scholarly journals The ionospheric responses to the 11 August 1999 solar eclipse: observations and modeling

2008 ◽  
Vol 26 (1) ◽  
pp. 107-116 ◽  
Author(s):  
H. Le ◽  
L. Liu ◽  
X. Yue ◽  
W. Wan
Keyword(s):  
Theoretical Model ◽  
Solar Radiation ◽  
Solar Eclipse ◽  
Ionospheric Disturbance ◽  
Low Latitude ◽  
Ionospheric Response ◽  
Latitude Range ◽  
Eclipse Observations ◽  
E Region ◽  
Low Latitude Ionosphere

Abstract. A total eclipse occurred on 11 August 1999 with its path of totality passing over central Europe in the latitude range 40°–50° N. The ionospheric responses to this eclipse were measured by a wide ionosonde network. On the basis of the measurements of foE, foF1, and foF2 at sixteen ionosonde stations in Europe, we statistically analyze the variations of these parameters with a function of eclipse magnitude. To model the eclipse effects more accurately, a revised eclipse factor, FR, is constructed to describe the variations of solar radiation during the solar eclipse. Then we simulate the effect of this eclipse on the ionosphere with a mid- and low-latitude ionosphere theoretical model by using the revised eclipse factor during this eclipse. Simulations are highly consistent with the observations for the response in the E-region and F1-region. Both of them show that the maximum response of the mid-latitude ionosphere to the eclipse is found in the F1-region. Except the obvious ionospheric response at low altitudes below 500 km, calculations show that there is also a small response at high altitudes up to about 2000 km. In addition, calculations show that when the eclipse takes place in the Northern Hemisphere, a small ionospheric disturbance also appeared in the conjugate hemisphere.

SOLAR ECLIPSE OBSERVATIONS OF THE IONOSPHERE

1948 ◽  
Vol 26a (3) ◽  
pp. 137-144 ◽  
Author(s):  
C. W. McLeish
Keyword(s):  
Solar Eclipse ◽  
Variable Coefficient ◽  
Negative Ion ◽  
Ion Density ◽  
Eclipse Observations ◽  
E Region ◽  
Made In

The results are presented of ionosphere measurements made in the region of totality during the eclipse of July 9, 1945. An analysis of the results shows effective recombination coefficients of 1.6 × 10−8 for E region, 1.4 × 10−8 for F1 region, and 1.0 × 10−9 for F2 region. Evidence of a variable coefficient for E region agrees with the suggestion of Massey and others of a high negative ion density at this level.

scholarly journals Effects of strong IMF <I>B<sub>z</sub></I> southward events on the equatorial and mid-latitude ionosphere

2009 ◽  
Vol 27 (3) ◽  
pp. 1175-1187 ◽  
Author(s):  
E. Astafyeva
Keyword(s):  
Electric Fields ◽  
Geomagnetic Storms ◽  
The Other ◽  
Negative Events ◽  
Equatorial Anomaly ◽  
Low Latitude ◽  
Sudden Drop ◽  
Ionospheric Response ◽  
Peak Structure ◽  
Low Latitude Ionosphere

Abstract. Dayside ionospheric response to five intense geomagnetic storms (Dst<−120 nT) that occurred in 2001–2005 was investigated by use of simultaneous TEC measurements by the CHAMP, SAC-C, TOPEX/Jason-1 satellites. Since the satellites passed over different longitudinal sectors and measured TEC in different range of altitudes, it was possible to obtain information about altitudinal and longitudinal ionosphere redistribution during these storms. Severe enhancements (up to ~350%) of the equatorial and mid-latitude TEC above ~430 km with concurrent traveling of the equatorial anomaly crests for a distance of 10–15° of latitude were observed during two of the five events analyzed here (6 November 2001 and 8 November 2004). This phenomenon, known as the dayside ionosphere uplift, or the "daytime super-fountain effect", occurred after sudden drop in IMF Bz and consequent penetration of the electric fields to the low-latitude ionosphere. However, the same order Bz negative events caused comparatively weak changes in the dayside TEC (up to ~80 TECU) during the other three events of 18 June 2003, 11 February 2004 and 24 August 2005. At the main phase of these storms there were mostly observed formation of the "typical" dual peak structure of the equatorial anomaly rather than the reinforcement of the fountain effect and the anomaly itself. Possible reasons and factors responsible for the development of the extreme ionosphere effects are discussed in the paper.

