Rights statement: Copyright 2012 by the American Geophysical Union
Final published version, 13.1 MB, PDF document
Available under license: CC BY-NC-SA
Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
}
TY - JOUR
T1 - A quantitative deconstruction of the morphology of high-latitude ionospheric convection
AU - Grocott, A.
AU - Milan, S. E.
AU - Imber, S. M.
AU - Lester, M.
AU - Yeoman, T. K.
N1 - Copyright 2012 by the American Geophysical Union
PY - 2012/5/17
Y1 - 2012/5/17
N2 - We present an analysis of ionospheric convection data derived from velocity measurements made by the Super Dual Auroral Radar Network (SuperDARN). Our analysis uses an established technique for combining the network data to produce maps of large-scale convection by fitting a spherical harmonic expansion of the ionospheric electric potential to the radar measurements. We discuss how the basis functions of the spherical harmonic expansion describe different characteristic elements of the ionospheric convection pattern and show how their associated coefficients can be used to quantify the morphology of the convection, much like the total transpolar voltage is used to quantify its strength, in relation to upstream interplanetary magnetic field conditions and associated magnetospheric activity. We find that similar to 2/3 of the voltage associated with the typical convection pattern is described by a simple twin vortex basis function. The magnitude of the twin vortex is strongly dependent on IMF B-Z and the degree of its (typically westward) rotation is weakly dependent on IMF B-Y. The remaining similar to 1/3 of the total voltage is associated with deviations from the basic twin vortex pattern, introduced by the addition of other basis functions, such as IMF B-Y associated dusk-dawn asymmetries, nightside convection features associated with tail activity, and "reverse" high-latitude convection cells associated with intervals of IMF B-Z > 0.
AB - We present an analysis of ionospheric convection data derived from velocity measurements made by the Super Dual Auroral Radar Network (SuperDARN). Our analysis uses an established technique for combining the network data to produce maps of large-scale convection by fitting a spherical harmonic expansion of the ionospheric electric potential to the radar measurements. We discuss how the basis functions of the spherical harmonic expansion describe different characteristic elements of the ionospheric convection pattern and show how their associated coefficients can be used to quantify the morphology of the convection, much like the total transpolar voltage is used to quantify its strength, in relation to upstream interplanetary magnetic field conditions and associated magnetospheric activity. We find that similar to 2/3 of the voltage associated with the typical convection pattern is described by a simple twin vortex basis function. The magnitude of the twin vortex is strongly dependent on IMF B-Z and the degree of its (typically westward) rotation is weakly dependent on IMF B-Y. The remaining similar to 1/3 of the total voltage is associated with deviations from the basic twin vortex pattern, introduced by the addition of other basis functions, such as IMF B-Y associated dusk-dawn asymmetries, nightside convection features associated with tail activity, and "reverse" high-latitude convection cells associated with intervals of IMF B-Z > 0.
KW - INTERPLANETARY MAGNETIC-FIELD
KW - DUAL LOBE RECONNECTION
KW - HF RADAR OBSERVATIONS
KW - STATISTICAL PATTERNS
KW - SUPERDARN
KW - SIGNATURES
KW - TIME
KW - FLOW
KW - IMF
U2 - 10.1029/2012JA017580
DO - 10.1029/2012JA017580
M3 - Journal article
VL - 117
JO - Journal of Geophysical Research
JF - Journal of Geophysical Research
SN - 0148-0227
IS - A5
M1 - 05317
ER -