scholarly journals Variations of Scale Height at F-Region Peak Based on Ionosonde Measurements during Solar Maximum over the Crest of Equatorial Ionization Anomaly Region

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Yu-Jung Chuo
Keyword(s):  
Critical Frequency ◽  
Peak Height ◽  
Scale Height ◽  
High Solar Activity ◽  
Upward Movement ◽  
Physical Processes ◽  
F Region ◽  
Equatorial Ionization Anomaly ◽  
Anomaly Region ◽  
Layer Peak

Scale height is an important parameter in characterizing the shape of the ionosphere and its physical processes. In this study, we attempt to examine and discuss the variation of scale height,Hm, around the F-layer peak height during high solar activity at the northern crest of the equatorial ionization anomaly (EIA) region.Hmexhibits day-to-day variation and seasonal variation, with a greater average daily variation during daytime in summer. Furthermore, the diurnal variation ofHmexhibits an abnormal peak at presunrise during all the seasons, particularly in winter. This increase is also observed in the F2-layer peak height for the same duration with an upward movement associated with thermospheric wind toward the equator; this upward movement increases the N2/O ratio andHm, but it causes a decrease in the F2-layer maximum critical frequency during the presunrise period.

scholarly journals Quiet-condition variations in the scale height at F2-layer peak at Jicamarca during solar minimum and maximum

2007 ◽  
Vol 25 (12) ◽  
pp. 2541-2550 ◽  
Author(s):  
C.-C. Lee ◽  
B. W. Reinisch
Keyword(s):  
Solar Minimum ◽  
Critical Frequency ◽  
Solar Maximum ◽  
Peak Height ◽  
Scale Height ◽  
Quiet Condition ◽  
Critical Frequency Fof2 ◽  
Two Parameters ◽  
Thickness Parameter ◽  
Layer Peak

Abstract. This study is the first attempt to examine the quiet-condition variations in scale height (Hm) near the F2-layer peak in the equatorial ionosphere. The data periods of Hm derived from the Jicamarca ionograms are January-December 1996 and April 1999–March 2000. The results show that the greatest and smallest Hm values are generally at 11:00–12:00 LT and 04:00–05:00 LT, respectively. Additionally, the sunrise peak occurs at 06:00 LT only during solar minimum. The post-sunset peaks in the equinoctial and summer months are more obvious during solar maximum. The Hm difference between solar minimum and maximum are significant from afternoon to midnight. On the other hand, the Hm values during 07:00–10:00 LT for solar minimum are close to those for solar maximum. Furthermore, the correlation of Hm with the critical frequency (foF2) of F2-layer is generally low. In contrast, the correlation between Hm and the peak height (hmF2) of F2-layer is high. For Hm and the thickness parameter (B0) of F2-layer, the correlation between these two parameters is almost perfect.

scholarly journals Wavenumber-4 structures observed in the low-latitude ionosphere during low and high solar activity periods using FORMOSAT/COSMIC observations

2018 ◽  
Vol 36 (2) ◽  
pp. 459-471 ◽  
Author(s):  
Amelia Naomi Onohara ◽  
Inez Staciarini Batista ◽  
Paulo Prado Batista
Keyword(s):  
Solar Activity ◽  
Peak Height ◽  
Diurnal Tide ◽  
High Solar Activity ◽  
Low Latitude ◽  
Peak Structure ◽  
F Region ◽  
E Region ◽  
Low Latitude Ionosphere ◽  
Layer Peak

Abstract. The main purpose of this study is to investigate the four-peak structure observed in the low-latitude equatorial ionosphere by the FORMOSAT/COSMIC satellites. Longitudinal distributions of NmF2 (the density of the F layer peak) and hmF2 (ionospheric F2-layer peak height) averages, obtained around September equinox periods from 2007 to 2015, were submitted to a bi-spectral Fourier analysis in order to obtain the amplitudes and phases of the main waves. The four-peak structure in the equatorial and low-latitude ionosphere was present in both low and high solar activity periods. This kind of structure possibly has tropospheric origins related to the tidal waves propagating from below that modulate the E-region dynamo, mainly the eastward non-migrating diurnal tide with wavenumber 3 (DE3, E for eastward). This wave when combined with the migrating diurnal tide (DW1, W for westward) presents a wavenumber-4 (wave-4) structure under a synoptic view. Electron densities observed during 2008 and 2013 September equinoxes revealed that the wave-4 structures became more prominent around or above the F-region altitude peak (∼  300–350 km). The four-peak structure remains up to higher ionosphere altitudes (∼  800 km). Spectral analysis showed DE3 and SPW4 (stationary planetary wave with wavenumber 4) signatures at these altitudes. We found that a combination of DE3 and SPW4 with migrating tides is able to reproduce the wave-4 pattern in most of the ionospheric parameters. For the first time a study using wave variations in ionospheric observations for different altitude intervals and solar cycle was done. The conclusion is that the wave-4 structure observed at high altitudes in ionosphere is related to effects of the E-region dynamo combined with transport effects in the F region.