Earth, sky and prayer in harmony: aspects of the interesting life of Father Edward Pigot, SJ, BA, MB, BCh (1858-1929), Part 2 (1911-1929)

2010 ◽  
Vol 29 (2) ◽  
pp. 232-263 ◽  
Author(s):  
David Branagan
Keyword(s):  
World War I ◽  
Solar Radiation ◽  
Solar Eclipse ◽  
Earth Tides ◽  
Theory Of Relativity ◽  
World War ◽  
Eclipse Observations

Edward Francis Pigot (1858-1929) spent the last twenty-four years of his life as Director of the Riverview Observatory of the Jesuit St Ignatius ‘Riverview’ College, Sydney. The onset of World War I caused the cancellation of the proposed International Seismological Congress in St Petersburg, Russia, in 1914. But he received plans of Galitsin's seismograph and one was later built in Sydney and installed at Riverview Observatory. From 1914, in addition to seismology Pigot participated in studies of earth deformation, earth tides, Foucault pendulums and solar radiation. In 1919, in preparation for astronomical work at Riverview, Pigot visited major US observatories. His support of US astronomers in the 1922 solar eclipse observations played a part in the attempts to confirm Einstein's Theory of Relativity.

scholarly journals Global Longitudinal Dependence Observation of the Neutral Wind and Ionospheric Density Distribution

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Endawoke Yizengaw
Keyword(s):  
Density Distribution ◽  
Lower Atmosphere ◽  
Wave Number ◽  
Wind Component ◽  
Equatorial Anomaly ◽  
Low Latitude ◽  
Wind Structure ◽  
E Region ◽  
Low Latitude Ionosphere ◽  
Longitudinal Variability

The statistical global view of the low-latitude ionospheric density stimulates further interest in studying the strong longitudinal variability of the ionospheric density structures in low-to-equatorial latitudes. However, we are not completely certain how the electrodynamics and ion-neutral coupling proceeds at low latitudes; in particular, the longitudinal difference in the dynamics of plasma structures in the low-to-mid latitude ionosphere is not yet fully understood. Numerical studies of latent heat release in the troposphere have indicated that the lower atmosphere can indeed introduce a longitudinal dependence and variability of the low-latitude ionosphere during quiet conditions. For the first time, we present simultaneous observations of the tidally modulated global wind structure, using TIDI observations, in the E-region and the ionospheric density distribution using ground (global GPS receivers) and space-based (C/NOFS in situ density and GPS TEC on CHAMP) instruments. Our results show that the longitudinally structured zonal wind component could be responsible for the formation of wave number four pattern of the equatorial anomaly.

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 The equatorial ionospheric response over Tirunelveli to the 15 January 2010 annular solar eclipse: observations

2012 ◽  
Vol 30 (9) ◽  
pp. 1371-1377 ◽  
Author(s):  
C. K. Nayak ◽  
D. Tiwari ◽  
K. Emperumal ◽  
A. Bhattacharyya
Keyword(s):  
Solar Eclipse ◽  
Equatorial Electrojet ◽  
Equatorial Ionosphere ◽  
Combined Effect ◽  
Maximum Phase ◽  
Ionospheric Response ◽  
Eclipse Observations ◽  
Annular Solar Eclipse

Abstract. In this paper we present a case study of the annular solar eclipse effects on the ionization of E and F regions of equatorial ionosphere over Tirunelveli [77.8° E, 8.7° N, dip 0.4° N] by means of digital ionosonde on 15 January 2010. The maximum obscuration of the eclipse at this station was 84% and it occurred in the afternoon. The E and F1 layers of the ionosphere showed very clear decrease in their electron concentrations, whereas the F2 layer did not show appreciable changes. A reduction of 30% was observed in the foF1 during the maximum phase of the eclipse. During the beginning phase of the eclipse, an enhancement of 0.97 MHz was observed in the foF2 as compared to that of the control days. But the foF2 decreased gradually as the eclipse progressed and a decrease of 0.59 MHz was observed towards the end phase of the eclipse. Observed variations in the h'F2 and hmF2 showed lower values than the control days, although hmF2 was found to increase a bit during the eclipse. Observed variability in the E, F1 and F2 layer ionospheric parameters on the eclipse day and their departure from the control days are discussed as the combined effect of annular eclipse and presence of counter equatorial electrojet (CEEJ).

VLF/LF (Very Low Frequency/Low Frequency) Reflection Properties of the Low Latitude Ionosphere

1988 ◽  
Author(s):  
Wayne I. Klemetti ◽  
Paul A. Kossey ◽  
John E. Rasmussen ◽  
Maria Sueli Da Silveira Macedo Moura
Keyword(s):  
Low Frequency ◽  
Low Latitude ◽  
Very Low Frequency ◽  
Low Latitude Ionosphere
Sign in / Sign up

Export Citation Format

Share Document