The seasonal behaviour of the F2-layer of the ionosphere

Torr, Marsha R.; Torr, D. G.

doi:10.1016/0021-9169(73)90140-2

Cited by 221 publications

(249 citation statements)

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“…An odd number of foF2 values under investigation leads us to determine foF2(med) as the middle value. The average of the Torr, 1973, andZou et al, 2000). Table 3 shows the arithmetical mean, <foF2(med)>, of the median values of foF2 at 16:00 UT (11:43 SLT) for January, June, July, and December calculated from the Argentine Island ionosonde foF2 data for low, moderate, and high solar activity during the 1957-1959 and 1962-1995 time periods.…”

Section: Statistical Study Of the Nmf2 Winter Anomaly: Results And DImentioning

confidence: 99%

“…Croom et al, 1960;King, 1961;Torr and Torr, 1973;Millward et al, 1996;Zou et al, 2000;Rishbeth et al, 2000;Tao Yu et al, 2000;Pavlova, 2005, 2008a, b). The winter/summer variations in the foF2 monthly noon medians were studied by Torr and Torr (1973) using the data of 140 ionosondes in 1958, 1964, and 1969. It follows from this study that the winter anomaly phenomenon in the foF2 monthly noon medians is more pronounced in the Northern Hemisphere than in the Southern Hemisphere and the region of existence and magnitude of the winter anomaly decrease with decreasing solar activity.…”

Section: Introductionmentioning

confidence: 99%

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Anomalous variations of <I>Nm</I>F2 over the Argentine Islands: a statistical study

Павлов

Павлова

2009

Ann. Geophys.

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Abstract. We present a statistical study of variations in the F2-layer peak electron density, NmF2, and altitude, hmF2, over the Argentine Islands ionosonde. The critical frequencies, foF2, and, foE, of the F2 and E-layers, and the propagation factor, M(3000)F2, measured by the ionosonde during the 1957-1959 and 1962-1995 time periods were used in the statistical analysis to determine the values of NmF2 and hmF2. The probabilities to observe maximum and minimum values of NmF2 and hmF2 in a diurnal variation of the electron density are calculated. Our study shows that the main part of the maximum diurnal values of NmF2 is observed in a time sector close to midnight in November, December, January, and February exhibiting the anomalous diurnal variations of NmF2. Another anomalous feature of the diurnal variations of NmF2 exhibited during November, December, and January when the minimum diurnal value of NmF2 is mainly located close to the noon sector. These anomalous diurnal variations of NmF2 are found to be during both geomagnetically quiet and disturbed conditions. Anomalous features are not found in the diurnal variations of hmF2. The statistical study of the NmF2 winter anomaly phenomena over the Argentine Islands ionosonde was carried out. The variations in a maximum daytime value, R, of a ratio of a geomagnetically quiet daytime winter NmF2 to a geomagnetically quiet daytime summer NmF2 taken at a given UT and for approximately the same level of solar activity were studied. The conditional probability of the occurrence of R in an interval of R, the most frequent value of R, the mean expected value of R, and the conditional probability to observe the F2-region winter anomaly during a daytime period were calculated for low, moderate, and high solar activity. The calCorrespondence to: A. V. Pavlov (pavlov@izmiran.ru) culations show that the mean expected value of R and the occurrence frequency of the F2-region winter anomaly increase with increasing solar activity.

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Section: Statistical Study Of the Nmf2 Winter Anomaly: Results And DImentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Anomalous variations of <I>Nm</I>F2 over the Argentine Islands: a statistical study

Павлов

Павлова

2009

Ann. Geophys.

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“…The Torr and Torr [1973] paper did provide insight into how the winter anomaly varied with solar cycle, despite the confusion with the annual anomaly. They found that the winter anomaly was small to nonexistent at solar minimum and large at solar maximum.…”

Section: Discussionmentioning

confidence: 99%

“…A number of studies extended Berkner et al's [1936] original work [e.g., Yonezawa, 1971;Torr and Torr, 1973;Rishbeth and MullerWodarg, 2006;Pavlov and Pavlova, 2009]. The Torr and Torr [1973] study described the difference in the winter anomaly at solar maximum and minimum. Their global map showed that the winter anomaly was large at solar maximum and small at solar minimum.…”