scholarly journals IRI-2001 model predictions compared with ionospheric data observed at Brazilian low latitude stations

2006 ◽  
Vol 24 (8) ◽  
pp. 2191-2200 ◽  
Author(s):  
F. Bertoni ◽  
Y. Sahai ◽  
W. L. C. Lima ◽  
P. R. Fagundes ◽  
V. G. Pillat ◽  
...  
Keyword(s):  
Reasonable Agreement ◽  
Critical Frequency ◽  
Peak Height ◽  
Low Latitude ◽  
F Region ◽  
Model Predictions ◽  
Critical Frequency Fof2

Abstract. In this work, the F-region critical frequency (foF2) and peak height (hmF2) measured by digital ionosondes at two Brazilian low-latitude stations, namely Palmas (10.17° S, 48.20° W, dip –10.80°) and São José dos Campos (23.20° S, 45.86° W, dip –38.41°), are compared with the IRI-2001 model predictions. The comparison at the latter station shows quite a reasonable agreement for both parameters. The former station exhibits a better agreement for hmF2 than for foF2. In general, the model generates good results, although some improvements are still necessary to implement in order to obtain better simulations for equatorial ionospheric regions.

scholarly journals Ionospheric effects on the F region during the sunrise for the annular solar eclipse over Taiwan on 21 May 2012

2013 ◽  
Vol 31 (11) ◽  
pp. 1891-1898 ◽  
Author(s):  
Y. J. Chuo
Keyword(s):  
Solar Eclipse ◽  
Peak Height ◽  
Scale Height ◽  
Rate Of Change ◽  
Slab Thickness ◽  
Electron Content ◽  
Total Electron ◽  
F Region ◽  
Northern Pacific ◽  
Annular Solar Eclipse

Abstract. On 21 May 2012 (20:56, Universal Time; UT, on 20 May), an annular solar eclipse occurred, beginning at sunrise over southeast China and moving through Japan, sweeping across the northern Pacific Ocean, and completing its passage over the western United States at sunset on 20 May 2012 (02:49 UT, 21 May). We investigated the eclipse area in Taiwan, using an ionosonde and global positioning system (GPS) satellite measurements. The measurements of foF2, hmF2, bottomside scale height around the peak height (Hm), and slab thickness (B0) were collected at the ionosonde station at Chung-Li Observatory. In addition, we calculated the total electron content (TEC) to study the differences inside and outside the eclipse area, using 3 receivers located at Marzhu (denoted as MATZ), Hsinchu (TNML), and Henchun (HENC). The results showed that the foF2 values gradually decreased when the annularity began and reached a minimum level of approximately 2.0 MHz at 06:30 LT. The hmF2 immediately decreased and then increased during the annular eclipse period. The TEC variations also appeared to deplete in the path of the eclipse and opposite the outside passing area. Further, the rate of change of the TEC values (dTEC / dt measured for 15 min) was examined to study the wave-like fluctuations. The scale height near the F2 layer peak height (Hm) also decreased and then increased during the eclipse period. To address the effects of the annular eclipse in the topside and bottomside ionosphere, this study provides a discussion of the variations between the topside and bottomside ionospheric parameters during the eclipse period.

scholarly journals Diurnal, seasonal, annual, and semi-annual variations of ionospheric parameters at different latitudes in East Asian sector during ascending phase of solar activity

