The differences in the relationship between ionospheric critical frequencies and sunspot number for different sunspot cycles

Ostrow, S. M.; PoKempner, M.

doi:10.1029/jz057i004p00473

Cited by 18 publications

(9 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Both the foF2 and R data shown in Figure 2 are 12-point running averages of monthly data. Figure 2 reproduces the evolution in R-foF2 space for two solar cycles, as presented by Ostrow and PoKempner (1952), and extends it to a third solar cycle. The lines show best-fit third-order polynomials for the three cycles.…”

Section: Ionospheric F-region Critical Frequencymentioning

confidence: 95%

“…Several authors noted the hysteresis effect whereby the relationship can be slightly different during the rising phase of the cycle than during the falling phase (e.g. Ostrow and PoKempner, 1952;Trísková and Chum, 1996;Özgüç, Ataç, and Pektaş, 2008). Furthermore it was noted that, in general, the foF2-R relationship varied from solar cycle to solar cycle (Ostrow and PoKempner, 1952;Smith and King, 1981;Ikubanni et al, 2013).…”

Section: Ionospheric F-region Critical Frequencymentioning

confidence: 99%

“…Ostrow and PoKempner, 1952;Trísková and Chum, 1996;Özgüç, Ataç, and Pektaş, 2008). Furthermore it was noted that, in general, the foF2-R relationship varied from solar cycle to solar cycle (Ostrow and PoKempner, 1952;Smith and King, 1981;Ikubanni et al, 2013). An example showing some hysteresis and cycle-to-cycle change in data from Washington, DC, USA is presented in Figure 2.…”

Section: Ionospheric F-region Critical Frequencymentioning

confidence: 99%

“…Thus this would imply a 41.5 % drift in the calibration of R in just three solar cycles. Clette et al (2015) used the R-foF2 plots of the Washington data for Cycles 17 and 18, as published by Ostrow and PoKempner (1952), to attribute all of the change between them to the Waldmeier discontinuity in R and, indeed, this will have made some contribution.…”

Section: Ionospheric F-region Critical Frequencymentioning

confidence: 99%

See 3 more Smart Citations

Tests of Sunspot Number Sequences: 1. Using Ionosonde Data

et al. 2016

View full text Add to dashboard Cite

More than 70 years ago, it was recognised that ionospheric F2-layer critical frequencies [foF2] had a strong relationship to sunspot number. Using historic datasets from the Slough and Washington ionosondes, we evaluate the best statistical fits of foF2 to sunspot numbers (at each Universal Time [UT] separately) in order to search for drifts and abrupt changes in the fit residuals over Solar Cycles 17 -21. This test is carried out for the original composite of the Wolf/Zürich/International sunspot number [R], the new "backbone" group sunspot number [R BB ], and the proposed "corrected sunspot number" [R C ]. Polynomial fits are made both with and without allowance for the white-light facular area, which has been reported as being associated with cycle-to-cycle changes in the sunspot-number-foF2 relationship. Over the interval studied here, R, R BB , and R C largely differ in their allowance for the "Waldmeier discontinuity" around 1945 (the correction factor for which for R, R BB , and R C is, respectively, zero, effectively over 20 %, and explicitly 11.6 %). It is shown that for Solar Cycles 18 -21, all three sunspot data sequences perform well, but that the fit residuals are lowest and most uniform for R BB . We here use foF2 for those UTs for which R, R BB , and R C all give correlations exceeding 0.99 for intervals both before and after the Waldmeier discontinuity. The error introduced by the Waldmeier discontinuity causes R to underestimate the fitted values based on the foF2 data for 1932 -1945, but R BB overestimates them by almost the same factor, implying that the correction for the Waldmeier discontinuity inherent in R BB is too large by a factor of two. Fit residuals are smallest and most uniform for R C , and the ionospheric data support the optimum discontinuity multiplicative correction factor derived from the independent Royal Greenwich Observatory (RGO) sunspot group data for the same interval.Sunspot Number Recalibration

