The Role of Field-Aligned Current Closure on the E and F-Region Coupled Thermosphere-Ionosphere

2020 ◽  
Author(s):  
Daniel Billett ◽  
Kathryn McWilliams ◽  
Mark Conde
Keyword(s):  
Temporal Structure ◽  
Plasma Velocity ◽  
Velocity Data ◽  
Neutral Winds ◽  
Doppler Imager ◽  
F Region ◽  
Radar Network ◽  
Field Aligned Current ◽  
Auroral Emissions

<p>In this study, the behaviour of both E and F-region neutral winds are examined in the vicinity of intense R1 and R2 field-aligned currents (FACs), measured by AMPERE. This is achieved through the dual sampling of both the green (557.5nm) and red (630nm) auroral emissions, sequentially, from a ground based Scanning Doppler Imager (SDI) located in Alaska.</p><p>With the addition of plasma velocity data from the Super Dual Auroral Radar Network (SuperDARN) and ionospheric parameters from the Poker Flat Incoheerent Scatter Radar (PFISR), we assess how the large closure of Pedersen currents (implied by the strong FACs) modifies the spatial and temporal structure of the neutral wind at different altitudes. We find that the thermosphere becomes significantly height dependent, which could indicate a broader altitude range where the Pedersen conductivity is more important during intense FAC closure.</p>

scholarly journals Multi-instrument Observations of Ion-Neutral Coupling in the Dayside Cusp

2020 ◽  
Author(s):  
James Wild ◽  
Daniel Billett ◽  
Keisuke Hosokawa ◽  
Adrian Grocott ◽  
Anasuya Aruliah ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Change ◽  
Neutral Winds ◽  
Cusp Region ◽  
Doppler Imager ◽  
F Region ◽  
Radar Network ◽  
Magnetic Field Change ◽  
Using Data

<p>Using data from the Scanning Doppler Imager, the Super Dual Auroral Radar Network, the EISCAT Svalbard Radar and an auroral all-sky imager, we examine an instance of F-region neutral winds which have been influenced by the presence of poleward moving auroral forms near the dayside cusp region. We observe a reduction in the time taken for the ion-drag force to re-orientate the neutrals into the direction of the convective plasma (on the order of minutes), compared to before the auroral activity began. Additionally, because the ionosphere near the cusp is influenced much more readily by changes in the solar wind via dayside reconnection, we observe the neutrals responding to an interplanetary magnetic field change within minutes of it occurring. This has implications on the rate that energy is deposited into the ionosphere via Joule heating, which we show to become dampened by the neutral winds.</p>

scholarly journals <i>E</i>-region wind-driven electrical coupling of patchy sporadic-<i>E</i> and spread-<i>F</i> at midlatitude

2005 ◽  
Vol 23 (6) ◽  
pp. 2095-2105 ◽  
Author(s):  
S. Shalimov ◽  
C. Haldoupis
Keyword(s):  
Electric Fields ◽  
Electrical Coupling ◽  
Neutral Winds ◽  
Medium Scale ◽  
F Region ◽  
Sporadic E Layers ◽  
Spread F ◽  
Sporadic E ◽  
Electric Fields And Currents

Abstract. This paper investigates the role of neutral winds in the generation of relatively large polarization electric fields across patchy sporadic-E layers, which then map upward to the F region, to create conditions for medium-scale spread-F. The calculations are based on an analytical model that uses the current continuity equation and field-aligned current closures to the F region in order to describe quantitatively a Hall polarization process inside sporadic-E plasma patches during nighttime. In applying this model we use experimentally known values for E and F region, conductances, the ambient electric fields and prevailing neutral winds, in order to estimate the polarization fields that build up inside sporadic-E. It is found that the relatively strong west-southwest neutral winds during summer nighttime can provide the free energy for the generation of sizable polarization electric fields, which have comparable eastward and north-upward components and reach values of several mV/m. Given that the sporadic-E patches have sizes from a few to several tens of kilometers, the polarization fields can map easily to the F region bottomside where they impact ExB plasma uplifts and westward bulk motions, in line with key observational properties of medium-scale spread-F. However, the present simple model needs further development to also include wind forcing of the F region plasma and possible polarization processes inside spread-F. Keywords. Ionosphere (Electric fields and currents; Ionospheric irregularities; Mid-latitude ionosphere)

scholarly journals A Statistical study of the Doppler spectral width of high-latitude ionospheric F-region echoes recorded with SuperDARN coherent HF radars