2017 ◽  
Vol 3 (2) ◽  
pp. 45-53
Author(s):  
Чжэн Ван ◽  
Zheng Wang ◽  
Цзянькуй Ши ◽  
Jiankui Shi ◽  
Гоцзюнь Ван ◽  
...  
Keyword(s):  
Solar Activity ◽  
East Asia ◽  
Seasonal Variations ◽  
Critical Frequency ◽  
East Asian ◽  
Peak Height ◽  
Scale Height ◽  
High Latitudes ◽  
Ionospheric Parameter ◽  
Annual Variations

We analyzed ionospheric parameters including the critical frequency of the F2 layer (foF2), the peak height of the F2 layer (hmF2), and the scale height at hmF2 (HT) from 2006 to 2012 (ascending phase of solar activity) at Hainan (19.5° N, 109.1° E, MLat. 9.7° N), Irkutsk (52.4° N, 104.3° E, MLat. 42.5° N), and Norilsk (69.2° N, 88.0° E, MLat. 59.8° N) stations (low, middle and high latitudes). We have used manual scaled digisonde ionogram data. Studies of foF2 and hmF2 di-urnal-seasonal variations continue those made earlier for East Asia. Features peculiar for the ascending phase of solar activity are mostly consistent to those for de-scending phase, except for the features of sunset and nighttime hmF2 variations. Features of annual and semi-annual variations recorded by a digisonde agree with those obtained by a satellite occultation and TEC map. We also obtained seasonal, diurnal, annual, and semi-annual variations of the ionospheric parameter HT (scale height at hmF2) from digisonde data, which differ from foF2 variations and hmF2 features.

scholarly journals Diurnal, seasonal, annual, and semi-annual variations of ionospheric parameters at different latitudes in East Asian sector during ascending phase of solar activity

2017 ◽  
Vol 3 (2) ◽  
pp. 43-50
Author(s):  
Чжэн Ван ◽  
Zheng Wang ◽  
Цзянькуй Ши ◽  
Jiankui Shi ◽  
Гоцзюнь Ван ◽  
...  
Keyword(s):  
Solar Activity ◽  
East Asia ◽  
Seasonal Variations ◽  
Critical Frequency ◽  
East Asian ◽  
Peak Height ◽  
Scale Height ◽  
High Latitudes ◽  
Ionospheric Parameter ◽  
Annual Variations

We analyzed ionospheric parameters including the critical frequency of the F2 layer (foF2), the peak height of the F2 layer (hmF2), and the scale height at hmF2 (HT) from 2006 to 2012 (ascending phase of solar activity) at Hainan (19.5° N, 109.1° E, MLat. 9.7° N), Irkutsk (52.4° N, 104.3° E, MLat. 42.5° N), and Norilsk (69.2° N, 88.0° E, MLat. 59.8° N) stations (low, middle and high latitudes). We have used manual scaled digisonde ionogram data. Studies of foF2 and hmF2 di-urnal-seasonal variations continue those made earlier for East Asia. Features peculiar for the ascending phase of solar activity are mostly consistent to those for de-scending phase, except for the features of sunset and nighttime hmF2 variations. Features of annual and semi-annual variations recorded by a digisonde agree with those obtained by a satellite occultation and TEC map. We also obtained seasonal, diurnal, annual, and semi-annual variations of the ionospheric parameter HT (scale height at hmF2) from digisonde data, which differ from foF2 variations and hmF2 features.

Equatorial F region evening vertical drift, and peak height, during southern winter months: A comparison of observational data with the IRI descriptions

2006 ◽  
Vol 37 (5) ◽  
pp. 1007-1017 ◽  
Author(s):  
M.A. Abdu ◽  
I.S. Batista ◽  
B.W. Reinisch ◽  
J.H.A. Sobral ◽  
A.J. Carrasco
Keyword(s):  
Observational Data ◽  
Peak Height ◽  
F Region ◽  
Vertical Drift

scholarly journals High-speed stream impacts on the equatorial ionization anomaly region during the deep solar minimum year 2008

2012 ◽  
Vol 117 (A10) ◽  
pp. n/a-n/a ◽  
Author(s):  
Jing Liu ◽  
Libo Liu ◽  
Biqiang Zhao ◽  
Yong Wei ◽  
Lianhuan Hu ◽  
...  
Keyword(s):  
Solar Minimum ◽  
High Speed ◽  
High Speed Stream ◽  
Equatorial Ionization Anomaly ◽  
Anomaly Region
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