Observations of AGW/TID propagation across the polar cap: a case study

Abstract. In this paper, we present observational evidence for the trans-polar propagation of large-scale Traveling Ionospheric Disturbances (TIDs) from their nightside source region to the dayside. On 13 February 2001, the 32 m dish of EISCAT Svalbard Radar (ESR) was directing toward the geomagnetic pole at low elevation (30°) during the interval 06:00–12:00 UT (MLT ≈ UT + 3 h), providing an excellent opportunity to monitor the ionosphere F-region over the polar cap. The TIDs were first detected by the ESR over the dayside north polar cap, propagating equatorward, and were subsequently seen by the mainland UHF radar at auroral latitudes around geomagnetic local noon. The propagation properties of the observed ionization waves suggest the presence of a moderately large-scale TIDs, propagating across the northern polar cap from the night-time auroral source during substorm conditions. Our results agree with the theoretical simulations by Balthazor and Moffett (1999) in which poleward-propagating large-scale traveling atmospheric disturbances were found to be self-consistently driven by enhancements in auroral heating.

[1]  J. Innis.  Deceleration of the high‐latitude thermospheric wind by polar cap gravity waves , 2000 .

[2]  P. Dyson,et al.  Evidence for thermospheric gravity waves in the southern polar cap from ground-based vertical velocity and photometric observations , 2001 .

[3]  M. J. Davis,et al.  On polar substorms as the source of large-scale traveling ionospheric disturbances , 1971 .

[4]  M. Conde,et al.  High-latitude thermospheric vertical wind activity from Dynamics Explorer 2 Wind and Temperature Spectrometer Observations: Indications of a source region for polar cap gravity waves , 2002 .

[5]  F. S. Johnson,et al.  Gravity waves near 300 km over the polar caps , 1995 .

[6]  M. Yamamoto,et al.  Ground observation and AMIE‐TIEGCM modeling of a storm‐time traveling ionospheric disturbance , 2007 .

[7]  S. Ma,et al.  Case studies of the propagation characteristics of auroral TIDS with EISCAT CP2 data using maximum entropy cross-spectral analysis , 1998 .

[8]  S. Oyama,et al.  Generation of atmospheric gravity waves associated with auroral activity in the polar F region , 2001 .

[9]  H. G. Muller,et al.  The generation and propagation of atmospheric gravity waves observed during the Worldwide Atmospheric Gravity-wave Study (WAGS) , 1988 .

[10]  Michael C. Kelley,et al.  The Earth's Ionosphere : Plasma Physics and Electrodynamics , 1989 .

[11]  S. Basu,et al.  Simultaneous observation of traveling ionospheric disturbances in the Northern and Southern Hemispheres , 2009 .

[12]  G. Kirchengast.  Characteristics of high‐latitude TIDs from different causative mechanisms deduced by theoretical modeling , 1997 .

[13]  G. Kirchengast.  Elucidation of the physics of the gravity wave‐TID relationship with the aid of theoretical simulations , 1996 .

[14]  K. Yeh,et al.  Acoustic‐gravity waves in the upper atmosphere , 1974 .

[15]  K. Hocke,et al.  The gravity wave-TID relationship: insight via theoretical model—EISCAT data comparison , 1996 .

[16]  Robert D. Hunsucker,et al.  Atmospheric gravity waves generated in the high‐latitude ionosphere: A review , 1982 .

[17]  D. Moorcroft,et al.  Finding gravity wave source positions using the Super Dual Auroral Radar Network , 1999 .

[18]  K. Hocke.  Tidal variations in the high-latitude E- and F-region observed by EISCAT , 1996 .

[19]  Feng Ding,et al.  A statistical study of large-scale traveling ionospheric disturbances observed by GPS TEC during major magnetic storms over the years 2003–2005 , 2008 .

[20]  K. Freeman,et al.  Worldwide atmospheric gravity-wave study in the European sector 1985–1990 , 1993 .

[21]  J. MacDougall,et al.  F region gravity waves in the central polar cap , 1997 .

[22]  S. E. Pryse,et al.  Evidence for the tongue of ionization under northward interplanetary magnetic field conditions , 2005 .

[23]  Arthur D. Richmond,et al.  Gravity wave generation, propagation, and dissipation in the thermosphere , 1978 .

[24]  R. L. Balthazor,et al.  Morphology of large-scale traveling atmospheric disturbances in the polar thermosphere , 1999 .

[25]  K. Hocke,et al.  A review of atmospheric gravity waves and travelling ionospheric disturbances: 1982-1995 , 1996 .

[26]  Samuel H. Francis,et al.  A theory of medium‐scale traveling ionospheric disturbances , 1974 .