J. P. Rozelot

Time Distributions of Large and Small Sunspot Groups Over Four Solar Cycles

Here we analyze solar activity by focusing on time variations of the number of sunspot groups (SGs) as a function of their modified Zurich class. We analyzed data for solar cycles 20-23 by using Rome (cycles 20 and 21) and Learmonth Solar Observatory (cycles 22 and 23) SG numbers. All SGs recorded during these time intervals were separated into two groups. The first group includes small SGs (A, B, C, H, and J classes by Zurich classification), and the second group consists of large SGs (D, E, F, and G classes). We then calculated small and large SG numbers from their daily mean numbers as observed on the solar disk during a given month. We report that the time variations of small and large SG numbers are asymmetric except for solar cycle 22. In general, large SG numbers appear to reach their maximum in the middle of the solar cycle (phases 0.45-0.5), while the international sunspot numbers and the small SG numbers generally peak much earlier (solar cycle phases 0.29-0.35). Moreover, the 10.7 cm solar radio flux, the facular area, and the maximum coronal mass ejection speed show better agreement with the large SG numbers than they do with the small SG numbers. Our results suggest that the large SG numbers are more likely to shed light on solar activity and its geophysical implications. Our findings may also influence our understanding of long-term variations of the total solar irradiance, which is thought to be an important factor in the Sun-Earth climate relationship.

Nonlinear Prediction of Solar Cycle 24

Sunspot activity is highly variable and challenging to forecast. Yet forecasts are important, since peak activity has profound effects on major geophysical phenomena including space weather (satellite drag, telecommunications outages) and has even been correlated speculatively with changes in global weather patterns. This paper investigates trends in sunspot activity, using new techniques for decadal-scale prediction of the present solar cycle (cycle 24). First, Hurst exponent H analysis is used to investigate the autocorrelation structure of the putative dynamics; then the Sugihara-May algorithm is used to predict the ascension time and the maximum intensity of the current sunspot cycle. Here we report H = 0.86 for the complete sunspot number data set (1700-2007) and H = 0.88 for the reliable sunspot data set (1848-2007). Using the Sugihara-May algorithm analysis, we forecast that cycle 24 will reach its maximum in 2012 December at approximately 87 sunspot units.

MAXIMUM CORONAL MASS EJECTION SPEED AS AN INDICATOR OF SOLAR AND GEOMAGNETIC ACTIVITIES

We investigate the relationship between the monthly averaged maximal speeds of coronal mass ejections (CMEs), international sunspot number (ISSN), and the geomagnetic Dst and Ap indices covering the 1996-2008 time interval (solar cycle 23). Our new findings are as follows. (1) There is a noteworthy relationship between monthly averaged maximum CME speeds and sunspot numbers, Ap and Dst indices. Various peculiarities in the monthly Dst index are correlated better with the fine structures in the CME speed profile than that in the ISSN data. (2) Unlike the sunspot numbers, the CME speed index does not exhibit a double peak maximum. Instead, the CME speed profile peaks during the declining phase of solar cycle 23. Similar to the Ap index, both CME speed and the Dst indices lag behind the sunspot numbers by several months. (3) The CME number shows a double peak similar to that seen in the sunspot numbers. The CME occurrence rate remained very high even near the minimum of the solar cycle 23, when both the sunspot number and the CME average maximum speed were reaching their minimum values. (4) A well-defined peak of the Ap index between 2002 May and 2004 August was co-temporal with the excess of the mid-latitude coronal holes during solar cycle 23. The above findings suggest that the CME speed index may be a useful indicator of both solar and geomagnetic activities. It may have advantages over the sunspot numbers, because it better reflects the intensity of Earth-directed solar eruptions.

Sunspot Count Periodicities in Different Zurich Sunspot Group Classes Since 1986

We used two methods to investigate the periodic behavior of sunspot counts in four categories for the time period January 1986u2009–u2009October 2013. These categories include the counts from simple (A and B), medium (C), large (D, E, and F), and final (final-stage;xa0H) sunspot groups. We used i) the multitaper method with red noise approximation, and ii) the Morlet wavelet transform for periodicity analysis. Our main findings are that 1) the solar rotation periodicity of about 25 to 37 days, which is of obvious significance, is found in all groups with at least a 95xa0% significance level; 2) the periodic behavior of a cycle is strongly related to its amplitude and group distribution during the cycle; 3) the appearance of periods follows the amplitude of the investigated solar cycles; and that 4) meaningful periods do not appear during the minimum phases of the investigated cycles.We would like to underline that the cyclic behavior of all categories is not exactly the same; there are some differences between these groups. This result can provide a clue for the better understanding of solar cycles.

