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A Simulation Study on the Relationship Between Field‐Aligned and Field‐Perpendicular Plasma Velocities in the Ionospheric F Region
Author(s) -
Chen Junjie,
Lei Jiuhou,
Zhang Shunrong,
Wang Wenbing,
Dang Tong
Publication year - 2020
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2019ja027350
Subject(s) - ionosphere , dynamo , physics , thermosphere , zonal and meridional , atmospheric sciences , convection , f region , geophysics , latitude , incoherent scatter , plasma , field line , electric field , forcing (mathematics) , dynamo theory , magnetic field , meteorology , astronomy , quantum mechanics
Abstract This study addresses a long‐standing scientific puzzle regarding ionospheric F 2 region dynamics. Incoherent scatter radar observations of F 2 region plasma drifts showed a strong anticorrelation between temporal variations of field‐aligned upward plasma velocity ( V i ‖ ) and field‐perpendicular poleward plasma drift ( V i ⊥ N ) over time scales from a few hours to a day at middle latitudes. The underlying physical processes remain a highly controversial issue, despite a number of speculations and qualitative inspections. Previous studies lacked especially quantitative analysis that could lead to decisive conclusions. In this study, we provide a comprehensive modeling study to explore the physical processes relating V i ‖ with V i ⊥ N variations using a self‐consistent Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model. It is found that the anticorrelation between V i ‖ and V i ⊥ N has strong altitudinal and latitudinal dependences. The anticorrelation between the diurnal variations of V i ‖ and V i ⊥ N is associated with the neutral wind dynamo. Poleward meridional winds result in downward V i ‖ and poleward V i ⊥ N , and vice versa. The anticorrelation between short‐term temporal disturbances of V i ‖ and V i ⊥ N is mainly caused by ion drag, in response to high‐latitude convection electric field forcing. This forcing penetrates to lower latitudes and affects poleward plasma drifts V i ⊥ N , which drags poleward meridional winds and modulates downward V i ‖ . As the enhanced convection electric fields subside, the anticorrelation is mainly associated with disturbance meridional wind dynamo. The storm time high‐latitude energy and momentum inputs change global meridional winds which modify zonal electric fields to induce V i ⊥ N changes. Furthermore, ambipolar diffusion plays a significant role in modulating the relationship between V i ‖ and V i ⊥ N .