show abstract

Section: Ionospheric F-region Critical Frequencymentioning

confidence: 95%

Section: Ionospheric F-region Critical Frequencymentioning

confidence: 99%

Section: Ionospheric F-region Critical Frequencymentioning

confidence: 99%

Section: Ionospheric F-region Critical Frequencymentioning

confidence: 99%

See 2 more Smart Citations

Tests of Sunspot Number Sequences: 1. Using Ionosonde Data

et al. 2016

View full text Add to dashboard Cite

show abstract

“…As stated in [11], there is a clear relation between the best successful transmitting frequencies and the sunspot numbers (SSN) which is a proxy of the solar activity reflecting the different solar variations and cycles. Other projects have been conducted to study the relations between the ionospheric channel and the Sun phenomena, as the presented by Angling et al in 1999 [12].…”

Section: Introductionmentioning

confidence: 99%

Interannual Variation of a 12,760 km Transequatorial Ionospheric Channel Availability and Its Dependence on Ionization

Orga

Altadill

Hervás

et al. 2016

Proceedings of the 1st International Electronic Conference on Atmospheric Sciences

View full text Add to dashboard Cite

Abstract:The ionosphere provides a channel able for long-haul and Non-Line-Of-Sight (NLOS) communications. Nonetheless, the amount of ionization depends on the Sun activity, whose diurnal and seasonal cycles transform the channel constantly. La Salle and the Observatori de l'Ebre have been sounding a 12,760 km ionospheric channel from Antarctica (62.7°S, 299.6°E) to Spain (41.0°N, 1.0°E) in order to find this evidence and to analyze the characteristics of this particular channel. The final goal of the project is to establish a stable communications link to be used as backup or for low rate data transmission. The aim of this paper is to prove the relation between the channel availability and the Sun phenomena affecting the ionization in four consecutive sounding campaigns.

show abstract

Revisiting the Sunspot Number

Clette¹,

Svalgaard²,

Vaquero³

et al. 2015

Space Sciences Series of ISSI

View full text Add to dashboard Cite

Abstract:Our knowledge of the long-term evolution of solar activity and of its primary modulation, the 11-year cycle, largely depends on a single direct observational record: the visual sunspot counts that retrace the last 4 centuries, since the invention of the astronomical telescope. Currently, this activity index is available in two main forms: the International Sunspot Number initiated by R. Wolf in 1849 and the Group Number constructed more recently by Hoyt and Schatten (1998a,b). Unfortunately, those two series do not match by various aspects, inducing confusions and contradictions when used in crucial contemporary studies of the solar dynamo or of the solar forcing on the Earth climate. Recently, new efforts have been undertaken to diagnose and correct flaws and biases affecting both sunspot series, in the framework of a series of dedicated Sunspot Number Workshops. Here, we present a global overview of our current understanding of the sunspot number calibration.After retracing the construction of those two composite series, we present the new concepts and methods used to self-consistently re-calibrate the original sunspot series. While the early part of the sunspot record before 1800 is still characterized by large uncertainties due to poorly observed periods, the more recent sunspot numbers are mainly affected by three main inhomogeneities: in 1880-1915 for the Group Number and in 1947 and 1980-2014 for the Sunspot Number.After establishing those new corrections, we then consider the implications on our knowledge of solar activity over the last 400 years. The newly corrected series clearly indicates a progressive decline of solar activity before the onset of the Maunder Minimum, while the slowly rising trend of the activity after the Maunder Minimum is strongly reduced, suggesting that by the mid 18 th century, solar activity had already returned to levels equivalent to those observed in recent solar cycles in the 20 th century. We finally conclude with future prospects opened by this epochal revision of the Sunspot Number, the first one since Wolf himself, and its reconciliation with the Group Number, a long-awaited modernization that will feed solar cycle research into the 21 st century.

show abstract

The differences in the relationship between ionospheric critical frequencies and sunspot number for different sunspot cycles

Cited by 18 publications

References 0 publications

Tests of Sunspot Number Sequences: 1. Using Ionosonde Data

Tests of Sunspot Number Sequences: 1. Using Ionosonde Data

Interannual Variation of a 12,760 km Transequatorial Ionospheric Channel Availability and Its Dependence on Ionization

Revisiting the Sunspot Number

Contact Info

Product

Resources

About