Solar Cycle 24: Curious Changes in the Relative Numbers of Sunspot Group Types

Here, we analyze different sunspot group (SG) behaviors from the points of view of both the sunspot counts (SSCs) and the number of SGs, in four categories, for the time period of 1982 January-2014 May. These categories include data from simple (A and B), medium (C), large (D, E, and F), and decaying (H) SGs. We investigate temporal variations of all data sets used in this study and find the following results. (1) There is a very significant decrease in the large groups SSCs and the number of SGs in solar cycle 24 (cycle 24) compared to cycles 21-23. (2) There is no strong variation in the decaying groups data sets for the entire investigated time interval. (3) Medium group data show a gradual decrease for the last three cycles. (4) A significant decrease occurred in the small groups during solar cycle 23, while no strong changes show in the current cycle (cycle 24) compared to the previous ones. We confirm that the temporal behavior of all categories is quite different from cycle to cycle and it is especially flagrant in solar cycle 24. Thus, we argue that the reduced absolute number of the large SGs is largely, if not solely, responsible for the weak cycle 24. These results might be important for long-term space weather predictions to understand the rate of formation of different groups of sunspots during a solar cycle and the possible consequences for the long-term geomagnetic activity.

Active Latitude Oscillations Observed on the Sun

We investigate periodicities in the mean heliographic latitudes of sunspot groups, called active latitudes, for the past six complete solar cycles (1945u2009–u20092008). For this purpose, the multitaper method and Morlet wavelet analysis were used. We found that solar rotation periodicities (26u2009–u200938 days) are present in active latitudes of both hemispheres for all the investigated cycles (18 to 23). Both in the northern and southern hemispheres, active latitudes drifted toward the equator from the beginning to the end of each cycle and followed an oscillating path. These motions are well described by a second-order polynomial. There are no meaningful periods of between 55 and about 300 days in either hemisphere for all cycles. A periodicity of 300 to 370 days appears in both hemispheres for Cycle 23, in the northern hemisphere for Cycle 20, and in the southern hemisphere for Cyclexa018.

New findings increasing solar trend that can change Earth climate

Early attempts to find how solar activity can influence the Earths climate involved comparison of many physical processes, such as dynamo mechanism, magnetic reconnection and eruptive activity, irradiance, open flux and particles variations, global atmospheric chemistry and dynamics.. . . However, such direct links seem to be weak even if the solar effects has been found to be stronger during extended maxima or minima of solar activity. Thus, temporal scales ranging from days to thousand of years must be investigated. A description of the most recent results on solar variability and its possible influence on the Earths climate and atmosphere will be here addressed, with a particular emphasize on modulations of about 120 years (and harmonics). The extrapolation indicates a significant negative decrease of the solar signal, and consequently a decrease of the global Earths temperature in the forthcoming years. Such a modulation is also testifying by other means, such as spectral observations of temperature sensitive lines indicating a decline of solar activity around 2015 (up to a new prolonged minimum). Prediction of global effects from the Suns influence over the climate is thus planted in a new way.

Unveiling Stellar Cores and Multipole Moments via their Flattening

Rotation, and more precisely differential rotation, has a major impact on the internal dynamics of stars (and the Sun) and induces many instabilities driving the transport of angular momentum. In this chapter we shall consider these effects on the shape of shelllular layers, and to first order, those concerning the apparent oblateness. Thanks to the advent of interferometry techniques, stellar shapes can now be measured with a great accuracy. We will review here some main results obtained so far on different stars and we will give their main physical parameters taking into account differential rotation. We will discuss how the core density can be reached. Gravitational moments are presented for these observed flattened stars, and for the Sun, for which some conflicting results are presented.

Possible traces of solar activity effect on the surface air temperature of mid-latitudes

In this study we investigate the effects of solar activity on the surface air temperature of mid-latitudes. This enables us to understand existence of solar activity effects on the tem- perature. We used surface air temperature and pressure data as climate parameters, and solar flare index data as solar activity indicator, for the 25 - 50 degree longitude and 30 - 70 degree latitude zone, including Turkey and European part of Russia. We considered the parameters temperature, pressure and flare index data for the period ranging from January 1975 to the end of December 2007, which covers almost three solar cycles, namely 21 st ,2 2 nd ,a nd 23 rd . We found some significant correlations between solar activity and surface air temperature for cycles 22 and 23 for some zones. We applied multitaper method to obtain the cyclic behavior of surface air temperature data sets. The most pronounced power peaks were found by this transform around 1.2 and 2.5 years which were reported earlier for some solar activity indicators. We concluded that signature of solar activity effect exists on surface air temperature of mid-latitudes where we studied.

On the Diffculty to Foresee Solar Cycles: A Non-Deterministic Approach

The so-called “sunspot number” is one of the longest running time series available in astronomy. It forms an observed data set providing an index of solar activity allowing to trace its variation on a time scale of about 400 years since around ad 1600. This long period of time covers a wide range of activity, from vanishing sunspots during great minima to very high peaks during these last 50 years. However, forecast of solar activity is still a matter of debate. This paper gives a review of the recent achievements and findings in long-term activity. We emphasize determinism and chaos in sunspot cyclicity, giving the new “standard mapping” of the Sun. We indicate that prolonged periods of suppressed activity can be interpreted in terms of phase changes. We describe the “phase catastrophe” during the Dalton minimum, likely leading to a lost numbered cycle. Based on this non-linear physics, the behavior of solar activity is tackled in a new way, and a review of the different methods (rescaled range analysis, Grassberger and Procaccia algorithms, Shugira and May methods) is presented. A consistent scenario is given for the next grand minimum, scheduled between 2010 and 2050. Such predictions are of high importance, not only to put constraints on solar dynamo theories, but also in a new field of research, the Space Weather Physics.