The summer evening anomaly and conjugate effects

Burns, A. G.; Solomon, Stanley C.; Wang, Wenbin; Jee, Geonhwa; Lin, Charles; Rocken, Christian; Kuo, Ying‐Hwa

doi:10.1029/2010ja015648

Cited by 34 publications

(57 citation statements)

References 23 publications

(33 reference statements)

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“…Lin et al (2009Lin et al ( , 2010 reported that the WSA-like feature in the Northern Hemisphere spanning the East Asia-East Pacific and Central Europe regions showed two-or threepeak regions. The feature was confirmed by Thampi et al (2009) using tomographic observation near East Asia (135°E longitude) and in situ measurement from the CHAMP satellites by Liu et al (2010) and Burns et al (2011). The phenomena in the Northern Hemisphere together with the WSA are generally referred to as the Mid-latitude Summer Nighttime Anomaly (MSNA) (Thampi et al 2009) or summer evening anomaly (Burns et al 2011).…”

Section: Introductionmentioning

confidence: 84%

“…The feature was confirmed by Thampi et al (2009) using tomographic observation near East Asia (135°E longitude) and in situ measurement from the CHAMP satellites by Liu et al (2010) and Burns et al (2011). The phenomena in the Northern Hemisphere together with the WSA are generally referred to as the Mid-latitude Summer Nighttime Anomaly (MSNA) (Thampi et al 2009) or summer evening anomaly (Burns et al 2011). Recently, de Larquier et al (2011 observed the MSNA feature using Super Dual Auroral Radar Network (SuperDARN) radars over North America and Japan as well as the Millstone Hill ISR (incoherent scatter radar) during the April-September period, and suggested that the phenomena may also occur near the equinox season.…”

Section: Introductionmentioning

confidence: 84%

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Three-dimensional electron density along the WSA and MSNA latitudes probed by FORMOSAT-3/COSMIC

et al. 2015

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In this paper, we employ electron density profiles derived by the GPS radio occultation experiment aboard the FORMOSAT-3/COSMIC (F3/C) satellites to examine the electron density on geographic latitudes of 40°to 80°in the Southern hemisphere and 30°to 60°in the Northern hemisphere at various global fixed local times from February 2009 to January 2010. The results reveal that an eastward shift of a single-peak plasma density feature occurs along the Weddell Sea Anomaly (WSA) latitudes, while a double-peak plasma density feature appears along the northern Mid-latitude Summer Nighttime Anomaly (MSNA) latitudes. A cross-comparison between three-dimensional F3/C electron density and HWM93 simulation confirms that the magnetic meridional effect and vertical effect caused by neutral winds exhibit the eastward shifts. Furthermore, we find that the eastward shift of the peaks when viewed as a function of local time suggests that they could be interpreted as being comprised of different tidal components with distinct zonal phase velocities in local time.

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Section: Introductionmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 84%

Three-dimensional electron density along the WSA and MSNA latitudes probed by FORMOSAT-3/COSMIC

et al. 2015

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“…Figures 1 and 2 show that at solar minimum, a western enhancement occurs for all seasons for the relative density, while the results from the present and previous studies (e.g., Jee et al, 2009;He et al, 2009) showed that the WSA occurs only in summer. In the evening, the equatorward magnetic meridional winds and the additional plasma source are considered as either the major cause of or important contributions to the WSA (Burns et al, 2008(Burns et al, , 2011Jee et al, 2009;He et al, 2010;Lin et al, 2010;Liu et al, 2010;Chen et al, 2011Chen et al, , 2012. For the WSA, the phase reversal of the density in a diurnal circle is also related to concurrent noontime depletion .…”

Section: The Wsa and The Electron Density Longitudinal Differencementioning

confidence: 99%

“…Similar but much weaker summer evening enhancements also occur in the North American sector and East Asian sector (Lin et al, 2009(Lin et al, , 2010, known as midlatitude summer nighttime anomaly (MSNA). Several mechanisms are applied to explain these interesting phenomena, including the equatorward neutral wind, electric field, photoionization and the downward plasma diffusion from the plasmasphere (Burns et al, 2008(Burns et al, , 2011Jee et al, 2009;He et al, 2009;Chen et al, 2011Chen et al, , 2012Liu et al, 2010;Lin et al, 2009;Zhang et al, 2011Zhang et al, , 2012aZhao et al, 2013). Among those explanations, the magnetic configuration and the neutral winds are considered as important and even major contributors.…”

