Currents associated with abnormal quiet days in Sq(H)

Butcher, E. C.

doi:10.1111/j.1365-246x.1987.tb01371.x

Cited by 9 publications

(14 citation statements)

References 13 publications

(14 reference statements)

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“…All these systems produce magnetic variations which are consistent with a conventionally paired vortex current system, one vortex in each hemisphere, and are symmetric about the equator (Butcher et al 1993). Butcher (1987) proposes that the magnetic effects on AQDs were caused by a SCV which flows clockwise and extended over both hemispheres. Thus, if a single vortex-type current were to flow in the ring current system, it may be possible for the focus to be pushed northward in northern winter as required on AQDs by the mechanism proposed by Malin and Isikara (1976).…”

Section: Discussionmentioning

confidence: 78%

“…6c and 9b, it is clear that the focus of the current vortex on AQDs is shifted to the lower latitudes between SHL and NGP. Butcher et al (1993) and Butcher (1987) suggest that an additional field occurring on AQDs may be represented by a SCV that has a focus in the latitude range 15°-20°N for the northern hemispheric AQDs based on 80 observatory data. The source for AQDs (during winter months) is SCV located in the ionosphere.…”

Section: Discussionmentioning

confidence: 99%

“…Butcher and Brown (1980) also found the connection between the occurrences of AQDs and the interplanetary magnetic field and suggested that the most likely source of the AQDs event would be an extra-terrestrial or magnetospheric origin. Analysis of H-data in both hemispheres along the same longitude meridian, Butcher (1987) proposes that the magnetic effects on AQDs were caused by single current vortex (SCV) that flows clockwise and extended over both hemispheres.…”

Section: Introductionmentioning

confidence: 99%

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Abnormal quiet day variations in Indian region along 75° E meridian

2015

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The present study mainly focuses on the anomalous characteristics observed in some abnormal quiet day (AQD) variations of the north-south (H) and east-west (D) components of geomagnetic field at 11 Indian stations for the years 2004, 2005, and 2009 during low solar activity period for summer and winter months. In this study, during some quiet days, horizontal component (H) at stations situated near equator to the Sq focus latitudes has shown double peak structure, exhibiting maximum in the forenoon and afternoon hours. Correspondingly, declination component (D) over the low latitudes has shown features outside the normal trend, i.e., westward-directed field in the morning hours and eastward-directed field in the afternoon hours and shows negative bay-type of variations. The technique of principal component analysis (PCA) has been applied to the data sets for presenting a quantitative estimate of the influence of day-to-day variability in the Sq current system on normal (NQD) and abnormal quiet (AQD) days. AQDs observed at the Indian stations are reflected in the second principal component PC-2. Anomalous changes in day-to-day variations (H and D) are interpreted as an influence of high latitude magnetospheric current systems as well as due to single current vortex (SCV) located in the ionosphere whose focus lie between 10°and 15°N geomagnetic latitude for the northern hemisphere winter AQDs.

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Section: Discussionmentioning

confidence: 78%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Abnormal quiet day variations in Indian region along 75° E meridian

2015

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“…On normal days, 2 January (Ap=5), 26 January (Ap=4) and 16 February (Ap=6), the effect of geomagnetic disturbance during the morning period seems to have brought out the changes in the expected current pattern. Butcher (1987) reported that the day-to-day variability in the Sq (H ) amplitudes has an obvious relation to the IMF-dependent complicated current system. On the abnormal days, a strong positive variation in H persisted up to the latitude location of ∼55…”

Section: Discussionmentioning

confidence: 99%

Day-to-day variability in the occurrence characteristics of Sq focus during d-months and its association with diurnal changes in the Declination component

Alex

Jadhav

2007

Earth Planet Sp

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Scrutiny of the geomagnetic observations of the Declination component 'D' from equatorial and low-latitude locations in the Indian longitude revealed anomalous variations during d-months. Examination of the Quiet day (Ap≤7) variations in the Declination component (Y in nT = H sin D) and Horizontal component (H ) during the d-months (November, December, January, February) of the low solar activity year 1977 revealed the salient features associated with the day-to-day changes observed in Sq current system over the latitude chain in the Indo-Russian longitude. Diurnal variations in the east-west component Y and north-south component H were used to depict the effect of changes in the Sq current pattern for a selected set of Quiet days, which are classified into normal and abnormal days based on the trend in the variation of the Declination component. Normal days designated in the study clearly showed the expected pattern of variation in Y (eastward-directed field) in the morning hours and westward-directed field in the afternoon hours, and diurnal variation of H simultaneously showed the presence of northern Sq focus within the low-latitude range. In contrast, the abnormal days projected by the variation in Y and H on certain days of d-months showed an almost complete absence of the focus formation within the expected latitude extent. Day-to-day variability characteristics of the Declination component discussed in the study are illustrated in relation to modifications in the expected Sq current system by the invasion of the prevalent southern hemisphere current whorl to the northern hemisphere during the winter months. Some of the anomalous changes observed in the day-to-day variation in the latitudinal pattern of Y and H components are also interpreted as suggesting an influence of high-latitude magnetospheric current systems on certain quiet days.

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“…Further evidence for correlations over inter-hemispheric distances was given by Butcher (1987) from a study of abnormal quiet days using declination data for six stations along a longitude meridian, extending over both northern and southern hemispheres. In order to explain the difference between the variations of the declination at these stations on abnormal quiet days and normal quiet days, it was suggested by Butcher that a large single current vortex was present on abnormal quiet days extending over both hemispheres, the current flowing clockwise on abnormal quiet days.…”

Section: Introductionmentioning

confidence: 99%

On the relation between days of small amplitude of Sq(H) and abnormal quiet days

Schlapp

Mann

Butcher

1988

Geophysical Journal International

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S U M M A R YIn order to explain the results of a previous study of the variations in declination at Hermanus on abnormal quiet days at Hartland, it has been proposed that a single current vortex system spanning both hemispheres links the variations at the two stations (Butcher 1987). Earlier work (Butcher & Brown 1981) suggested that an abnormal quiet day results from the combination of the Occurrence of a day of low range in S q ( H ) and a small magnetospheric substorm or mini-bay which therefore forms the minimum in H. In the present paper, results are presented which show that the single current vortex acts not only on abnormal quiet days, but more generally on days of small amplitude of S q ( H ) at stations like Hartland which are poleward of the Sq focus.

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Currents associated with abnormal quiet days in Sq(H)

Cited by 9 publications

References 13 publications

Abnormal quiet day variations in Indian region along 75° E meridian

Abnormal quiet day variations in Indian region along 75° E meridian

Day-to-day variability in the occurrence characteristics of Sq focus during d-months and its association with diurnal changes in the Declination component

On the relation between days of small amplitude of Sq(H) and abnormal quiet days

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