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Magnetic‐quadrupole source of Neptune “high‐latitude” radio emission
Author(s) -
Sawyer C. B.,
King N. V.,
Romig J. H.,
Warwick J. W.
Publication year - 1995
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 - 10.1029/95gl01420
Subject(s) - neptune , physics , dipole , magnetic field , uranus , quadrupole , radio occultation , astronomy , astrophysics , dipole model of the earth's magnetic field , multipole expansion , magnetic dipole , ionosphere , radio wave , geophysics , planet , interplanetary magnetic field , solar wind , atomic physics , quantum mechanics
We study the occultation of the dominant X‐mode component of Neptune's smooth “high‐latitude” emission. A dipole magnetic model relates the frequency dependence of observed times of maximum emission to radio‐source locations. Dipole‐based analysis leads to seemingly convincing auroral sources. Yet multipole models of Neptune's complex magnetic field yield quite different results. Steep slopes on each constant‐field radio‐source surface explain the radio cutoff at the corresponding gyrofrequency. With the observed sense of circular polarization, the modeled radio horizon at occultation locates the radio source at a low‐latitude magnetic quadrupole rather than in the expected auroral region.