Climatology of the mean total electron content derived from GPS global ionospheric maps

Liu, Libo; Wan, Weixing; Ning, Baiqi; Zhang, Man-Lian

doi:10.1029/2009ja014244

Cited by 122 publications

(125 citation statements)

References 72 publications

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“…The CODE GIMs data on every day from January 1996 to September 2013 were averaged globally to calculate the daily global average TEC (TEC) in a similar way to Hocke (2008) and Liu et al (2009). This index is thought to be able to reduce local noise, represent the global nature of the ionosphere, and excellently track the solar cycle variation and solar rotation modulations; thus it can be used as a practical ionospheric index (Hocke, 2008;Liu et al, 2009).…”

Section: Global Average Tec In Solar Cycles 23 and 24mentioning

confidence: 99%

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Weak ionization of the global ionosphere in solar cycle 24

et al. 2014

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Abstract. Following prolonged and extremely quiet solar activity from 2008 to 2009, the 24th solar cycle started slowly. It has been almost 5 years since then. The measurement of ionospheric critical frequency (foF2) shows the fact that solar activity has been significantly lower in the first half of cycle 24, compared to the average levels of cycles 19 to 23; the data of global average total electron content (TEC) confirm that the global ionosphere around the cycle 24 peak is much more weakly ionized, in contrast to cycle 23. The weak ionization has been more notable since the year 2012, when both the ionosphere and solar activity were expected to be approaching their maximum level. The undersupply of solar extreme ultraviolet (EUV) irradiance somewhat continues after the 2008-2009 minimum, and is considered to be the main cause of the weak ionization. It further implies that the thermosphere and ionosphere in the first solar cycle of this millennium would probably differ from what we have learned from the previous cycles of the space age.

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Section: Global Average Tec In Solar Cycles 23 and 24mentioning

confidence: 99%

“…This index is thought to be able to reduce local noise, represent the global nature of the ionosphere, and excellently track the solar cycle variation and solar rotation modulations; thus it can be used as a practical ionospheric index (Hocke, 2008;Liu et al, 2009).…”

Section: Global Average Tec In Solar Cycles 23 and 24mentioning

confidence: 99%

Weak ionization of the global ionosphere in solar cycle 24

et al. 2014

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“…Correspondence to: M. P. Natali (paula@fcaglp.unlp.edu.ar) F2-layer peak electron content (NmF2) and TEC (Rishbeth, 1998;Rishbeth et al, 2000;Zou et al, 2000;Liu et al, 2009;Zhao et al, 2005;Meza and Natali, 2008). These anomalies can be summarized as follows:…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, a database of ionospheric VTEC derived from GPS observations produced by a worldwide network of continuously tracking stations, has been used to investigate the local and regional characteristics of various anomalies (Huang and Cheng, 1996;Wu et al, 2004;Liu et al, 2009;Astafyeva et al, 2008). The worldwide GPS network above mentioned is managed by the International GNSS (Global Navigation Satellite System) Service, known as IGS.…”

Section: Introductionmentioning

confidence: 99%

Annual and semiannual variations of vertical total electron content during high solar activity based on GPS observations

Natali

Meza²

2011

Ann. Geophys.

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Abstract. Annual, semiannual and seasonal variations of the Vertical Total Electron Content (VTEC) have been investigated during high solar activity in 2000. In this work we use Global IGS VTEC maps and Principal Component Analysis to study spatial and temporal ionospheric variability. The behavior of VTEC variations at two-hour periods, at noon and at night is analyzed. Particular characteristics associated with each period and the geomagnetic regions are highlighted.The variations at night are smaller than those obtained at noon. At noon it is possible to see patterns of the seasonal variation at high latitude, and patterns of the semiannual anomaly at low latitudes with a slow decrease towards mid latitudes. At night there is no evidence of seasonal or annual anomaly for any region, but it was possible to see the semiannual anomaly at low latitudes with a sudden decrease towards mid latitudes. In general, the semiannual behavior shows March-April equinox at least 40 % higher than September one. Similarities and differences are analyzed also with regard to the same analysis done for a period of low solar activity.

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“…The ionosphere also contributes slightly to the DM but typically the total number of electrons along a path through the ionosphere is less than 100 TEC units (e.g. Liu et al 2009), which corresponds to a DM of just 3.24 × 10 −5 pc cm −3 . In practice, this contribution is small and follows a ν −2 law, making it indistinguishable from the dispersive delay of the ISM.…”

Section: Introductionmentioning

confidence: 99%

Wide-band simultaneous observations of pulsars: disentangling dispersion measure and profile variations

Hassall

Stappers

Hessels

et al. 2012

A&A

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Dispersion in the interstellar medium is a well known phenomenon that follows a simple relationship, which has been used to predict the time delay of dispersed radio pulses since the late 1960s. We performed wide-band simultaneous observations of four pulsars with LOFAR (at 40-190 MHz), the 76-m Lovell Telescope (at 1400 MHz) and the Effelsberg 100-m Telescope (at 8000 MHz) to test the accuracy of the dispersion law over a broad frequency range. In this paper we present the results of these observations which show that the dispersion law is accurate to better than 1 part in 10 5 across our observing band. We use this fact to constrain some of the properties of the interstellar medium along the line-of-sight and use the lack of any aberration or retardation effects to determine upper limits on emission heights in the pulsar magnetosphere. We also discuss the effect of pulse profile evolution on our observations, and the implications that it could have for precision pulsar timing projects such as the detection of gravitational waves with pulsar timing arrays.

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Climatology of the mean total electron content derived from GPS global ionospheric maps

Cited by 122 publications

References 72 publications

Weak ionization of the global ionosphere in solar cycle 24

Weak ionization of the global ionosphere in solar cycle 24

Annual and semiannual variations of vertical total electron content during high solar activity based on GPS observations

Wide-band simultaneous observations of pulsars: disentangling dispersion measure and profile variations

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