scholarly journals Long-term <i>hm</i>F2 trends in the Eurasian longitudinal sector from the ground-based ionosonde observations

2001 ◽  
Vol 19 (7) ◽  
pp. 761-772 ◽  
Author(s):  
D. Marin ◽  
A. V. Mikhailov ◽  
B. A. Morena ◽  
M. Herraiz
Keyword(s):  
Confidence Level ◽  
Solar Cycles ◽  
Natural Origin ◽  
Trend Magnitude ◽  
Longitudinal Sector ◽  
Trends Analysis ◽  
Long Term Trends ◽  
Atmosphere Interaction ◽  
Linear Trends

Abstract. The method earlier used for the foF2 long-term trends analysis is applied to reveal hmF2 long-term trends at 27 ionosonde stations in the European and Asian longitudinal sectors. Observed M(3000)F2 data for the last 3 solar cycles are used to derive hmF2 trends. The majority of the studied stations show significant hmF2 linear trends with a confidence level of at least 95% for the period after 1965, with most of these trends being positive. No systematic variation of the trend magnitude with latitude is revealed, but some longitudinal effect does take place. The proposed geomagnetic storm concept to explain hmF2 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.Key words. Ionosphere (ionosphere-atmosphere interaction)

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

2008 ◽  
Vol 26 (5) ◽  
pp. 1173-1179 ◽  
Author(s):  
L. Alfonsi ◽  
G. De Franceschi ◽  
A. De Santis
Keyword(s):  
Careful Analysis ◽  
Secular Change ◽  
Solar Cycles ◽  
Geomagnetic Reversal ◽  
Latitudinal Dependence ◽  
Hourly Data ◽  
Long Term Trends ◽  
Different Levels

Abstract. The analysis of the foF2 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 foF2 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.

scholarly journals F2-layer parameters long-term trends at the Argentine Islands and Port Stanley stations

2001 ◽  
Vol 19 (3) ◽  
pp. 341-349 ◽  
Author(s):  
A. D. Danilov ◽  
A. V. Mikhailov
Keyword(s):  
Critical Frequency ◽  
Geomagnetic Latitude ◽  
Ionospheric Disturbances ◽  
Ionospheric Storm ◽  
Geomagnetic Index ◽  
Critical Frequency Fof2 ◽  
Long Term Trends ◽  
Atmosphere Interaction ◽  
Ionospheric Sounding

Abstract. The ionospheric sounding data at two southern hemisphere stations, the Argentine Islands and Port Stanley, are analyzed using a method previously developed by the authors. Negative trends of the critical frequency foF2 are found for both stations. The magnitudes of the trends are close to those at the corresponding (close geomagnetic latitude) stations of the northern hemisphere, as considered previously by the authors. The values of the F2 layer height hmF2 absolute trends ΔhmF2 are considered. The effect of ΔhmF2 dependence on hmF2 found by Jarvis et al. (1998) is reproduced. A concept is considered that long-term changes of the geomagnetic activity may be an important (if not the only) cause of all the trends of foF2 and hmF2 derived by several groups of authors. The dependence of both parameters on the geomagnetic index Ap corresponds to a smooth scheme of the ionospheric storm physics and morphology; thus, a principal cause of the foF2 and hmF2 geomagnetic trends is most probably a trend found in several publications in the number and intensity of ionospheric storms.Key words. Ionosphere (ionosphere-atmosphere interaction; ionospheric disturbances)

scholarly journals <i>Letter to the Editor</i>: Spatial and seasonal variations of the <i>fo</i>F2 long-term trends

1999 ◽  
Vol 17 (9) ◽  
pp. 1239-1243 ◽  
Author(s):  
A. D. Danilov ◽  
A. V. Mikhailov
Keyword(s):  
Seasonal Variations ◽  
Critical Frequency ◽  
Geomagnetic Latitude ◽  
Seasonal Effect ◽  
Ionospheric Disturbances ◽  
Trend Magnitude ◽  
Letter To The Editor ◽  
Critical Frequency Fof2 ◽  
Long Term Trends

Abstract. Using a method suggested by the authors earlier, the long-term trends of the F2-layer critical frequency, foF2 are derived for a set of ionospheric stations with a wide latitudinal and longitudinal coverage. All the trends are found to be negative. A pronounced dependence on geomagnetic latitude is found, the trend magnitude increasing with the latter. No globe scale longitudinal effect in trends is detected. For the majority of the stations there is also a pronounced seasonal effect, the trend magnitude being higher in summer than in winter.Key words. Ionosphere (ionospheric disturbances; mid-latitude ionosphere)

scholarly journals How large should a cause of death be in order to be included in mortality trend analysis? Deriving a cut-off point from retrospective trend analyses in 21 European countries

BMJ Open ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. e031702 ◽  
Author(s):  
Marianna Mitratza ◽  
Jan W P F Kardaun ◽  
Anton E Kunst
Keyword(s):  
Infectious Diseases ◽  
Trend Analysis ◽  
Significant Trend ◽  
European Countries ◽  
Independent Effect ◽  
Secondary Outcome ◽  
Trends Analysis ◽  
Icd 10 ◽  
Long Term Trends

