scholarly journals Ion-neutral coupling in the high-latitude F-layer from incoherent scatter and Fabry-Perot interferometer measurements

2000 ◽  
Vol 18 (9) ◽  
pp. 1145-1153 ◽  
Author(s):  
K. Cierpka ◽  
M. J. Kosch ◽  
M. Rietveld ◽  
K. Schlegel ◽  
T. Hagfors
Keyword(s):  
High Latitude ◽  
Frictional Heating ◽  
Neutral Wind ◽  
Auroral Ionosphere ◽  
Quiet Period ◽  
Ion Temperature ◽  
Incoherent Scatter ◽  
F Region ◽  
Fabry Perot ◽  
Energy Sink

Abstract. Since the auroral ionosphere provides an important energy sink for the magnetosphere, ionosphere-thermosphere coupling must be investigated when considering the energy budget of the ionosphere-magnetosphere coupling. We present the first Scandinavian ground-based study of high-latitude F-region ion-neutral frictional heating where ion velocity and temperature are measured by the EISCAT incoherent scatter radar as well as neutral wind and temperature being measured simultaneously by a Fabry-Perot interferometer. A geomagnetically active period (Kp = 7– – 5–) and quiet period (Kp = 0+ – 0) were studied. Neglecting the neutral wind can result in errors of frictional heating estimates of 60% or more in the F-layer. About 96% of the local ion temperature enhancement over the neutral temperature is accounted for by ion-neutral frictional heating.Key words: Ionosphere (auroral ionosphere; ionosphere-atmosphere interactions)

scholarly journals A statistical study of ion frictional heating observed by EISCAT

1997 ◽  
Vol 15 (11) ◽  
pp. 1399-1411 ◽  
Author(s):  
J. A. Davies ◽  
M. Lester ◽  
I. W. McCrea
Keyword(s):  
Geomagnetic Activity ◽  
Large Scale ◽  
Frictional Heating ◽  
Selection Criterion ◽  
Ion Temperature ◽  
F Region ◽  
Diurnal Distribution ◽  
Statistical Survey ◽  
Uhf Radar ◽  
The Imf

Abstract. Results of a statistical survey of F-region ion frictional heating are presented, a survey which is based on over 4000 h of common programme observations taken by the European incoherent scatter (EISCAT) UHF radar facility. The criterion adopted in this study for the identification of ion frictional heating was that defined by McCrea et al., requiring an enhancement in the F-region field-parallel ion temperature exceeding 100 K over two consecutive integration periods, which was itself based on a selection criterion for frictional heating derived for the study of high-latitude F-region ion temperature observations from the Atmospheric Explorer-C satellite. In the present study, the diurnal distribution of ion frictional heating observed by EISCAT is established and, furthermore, its dependence on geomagnetic activity and the orientation of the interplanetary magnetic field (IMF) is investigated; results are interpreted with reference to corresponding distributions of enhanced ion velocity, again derived from the extended set of EISCAT UHF common programme observations. The radar, due to its location relative to the large-scale convection pattern, observes ion frictional heating principally during the night, although preferentially during the post-midnight hours where there is reduced coupling between the ion and neutral populations. There is an increased preponderance of frictional heating during intervals of high geomagnetic activity and for a southward z component of the IMF and, moreover, evidence of asymmetries introduced by the y component of the IMF.

scholarly journals Lower-thermospheric wind fluctuations measured with an FPI during pulsating aurora at Tromsø, Norway

2010 ◽  
Vol 28 (10) ◽  
pp. 1847-1857 ◽  
Author(s):  
S. Oyama ◽  
K. Shiokawa ◽  
J. Kurihara ◽  
T. T. Tsuda ◽  
S. Nozawa ◽  
...  
Keyword(s):  
Wind Velocity ◽  
Frictional Heating ◽  
Lower Thermosphere ◽  
Thermospheric Wind ◽  
F Region ◽  
Time Period ◽  
Fabry Perot ◽  
Eiscat Radar ◽  
Energy Dissipated ◽  
Uhf Radar

