On the solar cycle variation of the winter anomaly

Burns, A. G.; Wang, Wenbin; Qian, Liying; Solomon, Stanley C.; Zhang, Yongliang; Paxton, L. J.; Yue, Xinan

doi:10.1002/2013ja019552

Cited by 42 publications

(59 citation statements)

References 46 publications

(71 reference statements)

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“…This indicates that, in 2006, the ionospheric winter anomaly did not exist at an altitude of ~680 km for low solar activity. It agrees with the results of Liu et al [] based on DMSP measurements at ~840 km and is also consistent with the result of Burns et al [], who reported that winter anomaly was not seen in the COSMIC data for solar minimum conditions. On the other hand, the global averaged Ne in DS was evidently larger than that in JS.…”

Section: Resultssupporting

confidence: 93%

The correlation between electron temperature and density in the topside ionosphere during 2006–2009

Wang

Burns

et al. 2015

JGR Space Physics

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Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions satellite data have been used to investigate the global relationship between electron density (Ne) and electron temperature (Te) in the topside ionosphere (~680 km) from 2006 to 2009. Te and Ne were negatively correlated in most of the low and middle latitude regions at ~10:30 solar local time (LT). In these regions, photoelectron heating of the electrons was balanced by cooling through collisions with the ions. The negative correlation became weaker at midlatitudes, due to the increasing influence of heat conduction. The correlation was negative in most seasons during the daytime except at high latitudes in the northern winter, where a positive correlation occurred. There were wave‐like longitudinal structures in Ne and Te around the geomagnetic equator, but they had different patterns in the day and the night. However, no obvious longitudinal variations in the correlation were associated with these structures. A positive correlation occurred near the magnetic equator at ~22:30 LT, which depended on thermal equilibrium between the electrons, ions, and neutrals. A negative correlation occurred at midlatitudes. Around the September equinox, at night around the magnetic equator, the positive correlation had a wider latitudinal range. At midlatitudes, a negative correlation occurred in smaller areas than it did around the March equinox. Around the December solstice the direct nighttime coupling between Ne and Te was weaker than it was around the June solstice. The negative correlation depends on the collisions between the electrons and the ions and the heating source.

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Section: Resultssupporting

confidence: 93%

The correlation between electron temperature and density in the topside ionosphere during 2006–2009

Wang

Burns

et al. 2015

JGR Space Physics

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“…This phenomenon did not occur in June. The smaller winter crests in June might be related to the absence or weakness of winter anomaly in southern winter [ Torr and Torr , ; Burns et al ., ]. Overall, in the late afternoon hours, the dependence of hemispheric asymmetry of EIA on solar cycle is mainly associated with the weaker crests in local winter due to the weakness or absence of the vertical drifts in the solar minimum [ Scherliess and Fejer , ], as well as winter anomaly in the northern winter.…”

Section: Discussionmentioning

confidence: 99%

Interhemispheric asymmetry of the equatorial ionization anomaly in solstices observed by COSMIC during 2007–2012

et al. 2015

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The ionospheric radio occultation measurements from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites during [2007][2008][2009][2010][2011][2012] are utilized to analyze variations of the hemispheric asymmetry in the equatorial ionization anomaly (EIA) in solstice seasons. A hemispheric asymmetry index (A h ) is introduced to quantitatively characterize the relative interhemispheric asymmetry or north-south differences of the EIA crests. The seasonal, solar activity, and longitudinal dependences of the hemispheric asymmetry are investigated during these low to moderately high solar activity levels. Our main findings are as follows: (1) The transition of stronger crest from the winter to summer hemispheres generally took place during noon to afternoon hours (~11:00-14:00 LT), whereas the change of the EIA hemispheric asymmetry pattern toward a stronger summer crest actually started 2-3 h earlier.(2) Remarkable differences were observed in the EIA hemispheric asymmetry between June and December solstices. In June solstice, the transition from stronger winter to summer crests occurred later, and consequently, the duration with stronger winter crest lasted longer during the morning period. (3) In the afternoon hours, the magnitudes of relative interhemispheric asymmetry of EIA crests were obviously anticorrelated with the solar activity, while in the morning hours their solar activity dependence was weak. (4) Interhemispheric asymmetry of the crests and its transition time varied with longitudes. It is also found that the longitudinal and seasonal variations of the change rate of A h was generally consistent with the corresponding variations of hemispheric asymmetry in ion production rate. Our results indicate that the photochemical process may also play a role in the EIA hemispheric asymmetry, in addition to the important contribution from the transequatorial neutral wind and equatorial fountain effects.

