Observations of neutral winds and electric fields using backscatter from field-aligned irregularities

2004 ◽  
Vol 5 (1) ◽  
Author(s):  
A. V. Mikhailov
Keyword(s):  
Electric Fields ◽  
Neutral Winds ◽  
Field Aligned Irregularities

scholarly journals Simulations of the neutral structure within the dusk side aurora

2006 ◽  
Vol 24 (10) ◽  
pp. 2519-2532
Author(s):  
H. F. Parish ◽  
L. R. Lyons
Keyword(s):  
Electric Fields ◽  
Three Dimensional ◽  
Meridional Wind ◽  
Recovery Phase ◽  
Limited Area ◽  
Neutral Winds ◽  
E Region ◽  
Linear Interactions ◽  
Simulated Wind ◽  
Equivalent Conditions

Abstract. Observations of neutral winds from rocket release experiments within the premidnight and postmidnight substorm recovery phase aurora, show very large E-region neutral winds of several hundred m/s, where winds measured on the dusk side are even larger than those on the dawn side. These large winds are also associated with strong shears, and there is evidence that some of the regions below these shears may be unstable. The mechanisms which generate this strong vertical structure are not well understood. It is also not known whether the acceleration conditions in the pre and post midnight sectors of the aurora may produce significantly different neutral responses on the dawn and dusk sides. Simulations have been performed using a three-dimensional high resolution limited area thermosphere model to try to understand the neutral structure within the dawn and dusk side aurora. When simulations are performed using auroral forcing alone, for equivalent conditions within the dawn and dusk sectors, differences are found in the simulated response on each side. When measured values of auroral forcing parameters, and background winds and tides consistent with recent observations, are used as model inputs, some of the main features of the zonal and meridional wind observations are reproduced in the simulations, but the magnitude of the peak zonal wind around 140 km tends to be too small and the maximum meridional wind around 130 km is overestimated. The winds above 120 km altitude are found to be sensitive to changes in electric fields and ion densities, as was the case for the dawn side, but the effects of background winds and tides on the magnitudes of the winds above 120 km are found to be relatively small on the dusk side. The structure below 120 km appears to be related mainly to background winds and tides rather than auroral forcing, as was found in earlier studies on the dawn side, although the peak magnitudes of simulated wind variations in the 100 to 120 km altitude range are smaller than those observed. The source of the strong shears measured around 110 km altitude on the dusk side is uncertain, but may be related to different kinds of oscillations, such as gravity waves, non migrating semidiurnal tides, or secondary oscillations produced by non linear interactions between waves.

Auroral electrodynamics---investigation by a dual sounding rocket experiment

2020 ◽  
Author(s):  
Hassanali Akbari ◽  
Robert Pfaff ◽  
Keyword(s):  
Electric Fields ◽  
Sounding Rocket ◽  
Sounding Rockets ◽  
Neutral Winds ◽  
Incoherent Scatter ◽  
Ac Electric Fields ◽  
Numerical Studies ◽  
Rocket Experiment ◽  
N Wave

<p>We present results from a 2017 sounding rocket experiment in which two NASA sounding rockets were simultaneously launched into the auroral ionosphere. The rockets included comprehensive instrumentation to measure DC and AC electric fields, magnetic fields, energetic particles, plasma density, and neutral winds, among other parameters, and achieved apogees of 190 and 330 km. This unprecedented collection of in-situ measurements obtained at two altitudes over an auroral arc, along with conjugate ground-based measurements by the Poker Flat incoherent scatter radar and all-sky cameras, enable us to investigate the behavior of an aurora arc and its associated electrodynamics. A prominent feature of our observations is the presence of localized, large-amplitude Alfvén wave structures observed in both the electric field and magnetometers at altitudes as low as 190 km in the vicinity of up- and down-ward current regions. The observations are discussed in the context of ionospheric feedback instability. The results are compared to predictions of previously published numerical studies and other sounding rocket observations.</p>

Simultaneous observations of neutral winds and electric fields at spaced locations in the dawn auroral oval

1989 ◽  
Vol 94 (A12) ◽  
pp. 17235 ◽  
Author(s):  
M. F. Larsen ◽  
I. S. Mikkelsen ◽  
J. W. Meriwether ◽  
R. Niciejewski ◽  
K. Vickery
Keyword(s):  
Electric Fields ◽  
Auroral Oval ◽  
Neutral Winds

scholarly journals Calculation of meridional neutral winds in middle latitudes from the Irkutsk incoherent scatter radar data

2015 ◽  
Vol 1 (3) ◽  
pp. 37-48
Author(s):  
Александр Щербаков ◽  
Aleksandr Shcherbakov ◽  
Андрей Медведев ◽  
Andrey Medvedev ◽  
Дмитрий Кушнарев ◽  
...  
Keyword(s):  
Electric Fields ◽  
Radar Data ◽  
Special Technique ◽  
Incoherent Scatter Radar ◽  
Neutral Winds ◽  
Incoherent Scatter ◽  
Plasma Drift ◽  
Middle Latitudes ◽  
Scatter Radar ◽  
The Impact