2002 ◽  
Vol 20 (11) ◽  
pp. 1769-1781 ◽  
Author(s):  
J.-P. Villain ◽  
R. André ◽  
M. Pinnock ◽  
R. A. Greenwald ◽  
C. Hanuise
Keyword(s):  
High Latitude ◽  
Statistical Study ◽  
Spectral Width ◽  
Auroral Oval ◽  
F Region ◽  
Radar Network ◽  
Period 2 ◽  
Time Period ◽  
High Latitude Ionosphere ◽  
Data Points

Abstract. The HF radars of the Super Dual Auroral Radar Network (SuperDARN) provide measurements of the E × B drift of ionospheric plasma over extended regions of the high-latitude ionosphere. We have conducted a statistical study of the associated Doppler spectral width of ionospheric F-region echoes. The study has been conducted with all available radars from the Northern Hemisphere for 2 specific periods of time. Period 1 corresponds to the winter months of 1994, while period 2 covers October 1996 to March 1997. The distributions of data points and average spectral width are presented as a function of Magnetic Latitude and Magnetic Local Time. The databases are very consistent and exhibit the same features. The most stringent features are: a region of very high spectral width, collocated with the ionospheric LLBL/cusp/mantle region; an oval shaped region of high spectral width, whose equator-ward boundary matches the poleward limit of the Holzworth and Meng auroral oval. A simulation has been conducted to evaluate the geometrical and instrumental effects on the spectral width. It shows that these effects cannot account for the observed spectral features. It is then concluded that these specific spectral width characteristics are the signature of ionospheric/magnetospheric coupling phenomena.Key words. Ionosphere (auroral ionosphere; ionosphere-magnetosphere interactions; ionospheric irregularities)

Thermospheric Meridional Wind Control on Equatorial Scintillations and the Role of the Evening F-Region Height Rise, E × B Drift Velocities and F2-Peak Density Gradients

2010 ◽  
Vol 31 (5) ◽  
pp. 509-530 ◽  
Author(s):  
M. T. A. H. Muella ◽  
E. R. de Paula ◽  
P. R. Fagundes ◽  
J. A. Bittencourt ◽  
Y. Sahai
Keyword(s):  
Meridional Wind ◽  
Density Gradients ◽  
Peak Density ◽  
F Region

Investigation on the role of E-F region coupling processes on the generation of nighttime MSTIDs: Case studies over northern Germany

2021 ◽  
Author(s):  
Mani Sivakandan ◽  
Jorge L Chau ◽  
Carlos Martinis ◽  
Yuichi Otsuka ◽  
Jens Mielich ◽  
...  
Keyword(s):  
Gps Tec ◽  
F Region ◽  
Perkins Instability ◽  
Sporadic E Layers ◽  
Spread F ◽  
E Region ◽  
Sporadic E ◽  
Low Latitude Ionosphere ◽  
Atmospheric Gravity

&lt;p&gt;Northwest to southeast phase fronts with southwestward moving features are commonly observed in the nighttime midlatitude ionosphere during the solstice months at low solar activity. These features are identified as nighttime MSTIDs (medium scale traveling ionospheric disturbances). Initially, they were considered to be a manifestation of neutral atmospheric gravity waves. Later on, investigations showed that the nighttime MSTIDs are electrified in nature and mostly confined to the mid and low latitude ionosphere. Although the overall characteristics of the nighttime MSTIDs are mostly well understood, the causative mechanisms are not well known. Perkins instability mechanism was believed to be the cause of nighttime MSTIDs, however, the growth rate of the instability is too small to explain the perturbations observed. Recently, model simulations and observational studies suggest that coupling between sporadic-E layers and other type of E-region instabilities, and the F region may be relevant to explain the generation of the MSTIDs.&lt;/p&gt;&lt;p&gt;In the present study simultaneous observation from OI 630 nm all-sky airglow imager, GPS-TEC, ionosonde and Meteor radars, are used to investigate the role of E and F region coupling on the generation of MSTIDs .Nighttime MSTIDs observed on three nights (14 March 2020, 23 March 2020 and 28 May 2020) in the OI 630 nm airglow images over Kuehlungsborn (54&amp;#176;07'N; 11&amp;#176;46'E, 53.79N&amp;#160; mag latitude), Germany, are presented. Simultaneous detrended GPS-TEC measurements also shows presence of MSTIDs on these nights. In addition, simultaneous ionosonde observations over Juliusruh (54&amp;#176;37.7'N 13&amp;#176;22.5'E) show spread-F in the ionograms as well as sporadic-E layer occurrence.&amp;#160; Furthermore, we also investigate the MLT region wind variations during these nights. The role of Es-layers and the interplay between the winds and Es-layers role on the generation of the MSTIDs will be discussed in detail in this presentation.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

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