Long-term trends in foF2: A comparison of various methods

Laštovička, Jan; Mikhailov, A. V.; Ulich, Thomas; Bremer, J.; Elı́as, Ana G.; Adler, N. Ortiz de; Jara, V.; Río, R. Abarca del; Foppiano, A. J.; Ovalle, E.; Данилов, А. Д.

doi:10.1016/j.jastp.2006.02.009

Cited by 120 publications

(104 citation statements)

References 46 publications

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“…The method adopted to analyse the f oF 2 data was derived from Bremer (1992) and has been successively used by several authors (see, e.g., Lastovicka et al, 2006). The main steps of our data selection and processing are the followings: a) Selection of the "full-weight" f oF 2 hourly data, i.e.…”

Section: Methodsmentioning

confidence: 99%

Geomagnetic and ionospheric data analysis over Antarctica: a contribution to the long term trends investigation

2008

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Abstract. The analysis of the f oF 2 ionosonde data acquired at mid and high latitudes reveals a general decreasing of the F2 plasma frequency over more than two solar cycles, showing steeper trends over the high latitude stations and, in particular, over Antarctica. A careful analysis of the f oF 2 hourly data, opportunely catalogued in different levels of magneto-ionospheric conditions, highlights the role of the geomagnetic activity in the secular change of the ionosphere and confirms the latitudinal dependence of the trends. These results suggest interesting relations with some recent findings on the rapid decrease of some important physical and statistical quantities related to the geomagnetic field over the whole globe and mainly in Antarctica. In this paper we discuss the possibility of a connection between the ionospheric trends and a possible imminent geomagnetic reversal or excursion.

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Section: Methodsmentioning

confidence: 99%

Geomagnetic and ionospheric data analysis over Antarctica: a contribution to the long term trends investigation

2008

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“…[12] Regarding experimental values, a major debate in the matter of trend detection in the ionosphere is the methodology used to extract these trends from the experimental data [Lastovicka et al, 2006b], which ends in complex global patterns and different results among different authors. According to Bremer [2004Bremer [ , 2008, who used the same method as in the present paper to extract trends, the experimental global mean f o E trend is positive, agreeing with the greenhouse effect prediction, but is stronger than the model results.…”

Section: Trends Due To Increasing Greenhouse Gas Concentrationsmentioning

confidence: 99%

Trends in the solar quiet geomagnetic field variation linked to the Earth's magnetic field secular variation and increasing concentrations of greenhouse gases

2010

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Long‐term trends in solar quiet geomagnetic field variation (Sq) are studied in connection to the Earth's magnetic field secular variations and increasing greenhouse gas concentrations. Sq is mainly caused by ionospheric current systems that flow in the E region and depends, among other variables, on the ionospheric conductivities. These conductivities in turn depend on the Earth's main magnetic field (B) and the electron concentration in the E region, for which foE is a measure of its peak value. Since B shows secular variation, induced long‐term changes in Sq might be expected. Another possible mechanism that would be able to induce Sq trends is the increasing concentrations of greenhouse gases that produce a cooling effect in the upper atmosphere and, according to model predictions and experimental results, an increasing trend in foE. To detect if both mechanisms mentioned are able to induce trends in Sq, the Sq variation of the horizontal intensity (H) of three magnetic observatories (Apia, Fredericksburg, and Hermanus), for which B is decreasing, is analyzed for the period 1960–2001. We find significant increasing trends (6.6%, 5.4%, and 9.9%, respectively) which may be partially accounted for by B secular variations in the respective sites. The Sq trend expected from the theoretically predicted foE increase is low (∼0.5%), although positive, as is the observed trend.

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“…Laštovička (jla@ufa.cas.cz) of the F2 layer. Unfortunately, the results of different authors differ substantially, even as to sign and possible origin of long-term change in foF2 (see, e.g., brief review in Laštovička et al, 2006b;Yue et al, 2006). The determination and/or estimation of long-term trends in foF2 are difficult due to the overlapping effect of the 11-year solar cycle, which is many times larger than the effect of long-term trends over the 11 year period.…”

Section: Introductionmentioning

confidence: 99%

Long-term trends in <I>fo</I>F2: their estimating and origin

2008

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Abstract. This paper deals with two problems, methods of foF2 trend determination and origin of trends in foF2, both being controversial in current literature. We found that various regression-based methods and artificial neural networkbased method of Yue et al. (2006) provided comparable results within uncertainties caused mainly by various ways of removing/suppressing the dominant solar cycle effect. The role of geomagnetic activity in the observed trends in foF2 was probably substantial and might be still even rather dominant in the last quarter of the 20th century.

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Long-term trends in foF2: A comparison of various methods

Cited by 120 publications

References 46 publications

Geomagnetic and ionospheric data analysis over Antarctica: a contribution to the long term trends investigation

Geomagnetic and ionospheric data analysis over Antarctica: a contribution to the long term trends investigation

Trends in the solar quiet geomagnetic field variation linked to the Earth's magnetic field secular variation and increasing concentrations of greenhouse gases

Long-term trends in <I>fo</I>F2: their estimating and origin

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Long-term trends in foF2: A comparison of various methods

Cited by 120 publications

References 46 publications

Geomagnetic and ionospheric data analysis over Antarctica: a contribution to the long term trends investigation

Geomagnetic and ionospheric data analysis over Antarctica: a contribution to the long term trends investigation

Trends in the solar quiet geomagnetic field variation linked to the Earth's magnetic field secular variation and increasing concentrations of greenhouse gases

Long-term trends in &lt;I&gt;fo&lt;/I&gt;F2: their estimating and origin

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Long-term trends in <I>fo</I>F2: their estimating and origin