The paper sequentially presents technique for determining velocity of meridional neutral winds from the Irkutsk Incoherent Scatter Radar (IISR) data. Due to IISR specific features effective at other IS radars, techniques for determining ionosphere parameters, in particular plasma drift velocities, resulted in considerable variance of defined parameters. To measure the plasma drift velocity taking into account such IISR features, we have developed a special technique based on phase analysis of autocorrelation function of incoherent scatter signal. The technique needs to be tested, and for this purpose, an experiment was carried out to measure velocities of low-orbit satellites. However, methods for meridional neutral wind calculations used by many authors [Evans, 1970] with the use of drift velocities obtained before, resulted in great disagreements with empirical HWM93 and HWM07 wind models. In addition, simultaneous measurements at two frequencies at IISR showed that it was difficult to explain such differences without taking into account the cross-field movements. Possible underestimation of the impact of movements generated by electric fields can result in serious error in determining wind velocities. The paper considers improvements for methods of calculating winds, and shows that the results obtained with it are in a better agreement with wind models.

Global estimation of ionospheric drivers during extreme storms

2021 ◽  
Author(s):  
Aurora Lopez Rubio ◽  
Seebany Datta-Barua ◽  
Gary Bust
Keyword(s):  
Kalman Filter ◽  
Geomagnetic Storm ◽  
Electric Fields ◽  
Spherical Harmonics ◽  
Space Weather ◽  
Basis Function ◽  
Geomagnetic Storms ◽  
Vector Spherical Harmonics ◽  
Neutral Winds ◽  
Global Estimation

<p>During geomagnetic storms, the space environment can be drastically altered as the plasma in the upper atmosphere, or ionosphere, moves globally. This plasma redistribution is mainly caused by storm-time electric fields, but another important driver of the velocity of the ions in the plasma is the neutral winds. These winds refer to the movement of the neutral particles that are part of the thermospheric layer of the atmosphere, that can drag the plasma. Geomagnetic storms increase the neutral winds, due to the heating of the thermosphere that comes from the storm. In this study we want to understand how these ionospheric drivers affect the ionosphere behavior because, among other reasons, during geomagnetic storms the plasma can refract and diffract trans-ionospheric signals and, consequently, can cause problems in the navigation systems such as GNSS (Global Navigation Satellite System)/GPS (Global Positioning System) that use the information from the signals.</p><p>In this work, our objective is to estimate the electric fields and neutral winds globally during a geomagnetic storm. Global GNSS TEC (total electron content) measurements are ingested by the Ionospheric Data Assimilation 4-Dimensional (IDA4D) algorithm [1], whose output is the electron density rate over a grid at different time steps during a geomagnetic storm. The density rates are treated as “observations” in EMPIRE (Estimating Model Parameters from Ionospheric Reverse Engineering), which is a data assimilation algorithm based on the plasma continuity equation [2,3,4]. Then, the EMPIRE “observations” are used to estimate corrections to the electric field and neutral winds by solving a Kalman filter. To study these drivers with EMPIRE, basis functions are used to describe them. For the global potential field, spherical harmonics are used.</p><p>To have a global estimation of the neutral winds, we introduce vector spherical harmonics as the basis function for the first time in EMPIRE. The vector spherical harmonics are used to model orthogonal components of neutral wind in the zonal (east-west) and meridional (north-south) directions. EMPIRE’s Kalman filter needs the error covariance of the vector spherical harmonics decomposition. To calculate it, the basis function is fitted to the model HWM14 (Horizonal Wind Model) values of the neutral winds and the error between the fitting and the model is studied. Later, we study the global potential field and global neutral winds over time to understand how much each driver contributes to the plasma redistribution during the geomagnetic storm on October 25<sup>th</sup> 2011. We compare the results to FPI (Fabry-Perot Interferometer) neutral winds measurements to validate the results.   </p><p>[1] G.S.Bust, G.Crowley, T.W.Garner, T.L.G.II, R.W.Meggs, C.N.Mitchell, P.S.J.Spencer, P.Yin, and B.Zapfe, Four-dimensional gps imaging of space weather storms, Space Weather, 5 (2007),  doi:10.1029/2006SW000237.</p><p>[2] D.S.Miladinovich, S.Datta-Barua, G.S.Bust, and J.J.Makela, Assimilation of thermospheric measurements for ionosphere-thermosphere state estimation, Radio Science, 51 (2016).</p><p>[3] D.S.Miladinovich, S.Datta-Barua, A.Lopez, S. Zhang, and G.S.Bust, Assimilation of gnss measurements for estimation of high-latitude convection processes, Space Weather, 18 (2020).</p><p>[4] G.S.Bust and S.Datta-Barua, Scientific investigations using ida4d and empire, in Modeling the Ionosphere-Thermosphere System, J. Huba, R. Schunk, and G. Khazanov, eds., John Wiley & Sons, Ltd, 1 ed., 2014.</p>

Neutral winds and electric fields in the dusk auroral oval 2. Theory and model

1981 ◽  
Vol 86 (A3) ◽  
pp. 1525 ◽  
Author(s):  
I. S. Mikkelsen ◽  
T. S. Jørgensen ◽  
M. C. Kelley ◽  
M. F. Larsen ◽  
E. Pereira
Keyword(s):  
Electric Fields ◽  
Auroral Oval ◽  
Neutral Winds ◽  
Theory And Model
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