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“…Therefore, we support the belief that the thermospheric wind is one of the most important components of the MSNA Thampi et al 2009). The winter anomaly in the F2 region is defined as the condition in which a greater daytime electron density is seen at the F2 peak in winter than in summer (Burns et al 2014;Rishbeth and Garriot 1969). This anomaly is primarily due to greater winter to summer differences of [O]/[N2] at solar maximum than at solar minimum for daytime hours.…”

Section: Discussionmentioning

confidence: 99%

“…In this case, only 2001 data were used because the HMW07 does not change with solar cycle (Hagan 1993;Burns et al 2014).…”

Section: From the Hwm07 Modelmentioning

confidence: 99%

“…As was mentioned previously, the change in the winter to summer ratio [O]/[N2] is one of the drivers of the winter anomaly. The IRI 2012 uses the NRLMSIS-00 model to generate this relation (Bilitza et al 2014), and Burns et al (2014) Authors' contributions MPN and AM planned and led the study, interpreted the results, and drafted the manuscript. AM generated the IRI2012 and HWM07 grids.…”

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confidence: 99%

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PCA and vTEC climatology at midnight over mid-latitude regions

Natali

Meza

2017

Earth Planets Space

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The effect of the thermospheric vertical neutral wind on vertical total electron content (vTEC) variations including longitudinal anomaly, remaining winter anomaly, mid-latitude summer night anomaly, and semiannual anomaly is studied at mid-latitude regions around zero magnetic declination at midnight during high solar activity. By using the principal component analysis (PCA) numerical technique, this work studies the spatial and temporal variations of the ionosphere at midnight over mid-latitude regions during [2000][2001][2002]. PCA is applied to a time series of global vTEC maps produced by the International Global Navigation Satellite System (GNSS) Service. Four regions were studied in particular, each located at mid-latitude and approximately centered at zero magnetic declination, with two in the northern hemisphere and two in southern hemisphere, and all are located near and far from geomagnetic poles in each case. This technique provides an effective method to analyze the main ionospheric variabilities at mid-latitudes. PCA is also applied to the vTEC computed using the International Reference Ionosphere (IRI) 2012 model, to analyze the capability of this model to represent ionospheric variabilities at mid-latitude. Also, the Horizontal Wind Model 2007 (HWM07) is used to improve our climatology interpretation, by analyzing the relationship between vTEC and thermospheric wind, both quantitatively and qualitatively. At midnight, the behavior of mean vTEC values strongly responds to vertical wind variation, experiencing a decrease of about 10-15% with the action of the positive vertical component of the field-aligned neutral wind lasting for 2 h in all regions except for Oceania. Notable results include: a significant increase toward higher latitudes during summer in the South America and Asia regions, associated with the mid-latitude summer night anomaly, and an increase toward higher latitudes in winter in the North America and Oceania regions, highlighting the remnant effect of the winter anomaly. Finally, the longitudinal variations of eastwest differences, named longitudinal anomaly, show maximum values in March for North America, in December for South America and Oceania, and are not shown for Asia. Our results show that at mid-latitudes regions, the IRI model represents midnight ionospheric mean values with a similar spatial distribution, but the values are always lower than those obtained by GNSS. The differences between IRI and GNSS results include: the longitudinal anomaly is characterized by a stronger semiannual variation in both North America and South America, with a maximum in the equinoxes, while for the Asian region, the behavior is almost constant throughout the years, and finally, there is an absence of the winter anomaly remnant.

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On the solar cycle variation of the winter anomaly

Cited by 42 publications

References 46 publications

The correlation between electron temperature and density in the topside ionosphere during 2006–2009

The correlation between electron temperature and density in the topside ionosphere during 2006–2009

Interhemispheric asymmetry of the equatorial ionization anomaly in solstices observed by COSMIC during 2007–2012

PCA and vTEC climatology at midnight over mid-latitude regions

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