Observations and Fully Coupled Simulations of Nighttime Ionospheric Irregularities in the Subauroral E Region

Observations and theory of plasma density irregularities in subauroral sporadic E layers are presented. The irregularities produce so‐called quasiperiodic (QP) coherent scatter radar echoes, and imagery of the echoes reveals large‐scale structuring which normally takes the form of bands of backscatter elongated from northwest to southeast and propagating to the southwest in the northern hemisphere. We associate the large‐scale structuring with neutral dynamics in general and Ekman‐type instability in particular. This is an inflection point instability, a generalization of Kelvin‐Helmholtz instability in turning shears, the same shears that form sporadic E ionization layers in the first place. A key parameter for the instability is α $\alpha $ , the asymptotic direction of the neutral winds at the top of the shear spiral relative to magnetic east. The α $\alpha $ parameter controls the alignment of the rolls produced by inflection point instability. Numerical simulations involving fully coupled neutral and ionospheric dynamics reproduce many of the characteristics of the QP echoes. We argue that only angles α $\alpha $ within the first two quadrants are consistent with sporadic E layer formation, and only angles in the second quadrant are consistent with the production of strong field‐aligned currents which may be necessary for small‐scale field‐aligned plasma density irregularity creation. This may explain the alignment of QP‐echo striations observed by imaging radar.

• Publication year

  2025

• Venue

  Journal of Geophysical Research: Space Physics

• Publication date

  2025-08-01

• Fields of study

  Not labeled

• Identifiers
  DOI 10.1029/2025JA034247
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar

• No claims are published for this paper.

• No concepts are published for this paper.

• Simultaneous observations of irregular sporadic E structures using the LWA and a DPS4D

  2025cited by this paper
• Observations and Model of Subauroral Sporadic E Layer Irregularities Driven by Turning Shears and Dynamic Instability

  2024cited by this paper
• Self-consistent Global Transport of Metallic Ions with WACCM-X

  2021cited by this paper
• VHF Imaging Radar Observations and Theory of Banded Midlatitude Sporadic E Ionization Layers

  2021cited by this paper
• Vertical fine structure and time evolution of plasma irregularities in the Es layer observed by a high-resolution Ca+ lidar

  2019cited by this paper
• Dedalus: A flexible framework for numerical simulations with spectral methods

  2019cited by this paper
• The global climatology of the intensity of ionospheric sporadic E layer

  2018cited by this paper
• Major upwelling and overturning in the mid-latitude F region ionosphere

  2018cited by this paper
• for Discussion on the Ionosphere.

  2017cited by this paper
• Sporadic E ionization layers observed with radar imaging and ionospheric modification

  2014cited by this paper
• High time and height resolution neutral wind profile measurements across the mesosphere/lower thermosphere region using the Arecibo incoherent scatter radar

  2014cited by this paper
• Fine structure in midlatitude sporadic E layers

  2013cited by this paper
• Midlatitude Sporadic E. A Typical Paradigm of Atmosphere-Ionosphere Coupling

  2012cited by this paper
• Dynamic instability in the lower thermosphere inferred from irregular sporadic E layers

  2012influential reference
• Gravity wave heating and cooling of the thermosphere: Sensible heat flux and viscous flux of kinetic energy

  2011cited by this paper
• Overturning instability in the mesosphere and lower thermosphere: analysis of instability conditions in lidar data

  2009cited by this paper
• Emergence and Secondary Instability of Ekman Layer Rolls

  2008cited by this paper
• Three‐dimensional simulation of the coupled Perkins and Es‐layer instabilities in the nighttime midlatitude ionosphere

  2008cited by this paper
• Imaging coherent scatter radar, incoherent scatter radar, and optical observations of quasiperiodic structures associated with sporadic E layers

  2007influential reference
• Wavelength dependence of the linear growth rate of the E s layer instability

  2006cited by this paper
• Radio tomographic imaging of sporadic- E layers during SEEK-2

  2005cited by this paper
• Observations of overturning in the upper mesosphere and lower thermosphere and the implications for enhanced winds

  2004cited by this paper
• Common volume coherent and incoherent scatter radar observations of mid-latitude sporadic E-layers and QP echoes

  2004cited by this paper
• Hydrodynamic stability of the Ekman boundary layer including interaction with a compliant surface: a numerical framework

  2003cited by this paper
• A direction‐dependent instability of sporadic‐E layers in the nighttime midlatitude ionosphere

  2002cited by this paper
• Three‐fluid Ohm's law

  2001cited by this paper
• Optical remote sensing of the thermosphere with HF pumped artificial airglow

  2000cited by this paper
• HF radar observations of quasiperiodic E layer echoes over North America

  1999cited by this paper
• Structures in sporadic‐E observed with an impedance probe during the SEEK Campaign: Comparisons with neutral‐wind and radar‐echo observations

  1998cited by this paper
• The SEEK (Sporadic‐E Experiment over Kyushu) Campaign

  1998cited by this paper
• First 24.5‐MHz radar measurements of quasi‐periodic backscatter from field‐aligned irregularities in midlatitude sporadic E

  1998cited by this paper
• The SEEK Chemical Release Experiment: Observed neutral wind profile in a region of sporadic E

  1998cited by this paper
• Auroral electrojet plasma irregularity theory and experiment: A critical review of present understanding and future directions

  1996cited by this paper
• High‐frequency Doppler radar observations of magnetic aspect sensitive irregularities in the midlatitude E region ionosphere

  1995cited by this paper
• Observation of the modified two‐stream plasma instability in the midlatitude E region ionosphere

  1994cited by this paper
• A three dimensional study of E region irregularity patches in the equatorial anomaly region using the Chung-Li VHF radar

  1994cited by this paper
• A morphological study on mid-latitude E-region field-aligned irregularities observed with the MU radar

  1992cited by this paper
• Mid‐latitude E region field‐aligned irregularities observed with the MU radar

  1991cited by this paper
• A numerical study of the turbulent Ekman layer

  1990cited by this paper
• The influence of the horizontal component of Earth's angular velocity on the instability of the Ekman layer

  1985cited by this paper
• A two-dimensional numerical study of horizontal roll vortices in the neutral atmospheric boundary layer

  1980cited by this paper
• Incoherent scatter radar observations of irregular structure in mid‐latitude sporadic E layers

  1978cited by this paper
• Spread F and ionospheric currents

  1973cited by this paper
• Instability of Ekman Boundary Flow

  1967cited by this paper
• A Numerical Study of the Instability of the Laminar Ekman Boundary Layer

  1966cited by this paper
• Formation of the Sporadic E Layer in the Temperate Zones

  1960cited by this paper
• Some automatic records of wireless waves reflected from the ionosphere

  1934cited by this paper

• No citing papers are available for this paper.