Spatial and seasonal variations of the

Данилов, А. Д.; Mikhailov, A. V.

doi:10.1007/s005850050849

Cited by 24 publications

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“…(1), and N is the number of pairs considered. Although we are aware of the seasonal variations in trends (Danilov and Mikhailov, 1999), the later analysis has shown that diurnal variations may be much stronger than seasonal ones. Therefore, we have analyzed annual mean trends for a selected LT hours.…”

Section: The Methods and Datamentioning

confidence: 85%

“…A slightly modi®ed method earlier proposed by Danilov and Mikhailov (1999) was applied to the foF2 long-term trend analysis at 30 ionosonde stations. The slope K depends on latitude (Figs.…”

Section: Discussionmentioning

confidence: 99%

“…A slightly modi®ed version of a method proposed earlier by Danilov and Mikhailov (1999) was applied to the foF2 long-term trends analysis on 30 mid-and highlatitude ionosondes of the Northern Hemisphere. Years of solar minimum (m), maximum (M) and (M+m) were analyzed separately.…”

Section: Discussionmentioning

confidence: 99%

“…The method used for foF2 trend analysis is described by Danilov and Mikhailov (1999), but as it is being improved, the main points of the method are given. It should be stressed that dierent authors use dierent approaches to extract long-term trends from the ionospheric observations and the success of analysis depends to a great extent on the method used.…”

Section: The Methods and Datamentioning

confidence: 99%

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Geomagnetic control of the foF2 long-term trends

Михайлов

Marín

2000

Ann. Geophys.

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Abstract. Further development of the method proposed by Danilov and Mikhailov is presented. The method is applied to reveal the foF2 long-term trends on 30 Northern Hemisphere ionosonde stations. Most of them show signi®cant foF2 trends. A pronounced dependence of trend magnitude on geomagnetic (invariant) latitude is con®rmed. Periods of negative/positive foF2 trends corresponding to the periods of long-term increasing/ decreasing geomagnetic activity are revealed for the ®rst time. Pronounced diurnal variations of the foF2 trend magnitude are found. Strong positive foF2 trends in the post-midnight-early-morning LT sector and strong negative trends during daytime hours are found on the sub-auroral stations for the period with increasing geomagnetic activity. On the contrary middle and lower latitude stations demonstrate negative trends in the earlymorning LT sector and small negative or positive trends during daytime hours for the same period. All the morphological features revealed of the foF2 trends may be explained in the framework of contemporary F2-region storm mechanisms. This newly proposed F2-layer geomagnetic storm concept casts serious doubts on the hypothesis relating the F2-layer parameter long-term trends to the thermosphere cooling due to the greenhouse eect.

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Section: The Methods and Datamentioning

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: The Methods and Datamentioning

confidence: 99%

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Geomagnetic control of the foF2 long-term trends

Михайлов

Marín

2000

Ann. Geophys.

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“…Due to an increasing interest in the anthropogenic impact on the Earth's atmosphere the ionospheric parameter longterm trends are widely discussed in recent publications (Bremer, 1992(Bremer, , 1998Leshchenko, 1994, 1995;Danilov, 1997Danilov, , 1998Ulich and Turunen, 1997;Rishbeth, 1997;Jarvis et al, 1998;Upadhyay and Mahajan, 1998;Sharma et al, 1999;Foppiano et al, 1999;Danilov and Mikhailov, 1999;Mikhailov and Marin, 2000;Deminov et al, 2000;Danilov and Mikhailov, 2001). The interest in the ionospheric trend analysis was greatly stimulated by the model calculations of Rishbeth (1990) and Rishbeth and Roble (1992), who predicted the ionospheric effects of the atmosphere greenhouse gas concentration inCorrespondence to: A. V. Mikhailov (avm71@orc.ru) crease.…”

Section: Introductionmentioning

confidence: 99%

A revised approach to the ƒoF2 long-term trends analysis

et al. 2002

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Abstract. A new approach to extract foF2 long-term trends, which are free to a great extent from solar and geomagnetic activity effects, has been proposed. These trends are insensitive to the phase (increasing/decreasing) of geomagnetic activity, with long-term variations being small and insignificant for such relatively short time periods. A small but significant residual foF2 trend, with the slope K r = −2.2 × 10 −4 per year, was obtained over a 55-year period (the longest available) of observations at Slough. Such small trends have no practical importance. On the other hand, negative (although insignificant) residual trends obtained at 10 ionosonde stations for shorter periods (31 years) may be considered as a manifestation of a very long-term geomagnetic activity increase which did take place during the 20th century. All of the revealed foF2 long-term variations (trends) are shown to have a natural origin related to long-term variations in solar and geomagnetic activity. There is no indication of any manmade foF2 trends.

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Geomagnetic control of the midlatitude f_oF₁ and f_oF₂ long‐term variations: Recent observations in Europe

Perrone

Михайлов

2016

JGR Space Physics

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A new very simple method, allowing an easy control, has been applied to extract long‐term (11 year) δfoF2 11y and δfoF1 11y variations from June foF2 and foF1 monthly median observations at European Slough/Chilton and Juliusruh stations, including recent data until 2015. The aim of the analysis was to check the validity of the geomagnetic control of foF2 and foF1 long‐term variations in the 21st century with the main accent on the period including the last deep solar minimum in 2008–2009. The geomagnetic control was shown to be valid. Moreover, the dependence on geomagnetic activity has become more pronounced and explicit after 1990. A simultaneous analysis of foF2 and foF1 long‐term variations improves the reliability of the obtained conclusions and helps understand the physical mechanism of these variations. Due to common neutral composition and the similarity of photochemical processes noontime foF2 and foF1 demonstrate similar long‐term variations: the correlation coefficient between δfoF2 11y and δfoF1 11y is 0.834 at Slough/Chilton and 0.884 at Juliusruh with the 99% confidence level according to Fisher's F criterion. Midnight long‐term δfoF2 11y variations also manifest a pronounced dependence on Ap11y which may be interpreted in the framework of the geomagnetic control concept.

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Spatial and seasonal variations of the

Cited by 24 publications

References 0 publications

Geomagnetic control of the <i>fo</i>F2 long-term trends

Geomagnetic control of the <i>fo</i>F2 long-term trends

A revised approach to the ƒ<i>o</i>F2 long-term trends analysis

Geomagnetic control of the midlatitude f_oF₁ and f_oF₂ long‐term variations: Recent observations in Europe

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Spatial and seasonal variations of the

Cited by 24 publications

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Geomagnetic control of the &lt;i&gt;fo&lt;/i&gt;F2 long-term trends

Geomagnetic control of the &lt;i&gt;fo&lt;/i&gt;F2 long-term trends

A revised approach to the ƒ&lt;i&gt;o&lt;/i&gt;F2 long-term trends analysis

Geomagnetic control of the midlatitude foF1 and foF2 long‐term variations: Recent observations in Europe

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Geomagnetic control of the <i>fo</i>F2 long-term trends

Geomagnetic control of the <i>fo</i>F2 long-term trends

A revised approach to the ƒ<i>o</i>F2 long-term trends analysis

Geomagnetic control of the midlatitude f_oF₁ and f_oF₂ long‐term variations: Recent observations in Europe