scholarly journals Auroral <i>E</i>-region electron density gradients measured

2000 ◽  
Vol 18 (9) ◽  
pp. 1172-1181 ◽  
Author(s):  
C. Haldoupis ◽  
K. Schlegel ◽  
G. Hussey
Keyword(s):  
Electric Field ◽  
Density Gradient ◽  
Electron Density ◽  
Electric Fields ◽  
Plasma Waves ◽  
Density Gradients ◽  
Electron Density Gradient ◽  
E Region ◽  
Gradient Drift ◽  
Region Plasma

Abstract. In the theory of E-region plasma instabilities, the ambient electric field and electron density gradient are both included in the same dispersion relation as the key parameters that provide the energy for the generation and growth of electrostatic plasma waves. While there exist numerous measurements of ionospheric electric fields, there are very few measurements and limited knowledge about the ambient electron density gradients, ∇Ne, in the E-region plasma. In this work, we took advantage of the EISCAT CP1 data base and studied statistically the vertical electron density gradient length, Lz=Ne/(dNe/dz), at auroral E-region heights during both eastward and westward electrojet conditions and different ambient electric field levels. Overall, the prevailing electron density gradients, with Lz ranging from 4 to 7 km, are found to be located below 100 km, but to move steadily up in altitude as the electric field level increases. The steepest density gradients, with Lz possibly less than 3 km, occur near 110 km mostly in the eastward electrojet during times of strong electric fields. The results and their implications are examined and discussed in the frame of the linear gradient drift instability theory. Finally, it would be interesting to test the implications of the present results with a vertical radar interferometer.Key words: Ionosphere (auroral ionosphere; ionospheric irregularities; plasma waves and instabilities)  

scholarly journals Auroral E-region electron density height profile modificationby electric field driven vertical plasma transport:some evidence in EISCAT CP-1 data statistics

2004 ◽  
Vol 22 (3) ◽  
pp. 901-910 ◽  
Author(s):  
T. Bösinger ◽  
G. C. Hussey ◽  
C. Haldoupis ◽  
K. Schlegel
Keyword(s):  
Electric Field ◽  
Electron Density ◽  
Electric Fields ◽  
Plasma Transport ◽  
Plasma Convection ◽  
Ionosphere Plasma ◽  
E Region ◽  
Eiscat Radar ◽  
Electric Fields And Currents ◽  
Electron Density Profiles

Abstract. A model developed several years ago by Huuskonen et al. (1984) predicted that vertical transport of ions in the nocturnal auroral E-region ionosphere can shift the electron density profiles in altitude during times of sufficiently large electric fields. If the vertical plasma transport effect was to operate over a sufficiently long enough time, then the real height of the E-region electron maximum should be shifted some km upwards (downwards) in the eastward (westward) auroral electrojet, respectively, when the electric field is strong, exceeding, say, 50 mV/m. Motivated by these predictions and the lack of any experimental verification so far, we made use of the large database of the European Incoherent Scatter (EISCAT) radar to investigate if the anticipated vertical plasma transport is at work in the auroral E-region ionosphere and thus to test the Huuskonen et al. (1984) model. For this purpose a new type of EISCAT data display was developed which enabled us to order a large number of electron density height profiles, collected over 16 years of EISCAT operation, according to the electric field magnitude and direction as measured at the same time at the radar's magnetic field line in the F-region. Our analysis shows some signatures in tune with a vertical plasma transport in the auroral E-region of the type predicted by the Huuskonen et al. model. The evidence brought forward is, however, not unambiguous and requires more rigorous analysis. Key words. Ionosphere (auroral ionosphere; plasma convection; electric fields and currents)

Dependence of radio aurora at 398 MHz on electron density and electric field

1979 ◽  
Vol 57 (5) ◽  
pp. 687-697 ◽  
Author(s):  
D. R. Moorcroft
Keyword(s):  
Electric Field ◽  
Electron Density ◽  
Electric Fields ◽  
Statistical Study ◽  
Incoherent Scatter Radar ◽  
Electron Densities ◽  
Incoherent Scatter ◽  
E Region ◽  
To Come ◽  
Stream Instability

A statistical study has been made of the dependence of radio-auroral echoes obtained with the 398 MHz radar at Homer, Alaska on electric fields and election densities measured simultaneously with the Chatanika incoherent scatter radar. There is a dependence on the magnitude of the electric field which is consistent with a threshold electric field of about 23 mV/m. The results of the analysis have been compared with the predictions of several existing theories of radio aurora. The echoes apparently arise from secondary irregularities generated by a primary two-stream instability; it is most likely that secondary two-stream irregularities are involved. Many of the data were obtained when the electric field was directed southward, and during this time the radio-auroral echoes were found to come from heights at or below the height of the maximum E-region electron density. Surprisingly, no echoes were obtained for large electron densities, regardless of the strength of the electric field. This implies that the spatial anticorrelation between visual and radio aurora involves more than the reduction of the electric field within visual forms.

scholarly journals Is there a plasma density gradient role on the generation of short-scale Farley-Buneman waves?

