Premium
Universal time control of AKR: Earth is a spin‐modulated variable radio source
Author(s) -
Morioka Akira,
Miyoshi Yoshizumi,
Kurita Satoshi,
Kasaba Yasumasa,
Angelopoulos Vassilis,
Misawa Hiroaki,
Kojima Hirotsugu,
McFadden James P.
Publication year - 2013
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/jgra.50180
Subject(s) - magnetosphere , physics , earth's magnetic field , particle acceleration , ionosphere , acceleration , geophysics , universal time , astrophysics , atmospheric sciences , computational physics , magnetic field , astronomy , classical mechanics , quantum mechanics
Auroral kilometric radiation (AKR) is known to be transient emissions generated by rapidly accelerated electrons together with sudden auroral activation in the polar magnetosphere. In contrast, the characteristics and relationship with the auroral acceleration of rather continuous AKR emissions are not well understood. We examine the emission using long‐term data and report that the continuous AKR emission frequency changes with universal time (UT) as the Earth rotates, indicating that the Earth is a spin‐modulated variable radio source. The observed UT variation of AKR frequency means that the acceleration altitude changes periodically with planetary rotation. The observations indicate that the diurnal wobble of the tilted geomagnetic field in the solar wind flow alters the magnetosphere‐ionosphere (M‐I) coupling state in the polar magnetosphere, giving rise to periodic variation of auroral particle acceleration altitude. These observations of planetary radio wave properties provide insight into the physics of planetary particle acceleration.