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Upstream Pc3‐4 waves: Experimental evidence of propagation to the nightside plasmapause/plasmatrough
Author(s) -
Ponomarenko P. V.,
Waters C. L.,
StMaurice J.P.
Publication year - 2010
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 - 10.1029/2010gl045416
Subject(s) - physics , plasmasphere , geophysics , magnetosphere , magnetohydrodynamics , field line , computational physics , magnetohydrodynamic drive , wave propagation , magnetic field , shock wave , longitudinal wave , interplanetary magnetic field , solar wind , mechanics , optics , quantum mechanics
Compressional magnetohydrodynamic (MHD) waves in the Pc3‐4 frequency range (≃10–50 mHz) are generally believed to be generated upstream of the Earth's bow‐shock in reflected proton beams. Inside the closed field‐line geometry, these waves are conventionally considered to be a dayside phenomenon. However, recent studies suggest that some of the nighttime Pc4 pulsations may in fact have an upstream origin. In this letter, we report synchronous variations of the Pc3‐4 spectra near post‐dawn cusp and nightside plasmapause/plasmatrough as observed by HF radar and ground magnetometers. The measured Pc3‐4 frequency closely follows that of the upstream waves theoretically predicted based on the dynamics of the interplanetary magnetic field, which presents the most convincing evidence to date of upstream‐generated Pc3‐4 waves propagating to the nightside magnetosphere in the closed field‐line geometry. We conclude the letter with a brief discussion of a possible propagation scenario.