2005 ◽  
Vol 23 (10) ◽  
pp. 3323-3337 ◽  
Author(s):  
C. Haldoupis ◽  
T. Ogawa ◽  
K. Schlegel ◽  
J. A. Koehler ◽  
T. Ono
Keyword(s):  
Density Gradient ◽  
Electron Density ◽  
Plasma Density ◽  
Plasma Waves ◽  
Short Scale ◽  
Electron Density Gradient ◽  
Sporadic E Layers ◽  
Ion Acoustic ◽  
Sporadic E

Abstract. The physics of the unstable E-region plasma is based on the modified two stream, or Farley-Buneman, and the gradient drift instabilities. The theory combines both mechanisms into a single dispersion relation which applies for the directly generated short-scale plasma waves, known as type 1 irregularities. In the absence of a plasma gradient it is only the two stream mechanism acting which favors wave excitation if E×B electron drifts relative to the ions exceed a threshold slightly above the ion acoustic speed. On the other hand, the theory also predicts that a destabilizing (stabilizing) electron density gradient acts to decrease (increase) the ion acoustic threshold, and hence the wave phase velocities at threshold, depending on the gradient strength and the wavelength. Given a destabilizing plasma gradient, the threshold reduction is larger at longer than shorter wavelengths and thus the best way to test the gradient role is by simultaneous observations of type 1 waves at two or more radio backscatter frequencies. The present paper relies on dual frequency backscatter observations of 1.1 m and 3.1 m type 1 irregularities made simultaneously at 144 MHz and 50 MHz, respectively, in mid-latitude sporadic E-layers. Using as typical plasma gradient scale lengths for destabilized sporadic E-layers those that are obtained from rocket electron density profiles, the radar observations are compared with the predictions of kinetic theory. The results suggest that the plasma density gradient effect on meter scale Farley-Buneman waves is not important. This is reinforced further by the analysis of backscatter from destabilized meteor trail plasma when very steep gradients are expected in electron density. The present findings, and more from past studies, question the electron density gradient role in the generation of short-scale plasma waves as predicted by the linear instability theory. This deserves attention and more study.

scholarly journals Stabilization of electron-scale turbulence by electron density gradient in national spherical torus experiment

2015 ◽  
Vol 22 (12) ◽  
pp. 122501 ◽  
Author(s):  
J. Ruiz Ruiz ◽  
Y. Ren ◽  
W. Guttenfelder ◽  
A. E. White ◽  
S. M. Kaye ◽  
...  
Keyword(s):  
Density Gradient ◽  
Electron Density ◽  
Spherical Torus ◽  
Electron Density Gradient ◽  
Scale Turbulence

The effect of disturbed-time electric fields on the inner plasmasphere

1994 ◽  
Vol 12 (4) ◽  
pp. 296-303 ◽  
Author(s):  
H. F. Balmforth ◽  
R. J. Moffett ◽  
A. J. Smith ◽  
G. J. Bailey
Keyword(s):  
Mathematical Model ◽  
Electric Field ◽  
Electron Density ◽  
Electric Fields ◽  
Doppler Shift ◽  
Group Delay ◽  
Whistler Mode ◽  
L Value

Abstract. Results from a mathematical model provide a description of the mid-latitude, low L-shell ionosphere and plasmasphere. Variations in the composition and dynamics of the plasmasphere and changes in the nature of the coupling between the plasmasphere and the ionosphere are studied for moderately disturbed conditions. Modelled results are compared to group delay and Doppler shift measurements of whistler mode signals at Faraday, Antarctica (L ≈ 2.5), to investigate the effects of disturbed time electric fields on the inner plasmasphere and ionosphere. The disturbed time electric field causes a rapid outward drifting of the plasma leading to a decrease in modelled plasmaspheric electron density at a fixed L-value, which agrees with experimental observations. During the periods of outward drift, the modelled coupling flux is upwards to the plasmasphere which can lead to a significant depletion of NmF2 values.

scholarly journals High‐latitude GPS phase scintillation from E region electron density gradients during the 20–21 December 2015 geomagnetic storm

2017 ◽  
Vol 122 (7) ◽  
pp. 7473-7490 ◽  
Author(s):  
Diana Loucks ◽  
Scott Palo ◽  
Marcin Pilinski ◽  
Geoff Crowley ◽  
Irfan Azeem ◽  
...  
Keyword(s):  
Electron Density ◽  
Geomagnetic Storm ◽  
High Latitude ◽  
Density Gradients ◽  
E Region

scholarly journals Equatorial night-time F-region zonal electric fields

1995 ◽  
Vol 13 (8) ◽  
pp. 871-878 ◽  
Author(s):  
S. S. Hari ◽  
B. V. Krishna Murthy
Keyword(s):  
Seasonal Variation ◽  
Electric Field ◽  
Electric Fields ◽  
Night Time ◽  
Equatorial Station ◽  
F Region ◽  
Vertical Drift ◽  
Longitudinal Gradients ◽  
Cycle Maximum ◽  
E Region

Abstract. Night-time F-region vertical electrodynamic drifts at the magnetic equatorial station, Trivandrum are obtained for a period of 2 years, 1989 and 1990 (corresponding to solar cycle maximum epoch), using ionosonde h'F data. The seasonal variation of the vertical drift is found to be associated with the longitudinal gradients of the thermospheric zonal wind. Further, the seasonal variation of the prereversal enhancement of the vertical drift is associated with the time difference between the sunset times of the conjugate E-regions (magnetic field line linked to F-region) which is indicative of the longitudinal gradients of the conductivity (of the E-region). The vertical drifts and the causative zonal electric fields at Trivandrum are compared with those at Jicamarca and F-region zonal electric field models. It is seen that the night-time downward drift (as also the causative westward electric field) at Jicamarca is greater than that at Trivandrum. The prereversal enhancement of the drift is greater at Jicamarca than at Trivandrum during the summer and the equinoxes, whereas during the winter the opposite is the case.

Sign in / Sign up

Export Citation Format

Share Document