Section: Introductionmentioning

confidence: 93%

“…Their work, however, used a definition of the winter anomaly that effectively included the annual anomaly as well and did not attempt to describe how the winter anomaly developed over a solar cycle. Pavlov and Pavlova [2009] suggested that the Torr and Torr [1973] study might not make an accurate calculation of the intensity of the winter anomaly because of contamination by magnetically disturbed conditions. However, as geomagnetic storms are relatively rare events (as defined by Kp > 5), their contribution to the averages used by Torr and Torr was probably relatively small.…”

Section: Introductionmentioning

confidence: 99%

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On the solar cycle variation of the winter anomaly

et al. 2014

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Constellation Observing System for Meteorology, Ionosphere and Climate, Ionosonde, and Global Ultraviolet Imager data have been used to investigate the solar cycle changes in the winter anomaly (the winter anomaly is defined as the enhancement of the F 2 peak electron density in the winter hemisphere over that in the summer hemisphere) in the last solar cycle. There is no winter anomaly in solar minimum, and an enhancement of about 50% in winter over summer ones on the same day of the year at solar maximum. This solar cycle variation in the winter anomaly is primarily due to greater winter to summer differences of [O]/[N 2 ] in solar maximum than in solar minimum, with a secondary contribution from the effects of temperature on the recombination coefficient between O + and the molecular neutral gas. The greater winter increases in electron density in the Northern Hemisphere than in the Southern Hemisphere appear to be related to the greater annual variation of [O]/[N 2 ] in the north than in the south.

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Local time, seasonal, and solar cycle dependency of longitudinal variations of TEC along the crest of EIA over India

Sunda

Vyas

2013

JGR Space Physics

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[1] The global wave number 4 structure in the Indian longitudinal region spanning from 70 to 95°E forming the upward slope of the peak in the total electron content (TEC) are reported along the crest of equatorial ionization anomaly (EIA). The continuous and simultaneous measurements from five GPS stations of GPS Aided Geo Augmented Navigation (GAGAN) network are used in this study. The long-term database (2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012) is utilized for examining the local time, seasonal, and solar cycle dependency on the longitudinal variations of TEC. Our results confirm the existence of longitudinal variations of TEC in accordance with wave number 4 longitudinal structure including its strength. The results suggest that these variations, in general, start to develop at~09 LT, achieve maximum strength at 12-15 LT, and decay thereafter, the decay rate depending on the season. They are more pronounced in equinoctial season followed by summer and winter. The longitudinal variations persist beyond midnight in equinox seasons, whereas in winter, they are conspicuously absent. Interestingly, they also exhibit significant solar cycle dependence in the solstices, whereas in the equinoxes, they are independent of solar activity. The comparison of crest-to-trough ratio (CTR) in the eastern (92°E) and western (72°E) extreme longitudes reveals higher CTR on the eastern side than over the western extreme, suggesting the role of nonmigrating tides in modulating the ExB vertical drift and the consequential EIA crest formation.Citation: Sunda, S., and B. M. Vyas (2013), Local time, seasonal, and solar cycle dependency of longitudinal variations of TEC along the crest of EIA over India,

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The seasonal behaviour of the F2-layer of the ionosphere

Cited by 221 publications

References 22 publications

Anomalous variations of <I>Nm</I>F2 over the Argentine Islands: a statistical study

Anomalous variations of <I>Nm</I>F2 over the Argentine Islands: a statistical study

On the solar cycle variation of the winter anomaly

Local time, seasonal, and solar cycle dependency of longitudinal variations of TEC along the crest of EIA over India

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The seasonal behaviour of the F2-layer of the ionosphere

Cited by 221 publications

References 22 publications

Anomalous variations of &lt;I&gt;Nm&lt;/I&gt;F2 over the Argentine Islands: a statistical study

Anomalous variations of &lt;I&gt;Nm&lt;/I&gt;F2 over the Argentine Islands: a statistical study

On the solar cycle variation of the winter anomaly

Local time, seasonal, and solar cycle dependency of longitudinal variations of TEC along the crest of EIA over India

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Anomalous variations of <I>Nm</I>F2 over the Argentine Islands: a statistical study

Anomalous variations of <I>Nm</I>F2 over the Argentine Islands: a statistical study