Long-term trends in the ionospheric F2 region with different solar activity indices

Mielich, Jens; Bremer, J.

doi:10.5194/angeo-31-291-2013

Cited by 57 publications

(72 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Mielich and Bremer (2013) discuss in detail this point for hmF2 and foF2 data, showing that trends for increasing data intervals present more stable variations, and suggest that the derived mean hmF2 and foF2 trends are more reliable for longer data intervals. Figure 7 shows the foF2 trend estimated first for the 1960 to 1980 period and since then adding 1 year but beginning always in 1960.…”

Section: Length Of Periodmentioning

confidence: 84%

“…Recently, Mielich and Bremer (2013) analyzed more than 100 stations in order to detect the best index to filter solar activity from foF2 and hmF2. They conclude that a b F10.7 is a better index for the description of the solar activity than Rz.…”

Section: Discussionmentioning

confidence: 99%

“…One is not to include periods with F10.7 > 200, or at least test that the residuals for these periods are not systematically negative. The other two were already made by Mielich and Bremer (2013): use F10.7 instead of Rz, since it follows more closely EUV solar flux, and the length of period considered should be long enough so as to obtain a stable trend since at least the last 4 to 5 years of the data series considered (almost half a solar cycle).…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Filtering ionosphere parameters to detect trends linked to anthropogenic effects

Elı́as

2014

Earth Planet Space

View full text Add to dashboard Cite

The great concern about the global warming observed in the troposphere has generated a large interest in the study of long-term trends in the ionosphere since the early 1990s, which has now become a significant topic in global change investigations. Some research works link ionosphere trends to anthropogenic sources such as the increase in greenhouse gas concentration, and others to natural causes such as solar and geomagnetic activity long-term changes, and secular variations in the Earth's main magnetic field. In all the cases, in order to analyze ionospheric trends, solar activity effect must be filtered out first since around 90% of ionosphere parameter variance is due to solar variations. The filtering process can generate 'spurious' trends in the filtered data series which may lead to erroneous conclusions. foF2 data series which include solar cycle 23 are analyzed in the present work in order to detect the effect of different filtering procedures on the determination of long-term trends. In particular, solar cycle 23 seems to have had an extreme ultraviolet (EUV) emission greater than that deduced from traditional solar EUV proxies during the maximum epoch and lower during the minimum epoch. When solar activity is filtered assessing the residuals of a linear regression between foF2 and Rz, or between foF2 and F10.7, this fact may bias trend values especially because it is at the end of the time series. The length of the period considered for trend assessment, the saturation and hysteresis effect of some ionosphere parameters, and the solar EUV proxy used are also considered in this study in order to quantify a possible spurious trend that may result as a by-product of a filtering process. Since trends expected as a consequence of anthropogenic effects are relatively small, these spurious effects may surely mask, or enhance, trends expected from anthropogenic origins.

show abstract

Section: Length Of Periodmentioning

confidence: 84%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Filtering ionosphere parameters to detect trends linked to anthropogenic effects

Elı́as

2014

Earth Planet Space

View full text Add to dashboard Cite

show abstract

“…The solar activity effect has usually been removed or suppressed using solar activity proxies, particularly F10.7 (sunspot number is the worse option; see e.g. Mielich and Bremer, 2013), because decades-long homogeneous series of solar extreme ultraviolet (EUV) data are not available.…”

Section: Introductionmentioning

confidence: 99%

Stability of solar correction for calculating ionospheric trends

et al. 2016

View full text Add to dashboard Cite

Abstract. Global climate change affects the whole atmosphere, including the thermosphere and ionosphere. Calculations of long-term trends in the ionosphere are critically dependent on solar activity (solar cycle) correction of ionospheric input data. The standard technique is to establish an experimental model via calculating the dependence of ionospheric parameter on solar activity from the whole analysed data set, subtract these model data from observed data and analyse the trend of residuals. However, if the solar activity dependence changes with time, the solar correction calculated from the whole data set may result in miscalculating the ionospheric trends. To test this, data from two European ionospheric stations -Juliusruh and Slough/Chilton -which provide long-term reliable data, have been used for the period 1975-2014. The main result of this study is the finding that the solar activity correction used in calculating ionospheric long-term trends need not be stable, as was assumed in all previous investigations of ionospheric trends. During the previous solar cycle 23 and the current solar cycle 24, the solar activity correction appears to be different from that for the previous period and the Sun seems to behave in a different way than throughout the whole previous era of ionospheric measurements. In future ionospheric trend investigations the non-stability of solar activity correction has to be very seriously taken into account, because it can substantially affect calculated long-term trends of ionospheric parameters.

show abstract

“…Moreover, the dependence on geomagnetic activity was considered in the analysis of long-term variations in f o F2 med [Bremer, 1998;Laštovička et al, 2006;Mielich, Bremer, 2013]. The said works assumed linear or nonlinear dependences of f o F2 med on solar and geomagnetic activity indices.…”

Section: Introductionmentioning

confidence: 99%

Dependence of the F2-layer critical frequency median at midlatitudes on geomagnetic activity

Dëminov¹,

Deminova²,

Depuev³

et al. 2017

Solar-Terrestrial Physics

View full text Add to dashboard Cite

Abstract. We put forward a method of separating the geomagnetic activity contribution to the F2-layer critical frequency median, f o F2 med , at middle latitudes. It is based on the analysis of δf o F2, which is the ratio f o F2 med /f o F2 q in percent, where f o F2 q is the F2-layer critical frequency for quiet conditions. The quantities f o F2 q and δf o F2 depend on solar and geomagnetic activity respectively. These dependences are taken into account using indices F 12 (annual average solar radio emission flux at 10.7 cm) and Ap m (monthly average Ap index), thus facilitating the use of this method for forecasting f o F2 med . With this method, from Slough station (51.5° N, 0.6° W) data for midday and midnight for 1954 to 1995 we have found that at midnight the δf o F2 dependence on Ap m is significant at the 95 % confidence level for equinoxes and summer. For midday, this dependence is less pronounced and is significant only from April to July. At equinoxes and summer, an Ap m increase causes a δf o F2 decrease. For midnight, this feature is more pronounced than for midday. This regularity is also valid for annual average Ap m and δf o F2.

show abstract

Long-term trends in the ionospheric F2 region with different solar activity indices

Cited by 57 publications

References 32 publications

Filtering ionosphere parameters to detect trends linked to anthropogenic effects

Filtering ionosphere parameters to detect trends linked to anthropogenic effects

Stability of solar correction for calculating ionospheric trends

Dependence of the F2-layer critical frequency median at midlatitudes on geomagnetic activity

Contact Info

Product

Resources

About