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

2002 ◽  
Vol 20 (10) ◽  
pp. 1663-1675 ◽  
Author(s):  
A. V. Mikhailov ◽  
D. Marin ◽  
T. Yu. Leschinskaya ◽  
M. Herraiz
Keyword(s):  
Geomagnetic Activity ◽  
Practical Importance ◽  
Ionospheric Disturbances ◽  
Activity Increase ◽  
New Approach ◽  
Long Term Trends ◽  
Time Periods ◽  
Short Time ◽  
Long Term Variations

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 Kr = - 2.2 × 10-4 per year, was obtained over a 55-year period (the longest avail-able) 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.  Key words. Ionosphere (ionosphere-atmosphere interactions, ionospheric disturbances)

scholarly journals Long-term trends of <i>f</i>oE and geomagnetic activity variations

2003 ◽  
Vol 21 (3) ◽  
pp. 751-760 ◽  
Author(s):  
A. V. Mikhailov ◽  
B. A. de la Morena
Keyword(s):  
Geomagnetic Activity ◽  
Lower Thermosphere ◽  
Chemical Pollution ◽  
Anthropogenic Activity ◽  
Ionospheric Disturbances ◽  
Time Period ◽  
Long Term Trends ◽  
First Time ◽  
Long Term Variations

Abstract. A relationship between foE trends and geomagnetic activity long-term variations has been revealed for the first time. By analogy with earlier obtained results on the foF2 trends it is possible to speak about the geomagnetic control of the foE long-term trends as well. Periods of increasing geomagnetic activity correspond to negative foE trends, while these trends are positive for the decreasing phase of geomagnetic activity. This "natural" relationship breaks down around 1970 (on some stations later) when pronounced positive foE trends have appeared on most of the stations considered. The dependence of foE trends on geomagnetic activity can be related with nitric oxide variations at the E-layer heights. The positive foE trends that appeared after the "break down" effect may also be explained by the [NO] decrease which is not related to geomagnetic activity variations. But negative trends or irregular foE variations on some stations for the same time period require some different mechanism. Chemical pollution of the lower thermosphere due to the anthropogenic activity may be responsible for such abnormal foE behavior after the end of the 1960s.Key words. Ionosphere (ionosphere-atmosphere interactions; ionospheric disturbances)

Long-term variations in the geomagnetic activity level Part II: Ascending phases of sunspot cycles

1994 ◽  
Vol 12 (10/11) ◽  
pp. 1065-1070 ◽  
Author(s):  
V. Mussino ◽  
O. Borello Filisetti ◽  
M. Storini ◽  
H. Nevanlinna
Keyword(s):  
Correlation Coefficient ◽  
Geomagnetic Activity ◽  
Activity Level ◽  
Activity Levels ◽  
Data Set ◽  
The Past ◽  
Long Term Trends ◽  
A Minor ◽  
Long Term Variations

Abstract. Monthly averages of the Helsinki Ak-values have been reduced to the equivalent aa-indices to extend the aa-data set back to 1844. A periodicity of about five cycles was found for the correlation coefficient (r) between geomagnetic indices and sunspot numbers for the ascending phases of sunspot cycles 9 to 22, confirming previous findings based on a minor number of sunspot cycles. The result is useful to researchers in topics related to solar-terrestrial physics, particularly for the interpretation of long-term trends in geomagnetic activity during the past, and to forecast geomagnetic activity levels in the future.

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

2000 ◽  
Vol 18 (6) ◽  
pp. 653-665 ◽  
Author(s):  
A. V. Mikhailov ◽  
D. Marin
Keyword(s):  
Geomagnetic Activity ◽  
Early Morning ◽  
Lower Latitude ◽  
Ionospheric Disturbances ◽  
Trend Magnitude ◽  
Layer Parameter ◽  
Long Term Trends ◽  
First Time ◽  
Further Development

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 significant foF2 trends. A pronounced dependence of trend magnitude on geomagnetic (invariant) latitude is confirmed. Periods of negative/positive foF2 trends corresponding to the periods of long-term increasing/decreasing geomagnetic activity are revealed for the first 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 early-morning 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 effect.Key words: Ionosphere (ionosphere-atmosphere interactions; ionospheric disturbances)

scholarly journals Ionospheric F1 layer long-term trends and the geomagnetic control concept

2008 ◽  
Vol 26 (12) ◽  
pp. 3793-3803 ◽  
Author(s):  
A. V. Mikhailov
Keyword(s):  
Geomagnetic Activity ◽  
Temperature Changes ◽  
Term Variation ◽  
Control Concept ◽  
E Region ◽  
Long Term Trends ◽  
Long Term Trend ◽  
The Magnetic Field ◽  
Long Term Variations

