TY - JOUR
T1 - Birkeland current boundary flows
AU - Archer, W. E.
AU - Knudsen, D. J.
AU - Burchill, J. K.
AU - Jackel, B.
AU - Donovan, E.
AU - Connors, M.
AU - Juusola, L.
N1 - Funding Information:
This study is based on Level 1B and Level 2 Swarm data available at https://earth.esa.int/web/guest/swarm/data-access. Swarm is a project of the European Space Agency. William Archer was supported by grants from the Canadian Space Agency and the Natural Sciences and Engineering Council of Canada. The ASI data used in this study were produced with funding from the Canadian Space Agency and National Science Foundation. THEMIS ASI data can be viewed via the University of Calgary data portal located at http://data-portal.phys.ucalgary.ca/. We thank the institutes who maintain the IMAGE Magnetometer Array. IMAGE data are available at http://www.space.fmi.fi/image/. Magnetometer data from the Greenland Magnetometer Array were provided by the National Space Institute at the Technical University of Denmark (DTU Space), gathered from CDAWeb (http://cdaweb.gsfc.nasa.gov/). We would like to thank Alexei Kouznetsov for his software used to trace IGRF12 magnetic field lines.
Publisher Copyright:
©2017. The Authors.
PY - 2017/4/1
Y1 - 2017/4/1
N2 - Intense zonal ion velocity jets in the northern nightside auroral zone are measured during quiet geomagnetic conditions by the Swarm satellites around 500 km altitude. These velocity jets, exceeding 1 km/s in over 50% of orbits measured, range from 20 to 100 km in meridional thickness and reach a maximum at the boundary between upward and downward field-aligned current. On average they represent a potential difference of approximately 3 kV between the R1/R2 currents. This boundary also separates different regions of electron temperature and meridional flow and is associated with ion upflows and anisotropic heating. Both dawnward and duskward velocity jets are observed, including some oppositely directed pairs bounding regions of upward field-aligned current. Coincident ground-based observations place ion velocity jets adjacent to auroral arcs, embedded in the auroral electrojets. Previous literature has focused on fast flows occurring in regions of relative low conductivity surrounding auroral arcs, typically during geomagnetically active conditions, and does not address the occurrence frequency of these events. We show ion velocity jets to be a persistent and ubiquitous property of the electrodynamics of quiet time R1/R2 current closure near midnight in the winter hemisphere.
AB - Intense zonal ion velocity jets in the northern nightside auroral zone are measured during quiet geomagnetic conditions by the Swarm satellites around 500 km altitude. These velocity jets, exceeding 1 km/s in over 50% of orbits measured, range from 20 to 100 km in meridional thickness and reach a maximum at the boundary between upward and downward field-aligned current. On average they represent a potential difference of approximately 3 kV between the R1/R2 currents. This boundary also separates different regions of electron temperature and meridional flow and is associated with ion upflows and anisotropic heating. Both dawnward and duskward velocity jets are observed, including some oppositely directed pairs bounding regions of upward field-aligned current. Coincident ground-based observations place ion velocity jets adjacent to auroral arcs, embedded in the auroral electrojets. Previous literature has focused on fast flows occurring in regions of relative low conductivity surrounding auroral arcs, typically during geomagnetically active conditions, and does not address the occurrence frequency of these events. We show ion velocity jets to be a persistent and ubiquitous property of the electrodynamics of quiet time R1/R2 current closure near midnight in the winter hemisphere.
KW - Birkeland Current
KW - Fast Flow
KW - Swarm Satellite
UR - http://www.scopus.com/inward/record.url?scp=85018612901&partnerID=8YFLogxK
U2 - 10.1002/2016JA023789
DO - 10.1002/2016JA023789
M3 - Journal Article
AN - SCOPUS:85018612901
SN - 2169-9380
VL - 122
SP - 4617
EP - 4627
JO - Journal of Geophysical Research: Space Physics
JF - Journal of Geophysical Research: Space Physics
IS - 4
ER -