scholarly journals Influences of the state of ionospheric background on ionospheric heating effects

2014 ◽  
Vol 56 (5) ◽  
Author(s):  
Shuji Hao ◽  
Li Qingliang ◽  
Che haiqin ◽  
Yang Jutao ◽  
Yan Yubo ◽  
...  
Keyword(s):  
Density Gradient ◽  
Electron Density ◽  
Large Scale ◽  
Ionospheric Heating ◽  
Adverse Conditions ◽  
F Region ◽  
Heating Effects ◽  
Reflection Height ◽  
Electron Density Gradient ◽  
Radiative Power

According to the well-performed ionospheric heating experiments at Arecibo in the low latitudes as well as at Tromsø in the high latitudes, the large-scale modification effects are simulated under an assumption of equivalent conditions, i.e., with the same effective radiative power and the same ratio of the heating frequency fHF to the critical frequency of ionospheric F region foF2. The findings are extensively exploited to verify the validation of our model by comparison to the experimental results. Further, a detailed study is carried out on the influences of the background electron density gradient as well as the ratio of fHF to foF2 on heating effects. Conclusions are drawn as follows: under certain conditions, a smaller electron density gradient of background ionospheric F region leads to a better ionospheric heating effect; during over-dense heating, the heating effects are enhanced if the ratio of fHF to foF2 increases, which is slightly limited by the resultant elevation of the reflection height. However, there might be a better ratio range with small values of the ratio of fHF to foF2, e.g., [0.5, 0.7] in the current study. Finally, we analyzed how to select heating parameters efficiently under adverse conditions so to obtain relatively effective results.

scholarly journals Study of mid-latitude nighttime enhancement in F-region electron density using tomographic images over the UK

2003 ◽  
Vol 21 (12) ◽  
pp. 2323-2328 ◽  
Author(s):  
R. S. Dabas ◽  
L. Kersley
Keyword(s):  
Electron Density ◽  
Magnetic Activity ◽  
Electron Content ◽  
Equatorial Anomaly ◽  
Tomographic Images ◽  
F Region ◽  
Electron Density Gradient ◽  
Modeling And Forecasting ◽  
Ionospheric Electron Content ◽  
The Uk

Abstract. Nighttime enhancements in ionospheric electron content (IEC)/peak electron density (NmF2) have been studied by various workers in the equatorial anomaly and mid-latitude regions. Such studies give an idea about their enhancement over that location only. In the present study tomographic images over the UK, which give a latitudinal versus height distributions of ionospheric electron density in a much wider area, have been used to study the anomalous increases in nighttime F-region electron density at mid-latitudes. From the analysis of four seasonal representative months (November 1997, March, June and October 1998) data it was noted that the majority of the cases of nighttime enhancements were observed after local midnight, with a maximum between 03:00–04:00 LT in the month of November 1997. Enhancements were observed mostly between 45–50° N latitudes, and their positions are not affected by magnetic activity (Kp ) variations, whereas the separation between the mid-latitude trough and enhancement decreases with increases in magnetic activity. This finding shows that only the trough moves equatorward with the increase in magnetic activity. It is also noted that the electron density gradient from the trough to the enhancement increases with an increase in Kp. Results are discussed in terms of downward plasma transport from the protonosphere to the ionosphere and the nighttime neutral winds.Key words. Ionosphere (mid-latitude ionosphere; modeling and forecasting; instruments and techniques)

scholarly journals Observing the north polar ionosphere on 30 October 2003 by GPS imaging and IS radars

2006 ◽  
Vol 24 (1) ◽  
pp. 107-113 ◽  
Author(s):  
C. Stolle ◽  
J. Lilensten ◽  
S. Schlüter ◽  
Ch. Jacobi ◽  
M. Rietveld ◽  
...  
Keyword(s):  
Time Series ◽  
Electron Density ◽  
Large Scale ◽  
Electron Content ◽  
Polar Ionosphere ◽  
Storm Main Phase ◽  
The North ◽  
F Region ◽  
Longitudinal Band ◽  
North Polar

Abstract. The evening of 30 October 2003 was subject to a major storm main phase. For this time, we combine large-scale electron content maps from GPS imaging with time series of electron density and temperature of two EISCAT radars in Tromsø and Svalbard and the Sondrestrom radar, for observing the north polar ionosphere. The GPS assimilations resulted in the image of the electron content trace of an anti-sunward polar Tongue Of Ionisation (TOI) consecutively to 20:00 UT. In combination with the radar observations we concluded that the TOI persisted during the whole period of continuous southward IMF Bz until about 22:40 UT while its largest extension toward the nightside auroral region was found between 21:00-22:00 UT. A typical F region electron temperature of ~2000 K and the plasma velocity of ~800 ms-1 support its convective origin from the dayside mid-latitudes. Due to the structured appearance of the electron content distribution and the radar electron density time series we believe that discrete plasma patches formed inside the anti-sunward drift pattern. After two large oscillations of the IMF Bz the nightside plasma density was observed to re-enhance after 23:00 UT along a longitudinal band below 70 N. Coinciding electron temperatures of ~2000 K suggest again the convective nature of the plasma, while a modified convection pattern is expected.

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

Ray Tracing over a Transequatorial Path

1972 ◽  
Vol 50 (10) ◽  
pp. 976-990
Author(s):  
N. C. Gerson
Keyword(s):  
Ray Tracing ◽  
Density Gradient ◽  
Electron Density ◽  
Time Of Day ◽  
Horizontal Gradient ◽  
Strong Electron ◽  
Trapped Mode ◽  
Electron Density Gradient ◽  
The Magnetic Field ◽  
Ray Paths

Ray tracing procedures including the magnetic field were employed in an attempt to explain the mechanism of transequatorial propagation. The analysis was based upon (a) 41 MHz backscatter soundings south from Mayaguez, Puerto Rico and (b) vertical-incidence observations from the ionosonde chain near 75 °W. The latter were converted into electron density versus true height profiles. Data from both sources obtained during the same month were utilized.The computed ray tracings show the expected effects for refraction from the F layer: skip and horizon focusing, predawn blackout (0200–0600 LST), escape of all rays launched above 18° irrespective of time of day, diurnal variation in one-hop propagation distances, etc. Some calculated rays attain TE distances (6000–11 000 km without intervening ground reflections) at 0800 LST, 1600–2000 LST and 2400 LST. Others are trapped to distances exceeding 11 000 km at 0800 LST and 1400–2400 LST. Fair agreement is found between TE observations and TE calculated ray paths. Specific hours and distances showed some correlation. Qualitatively the general features of TE seem clarified. The calculations imply that rays launched within 9° of the horizon southward across the (magnetic) equator are responsible for TE propagation. These rays are injected into an ionospheric trapped mode by a strong electron density gradient. For a ray launched at the ground to propagate to TE distances, two requirements must be satisfied: (a) vertical refractivity gradients propitious for radiowave trapping, and (b) horizontal refractivity gradients allowing injection and ejection of the ray into and out of the duct. TE concurrences near 0800 LST may arise because of the rapid strengthening of the postsunrise electron density gradient near 20° geomagnetic. This strong horizontal gradient then disappears, possibly because of an atmospheric expansion, and does not reappear until late afternoon. The trapping conditions, however, remain from about sunrise to midnight.The results imply that at the same or a higher frequency more TE would be observed if more energy was emitted at lower launch angles.

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