Open AccessGeneration of atmospheric gravity waves associated with auroral activity in the polar F region
Author(s) -
Oyama S.,
Ishii M.,
Murayama Y.,
Shinagawa H.,
Buchert S. C.,
Fujii R.,
Kofman W.
Publication year - 2001
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2001ja900032
Subject(s) - physics , polar , geophysics , oscillation (cell signaling) , gravity wave , phase velocity , phase (matter) , radar , earth's magnetic field , geology , geodesy , gravitational wave , magnetic field , astrophysics , optics , astronomy , telecommunications , genetics , quantum mechanics , computer science , biology
Relations between auroral activities and the generation of neutral‐wind oscillations in the polar F region (150–300 km) were investigated using data from the European Incoherent Scatter (EISCAT) radar, the all‐sky auroral camera, and the IMAGE (International Monitor for Auroral Geomagnetic Effects) magnetograms. We dealt with two cases: observations on March 1, 1995 (case 1), and on March 29, 1995 (case 2). For both cases the field‐aligned component of the neutral‐wind velocity estimated from EISCAT radar data had dominant oscillation periods of 20–30 min, which are longer than the typical Brunt‐Väisälä period in the polar F region (≃13 min). The observed oscillations showed the downward propagation of the phase with time. These properties on the oscillation period and the phase are general ones of atmospheric gravity waves (AGWs). For case 1 the all‐sky auroral images obtained at Kilpisjärvi showed the auroral arc extending in an almost zonal direction near a distance estimated using wave parameters derived from the equation of the dispersion relation for AGWs applicable to the observed oscillations. This suggested that the auroral arc appeared to be the effective generator of the observed oscillations. The comparison of observed phase lines with predicted ones using models by Francis [1974] and Kato et al. [1977] showed agreements between the two for both cases. The comparison suggests that effective parameters of the wave source in characterizing neutral‐wind oscillations would be the horizontal distribution of the wave source and the distance between the observing point and the source region. It was concluded that geomagnetic activities on March 1 and 29, 1995, in northern Scandinavia significantly related to the generation of the observed oscillations. The conclusion implies that geomagnetic activities at high latitudes are an important source to generate AGWs, as indicated by previous theoretical studies.