Abstract. Simultaneous observations were conducted with a Fabry-Perot Interferometer (FPI) at a wavelength of 557.7 nm, an all-sky camera at a wavelength of 557.7 nm, and the European Incoherent Scatter (EISCAT) UHF radar during the Dynamics and Energetics of the Lower Thermosphere in Aurora 2 (DELTA-2) campaign in January 2009. This paper concentrated on two events during periods of pulsating aurora. The lower-thermospheric wind velocity measured with the FPI showed obvious fluctuations in both vertical and horizontal components. Of particular interest is that the location of the fluctuations was found in a darker area that appeared within the pulsating aurora. During the same time period, the EISCAT radar observed sporadic enhancements in the F-region backscatter echo power, which suggests the presence of low-energy electron (1 keV or lower) precipitation coinciding with increase in amplitude of the electromagnetic wave (at the order of 10 Hz or higher). While we have not yet identified the dominant mechanism causing the fluctuations in FPI-derived wind velocity during the pulsating aurora, the frictional heating energy dissipated by the electric-field perturbations may be responsible for the increase in ionospheric thermal energy thus modifying the local wind dynamics in the lower thermosphere.

Ion temperature anisotropy effects on the dispersion relation and threshold conditions of a sheared current-driven electrostatic ion-acoustic instability with applications to the collisional high-latitude F-region

2014 ◽  
Vol 81 (1) ◽  
Author(s):  
Patrick J.G. Perron ◽  
J.-M. Noël ◽  
J.-P. St-Maurice ◽  
K. Kabin
Keyword(s):  
Dispersion Relation ◽  
Wave Vector ◽  
High Latitude ◽  
Instability Threshold ◽  
Larmor Radius ◽  
Ion Temperature ◽  
Temperature Anisotropy ◽  
F Region ◽  
Threshold Conditions ◽  
Ion Acoustic

Plasma instabilities play a important role in producing small-scale irregularities in the ionosphere. In particular, current-driven electrostatic ion-acoustic (CDEIA) instabilities contribute to high-latitude F-region electrodynamics. Ion temperature anisotropies with enhanced perpendicular temperature often exist in the high-latitude F-region. In addition to temperature anisotropies, ion velocity shears are observed near auroral arc edges, sometimes coexisting with thermal ion upflow processes and field-aligned currents (FAC). We investigated whether ion temperature anisotropy lowers the threshold conditions required for the onset of sheared CDEIA instabilities. We generalised a dispersion relation to include ion thermal anisotropy, finite Larmor radius corrections and collisions. We derived new fluid-like analytical expressions for the threshold conditions required for instability that depend explicitly on ion temperature anisotropy. We studied how the instability threshold conditions vary as a function of the wave vector direction in both fluid and kinetic regimes. We found that, despite the dampening effect of collisions on ion-acoustic waves, ion temperature anisotropy lowers in some cases the threshold drift requirements for a large range of oblique wave vector angles. More importantly, realistic ion temperature anisotropies contribute to reducing the instability threshold velocity shears that are associated with small drift thresholds, for modes propagating almost perpendicularly to the geomagnetic field. Small shear thresholds that seem to be sustainable in the ionospheric F-region are obtained for low-frequency waves. Such instabilities could play a role in the direct generation of field-aligned irregularities in the collisional F-region that could be observed with the Super Dual Auroral Radar Network (SuperDARN) array of high-frequency radars. These modes would be very sensitive to the radar probing direction since they are restricted to very narrow angular intervals. The ion temperature anisotropy is an important parameter that needs to be considered in the studies of sheared and collisional CDEIA waves and instabilities in the high-latitude F-region.

scholarly journals Self-consistent modelling of the daytime electron density profile in the ionospheric F region

1997 ◽  
Vol 15 (3) ◽  
pp. 314-326 ◽  
Author(s):  
A. Mikhailov ◽  
K. Schlegel
Keyword(s):  
Electron Density ◽  
Molecular Nitrogen ◽  
Molecular Ions ◽  
Ion Composition ◽  
Ion Temperature ◽  
Incoherent Scatter ◽  
Plasma Drift ◽  
F Region ◽  
Self Consistent ◽  
Exospheric Temperature

