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 Poker Flat Incoherent Scatter Radar observations of anomalous electron heating in the E region

2013 ◽  
Vol 31 (7) ◽  
pp. 1163-1176 ◽  
Author(s):  
R. A. Makarevich ◽  
A. V. Koustov ◽  
M. J. Nicolls
Keyword(s):  
Electric Field ◽  
Electron Temperature ◽  
Electric Fields ◽  
Linear Trend ◽  
Incoherent Scatter Radar ◽  
Electron Heating ◽  
Incoherent Scatter ◽  
Convection Electric Field ◽  
Scatter Radar ◽  
E Region

Abstract. A comprehensive 2-year dataset collected with the Poker Flat Incoherent Scatter Radar (PFISR) located near Fairbanks, Alaska (MLAT = 65.4° N) is employed to identify and analyse 22 events of anomalous electron heating (AEH) in the auroral E region. The overall AEH occurrence probability is conservatively estimated to be 0.3% from nearly-continuous observations of the E region by PFISR, although it increases to 0.7–0.9% in the dawn and dusk sectors where all AEH events were observed. The AEH occurrence variation with MLT is broadly consistent with those of events with high convection velocity (>1000 m s−1) or electron temperature (> 800 K), except for much smaller AEH probability and absence of AEH events near magnetic midnight. This suggests that high convection electric field by itself is necessary but not sufficient for measurable electron heating by two-stream plasma waves. The multi-point observations are utilised to investigate the fundamental dependence of the electron temperature on the convection electric field, focusing on the previously-proposed saturation effects at extreme electric fields. The AEH dataset was found to exhibit considerable scatter and, on average, similar rate of the electron temperature increase with the electric field up to 100 mV m−1 as compared with previous studies. At higher (highest) electric fields, the electron temperatures are below the linear trend on average (within uncertainty). By employing a simple fluid model of AEH, it is demonstrated that some of this deviation from the linear trend may be due to a stronger vibrational cooling at very large temperatures and electric fields.

scholarly journals Quasi-periodic precipitation with periods between 40 and 60 minutes

1996 ◽  
Vol 14 (7) ◽  
pp. 707-715 ◽  
Author(s):  
K. Rinnert
Keyword(s):  
Electric Field ◽  
Electron Density ◽  
Electron Precipitation ◽  
Statistical Characteristics ◽  
Geomagnetic Disturbances ◽  
Maximum Probability ◽  
Dst Index ◽  
Incoherent Scatter ◽  
Magnetospheric Tail ◽  
E Region

Abstract. Intervals of periodic enhancements of E-region electron density have been found in EISCAT (European Incoherent SCATter) data. The periods are typically between 40 and 60 min. The phenomenon is observed during relatively quiet times, though after geomagnetic disturbances; it may last up to 6 h. The events can occur at all times of day with a maximum probability in the MLT morning sector. Using the EISCAT database from recent years, the statistical characteristics of these events, and their relation to magnetospheric conditions defined by the Dst index and the d.c. electric field perpendicular to B\\= have been derived. The latitudinal extent is found to be several degrees, but the longitudinal extent is not known. It is concluded that these events are due to the periodically modulated flux of electron precipitation controlled by oscillations in the magnetospheric tail.

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)

scholarly journals Incoherent scatter radar observation of E-region vertical electric field at Arecibo

2011 ◽  
Vol 38 (1) ◽  
pp. n/a-n/a ◽  
Author(s):  
Q. H. Zhou ◽  
Y. T. Morton ◽  
C. M. Huang ◽  
N. Aponte ◽  
M. Sulzer ◽  
...  
Keyword(s):  
Electric Field ◽  
Radar Observation ◽  
Incoherent Scatter Radar ◽  
Incoherent Scatter ◽  
Scatter Radar ◽  
Vertical Electric Field ◽  
E Region

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 Variations of topside ionospheric scale heights over Millstone Hill during the 30-day incoherent scatter radar experiment

2007 ◽  
Vol 25 (9) ◽  
pp. 2019-2027 ◽  
Author(s):  
L. Liu ◽  
W. Wan ◽  
M.-L. Zhang ◽  
B. Ning ◽  
S.-R. Zhang ◽  
...  
Keyword(s):  
Electron Density ◽  
Thermal Structure ◽  
Plasma Temperature ◽  
Scale Height ◽  
Incoherent Scatter Radar ◽  
Density Profiles ◽  
Incoherent Scatter ◽  
Scatter Radar ◽  
Vertical Scale ◽  
Electron Density Profiles

Abstract. A 30-day incoherent scatter radar (ISR) experiment was conducted at Millstone Hill (288.5° E, 42.6° N) from 4 October to 4 November 2002. The altitude profiles of electron density Ne, ion and electron temperature (Ti and Te), and line-of-sight velocity during this experiment were processed to deduce the topside plasma scale height Hp, vertical scale height VSH, Chapman scale height Hm, ion velocity, and the relative altitude gradient of plasma temperature (dTp/dh)/Tp, as well as the F2 layer electron density (NmF2) and height (hmF2). These data are analyzed to explore the variations of the ionosphere over Millstone Hill under geomagnetically quiet and disturbed conditions. Results show that ionospheric parameters generally follow their median behavior under geomagnetically quiet conditions, while the main feature of the scale heights, as well as other parameters, deviated significantly from their median behaviors under disturbed conditions. The enhanced variability of ionospheric scale heights during the storm-times suggests that the geomagnetic activity has a major impact on the behavior of ionospheric scale heights, as well as the shape of the topside electron density profiles. Over Millstone Hill, the diurnal behaviors of the median VSH and Hm are very similar to each other and are not so tightly correlated with that of the plasma scale height Hp or the plasma temperature. The present study confirms the sensitivity of the ionospheric scale heights over Millstone Hill to thermal structure and dynamics. The values of VSH/Hp tend to decrease as (dTp/dh)/Tp becomes larger or the dynamic processes become enhanced.

Sign in / Sign up

Export Citation Format

Share Document