Abstract. A previous approach to the ionospheric long-term trend analysis has been applied to the foF1 observations from Slough and Rome in order to investigate a possible relationship between the foF1 and the long-term variation of geomagnetic activity. A 40-year period, starting in 1962, has been used for the analysis. According to the results obtained earlier for F2 and E-region trends, geomagnetic control of the long-term variation has also been revealed for the foF1. Thus, it is now possible to speak about the geomagnetic control of the ionospheric trends in the whole ionosphere. This is not surprising as the Earth's ionosphere is a single entity that is strongly controlled, either directly or indirectly, by the magnetic field. As with the F2-region, this geomagnetic control is provided via neutral composition and temperature changes. A very long-term (centennial) increase in geomagnetic activity in the 20th century is seen in the long-term foF1 variations as well. After its removal, the residual foF1 trends are very small and insignificant. In principal, this means that the observed foF1 long-term variations have a natural origin and can be attributed to solar and geomagnetic activity long-term variations. However, the situation in the thermosphere has been changing since 1997 and available foF2 observations at the two stations reveal information about the "break down" of the geomagnetic control in the F2-region. Possible reasons of these changes are discussed.

scholarly journals Long-term trends of <i>fo</i>F2 independent of geomagnetic activity

2003 ◽  
Vol 21 (5) ◽  
pp. 1167-1176 ◽  
Author(s):  
A. D. Danilov
Keyword(s):  
Detailed Analysis ◽  
Local Time ◽  
Geomagnetic Activity ◽  
Geomagnetic Latitude ◽  
Ionospheric Disturbances ◽  
Strong Argument ◽  
Long Term Changes ◽  
Long Term Trends ◽  
The Difference

Abstract. A detailed analysis of the foF2 data at a series of ionospheric stations is performed to reveal long-term trends independent of the long-term changes in geomagnetic activity during the recent decades (nongeomagnetic trends). The method developed by the author and published earlier is used. It is found that the results for 21 out of 23 stations considered agree well and give a relative nongeomagnetic trend of -0.0012 per year (or an absolute nongeomagnetic trend of about -0.012 MHz per year) for the period between 1958 and the mid-nineties. The trends derived show no dependence on geomagnetic latitude or local time, a fact confirming their independence of geomagnetic activity. The consideration of the earlier period (1948–1985) for a few stations for which the corresponding data are available provides significantly lower foF2 trends, the difference between the later and earlier periods being a factor of 1.6. This is a strong argument in favor of an anthropogenic nature of the trends derived.Key words. Ionosphere (ionosphere-atmosphere interactions; ionospheric disturbances; mid-latitude ionosphere)

scholarly journals An interpretation of the <i>ƒo</i>F2 and <i>hm</i>F2 long-term trends in the framework of the geomagnetic control concept

2001 ◽  
Vol 19 (7) ◽  
pp. 733-748 ◽  
Author(s):  
A. V. Mikhailov ◽  
D. Marin
Keyword(s):  
Geomagnetic Activity ◽  
Electron Precipitation ◽  
Ionospheric Disturbances ◽  
Temperature Changes ◽  
Layer Parameter ◽  
Latitudinal Dependence ◽  
Control Concept ◽  
Long Term Trends ◽  
Frame Work

Abstract. Earlier revealed morphological features of the foF2 and hmF2 long-term trends are interpreted in the scope of the geomagnetic control concept based on the contemporary F2-layer storm mechanisms. The F2-layer parameter trends strongly depend on the long-term varying geomagnetic activity whose effects cannot be removed from the trends using conventional indices of geomagnetic activity. Therefore, any interpretation of the foF2 and hmF2 trends should consider the geomagnetic effects as an inalienable part of the trend analysis. Periods with negative and positive foF2 and hmF2 trends correspond to the periods of increasing or decreasing geomagnetic activity with the turning points around 1955, and the end of 1960s and 1980s, where foF2 and hmF2 trends change their signs. Such variations can be explained by neutral composition, as well as temperature and thermospheric wind changes related to geomagnetic activity variations. In particular, for the period of increasing geomagnetic activity (1965–1991) positive at lower latitudes, but negative at middle and high latitudes, foF2 trends may be explained by neutral composition and temperature changes, while soft electron precipitation determines nighttime trends at sub-auroral and auroral latitudes. A pronounced dependence of the foF2 trends on geomagnetic (invariant) latitude and the absence of any latitudinal dependence for the hmF2 trends are due to different dependencies of NmF2 and hmF2 on main aeronomic parameters. All of the revealed latitudinal and diurnal foF2 and hmF2 trend variations may be explained in the frame-work of contemporary F2-region storm mechanisms. The newly proposed geomagnetic storm concept used to explain F2-layer parameter long-term trends proceeds from a natural origin of the trends rather than an artificial one, related to the thermosphere cooling due to the greenhouse effect. Within this concept, instead of cooling, one should expect the thermosphere heating for the period of increasing geomagnetic activity (1965–1991).Key words. Ionosphere (ionosphere-atmosphere interactions; ionospheric disturbances)