Abstract. A theoretical self-consistent method for the description of daytime Ne(h) profiles in the ionospheric F region measured by EISCAT is proposed. It is based on the use of a theoretical F-region model and measured electron density, Ne(h), electron, Te(h), and ion temperature, Ti(h), and field-aligned plasma drift Vl(h) profiles. The method describes the observed Ne(h) profile with high accuracy for quiet and disturbed conditions. Two versions of the method are considered: in the first the exospheric temperature Tex is derived from a procedure minimizing [log(Ne(h)obs / Ne(h)cal]2, in the second Tex is deduced from the ion energy conservation in the F region. The method allows us to infer from the incoherent-scatter observations: concentrations of atomic oxygen, [O], molecular oxygen, [O2], molecular nitrogen, [N2] the vertical plasma drift, W, the exospheric temperature. Tex, and the shape parameter S in the neutral temperature profile. The ratio ([O+]/Ne) calculated by the theoretical model is used to correct Te(h), Ti(h) and Ne(h) profiles routinely measured with EISCAT which are known to depend strongly on the actual applied ion-composition model. Such a correction is especially important for geomagnetically disturbed periods when the F region is strongly enriched with molecular ions. We conclude that four of the six thermospheric parameters, namely [O], [N2], W and Tex can be confidently inferred from the EISCAT observations, while the other two derived parameters, [O2] ans S are less reliable. The method can be used for the analysis of long-term (seasonal, solar cycle) as well as for day-to-day variations of the thermospheric parameters and the F-region ion composition using daytime incoherent-scatter observations.

scholarly journals Irregular structures of the F layer at high latitudes during ionospheric heating

2000 ◽  
Vol 18 (9) ◽  
pp. 1197-1209 ◽  
Author(s):  
E. D. Tereshchenko ◽  
M. O. Kozlova ◽  
O. V. Evstafiev ◽  
B. Z. Khudukon ◽  
T. Nygrén ◽  
...  
Keyword(s):  
Small Scale ◽  
Auroral Ionosphere ◽  
Perpendicular Anisotropy ◽  
Ionospheric Heating ◽  
Incoherent Scatter ◽  
Active Experiments ◽  
F Region ◽  
Irregular Structures ◽  
Heating Region ◽  
Region Plasma

Abstract. Results on heating the ionospheric F region above Tromsø, Norway are presented. The ionosphere was monitored by satellite tomography and amplitude scintillation methods as well as the EISCAT incoherent scatter radar. No effect of heating was observed in the daytime. In the evening and in the pre-midnight sector, noticeable tilts of the F region were observed during heating periods. The tilts overlapped the heating cone, where the electron density decreased and irregularities exceeding 10 km in size appeared. Between the heating periods the F layer was restored to its horizontal shape. The anisotropic parameters of small-scale irregularities with scale lengths of hundreds of metres were also determined. It was found that the perpendicular anisotropy points in the direction of F region plasma flow. In some cases the results can be explained by assuming that the small-scale irregularities were generated within the heating cone and drifted out of the heating region where they were subsequently observed.Key words: Ionosphere (active experiments; auroral ionosphere; ionospheric irregularities)

scholarly journals Dynamic variability in F-region ionospheric composition at auroral arc boundaries

2010 ◽  
Vol 28 (2) ◽  
pp. 651-664 ◽  
Author(s):  
M. Zettergren ◽  
J. Semeter ◽  
B. Burnett ◽  
W. Oliver ◽  
C. Heinselman ◽  
...  
Keyword(s):  
Theoretical Calculations ◽  
Frictional Heating ◽  
Short Time Scale ◽  
Data Sets ◽  
Ion Temperature ◽  
Ion Density ◽  
F Region ◽  
Plasma Depletions ◽  
Auroral Arcs ◽  
Short Time

Abstract. The work presents a data-model synthesis examining the response of the auroral F-region ion temperature, composition, and density to short time scale (<1 min) electric field disturbances associated with auroral arcs. Ion temperature profiles recorded by the Sondrestrom incoherent scatter radar (ISR) are critically analyzed with the aid of theoretical calculations to infer ion composition variability. The analyses presented include a partial accounting for the effects of neutral winds on frictional heating and show promise as the groundwork for future attempts to address ion temperature-mass ambiguities in short-integration ISR data sets. Results indicate that large NO+ enchancements in the F-region can occur in as little as 20 s in response to impulsive changes in ion frictional heating. Enhancements in molecular ion density result in recombination and a depletion in plasma, which is shown to occur on time scales of several minutes. This depletion process, thus, appears to be of comparable importance to electrodynamic evacuation processes in producing auroral arc-related plasma depletions. Furthermore, the potential of ionospheric composition in regulating the amounts and types of ions supplied to the magnetosphere is outlined.

