Geomagnetic lunar and solar daily variations during the last 100 years

Yamazaki, Yosuke; Kosch, M. J.

doi:10.1002/2014ja020203

Cited by 26 publications

(30 citation statements)

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“…That is, the phase of these Fourier components shifts to later local times as solar activity increases. Yamazaki and Kosch (2014) also found a similar solar cycle effect on the phase of Sq variations. Olsen (1993) showed that the Sq current foci move to later local times during solar maximum, which is consistent with our results in Fig.…”

Section: Sq Focus Positionssupporting

confidence: 57%

“…Butcher (1980) and Matsushita and Xu (1984) discussed that L currents flowing in the F region is improbable, and both L and Sq currents are likely to flow in the dynamo region. Yamazaki and Kosch (2014) evaluated the lunar semidiurnal variation using a slightly different method than previous authors. Instead of examining the luni-solar variation based on Chapman's phase law (Eq.…”

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confidence: 99%

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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: Sq Focus Positionssupporting

confidence: 57%

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confidence: 99%

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

2016

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“…According to numerical simulations, that pattern could be also due to a phase shift in the solar semidiurnal tide [e.g., Pedatella and Liu , ]. The presence of M 2 during SSWs has been also reported from other ground‐based observations as well as in situ observations on‐board satellites [e.g., Stening , ; Gasperini and Forbes , ; Lühr et al , ; Park et al , ; Yamazaki et al , ; Yamazaki , , ; Yamazaki and Kosch , ; Zhang et al , ]. Lunar tides in the ionosphere have been observed at other times, but their amplitudes are much smaller than at times of SSWs, i.e., northern hemispheric winter [e.g., Bartels , ; Chapman and Lindzen , ; Matsushita , ; Stening and Fejer , ; Stening and Rastogi , ; Pedatella and Forbes , ; Aveiro and Hysell , ; Eccles et al , ].…”

Section: Introductionmentioning

confidence: 73%

Upper mesospheric lunar tides over middle and high latitudes during sudden stratospheric warming events

et al. 2015

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In recent years there have been a series of reported ground‐ and satellite‐based observations of lunar tide signatures in the equatorial and low latitude ionosphere/thermosphere around sudden stratospheric warming (SSW) events. This lower atmosphere/ionosphere coupling has been suggested to be via the E region dynamo. In this work we present the results of analyzing 6 years of hourly upper mesospheric winds from specular meteor radars over a midlatitude (54°N) station and a high latitude (69°N) station. Instead of correlating our results with typical definitions of SSWs, we use the definition of polar vortex weaking (PVW) used by Zhang and Forbes (). This definition provides a better representation of the strength in middle atmospheric dynamics that should be responsible for the waves propagating to the E region. We have performed a wave decomposition on hourly wind data in 21 day segments, shifted by 1 day. In addition to the radar wind data, the analysis has been applied to simulations from Whole Atmosphere Community Climate Model Extended version and the thermosphere‐ionosphere‐mesosphere electrodynamics general circulation model. Our results indicate that the semidiurnal lunar tide (M2) enhances in northern hemispheric winter months, over both middle and high latitudes. The time and magnitude of M2 are highly correlated with the time and associated zonal wind of PVW. At middle/high latitudes, M2 in the upper mesosphere occurs after/before the PVW. At both latitudes, the maximum amplitude of M2 is directly proportional to the strength of PVW westward wind. We have found that M2 amplitudes could be comparable to semidiurnal solar tide amplitudes, particularly around PVW and equinoxes. Besides these general results, we have also found peculiarities in some events, particularly at high latitudes. These peculiarities point to the need of considering the longitudinal features of the polar stratosphere and the upper mesosphere and lower thermosphere regions. For example, during SSW 2009, we found that M2 enhances many days before PVW which is not in agreement with most of our results.

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“…The Sq variations originate from electric currents flowing in the ionospheric dynamo region (80-160 km),where the electromotive force are driven by the neutral wind into the ionospheric wind dynamo system (e.g. Adebesin et al 2013a;Richmond and Maute 2014;Yamazaki and Kosch 2014). On the other hand, geomagnetic activities originate as a consequence of the interaction between the solar wind and the magnetosphere (e.g.…”

Section: Introductionmentioning

confidence: 99%

Investigation into the linear relationship between the AE, Dst and ap indices during different magnetic and solar activity conditions

Adebesin

2015

Acta Geod Geophys

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There are numerous geomagnetic indices used in monitoring various magnetospheric and ionospheric phenomena. Some of the most widely used indices are the ap, AE and Dst. In this work, the relationship between these three geomagnetic indices is investigated at different levels of solar and magnetic activity. 3-h average data spanning 8-years were used-high (HSA), moderate (MSA) and low solar activity (LSA) periods cover the years 1999-2001, 2004-2005, and 2006, 2009-2010 respectively. All the investigated correlation pairs recorded the highest/lowest during the LSA/HSA periods. The ap/AE correlation was found to be highest ranging within 70-78 % at any solar activity. The ap versus AE and Dst multiple correlation reached 94.0, 92.1, and 89.2 % for HSA, MSA, and LSA conditions, respectively, and 72.1, 83.3, and 80.0 % for the main phase, recovery phase and quiet conditions respectively. Moreover, higher percentage correlations were observed for the ap/AE pair at any geomagnetic conditions than for the ap/Dst and AE/Dst pairs. The ring current index Dst is observed to have a greater influence on ap during geomagnetic storm periods.

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Geomagnetic lunar and solar daily variations during the last 100 years

Cited by 26 publications

References 103 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

Upper mesospheric lunar tides over middle and high latitudes during sudden stratospheric warming events

Investigation into the linear relationship between the AE, Dst and ap indices during different magnetic and solar activity conditions

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