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

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 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 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 Variations in Solar Wind Parameters, Magnetopause Location, and Geomagnetic Activity Over the Last Five Solar Cycles

2019 ◽  
Vol 124 (6) ◽  
pp. 4049-4063 ◽  
Author(s):  
A. A. Samsonov ◽  
Y. V. Bogdanova ◽  
G. Branduardi‐Raymont ◽  
J. Safrankova ◽  
Z. Nemecek ◽  
...  
Keyword(s):  
Solar Wind ◽  
Geomagnetic Activity ◽  
Solar Cycles ◽  
Solar Wind Parameters ◽  
Long Term Variations

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)

scholarly journals Influence of geomagnetic activity on mesopause temperature over Yakutia

2017 ◽  
Author(s):  
Galina Gavrilyeva ◽  
Petr Ammosov
Keyword(s):  
Geomagnetic Activity ◽  
Rotational Temperature ◽  
Activity Level ◽  
Neutral Atmosphere ◽  
Solar Cycles ◽  
Temperature Changes ◽  
Atmosphere Temperature ◽  
Ap Index ◽  
Mesopause Temperature

Abstract. The long-term temperature changes of the mesopause region at the hydroxyl molecule OH (6-2) nighttime height and its connection with the geomagnetic activity during the 23rd and beginning 24th solar cycles are presented. Measurements were conducted with an infrared digital spectrograph at the Maimaga station (63° N, 129.5° E). The hydroxyl rotational temperature (TOH) is assumed to be equal to the neutral atmosphere temperature at altitude of ~ 87 km. The average temperatures obtained for the period 1999 to 2015 are considered. The season of observations starts at the beginning of August and lasts until the middle of May. The maximum of the seasonally averaged temperatures is delayed by 2 years relative to the maximum of flux of radio emission from the Sun with a wavelength of 10.7 cm, and correlates with a change in geomagnetic activity. Ap-index as a measure of geomagnetic activity is taken. Temperature grouping in accordance with the geomagnetic activity level showed that in years with high activity (Ap > 8), the mesopause temperature from October to February is about ∙10 K higher than in years with low activity (Ap 

scholarly journals Long-term variations of geomagnetic activity and their solar sources

2013 ◽  
Vol 53 (7) ◽  
pp. 813-817 ◽  
Author(s):  
B. Kirov ◽  
V. N. Obridko ◽  
K. Georgieva ◽  
E. V. Nepomnyashtaya ◽  
B. D. Shelting
Keyword(s):  
Geomagnetic Activity ◽  
Long Term Variations
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