scholarly journals The dynamics and relationships of precipitation, temperature and convection boundaries in the dayside auroral ionosphere

2004 ◽  
Vol 22 (6) ◽  
pp. 1973-1987 ◽  
Author(s):  
J. Moen ◽  
M. Lockwood ◽  
K. Oksavik ◽  
H. C. Carlson ◽  
W. F. Denig ◽  
...  
Keyword(s):  
Frictional Heating ◽  
Mixing Layer ◽  
Latitudinal Gradients ◽  
Alfven Wave ◽  
Closed Field ◽  
Auroral Ionosphere ◽  
Ion Temperature ◽  
Vhf Radar ◽  
Boundary Mixing ◽  
Open Flux

Abstract. A continuous band of high ion temperature, which persisted for about 8h and zigzagged north-south across more than five degrees in latitude in the dayside (07:00-15:00MLT) auroral ionosphere, was observed by the EISCAT VHF radar on 23 November 1999. Latitudinal gradients in the temperature of the F-region electron and ion gases (Te and Ti, respectively) have been compared with concurrent observations of particle precipitation and field-perpendicular convection by DMSP satellites, in order to reveal a physical explanation for the persistent band of high Ti, and to test the potential role of Ti and Te gradients as possible markers for the open-closed field line boundary. The north/south movement of the equatorward Ti boundary was found to be consistent with the contraction/expansion of the polar cap due to an unbalanced dayside and nightside reconnection. Sporadic intensifications in Ti, recurring on ~10-min time scales, indicate that frictional heating was modulated by time-varying reconnection, and the band of high Ti was located on open flux. However, the equatorward Ti boundary was not found to be a close proxy of the open-closed boundary. The closest definable proxy of the open-closed boundary is the magnetosheath electron edge observed by DMSP. Although Te appears to be sensitive to magnetosheath electron fluxes, it is not found to be a suitable parameter for routine tracking of the open-closed boundary, as it involves case dependent analysis of the thermal balance. Finally, we have documented a region of newly-opened sunward convecting flux. This region is situated between the convection reversal boundary and the magnetosheath electron edge defining the open-closed boundary. This is consistent with a delay of several minutes between the arrival of the first (super-Alfvénic) magnetosheath electrons and the response in the ionospheric convection, conveyed to the ionosphere by the interior Alfvén wave. It represents a candidate footprint of the low-latitude boundary mixing layer on sunward convecting open flux.

scholarly journals Novel Fabry-Perot interferometer measurements of F-region ion temperature

2003 ◽  
Vol 30 (6) ◽  
Author(s):  
K. Cierpka ◽  
M. J. Kosch ◽  
H. Holma ◽  
A. J. Kavanagh ◽  
T. Hagfors
Keyword(s):  
Ion Temperature ◽  
F Region ◽  
Fabry Perot

scholarly journals F region dusk ion temperature spikes at the equatorward edge of the high-latitude convection pattern

2014 ◽  
Vol 41 (2) ◽  
pp. 300-307 ◽  
Author(s):  
L. Goodwin ◽  
J.-P. St.-Maurice ◽  
P. Richards ◽  
M. Nicolls ◽  
M. Hairston
Keyword(s):  
High Latitude ◽  
Ion Temperature ◽  
Convection Pattern ◽  
F Region

scholarly journals Meridional thermospheric neutral wind at high latitude over a full solar cycle

1998 ◽  
Vol 16 (10) ◽  
pp. 1400-1409 ◽  
Author(s):  
O. Witasse ◽  
J. Lilensten ◽  
C. Lathuillere ◽  
B. Pibaret
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Universal Time ◽  
Neutral Wind ◽  
High Latitudes ◽  
Auroral Ionosphere ◽  
Neutral Winds ◽  
F Region ◽  
Eiscat Radar ◽  
Thermospheric Dynamics

Abstract. EISCAT radar experiments over a full solar cycle between January 1984 and March 1995 have been used to construct meridional neutral wind patterns in the ionospheric F region. For locally geomagnetically quiet periods the neutral winds have been binned according to season, solar activity, and universal time. The diurnal and seasonal behaviors and the effect of the solar flux are described. An empirical model of the meridional neutral wind for the high latitudes at eight altitudes in the ionospheric F region over a full solar cycle is presented. Results are compared with other recent empirical models.Key words. Auroral ionosphere · Thermospheric dynamics · EISCAT

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