Phenomena during the growth and decay of spread-F

1963 ◽  
Vol 25 (5) ◽  
pp. 445
Author(s):  
M.S.V. Gopala rao ◽  
B. Ramachandra rao
Keyword(s):  
Spread F

scholarly journals Investigation of Low Latitude Spread-F Triggered by Nighttime Medium-Scale Traveling Ionospheric Disturbance

2021 ◽  
Vol 13 (5) ◽  
pp. 945
Author(s):  
Zhongxin Deng ◽  
Rui Wang ◽  
Yi Liu ◽  
Tong Xu ◽  
Zhuangkai Wang ◽  
...  
Keyword(s):  
Ionospheric Disturbance ◽  
Phase Speed ◽  
Morphological Processing ◽  
Wave Number ◽  
Occurrence Rate ◽  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
Medium Scale ◽  
Spread F

In the current study, we investigated the mechanism of medium-scale traveling ionospheric disturbance (MSTID) triggering spread-F in the low latitude ionosphere using ionosonde observation and Global Navigation Satellite System-Total Electron Content (GNSS-TEC) measurement. We use a series of morphological processing techniques applied to ionograms to retrieve the O-wave traces automatically. The maximum entropy method (MEM) was also utilized to obtain the propagation parameters of MSTID. Although it is widely acknowledged that MSTID is normally accompanied by polarization electric fields which can trigger Rayleigh–Taylor (RT) instability and consequently excite spread-F, our statistical analysis of 13 months of MSTID and spread-F occurrence showed that there is an inverse seasonal occurrence rate between MSTID and spread-F. Thus, we assert that only MSTID with certain properties can trigger spread-F occurrence. We also note that the MSTID at night has a high possibility to trigger spread-F. We assume that this tendency is consistent with the fact that the polarization electric field caused by MSTID is generally the main source of post-midnight F-layer instability. Moreover, after thorough investigation over the azimuth, phase speed, main frequency, and wave number over the South America region, we found that the spread-F has a tendency to be triggered by nighttime MSTID, which is generally characterized by larger ΔTEC amplitudes.

Equatorial Spread-F and Magnetic Activity

Nature ◽  
1958 ◽  
Vol 181 (4625) ◽  
pp. 1724-1725 ◽  
Author(s):  
A. J. LYON ◽  
N. J. SKINNER ◽  
R. W. WRIGHT
Keyword(s):  
Magnetic Activity ◽  
Equatorial Spread F ◽  
Spread F

scholarly journals Seasonal dependence of the "forecast parameter" based on the EIA characteristics for the prediction of Equatorial Spread F (ESF)

2008 ◽  
Vol 26 (7) ◽  
pp. 1751-1757 ◽  
Author(s):  
S. V. Thampi ◽  
S. Ravindran ◽  
T. K. Pant ◽  
C. V. Devasia ◽  
R. Sridharan
Keyword(s):  
Seasonal Variability ◽  
Seasonal Pattern ◽  
Onset Time ◽  
Critical Value ◽  
Latitudinal Gradients ◽  
Electron Content ◽  
Total Electron ◽  
Equatorial Spread F ◽  
Spread F ◽  
Definite Role

Abstract. In an earlier study, Thampi et al. (2006) have shown that the strength and asymmetry of Equatorial Ionization Anomaly (EIA), obtained well ahead of the onset time of Equatorial Spread F (ESF) have a definite role on the subsequent ESF activity, and a new "forecast parameter" has been identified for the prediction of ESF. This paper presents the observations of EIA strength and asymmetry from the Indian longitudes during the period from August 2005–March 2007. These observations are made using the line of sight Total Electron Content (TEC) measured by a ground-based beacon receiver located at Trivandrum (8.5° N, 77° E, 0.5° N dip lat) in India. It is seen that the seasonal variability of EIA strength and asymmetry are manifested in the latitudinal gradients obtained using the relative TEC measurements. As a consequence, the "forecast parameter" also displays a definite seasonal pattern. The seasonal variability of the EIA strength and asymmetry, and the "forecast parameter" are discussed in the present paper and a critical value for has been identified for each month/season. The likely "skill factor" of the new parameter is assessed using the data for a total of 122 days, and it is seen that when the estimated value of the "forecast parameter" exceeds the critical value, the ESF is seen to occur on more than 95% of cases.

Observational investigation of the possible correlation between medium-scale TIDs and mid-latitude spread F

2016 ◽  
Vol 58 (3) ◽  
pp. 349-357 ◽  
Author(s):  
Shimei Yu ◽  
Zuo Xiao ◽  
Ercha Aa ◽  
Yongqiang Hao ◽  
Donghe Zhang
Keyword(s):  
Medium Scale ◽  
Spread F

High frequency drift waves with wavelengths below the ion gyroradius in equatorial spread F

1978 ◽  
Vol 5 (8) ◽  
pp. 695-698 ◽  
Author(s):  
J. D. Huba ◽  
P. K. Chaturvedi ◽  
S. L. Ossakow ◽  
D. M. Towle
Keyword(s):  
High Frequency ◽  
Frequency Drift ◽  
Drift Waves ◽  
Equatorial Spread F ◽  
Spread F

Spread F modeling over Brazil

2017 ◽  
Vol 161 ◽  
pp. 98-104 ◽  
Author(s):  
A.J. Carrasco ◽  
I.S. Batista ◽  
J.H.A. Sobral ◽  
M.A. Abdu
Keyword(s):  
Spread F

scholarly journals HF Doppler radar observations of low-latitude spread F

Radio Science ◽  
2009 ◽  
Vol 44 (3) ◽  
pp. n/a-n/a ◽  
Author(s):  
C. R. Reddi ◽  
M. S. S. R. K. N. Sarma ◽  
K. Niranjan
Keyword(s):  
Doppler Radar ◽  
Low Latitude ◽  
Radar Observations ◽  
Spread F
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