Geomagnetic Crochets and Associated Ionospheric Current Systems

Richmond, A. D.; Venkateswaran, S.

doi:10.1029/rs006i002p00139

Cited by 53 publications

(53 citation statements)

References 93 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A geomagnetic crochet often consists of two components (Richmond and Venkateswaran 1971); a "fast component" is presumably produced by a rapid increase in the EUV radiation and a "slow component", which peaks a few minutes after the fast component, corresponds to a slow increase in soft X rays. Although the conductivity enhancement during solar flares is limited to the dayside ionosphere, several authors found evidence of solar flare effects during the nighttime (Ohshio et al 1963;Sastri 1975;Sastri and Murthy 1975).…”

Section: Storm Effectmentioning

confidence: 99%

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

2016

View full text Add to dashboard Cite

A record of the geomagnetic field on the ground sometimes shows smooth daily variations on the order of a few tens of nano teslas. These daily variations, commonly known as Sq, are caused by electric currents of several μA/m 2 flowing on the sunlit side of the Eregion ionosphere at about 90-150 km heights. We review advances in our understanding of the geomagnetic daily variation and its source ionospheric currents during the past 75 years. Observations and existing theories are first outlined as background knowledge for the nonspecialist. Data analysis methods, such as spherical harmonic analysis, are then described in detail. Various aspects of the geomagnetic daily variation are discussed and interpreted using these results. Finally, remaining issues are highlighted to provide possible directions for future work.

show abstract

Section: Storm Effectmentioning

confidence: 99%

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

2016

View full text Add to dashboard Cite

show abstract

“…Ohshio et al (1967) studied sfe on geomagnetic field on global basis and suggested that the seat of ionospheric current due to solar flares is a little lower than the layer for Sq current system. Richmond and Venkateswaran (1971) suggested that the crochet consists of a 'fast' component presumably due to EUV radiation (100-1000Å) and a 'slow' component produced by soft X-rays (1-100Å). Forbush and Casaverde (1961) first took a proper attention to the crochet at equatorial electrojet region and showed that the enhancement of sfe in H at Peruvian stations varied in a manner similar to the enhancement of Sq (H ) itself.…”

Section: Introductionmentioning

confidence: 99%

Solar flare effects on the geomagnetic elements during normal and counter electrojet periods

et al. 2014

View full text Add to dashboard Cite

The paper describes the study of solar flare effects (sfe) on horizontal (H ), eastward (Y ) and vertical (Z ) components of the geomagnetic field at the Indo-USSR chain of magnetic observatories extending from the magnetic latitudes 0• to 45• N, a network not available any where else in the world. Events are selected when strong, normal and reversed (counter) equatorial electrojet are in existence as well as when only a partial counter electrojet is present.During a strong and normal electrojet event time, sfe consists of a positive impulse in H at all stations, the amplitude of H following the latitudinal variation similar to that of the quiet day monthly mean, Sq (H ). The sfe in Y is negative at all the stations. Sfe in Z shows positive impulse at the four-electrojet stations and negative at other stations. During a counter electrojet period the effect of solar flare on H field is negative impulse at electrojet stations, positive at low latitude and again negative at stations north of Sq focus. Sfe in Y is small at all the equatorial and negative at higher latitude stations. However, sfe (Z ) is negative at the equatorial latitudes.During a partial counter electrojet period the observed effect is the combination of an increase of the planetary current component and the decrease of the electrojet component, giving rise to a negative impulse in H at equatorial stations and a positive impulse in H , increasing with increasing distance from the equator. These results are presented and discussed.

show abstract

“…An interpretation of SFE in terms of enhanced electrical conductivity due to solar X-ray flare flux enhancement in the band 1-20A was made by OHSHIO (1964) from a study of selected SFE events observed during I. G. Y. A recent study indicated that SFE is due to extra ionization produced by solar XUV (1-1000A) flare radiation and the SFE's often exhibit a composite structure consisting of a 'fast' component presumably due to EUV radiation (100-1000A) and a 'slow' component produced by soft X-rays (1-100A) (RICHMOND and VENKATESWARAN, 1971). A very recent study made by the authors using SFE's observed (on normal run magnetograms) at Kodaikanal (Lat: 10.20N;Long: 77.50E,Dip: 3.50N) showed that the amplitude of SFE is linearly correlated with peak solar X-ray flux level in the bands: 1-8A and 8-20A (monitored by SOLRAD-9) lending support to the interpretation that SFE is due to enhanced ionization produced by solar soft X-rays (SASTRI and MURTHY, 1975).…”

Section: Introductionmentioning

confidence: 99%