ObjectivesThe International Classification of Diseases (ICD-10) distinguishes a large number of causes of death (CODs) that could each be studied individually when monitoring time-trends. We aimed to develop recommendations for using the size of CODs as a criterion for their inclusion in long-term trend analysis.DesignRetrospective trend analysis.Setting21 European countries of the WHO Mortality Database.ParticipantsDeaths from CODs (3-position ICD-10 codes) with ≥5 average annual deaths in a 15-year period between 2000 and 2016.Primary and secondary outcome measuresFitting polynomial regression models, we examined for each COD in each country whether or not changes over time were statistically significant (with α=0.05) and we assessed correlates of this outcome. Applying receiver operating characteristicROC curve diagnostics, we derived COD size thresholds for selecting CODs for trends analysis.ResultsAcross all countries, 64.0% of CODs had significant long-term trends. The odds of having a significant trend increased by 18% for every 10% increase of COD size. The independent effect of country was negligible. As compared to circulatory system diseases, the probability of a significant trend was lower for neoplasms and digestive system diseases, and higher for infectious diseases, mental diseases and signs-and-symptoms. We derived a general threshold of around 30 (range: 28–33) annual deaths for inclusion of a COD in trend analysis. The relevant threshold for neoplasms was around 65 (range: 61–70) and for infectious diseases was 20 (range: 19–20).ConclusionsThe likelihood that long-term trends are detected with statistical significance is strongly related to COD size and varies between ICD-10 chapters, but has no independent relation to country. We recommend a general size criterion of 30 annual deaths to select CODs for long-term mortality-trends analysis in European countries.

scholarly journals Latitudinal variation of <I>fo</I>F2 hysteresis of solar cycles 20, 21 and 22 and its application to the analysis of long-term trends

2008 ◽  
Vol 26 (5) ◽  
pp. 1269-1273 ◽  
Author(s):  
N. Ortiz de Adler ◽  
A. G. Elias
Keyword(s):  
Time Series ◽  
Solar Cycle ◽  
Geomagnetic Latitude ◽  
Activity Levels ◽  
Solar Cycles ◽  
Long Term Trends ◽  
The Difference ◽  
Long Term Trend ◽  
Term Data

Abstract. Noon foF2 monthly median values for equinoctial months of solar cycles 20, 21 and 22, were analyzed for 37 worldwide stations. For each solar cycle and for a given Rz, the difference between foF2 in the falling branch of the cycle and the corresponding value of the rising branch is evaluated. The maximum difference, considered as the hysteresis magnitude, varies systematically with geomagnetic latitude. The pattern is similar for every cycle, with greater hysteresis magnitudes for stronger solar cycles. It is positive between 45° S and 45° N, with minimum values at equatorial latitudes and maximum at around 25°–30° on either side of the equator. For latitudes greater than 50° negative values are observed. At around 25°–30° and at high latitudes the hysteresis magnitude reaches 2 MHz for solar cycle with high activity levels, which represents around 20% of foF2. The effects of foF2 hysteresis on the analysis of long-term data sequences is analyzed. In the case of long-term trend analysis, the hysteresis behavior may induce spurious trends as a consequence of the filtering processes applied to foF2 time series previous to trend values estimation. This problem may be solved by considering time series covering several solar cycles.

scholarly journals The “Pause” in Global Warming: Turning a Routine Fluctuation into a Problem for Science

2016 ◽  
Vol 97 (5) ◽  
pp. 723-733 ◽  
Author(s):  
Stephan Lewandowsky ◽  
James S. Risbey ◽  
Naomi Oreskes
Keyword(s):  
Global Warming ◽  
Scientific Community ◽  
Climate Science ◽  
Warming Trend ◽  
Recent Period ◽  
Term Trend ◽  
Long Term Trends ◽  
Published Research ◽  
Linear Trends

Abstract There has been much recent published research about a putative “pause” or “hiatus” in global warming. We show that there are frequent fluctuations in the rate of warming around a longer-term warming trend, and that there is no evidence that identifies the recent period as unique or particularly unusual. In confirmation, we show that the notion of a pause in warming is considered to be misleading in a blind expert test. Nonetheless, the most recent fluctuation about the longer-term trend has been regarded by many as an explanatory challenge that climate science must resolve. This departs from long-standing practice, insofar as scientists have long recognized that the climate fluctuates, that linear increases in CO2 do not produce linear trends in global warming, and that 15-yr (or shorter) periods are not diagnostic of long-term trends. We suggest that the repetition of the “warming has paused” message by contrarians was adopted by the scientific community in its problem-solving and answer-seeking role and has led to undue focus on, and mislabeling of, a recent fluctuation. We present an alternative framing that could have avoided inadvertently reinforcing a misleading claim.

Long-Term Trends in Forbush Decrease Activity over the Last Six Solar Cycles

2019 ◽  
Vol 83 (5) ◽  
pp. 566-568
Author(s):  
A. A. Melkumyan ◽  
A. V. Belov ◽  
M. A. Abunina ◽  
A. A. Abunin ◽  
E. A. Eroshenko ◽  
...  
Keyword(s):  
Forbush Decrease ◽  
Solar Cycles ◽  
Long Term Trends
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