Rights statement: An edited version of this paper was published by AGU. Copyright 2017 American Geophysical Union.
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Rights statement: ©2017. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
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Available under license: CC BY: Creative Commons Attribution 4.0 International License
Final published version
Licence: CC BY: Creative Commons Attribution 4.0 International License
Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
}
TY - JOUR
T1 - Average field-aligned ion velocity over the EISCAT radars
AU - Yamazaki, Yosuke
AU - Kosch, Michael Jurgen
AU - Ogawa, Yasunobu
N1 - ©2017. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
PY - 2019/5/31
Y1 - 2019/5/31
N2 - Long-term measurements by the European Incoherent Scatter (EISCAT) radars at Tromsø (69.6° N, 19.2° E) and Svalbard (78.2° N, 16.0° E) are used to determine the climatology of the field-aligned ion velocity in the F-region ionosphere (175–475 km) at high latitudes. The average ion velocity is calculated at various altitudes and times of day. The magnitude of the average field-aligned ion velocity is on the order of 10 m/s, similar to previous results at middle and low latitudes. The results obtained for the two radars are in good agreement. During daytime the direction of the average field-aligned ion velocity changes from downward to upward around 350 km, while during nighttime it is upward at all heights. The reversal height of the daytime field-aligned ion velocity depends on solar activity. It is elevated by more than 100 km during high solar flux periods compared to low solar flux periods. The Thermosphere Ionosphere Electrodynamics General Circulation Model (TIE-GCM) reproduces the main features of the field-aligned ion velocity climatology. The simulation results suggest that the plasma pressure gradient force and gravity force play a dominant role for the daytime field-aligned ion motion. The height pattern of the field-aligned ion velocity tends to be preserved in different solar activity conditions at constant pressure surfaces, but not at constant altitudes, which explains the observed dependence on solar activity. During nighttime, the effect of the neutral wind dominates the field-aligned ion velocity.
AB - Long-term measurements by the European Incoherent Scatter (EISCAT) radars at Tromsø (69.6° N, 19.2° E) and Svalbard (78.2° N, 16.0° E) are used to determine the climatology of the field-aligned ion velocity in the F-region ionosphere (175–475 km) at high latitudes. The average ion velocity is calculated at various altitudes and times of day. The magnitude of the average field-aligned ion velocity is on the order of 10 m/s, similar to previous results at middle and low latitudes. The results obtained for the two radars are in good agreement. During daytime the direction of the average field-aligned ion velocity changes from downward to upward around 350 km, while during nighttime it is upward at all heights. The reversal height of the daytime field-aligned ion velocity depends on solar activity. It is elevated by more than 100 km during high solar flux periods compared to low solar flux periods. The Thermosphere Ionosphere Electrodynamics General Circulation Model (TIE-GCM) reproduces the main features of the field-aligned ion velocity climatology. The simulation results suggest that the plasma pressure gradient force and gravity force play a dominant role for the daytime field-aligned ion motion. The height pattern of the field-aligned ion velocity tends to be preserved in different solar activity conditions at constant pressure surfaces, but not at constant altitudes, which explains the observed dependence on solar activity. During nighttime, the effect of the neutral wind dominates the field-aligned ion velocity.
KW - EISCAT
KW - ion velocity
KW - solar cycle variation
KW - ionosphere
KW - high latitude
KW - TIE-GCM
U2 - 10.1002/2017JA023974
DO - 10.1002/2017JA023974
M3 - Journal article
VL - 122
SP - 5630
EP - 5642
JO - Journal of Geophysical Research: Space Physics
JF - Journal of Geophysical Research: Space Physics
SN - 2169-9402
IS - 5
ER -