Mid-latitude solar eclipses and their influence on ionospheric current systems

Tomás, A. T.; Lühr, H.; Rother, M.

doi:10.5194/angeo-27-4449-2009

Cited by 17 publications

(21 citation statements)

References 16 publications

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“…Most studies on ionospheric eclipse had been focused on the midlatitude ionosphere, though on different measurements and methodology. Among these are Müller-Wodarg et al [1998], Afraimovich et al [2002], Le et al [2008aLe et al [ , 2009, Tomás et al [2009], Wang et al [2010], Chuo [2013] and Adekoya and Chukwuma [2012]. Some of these studies discuss observations exclusively on the assumption that solar eclipse at midlatitude is largely controlled by plasma diffusion.…”

Section: Introductionmentioning

confidence: 99%

“…A gravity wave is generated in the neutral atmosphere and propagates into the opposite hemisphere at around 300 m/s [Müller-Wodarg et al, 1998]. Tomás et al [2009] observed the influence of midlatitude solar eclipse on ionospheric current systems; they address in particular the effects of the solar eclipses on the interhemispheric field-aligned currents and on the solar quiet current (Sq) system. They found that the eclipses might affect the direction and intensity of the interhemispheric currents and possibly influence the direction of zonal winds, therefore changing the direction of the prevailing F region dynamo currents.…”

Section: Introductionmentioning

confidence: 99%

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Ionospheric vertical plasma drift and electron density response during total solar eclipses at equatorial/low latitude

2015

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The response of the vertical plasma drift (Vz) and the electron density (NmF2) during different solar eclipses was investigated. The diurnal values of the direct scaled measurement of F2 peak height and the one derived from M(3000) F2 data, acquired over an equatorial/low‐latitude stations, have been used to determine the vertical plasma drift. The ionosphere during a solar eclipse is significantly affected by the E × B vertical drift; the large depletion of electron density at low altitudes can be transported to high altitudes through the plasma vertical drift. The loss in ionization density during the eclipse phase decreases the electron density, which was accompanied by rapid increase in hmF2. This deviation in the NmF2 during eclipse compared to control days can be related to the increase in the loss rate due to recombination, as a result of reduction in thermal energy. However, the maximum reduction in NmF2 is not synchronous with the time of maximum totality but some minutes later. The differences in the solar epochs may contribute to the observed relative changes in the ionospheric F2 region behavior during the eclipse window. Lastly, it is very difficult to separate the influence of magnetic disturbances from solar eclipse. The deviation in NmF2 is higher during magnetic disturbed days than the quiet day. The reverse is the case for hmF2 observation. However, the NmF2 variation increases with an increase in solar activity.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ionospheric vertical plasma drift and electron density response during total solar eclipses at equatorial/low latitude

2015

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“…In the dayside ionospheric E-region there exists a current vortex in each hemisphere, which is known as solar-quiet (Sq) current system (e.g., van Sabben, 1964). The currents flow counterclockwise (clockwise) in the Northern (Southern) Hemisphere with the focuses around 30 • -35 • dip latitudes (e.g., Matsushita and Maeda, 1965).…”

Section: Introductionmentioning

confidence: 99%

“…A north-south asymmetry of the Sq vortices (especially during solstices) is expected to create a potential difference between the hemispheres (e.g., van Sabben, 1966;Fukushima, 1979;Onwumechili, 1997;Tomás et al, 2009), resulting in inter-hemispheric field-aligned currents (IHFACs). Asymmetries in neutral wind and conductivity (e.g., Maeda, 1974;Takeda et al, 2003) are known to contribute to the IHFAC generation.…”

Section: Introductionmentioning

confidence: 99%

Climatology of the inter-hemispheric field-aligned current system in the equatorial ionosphere as observed by CHAMP

2011

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Abstract. From geomagnetic field observations of CHAMP during [2001][2002][2003][2004][2005][2006][2007][2008][2009] we extracted characteristic signatures of inter-hemispheric field-aligned currents (IHFACs) in the equatorial ionosphere. The results are in general agreement with previous observations. Nighttime IHFACs are negligibly small. Solstitial IHFACs flow from the summer to winter (from winter to summer) hemisphere at dawn (around noon). Duskside IHFACs flow southbound irrespective of season. We have also found some new IHFAC properties, which may have been predicted by theories, but are not yet given observational support. IHFACs clearly exhibit a longitude dependence, which is modulated by the South Atlantic Anomaly, the offset between geographic and magnetic equators, and tidal waves. IHFACs show little dependence on the solar cycle. We provide a comprehensive assessment of the IHFAC modulation by non-migrating tides.

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“…The paths of the total solar eclipse on 22nd July, 2009 and annular solar eclipse on 15th January, 2010, lied totally inside the equatorial tropical zone of the Earth which enabled several researchers to study its effects on the equatorial ionosphere [ Guha et al , 2010; Sharma et al , 2010; Tomás et al , 2009; Zhang et al , 2010]. It was also a unique opportunity to investigate the effects of the eclipses on the propagational characteristics of VLF sferics as more than 70% of the total lightning activities around the globe occur inside the tropical region of the Earth [ Williams , 1992].…”

Section: Introductionmentioning

confidence: 99%

Spectral character of VLF sferics propagating inside the Earth‐ionosphere waveguide during two recent solar eclipses

Guha

Choudhury

et al. 2012

J. Geophys. Res.

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Effects of solar eclipses on the propagation characteristics of worldwide VLF sferics from lightning activity require more investigation. An attempt was made on the occasion of two solar eclipses during 22nd July, 2009 and 15th January, 2010 to study the effects of the two eclipses on the propagation characteristics of VLF sferics in the Earth‐ionosphere waveguide. Identical experimental setups were used to study the VLF sferics during the two eclipse events. The spectral character of VLF sferics propagating inside the waveguide is studied at a fixed receiver location (23.75°N, 91.25°E) at six discrete frequencies in between 3 and 20 kHz. During both the eclipse events, it is observed that VLF sferics at all the six discrete frequencies is increased from the mean normal average ambient level. The increment peaks around 10–12 kHz with an overall increment of 6.4 dB with respect to its ambient level. The VLF spectral character of enhancement of sferics show similar characters in two eclipses. The percentage decrease in electron density using standard modeling equations is found to be 90% at the height of 71 km for both the eclipses, supporting linear variation of electron density with solar radiation at the D‐region of the ionosphere. The results are explained qualitatively on the basis of a decrease in electron density at the lower ionosphere modifying the reflection coefficient which affected the propagation of VLF sferics in Earth‐ionosphere waveguide during eclipsed condition.

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Mid-latitude solar eclipses and their influence on ionospheric current systems

Abstract: Abstract.Using CHAMP magnetic field data we study the behaviour of the geomagnetic field during two mid latitude eclipses on

Cited by 17 publications

References 16 publications

Ionospheric vertical plasma drift and electron density response during total solar eclipses at equatorial/low latitude

Ionospheric vertical plasma drift and electron density response during total solar eclipses at equatorial/low latitude

Climatology of the inter-hemispheric field-aligned current system in the equatorial ionosphere as observed by CHAMP

Spectral character of VLF sferics propagating inside the Earth‐ionosphere waveguide during two recent solar eclipses

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