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Verma, V. K.

doi:10.1023/a:1005232619582

Cited by 25 publications

(17 citation statements)

References 11 publications

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“…Mavromichalaki et al (1994) and Tritakis et al (1997) have also reported a significant E−W asymmetry in the optical emissions of the solar corona. Verma (2000) studied the E−W distribution of SAP events from 1957−1998 and did not find any significant asymmetry.…”

Section: Introductionmentioning

confidence: 96%

“…The north-south (N−S) and east-west (E−W) distributions, including asymmetries, of several solar activity indices such as flares, filaments, magnetic flux, relative sunspot numbers and sunspot areas have been investigated by various authors (Howard 1974;Hensen & Hensen 1975;Roy 1977;Swinson et al 1986;Vizoso & Ballester 1987;Garcia 1990;Heras et al 1990;Verma 1993;Joshi 1995;Ataç & Özgüç 1996;Li et al 1998;Verma 2000;Temmer et al 2001, Temmer et al 2002Joshi & Joshi 2004;Knaack et al 2004). These studies indicate that there exists an asymmetry in the N−S distribution of solar activity.…”

Section: Introductionmentioning

confidence: 99%

“…In both the above investigations a southern dominance was prevalent. Verma (2000) examined the latitudinal distribution of solar active prominences (SAP) for the period 1957−1998 and found that the SAP events are most prolific in the 11−20…”

Section: Introductionmentioning

confidence: 99%

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Distribution of Hα flares during solar cycle 23

Joshi

Pant

2005

A&A

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Abstract. The paper presents the results of an analysis of the north-south (N−S) and east-west (E−W) distribution of Hα solar flares from 1996 to 2003. This period of investigation corresponds to the ascending phase, the maximum and part of descending phase of solar cycle 23. It has been found that the flare activity during this cycle is low compared to previous solar cycles. The pattern of N−S distribution of flare occurrence shows that after solar activity minimum in 1996 the northern hemisphere was more active in producing flares than the southern one. The dominance of northern hemisphere is shifted towards the southern hemisphere after the solar maxima in 2000 and remained there in successive years. In both hemispheres (N and S), the flares are most prolific between 11• to 20• latitudes. Although the asymmetry in the E−W distribution of flare events is low, a consistent western dominance has been found. In more intense flares (Importance ≥1) there are some longitudinal bands where flare occurrence is higher than in adjacent bands.

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Distribution of Hα flares during solar cycle 23

Joshi

Pant

2005

A&A

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“…For example, for solar cycle 21, there is a controversy about the dominant hemisphere of solar activity as some solar active phenomena show a north dominance, while some show a south dominance. Moreover, according to Bai (1990) the N-S asymmetry is zero (Verma 2000;. In the present study, the dominant hemisphere of solar activity in each of solar cycles 12 to 22 is investigated by calculating the actual probability of the hemispherical distribution of several solar activity phenomena based on the long-term observational records.…”

Section: Introductionmentioning

confidence: 99%

Regularity of the north-south asymmetry of solar activity

Wang

Xiong

et al. 2002

A&A

114

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Abstract. In the present work, the dominant hemisphere of solar activity in each of solar cycles 12 to 22 has been clarified by calculating the actual probability of the hemispheric distribution of several solar activity phenomena using long-term observational records. An attempt is made to demonstrate that a long characteristic time scale, about 12-cycle length, is inferred to occur in solar activity.

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“…-The daily north and south hemispheric sunspot numbers , compiled by Temmer et al (2006), which can be downloaded from http://cdsweb.u-strasbg.fr/ cgi-bin/qcat?J/A+A/447/735, with 21 915 data points. -The yearly north and south number of active prominences , obtained from Verma (2000), with 42 data points. -The daily north and south X-ray flares , detected by the GOES satellites, which can be downloaded from http://www.ngdc.noaa.gov/stp/SOLAR/ ftpsolarflares.html, with 11 323 data points.…”

Section: Datamentioning

confidence: 99%

The statistical significance of the North-South asymmetry of solar activity revisited

Carbonell¹,

Terradas

Oliver

et al. 2007

A&A

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Aims. Many studies of the North-South asymmetry of solar activity and its features have been performed. However, most of these studies do not consider whether or not the asymmetry of the time series under consideration is statistically significant. If the asymmetry is statistically insignificant, any study about its behavior is meaningless. Here, we discuss the difficulties found when trying to assess the statistical significance of the North-South asymmetry (hereafter SSNSA) of the most usually considered time series of solar activity. Methods. We distinguish between solar activity time series composed of integer or non-integer and dimensionless data, or composed of non-integer and dimensional data. For each of these cases, we discuss the most suitable statistical tests which can be applied and highlight the difficulties in obtaining valid information about the statistical significance of solar activity time series. Results. Our results suggest that, apart from the need to apply suitable statistical tests, other effects such as data binning, the considered units and the need, in some tests, to consider groups of data, substantially affect the determination of the statistical significance of the asymmetry. Conclusions. The assessment of the statistical significance of the N-S asymmetry of solar activity is difficult and an absolute answer cannot be given, since many different effects influence the results given by the statistical tests. The quantitative results about the statistical significance of the N-S asymmetry of solar activity provided by different authors, as well as studies of its behaviour, must be considered with care because they depend on the chosen values of different parameters or on the considered units.

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Cited by 25 publications

References 11 publications

Distribution of Hα flares during solar cycle 23

Distribution of Hα flares during solar cycle 23

Regularity of the north-south asymmetry of solar activity

The statistical significance of the North-South asymmetry of solar activity revisited

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