scholarly journals Ionospheric long-term trends: can the geomagnetic control and the greenhouse hypotheses be reconciled?

2006 ◽  
Vol 24 (10) ◽  
pp. 2533-2541 ◽  
Author(s):  
A. V. Mikhailov
Keyword(s):  
Geomagnetic Activity ◽  
Western Europe ◽  
Temperature Changes ◽  
Neutral Temperature ◽  
Control Concept ◽  
Long Term Trends ◽  
The 1960S ◽  
Strongly Damped ◽  
Long Term Variations

Abstract. The ionospheric F2-layer parameter long-term trends are considered from the geomagnetic control concept and the greenhouse hypothesis points of view. It is stressed that long-term geomagnetic activity variations are crucial for ionosphere long-term trends, as they determine the basic natural pattern of foF2 and hmF2 long-term variations. The geomagnetic activity effects should be removed from the analyzed data to obtain real trends in ionospheric parameters, but this is not usually done. Only a thermosphere cooling, which is accepted as an explanation for the neutral density decrease, cannot be reconciled with negative foF2 trends revealed for the same period. A more pronounced decrease of the O/N2 ratio is required which is not provided by empirical thermospheric models. Thermospheric cooling practically cannot be seen in foF2 trends, due to a weak NmF2 dependence on neutral temperature; therefore, foF2 trends are mainly controlled by geomagnetic activity long-term variations. Long-term hmF2 variations are also controlled by geomagnetic activity variations, as both parameters, NmF2 and hmF2 are related by the F2-layer formation mechanism. But hmF2 is very sensitive to neutral temperature changes, so strongly damped hmF2 long-term variations observed at Slough after 1972 may be considered as a direct manifestation of the thermosphere cooling. Earlier revealed negative hmF2 trends in western Europe, where magnetic declination D<0 and positive trends at the eastern stations (D>0), can be related to westward thermospheric wind whose role has been enhanced due to a competition between the thermosphere cooling (CO2 increase) and its heating under increasing geomagnetic activity after the end of the 1960s.

“The Death of Liberal Internationalism?: Donald Trump, Walmart, and the Two Koreas”

2018 ◽  
Vol 25 (2) ◽  
pp. 169-197
Author(s):  
Mitchell B. Lerner
Keyword(s):  
United States ◽  
The United States ◽  
Business Practices ◽  
Short Term ◽  
New Approach ◽  
Liberal Internationalism ◽  
The People ◽  
Modern Business ◽  
Short Time

The election of Donald J. Trump unsettled many areas of U.S. foreign policy, but few more than the nation’s relationship with Korea. This article argues that the Trump administration’s vision for the world represents a stark break from the tradition of liberal internationalism and instead seeks to take the United States down a path that reflects the modern business practices of giant American corporations. A suitable label for this vision, as the following pages will show, is “Walmart unilateralism.” This framework abandons the traditional American policies of nation building and alliances based on shared ideological values. Instead, it embraces a more short-term approach rooted in financial bottom lines, flexible alliances and rivalries, and the ruthless exploitation of power hierarchies. This new approach, this article concludes, may dramatically transform the American relationship with Korea. Walmart unilateralism in Korea almost certainly will have some short-time positive ramifications for the United States, but its larger failure to consider the history and values of the people living on the Korean Peninsula may generate serious long-term problems for the future experience of the United States in the region.

Long-term variations in the geomagnetic activity level Part II: Ascending phases of sunspot cycles

1994 ◽  
Vol 12 (10) ◽  
pp. 1065 ◽  
Author(s):  
V. Mussino ◽  
O. Borello Filisetti ◽  
M. Storini ◽  
H. Nevanlinna
Keyword(s):  
Geomagnetic Activity ◽  
Activity Level ◽  
Long Term Variations
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