Equivalent current systems for the annual and semiannual Sq variations observed along the 210°MM CPMN stations

Yamazaki, Yosuke; Yumoto, K.; Уозуми, Т.; Yoshikawa, Akimasa; Cardinal, M. G.

doi:10.1029/2009ja014638

Cited by 22 publications

(52 citation statements)

References 55 publications

(64 reference statements)

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“…Yamazaki et al (2009) found that the equivalent S q current system undergoes semi-annual variations keeping its two-vortex pattern. Thus, they naturally concluded that the diurnal tidal wind field causes the semi-annual S q variations.…”

Section: Discussionmentioning

confidence: 99%

“…Thus, they naturally concluded that the diurnal tidal wind field causes the semi-annual S q variations. For the annual S q variations, Yamazaki et al (2009) pointed out that the equivalent S q current system for the annual S q variations is characterized by a single-vortex pattern (see Fig. 1 of this paper).…”

Section: Discussionmentioning

confidence: 99%

“…The annual and semi-annual S q variations have been observed worldwide (e.g., Wagner, 1969;Campbell, 1982;Rastogi et al, 1994;Yamazaki et al, 2009). Rastogi and Iyer (1976), and Rastogi et al (1994) demonstrated a linear relationship between the yearly-averaged S q (H ) range and the amplitude of semi-annual S q variations at the dip-equatorial latitudes, which indicates a significant influence of solar activity on the semi-annual S q variations.…”

Section: Introductionmentioning

confidence: 99%

“…That is, equivalent current systems for the stationary and semi-annual components have a dayside vortex in each hemisphere, while the equivalent current system for the annual component has a single vortex centered at the equatorial region in the morning sector. Figure 1 shows the equivalent current systems for the stationary (the top panel), annual (the middle four panels) and semi-annual (the bottom four panels), components originally given by Yamazaki et al (2009). Since their analysis was based on data from only one solar cycle, it was difficult to investigate the solarcycle variation of the stationary, annual and semi-annual components.…”

Section: Introductionmentioning

confidence: 99%

“…Stening (1991) found that the semi-annual S q variation near the dip equator is clear in the morning hours, but practically disap- 9 1958-2006 pears in the afternoon. Yamazaki et al (2009) pointed out that, on a seasonal time scale, S q variations can be regarded as the superposition of the stationary, annual and semi-annual components. They analyzed ground-magnetometer data of 19 stations covering both the northern and southern hemispheres along the 210…”

Section: Introductionmentioning

confidence: 99%

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Long-term behavior of annual and semi-annual S q variations

Yamazaki

Yumoto

2012

Earth Planet Sp

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We have examined the long-term behavior (solar-cycle time scale) of annual and semi-annual S q variations. We analyzed geomagnetic data observed at locations that were roughly geographically conjugate in the west Pacific region (Kakioka and Gnangara) during the last five solar cycles . Three-year compound data were constructed for each station for each year. The stationary component {S q } 0 , annual component {S q } 1 , and the semi-annual component {S q } 2 , of the S q variations were derived from the compound data. The solar-activity dependence of the derived three components was evaluated in comparison with the sunspot number (R). It was found that the amplitudes of all three components ({S q } 0 , {S q } 1 and {S q } 2 ) have a positive linear correlation with the sunspot number. The most remarkable result is that the linear regression coefficient for {S q } 0 is much bigger than those of {S q } 1 and {S q } 2 . The physical mechanisms involved are yet to be understood.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Long-term behavior of annual and semi-annual S q variations

Yamazaki

Yumoto

2012

Earth Planet Sp

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Possible Anomalous Changes in Solar Quiet Daily Geomagnetic Variation (Sq) Related to the 2011 off the Pacific coast of Tohoku Earthquake (Mw 9.0)

Liu

Hattori

Han

et al. 2019

Pure Appl. Geophys.

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Sq solar variation at Medea Observatory (Algeria), from 2008 to 2011

Anad

Amory‐Mazaudier

Hamoudi

et al. 2016

Advances in Space Research

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International audienceThis paper presents the regular variations of terrestrial magnetic field recorded by a new magnetic observatory Medea, Algeria (geographic latitude: 36.85 • N, geographic longitude: 2.93 • E, geomagnetic latitude: 27.98 • N, geomagnetic longitude: 77.7 • E) during 2008-2011. The diurnal and seasonal variations of the solar quiet (Sq) variations are analyzed. The results show differences in the diurnal pattern of the northward-component Sq variation (SqX) at different seasons. The seasonal variation of SqX is similar in different years. The diurnal pattern of SqX from July through September cannot be explained by an equivalent current system that is symmetric about the noon time sector. The observations indicate that the major axis of the elliptic current system is tilted towards the equator in the morning hours during those months. The diurnal pattern of SqY indicates southward currents in the morning and northward currents in the afternoon, except during February-March 2009 when there is apparently no southward current during the morning. For the other months, the observations indicate that the maximum northward current intensity in the afternoon tends to be greater than the maximum southward current intensity in the morning. This is because of the UT variation of the Sq current system. That is, the pattern and strength of the Sq current system are different when SqY is measured in the morning around 8 UT and in the afternoon around 14 UT. The amplitude of these extreme varies linearly with the solar cycle. For the SqY component, the changes in the morning maximum have an annual variation while that of the afternoon minimum has a semi-annual variation. These variations are attributed to seasonal variations in the ionospheric E-region conductivity and atmospheric tidal winds. The field-aligned currents can also contribute to the seasonal variation of SqY. However, the two-dimensional approach used in this article does not allow us to quantitatively determine their influences

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Equivalent current systems for the annual and semiannual S_q variations observed along the 210°MM CPMN stations

Cited by 22 publications

References 55 publications

Long-term behavior of annual and semi-annual S q variations

Long-term behavior of annual and semi-annual S q variations

Possible Anomalous Changes in Solar Quiet Daily Geomagnetic Variation (Sq) Related to the 2011 off the Pacific coast of Tohoku Earthquake (Mw 9.0)

Sq solar variation at Medea Observatory (Algeria), from 2008 to 2011

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