Section: Introductionmentioning

confidence: 99%

“…It can occur at wide latitudinal locations (∼ 30-70 • S) in summer in the Southern Hemisphere, and the strongest summer evening enhancement of F2-layer peak density occurs centered around 50-60 • S, 90 • W at midlatitudes (He et al, 2009;Lin et al, 2010;Liu et al, 2011;Burns et al, 2011). In recent years, longitudinal differences of electron density, or the density longitudinal asymmetries, have been studied over east-west regions of the continental US and the Far East area at northern midlatitudes (Zhang et al, 2011(Zhang et al, , 2012aZhao et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

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Seasonal dependence of the longitudinal variations of nighttime ionospheric electron density and equivalent winds at southern midlatitudes

Luan

Dou

2013

Ann. Geophys.

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Abstract. It has been indicated that the observed Weddell Sea anomaly (WSA) appeared to be an extreme manifestation of the longitudinal variations in the Southern Hemisphere, since the WSA is characterized by greater evening electron density than the daytime density in the region near the Weddell Sea. In the present study, the longitudinal variations of the nighttime F2-layer peak electron density at southern midlatitudes are analyzed using the observations of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites between 2006 and 2008. It is found that significant longitudinal difference (> 150 %) relative to the minimum density at each local time prevails in all seasons, although the WSA phenomenon is only evident in summer under this solar minimum condition. Another interesting feature is that in summer, the maximum longitudinal differences occur around midnight (∼ 23:00-00:00 LT) rather than in the evening (19:00-21:00 LT) in the evening, when the most prominent electron density enhancement occurs for the WSA phenomenon. Thus the seasonallocal time patterns of the electron density longitudinal variations during nighttime at southern midlatitudes cannot be simply explained in terms of the WSA. Meanwhile, the variations of the geomagnetic configuration and the equivalent magnetic meridional winds/upward plasma drifts are analyzed to explore their contributions to the longitudinal variations of the nighttime electron density. The maximum longitudinal differences are associated with the strongest windinduced vertical plasma drifts after 21:00 LT in the Western Hemisphere. Besides the magnetic declination-zonal wind effects, the geographic meridional winds and the magnetic inclination also have significant effects on the upward plasma drifts and the resultant electron density.

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Seasonal trends of nighttime plasma density enhancements in the topside ionosphere

Slominska¹,

Błȩcki

Lebreton

et al. 2014

JGR Space Physics

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In situ registrations of electron density from the Langmuir probe on board Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions satellite are used to study spatial and temporal evolution of nighttime plasma density enhancements (NPDEs). The study introduces the normalized density difference index I NDD in order to provide global estimates of the phenomenon. In the validation test, in situ data are compared with synthetic data set generated with the International Reference Ionosphere model. We find signatures of two most common examples of NPDEs, the Weddell Sea Anomaly (WSA) and midlatitude nighttime summer anomaly (MSNA) with proposed index, in the topside ionosphere. The study provides evidence that the occurrence of the WSA and MSNA is not limited to the local summer conditions. Analyzed annual trend of I NDD and in particular spatial pattern obtained during equinoxes suggest that mechanisms governing the behavior of the equatorial ionosphere cannot be neglected in the explanation of the development of NPDEs.

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The summer evening anomaly and conjugate effects

Cited by 34 publications

References 23 publications

Three-dimensional electron density along the WSA and MSNA latitudes probed by FORMOSAT-3/COSMIC

Three-dimensional electron density along the WSA and MSNA latitudes probed by FORMOSAT-3/COSMIC

Seasonal dependence of the longitudinal variations of nighttime ionospheric electron density and equivalent winds at southern midlatitudes

Seasonal trends of nighttime plasma density enhancements in the topside ionosphere

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