of Alfvén waves and form a 3D wing structure but no long phantom loop due to cross‐field Hall current shunting.