Distribution of H<i>α</i> flares during solar cycle 23

Joshi, Bhuwan; Pant, P.

doi:10.1051/0004-6361:20041986

Cited by 43 publications

(27 citation statements)

References 23 publications

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“…Further, Gopalswamy et al (2003) separated all CME events into two classes according to the location of their source region and reported that high-latitude CMEs ceased by the first quarter of 2002, which implies that the delayed excess of CMEs during the declining phase of the solar cycle (2003)(2004)(2005) was caused by low-latitude CMEs related to both filaments and flares. While Joshi & Pant (2004) found that Hα flare activity between 1996 and 2003 was low compared to previous solar cycles, Bai (2006), in turn, analyzed distribution of X-ray solar flares and reported that the weaker solar cycles 20 and 23 produced larger number of major flares in their declining phases, as compared to stronger solar cycles 21 and 22. Bai's (2006) report agrees well with our findings on the domination of large groups in the declining phase and may suggest, according to Bai, that the Sun could became more efficient in transporting magnetic fields from the base of convection zone to the surface during the declining phase of the solar cycle.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

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

Kılçık

Yurchyshyn

Abramenko

et al. 2011

ApJ

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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.

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Section: Conclusion and Discussionmentioning

confidence: 99%

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

Kılçık

Yurchyshyn

Abramenko

et al. 2011

ApJ

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“…The catalogue is available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/447/735 Ružičková-Topolová 1974;Garcia 1990;Verma 1993;Ataç & Özgüç 1996;Li et al 1998;Ataç & Özgüç 2001;Temmer et al 2001;Joshi & Joshi 2004;Joshi & Pant 2005), coronal greenline intensity (Waldmeier 1971;Özgüç & Ücer 1987;Tritakis et al 1988;Storini & Sýkora 1995;Sýkora & Rybák 2005), prominences/filaments (e.g. Hansen & Hansen 1975;Duchlev 2001;Gigolashvili et al 2005), and photospheric magnetic fields (e.g.…”

Section: Introductionmentioning

confidence: 99%

Hemispheric sunspot numbers ${R_{n}}$ and ${R_{s}}$ from 1945–2004: catalogue and N-S asymmetry analysis for solar cycles 18–23

Temmer

Rybák

Bendík

et al. 2006

A&A

184

148

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From sunspot drawings provided by the Kanzelhöhe Solar Observatory, Austria, and the Skalnaté Pleso Observatory, Slovak Republic, we extracted a data catalogue of hemispheric Sunspot Numbers covering the time span 1945−2004. The validated catalogue includes daily, monthlymean, and smoothed-monthly relative sunspot numbers for the northern and southern hemispheres separately and is available for scientific use. These data we then investigated with respect to north-south asymmetries for almost 6 entire solar cycles (Nos. 18−23). For all the cycles studied, we found that the asymmetry based on the absolute asymmetry index is enhanced near the cycle maximum, which contradicts to previous results that are based on the normalized asymmetry index. Moreover, the weak magnetic interdependence between the two solar hemispheres is confirmed by their self-contained evolution during a cycle. For the time span 1945−2004, we found that the cycle maxima and also the declining and increasing phases are clearly shifted, whereas the minima seem to be in phase for both hemispheres. The asymmetric behavior reveals no obvious connection to either the sunspot cycle period of ∼11-or the magnetic cycle of ∼22-years. The most striking excess of activity is observed for the northern hemisphere in cycles 19 and 20.

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“…In both the above investigations a southern dominance was prevalent. Joshi and Pant (2005) analysed the data of solar Hα flares during solar cycle 23 to investigate their spatial distribution. Recently Knaack et al (2004Knaack et al ( , 2005 studied the temporal and spatial variations in the photospheric magnetic flux between the northern and southern hemisphere of the Sun from 1975 to 2003 and reported significant periodic variations of magnetic activity between the two hemispheres.…”

Section: Introductionmentioning

confidence: 99%

North-south distribution of solar flares during cycle 23

2006

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In this paper, we investigate the spatial distribution of solar flares in the northern and southern hemisphere of the Sun that occurred during the period 1996 to 2003. This period of investigation includes the ascending phase, the maximum and part of descending phase of solar cycle 23. It is revealed that the flare activity during this cycle is low compared to previous solar cycle, indicating the violation of Gnevyshev-Ohl rule. The distribution of flares with respect to heliographic latitudes shows a significant asymmetry between northern and southern hemisphere which is maximum during the minimum phase of the solar cycle. The present study indicates that the activity dominates the northern hemisphere in general during the rising phase of the cycle (1997)(1998)(1999)(2000). The dominance of northern hemisphere is shifted towards the southern hemisphere after the solar maximum in 2000 and remained there in the successive years. Although the annual variations in the asymmetry time series during cycle 23 are quite different from cycle 22, they are comparable to cycle 21.

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Distribution of Hα flares during solar cycle 23

Cited by 43 publications

References 23 publications

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

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

Hemispheric sunspot numbers ${R_{n}}$ and ${R_{s}}$ from 1945–2004: catalogue and N-S asymmetry analysis for solar cycles 18–23

North-south distribution of solar flares during cycle 23

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