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On the occurrence of magnetic enhancements caused by solar wind interaction with lunar crustal fields
Author(s) -
Halekas J. S.,
Brain D. A.,
Mitchell D. L.,
Lin R. P.,
Harrison L.
Publication year - 2006
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 - 10.1029/2006gl025931
Subject(s) - solar wind , geology , geophysics , shock (circulatory) , mach number , bow shock (aerodynamics) , upstream (networking) , shock wave , physics , magnetic field , mechanics , quantum mechanics , medicine , computer network , computer science
We use Lunar Prospector data to identify 990 magnetic enhancements, previously termed “limb shocks” or “limb compressions”, external to the lunar wake. We find that they are clearly associated with lunar crustal sources, and sometimes occur far upstream from the limb at altitudes of ∼100 km. This is inconsistent with compressional disturbances convecting downstream with the solar wind, and implies that crustal fields are sometimes strong and coherent enough to produce a fluid‐like interaction where compressional waves steepen to form a shock extending upstream from their source. The likelihood of observing enhancements partly depends on upstream solar wind conditions, with low proton gyroradius and low β particularly favored. Low Mach numbers, implying a larger shock standoff distance, are also favored for observations which suggest shock‐like behavior.