Review 1: On the relation between ionospheric parameters and sunspot number (original) (raw)
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Journal of Atmospheric and Solar-Terrestrial Physics
The long term solar activity dependencies of ionospheric F 1 and F 2 regions' critical frequencies (f 0 F 1 and f 0 F 2) are analyzed for the last four solar cycles (1976-2015). We show that the ionospheric F 1 and F 2 regions have different solar activity dependencies in terms of the sunspot group (SG) numbers: F 1 region critical frequency (f 0 F 1) peaks at the same time with the small SG numbers, while the f 0 F 2 reaches its maximum at the same time with the large SG numbers, especially during the solar cycle 23. The observed differences in the sensitivity of ionospheric critical frequencies to sunspot group (SG) numbers provide a new insight into the solar activity effects on the ionosphere and space weather. While the F 1 layer is influenced by the slow solar wind, which is largely associated with small SGs, the ionospheric F 2 layer is more sensitive to Coronal Mass Ejections (CMEs) and fast solar winds, which are mainly produced by large SGs and coronal holes. The SG numbers maximize during of peak of the solar cycle and the number of coronal holes peaks during the sunspot declining phase. During solar minimum there are relatively less large SGs, hence reduced CME and flare activity. These results provide a new perspective for assessing how the different regions of the ionosphere respond to space weather effects.
DIAS effective sunspot number as an indicator of the ionospheric activity level over Europe
Acta Geophysica, 2010
A b s t r a c t DIAS (European Digital Upper Atmosphere Server) effective sunspot number -R12eff was recently introduced as a proxy of the ionospheric conditions over Europe for regional ionospheric mapping purposes. Although a pre-processing step for the real-time update of the Simplified Ionospheric Regional Model (SIRM) to real-time conditions, R12eff is available in real time by DIAS system (http://dias.space.noa.gr) for independent operational use. In this paper we discuss the efficiency of R12eff to specify ionospheric conditions over Europe. For this purpose, the diurnal R12eff's reference pattern was determined on monthly basis and for different solar cycle phases. The deviation of the real-time R12eff estimates from the reference values, ΔR12eff was found to be highly correlated with the foF2 storm-time disturbances, especially during large scale effects indicating that DIAS-R12eff can provide a reliable estimator of the ionospheric activity level over a substantial part of Europe and a powerful tool for ionospheric specification applications.
Response of low-latitude ionosphere to medium-term changes of solar and geomagnetic activity
Journal of Geophysical Research, 2012
The paper describes results of the studies devoted to the solar activity impact on the Earth's upper atmosphere and ionosphere, conducted within the frame of COST ES0803 Action. Aim: The aim of the paper is to represent results coming from different research groups in a unified form, aligning their specific topics into the general context of the subject. Methods: The methods used in the paper are based on data-driven analysis. Specific databases are used for spectrum analysis, empirical modeling, electron density profile reconstruction, and forecasting techniques. Results: Results are grouped in three sections: Medium-and long-term ionospheric response to the changes in solar and geomagnetic activity, storm-time ionospheric response to the solar and geomagnetic forcing, and modeling and forecasting techniques. Section 1 contains five subsections with results on 27-day response of low-latitude ionosphere to solar extreme-ultraviolet (EUV) radiation, response to the recurrent geomagnetic storms, long-term trends in the upper atmosphere, latitudinal dependence of total electron content on EUV changes, and statistical analysis of ionospheric behavior during prolonged period of solar activity. Section 2 contains a study of ionospheric variations induced by recurrent CIR-driven storm, a case-study of polar cap absorption due to an intense CME, and a statistical study of geographic distribution of so-called E-layer dominated ionosphere. Section 3 comprises empirical models for describing and forecasting TEC, the F-layer critical frequency foF2, and the height of maximum plasma density. A study evaluates the usefulness of effective sunspot number in specifying the ionosphere state. An original method is presented, which retrieves the basic thermospheric parameters from ionospheric sounding data.
Kirkuk University Journal-Scientific Studies
In this work, the effect of sunspots number (Ri) on the Total electronic content (TEC) were studied for the years (2008, 2014, 2018) which represents the rising phase, the peak and the down phase of the solar cycle 24 over Kirkuk station in Iraq at latitude 35° North and longitude 44° East, by finding the TEC values for the Elayer, the layer ' s impression times are determined for the days of solstice and equinox. In this study the International Reference Ionosphere program (IRI) program have been applied to find the values of TEC which provided by the space research committee (COSPAR) and International Union of Radio Sciences (URSI), IRI have three upper side electron density options. The accuracy of this study was verified by the application conducted of the university of Hacettepe in Ankara, Turkey by matching the reading of TEC from Global Position System (GPS) with output data of TEC from the IRI for Ankara station which located at (39.7 N;32.76 E). And from this investigation turns out that the output data from the option IRI2001 was more consistent with reading of the GPS, than the rest of the other options. From this study by using the statistical program Minitab version 2018. There is a strong correlation between the Total Electron Content (TEC) of Ionospheric layer E and Sunspot number for solar cycle 24.
