Solar and lunar geomagnetic variations in the northwestern part of Turkey

Çelik, Cengiz; Tunçer, Mustafa; Tolak-Ciftci, Elif; Zobu, M.; Oshiman, Naoto; Tank, Sabri Bülent

doi:10.1111/j.1365-246x.2012.05382.x

Cited by 10 publications

(3 citation statements)

References 14 publications

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“…Malin's technique has been used in many studies to evaluate the ocean dynamo effect (e.g., Sastri and Rao 1971;Shiraki 1978Shiraki , 1981Stening and Winch 1979;McKnight 1995;Çelik et al 2012). Satellite magnetic measurements confirmed the presence of lunar tidal signals associated with the ocean dynamo during night (Tyler et al 2003;Maus and Kuvshinov 2004;Sabaka et al 2016).…”

Section: Determination Of Lmentioning

confidence: 84%

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

2016

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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.

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Section: Determination Of Lmentioning

confidence: 84%

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

2016

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“…The midlatitude S q current intensity during solar maximum is approximately twice as high as that during solar minimum [ Takeda , ]. The amplitude and phase of seasonal S q variations are also modulated by solar activity [ Yamazaki and Yumoto , ; Çelik et al , ]. The solar activity dependence of S q variations is mainly due to enhanced ionospheric conductivities during high solar activity periods, which lead to increased ionospheric currents [ Takeda et al , ].…”

Section: Introductionmentioning

confidence: 99%

Geomagnetic lunar and solar daily variations during the last 100 years

Yamazaki

Kosch

2014

JGR Space Physics

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This paper describes long-term changes in the geomagnetic lunar (L) and solar (S) daily variations. We analyze the eastward component of the geomagnetic field observed at eight midlatitude stations during 1903-2012. The amplitude and phase for the semidiurnal component of the L and S variations are examined. Both L and S amplitudes correlate with the solar activity index F 10.7 , revealing a prominent 11 year solar cycle. In both cases, the correlation is slightly better with √ F 10.7 than F 10.7 . The sensitivity of the L variation to solar activity is comparable with that of the S variation. The solar cycle effect is also found in the phase of the S variation but not apparent in the phase of the L variation. The ratio in the amplitude of the L to S variation shows a long-term decrease (approximately 10% per century), which may be due to a reduction in lunar tidal waves from the lower atmosphere to the upper atmosphere in association with climate change.

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“…The L amplitudes were determined by fitting the following equation independently to data from each SC period.

L ((),, t, ν) = \sum_{n = 1}^{4} A_{n} \cdot \sqrt{F 10.7} \cdot italicsin ((), n \frac{2 π}{24} t - 2 \frac{2 π}{24} ν + ε_{n}) .

Equation is based on Chapman's phase law (Chapman, 1919), where t and ν are the local time and lunar age (phase) in hours, and A n and ε n are amplitude and phase parameters determined through ordinary least squares inversion (Çelik et al, 2012; Malin, 1970; Malin & Chapman, 1970). The F10.7 term included in Equation acts as a weighting factor and a solar flux of 100 sfu is used for normalization when calculating predicted L variations.…”

Section: Resultsmentioning

confidence: 99%

Evolution of the Geomagnetic Daily Variation at Tatuoca, Brazil, From 1957 to 2019: A Transition From Sq to EEJ

et al. 2020

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The magnetic equator in the Brazilian region has moved over 1,100 km northward since 1957, passing the geomagnetic observatory Tatuoca (TTB), in northern Brazil, around 2013. We recovered and processed TTB hourly mean values of the geomagnetic field horizontal (H) component from 1957 until 2019, allowing the investigation of long-term changes in the daily variation due to the influence of secular variation, solar activity, season, and lunar phase. The H day-today variability and the occurrence of the counter electrojet at TTB were also investigated. Until the 1990s, ionospheric solar quiet currents dominated the quiet-time daily variation at TTB. After 2000, the magnitude of the daily variation became appreciably greater due to the equatorial electrojet (EEJ) contribution. The H seasonal and day-today variability increased as the magnetic equator approached, but their amplitudes normalized to the average daily variation remained at similar levels. Meanwhile, the amplitude of the lunar variation, normalized in the same way, increased from 5% to 12%. Within the EEJ region, the occurrence rate of the morning counter electrojet (MCEJ) increased with proximity to the magnetic equator, while the afternoon counter electrojet (ACEJ) did not. EEJ currents derived from CHAMP and Swarm satellite data revealed that the MCEJ rate varies with magnetic latitude within the EEJ region while the ACEJ rate is largely constant. Simulations with the Thermosphere-Ionosphere-Electrodynamics General Circulation Model based on different geomagnetic main field configurations suggest that long-term changes in the geomagnetic daily variation at TTB can be attributed to the main field secular variation.

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Solar and lunar geomagnetic variations in the northwestern part of Turkey

Cited by 10 publications

References 14 publications

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

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

Geomagnetic lunar and solar daily variations during the last 100 years

Evolution of the Geomagnetic Daily Variation at Tatuoca, Brazil, From 1957 to 2019: A Transition From Sq to EEJ

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