Zobrazeno 1 - 10
of 265
pro vyhledávání: '"A. D. M. Walker"'
Publikováno v:
Annales Geophysicae, Vol 34, Pp 857-870 (2016)
HF (high-frequency) radars belonging to SuperDARN (Super Dual Auroral Radar Network) receive backscatter over substantial fields of view which, when combined, allow for simultaneous returns over extensive regions of the polar caps and midlatitudes.
Externí odkaz:
https://doaj.org/article/dd15b92018a64fa0919a2d6aaaefac0f
Autor:
A. D. M. Walker, G. J. Sofko
Publikováno v:
Annales Geophysicae, Vol 34, Pp 55-65 (2016)
When studying magnetospheric convection, it is often necessary to map the steady-state electric field, measured at some point on a magnetic field line, to a magnetically conjugate point in the other hemisphere, or the equatorial plane, or at the
Externí odkaz:
https://doaj.org/article/4b56c784745f4c3c9eaad6bbde81c779
Autor:
A. D. M. Walker
Publikováno v:
Annales Geophysicae, Vol 34, Pp 67-73 (2016)
A method of mapping electric fields along geomagnetic field lines is applied to the IGRF (International Geomagnetic Reference Field) model. The method involves integrating additional sets of first order differential equations simultaneously with
Externí odkaz:
https://doaj.org/article/2fba326dc30143469ac395c63f700e6e
Autor:
A. D. M. Walker
Publikováno v:
Annales Geophysicae, Vol 32, Pp 1495-1510 (2014)
Magnetohydrodynamic (MHD) waves in the solar wind and magnetosphere are propagated in a medium whose velocity is comparable to or greater than the wave velocity and which varies in both space and time. In the approximation where the scales of the
Externí odkaz:
https://doaj.org/article/f12005834f2643599f96cba7d08d2baf
Autor:
A. D. M. Walker, J. A. E. Stephenson
Publikováno v:
Annales Geophysicae, Vol 32, Pp 1217-1221 (2014)
A case study of a magnetohydrodynamic (MHD) wave in the solar wind that is strongly correlated with a magnetospheric field line resonance observed by the SuperDARN (Super Dual Auroral Radar Network) radar at Sanae, Antarctica is presented. The dat
Externí odkaz:
https://doaj.org/article/60088618a8fc4a1193d8fa37d79f4be1
Autor:
J. A. E. Stephenson, A. D. M. Walker
Publikováno v:
Annales Geophysicae, Vol 28, Pp 47-59 (2010)
Field line resonances have been observed for decades by ground-based and in situ instruments. The driving mechanism(s) are still unclear, although previous work has provided strong grounds that coherent waves in the solar wind may be a source. Her
Externí odkaz:
https://doaj.org/article/6cdd24c3abdd45c994491c5161372bac
Publikováno v:
Annales Geophysicae, Vol 27, Pp 3287-3296 (2009)
In this paper we present the results from the observation of ultra low frequency (ULF) pulsations in the Doppler velocity data from SuperDARN HF radar located at Goose Bay (61.94° N, 23.02° E, geomagnetic). Fourier spectral techniques were used
Externí odkaz:
https://doaj.org/article/5bc894e0183c439e8ba82573a47c0a56
Autor:
A. D. M. Walker
Publikováno v:
Annales Geophysicae, Vol 23, Pp 3375-3388 (2005)
Field line resonances are thought to be excited by sources either at the magnetopause or outside it. Recent observations suggest that they may be associated with coherent oscillations or pressure pulses in the solar wind. In either case the excita
Externí odkaz:
https://doaj.org/article/9f5eda84ccff4942a16c29ab82cc77bb
Publikováno v:
Annales Geophysicae, Vol 23, Pp 2679-2686 (2005)
Three ULF wave events, all occurring in the dayside magnetopshere during magnetically quiet times, are studied using the Cluster satellites. The multi-point measurements obtained from Cluster are used to determine the azimuthal wave number for the
Externí odkaz:
https://doaj.org/article/a455d5333bd84bc1b98a7a11d57fe075
Publikováno v:
Annales Geophysicae, Vol 20, Pp 29-40 (2002)
The HF radar Doppler spectral width boundary (SWB) in the cusp represents a very good proxy for the equatorward edge of cusp ion precipitation in the dayside ionosphere. For intervals where the Interplanetary Magnetic Field (IMF) has a southwar
Externí odkaz:
https://doaj.org/article/cf108ba17d3e4e9ba337c6e179bfb6bb