Cyclic and Long-Term Variation of Sunspot Magnetic Fields
Solar Physics, 2014
Measurements from the Mount Wilson Observatory (MWO) are used to study the long-term variations of sunspot field strengths from 1920 to 1958. Following a modified approach similar to that in , for each observing week we select a single sunspot with the strongest field strength measured that week and then compute monthly averages of these weekly maximum field strengths. The data show the solar cycle variation of the peak field strengths with an amplitude of about 500-700 gauss (G), but no statistically significant long-term trends. Next, we use the sunspot observations from the Royal Greenwich Observatory (RGO) to establish a relationship between the sunspot areas and the sunspot field strengths for Cycles 15-19. This relationship is then used to create a proxy of peak magnetic field strength based on sunspot areas from the RGO and the USAF/NOAA network for the period from 1874 to early 2012. Over this interval, the magnetic field proxy shows a clear solar cycle variation with an amplitude of 500-700 G and a weaker long-term trend. From 1874 to around 1920, the mean value of magnetic field proxy increases by about 300-350 G, and, following a broad maximum in 1920-1960, it decreases by about 300 G. Using the proxy for the magnetic field strength as the reference, we scale the MWO field measurements to the measurements of the magnetic fields in to construct a combined data set of maximum 2 Pevtsov et al.
On a positive correlation between the ionospheric characteristich'F and the solar index activityR
Il Nuovo Cimento C, 1989
The hourly median monthly values of h'F, the lowest virtual height of the ionospheric F layer, are analysed during more than two solar cycles for two middle latitude ionospheric stations: Rome and Poitiers. A moderate but evident correlation between the h'F and the solar index activity R is shown especially comparing their 12 months running mean behaviours. Some coincidences with the behaviour of the hm F2, the height of the maximum electron concentration, suggest that temperature changes, induced by the solar activity, could influence all F region to the bottom of the layer.
Preface to Topical Issue: Recalibration of the Sunspot Number
Solar Physics, 2016
This topical issue contains articles on the effort to recalibrate the sunspot number (SN) that was initiated by the Sunspot Number Workshops. These workshops led to a revision of the Wolf sunspot number (WSN) and a new construction of the group sunspot number (GSN), both published herein. In addition, this topical issue includes three independently proposed alternative SN time series (two Wolf and one group), as well as articles providing historical context, critical assessments, correlative analyses, and observational data, both historical and modern, pertaining to the sunspot-number time series. The ongoing effort to understand and reconcile the differences between the various new sunspot number series is briefly discussed.
Analysis of the Hemispheric Sunspot Number Time Series for the Solar Cycles 18 to 24
Solar Physics, 2019
In this article, we investigate temporal and periodic variations of the hemispheric sunspot number using sunspot data from Kanzelhöhe Solar Observatory (KSO) for the time period of 1944-2017, which covers Solar Cycles 18 to 23 and almost the entire Solar Cycle 24 (2009-2017). The KSO data set was verified against the International Sunspot Number (ISSN) data. Temporal and periodic variations in the KSO data were analyzed using cross-correlation analysis, Morlet wavelet and multitaper (MTM) period analysis methods. We find that: i) sunspot numbers, as derived from both KSO and ISSN time series, are highly correlated with one another; ii) the temporal evolution of the sunspot number differs from one hemisphere to another with the solar cycle peaking at different times in each hemisphere; iii) the northern hemisphere showed two-and seven-month lead in Solar Cycles 18 and 19, respectively, while the southern hemisphere was leading in the rest of the cycles with the varying lead time ranging from 2 to 14 months; iv) apart from the fundamental mode B P. Chowdhury
Recalibration of the Sunspot-Number: Status Report
Solar Physics, 2023
We report progress on the ongoing recalibration of the Wolf sunspot number (S N) and groupsunspot number (G N) following the release of version 2.0 of S N in 2015. This report constitutes both an update of the efforts reported in the 2016 Topical Issue of Solar Physics and a summary of work by the International Space Science Institute (ISSI) International Team formed in 2017 to develop optimal S N and G N reconstruction methods while continuing to expand the historical sunspot-number database. Significant progress has been made on the database side while more work is needed to bring the various proposed S N and (primarily) G N reconstruction methods closer to maturity, after which the new reconstructions (or combinations thereof) can be compared with (a) "benchmark" expectations for any normalization scheme (e.g., a general increase in observer normalization factors going back in time), and (b) independent proxy data series such as F10.7 and the daily range of variations of Earth's undisturbed magnetic field. New versions of the underlying databases for S N and G N will shortly become available for years through 2022 and we anticipate the release of the next versions of these two time series in 2024.
Space Science Reviews, 2014
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.