Asymmetric behavior of different solar activity features over solar cycles 20–23

This paper presents the study of normalized north–south asymmetry, cumulative normalized north–south asymmetry and cumulative difference indices of sunspot areas, solar active prominences (at total, low (?40°) and high (?50°) latitudes) and Hα solar flares from 1964 to 2008 spanning the solar cycles 20–23. Three different statistical methods are used to obtain the asymmetric behavior of different solar activity features. Hemispherical distribution of activity features shows the dominance of activities in northern hemisphere for solar cycle 20 and in southern hemisphere for solar cycles 21–23 excluding solar active prominences at high latitudes. Cumulative difference index of solar activity features in each solar cycle is observed at the maximum of the respective solar cycle suggesting a cyclic behavior of approximately one solar cycle length. Asymmetric behavior of all activity features except solar active prominences at high latitudes hints at the long term periodic trend of eight solar cycles. North–south asymmetries of SAP (H) express the specific behavior of solar activity at high solar latitudes and its behavior in long-time scale is distinctly opposite to those of other activity features. Our results show that in most cases the asymmetry is statistically highly significant meaning thereby that the asymmetries are real features in the N–S distribution of solar activity features.     

Rainfall variability and indices of extreme rainfall-analysis and perception study for two stations over Central Himalaya,India

The analysis of rainfall pattern and indices of extreme rainfall events is performed for two meteorological stations located in the Central Himalayan Region which is highly vulnerable to rain-induced hazards. The records of these rain-induced disasters suggest that such events are generally observed in later part of monsoon season, when soil is saturated after monsoon rains. An attempt is made here to test trends of 19 different extreme rainfall indices that have been widely used in the literature, using daily rainfall data for two urban centres (Nainital and Almora) over the period 1992–2005. We have used statistical tools such as Sen’s method and Mann–Kendall test for detection of trend in annual rainfall, monsoon rainfall, number of rainy days and 1-day extreme rainfall. Principal component analysis gives the correlation between different extreme rainfall indices. Time series of principal components are representing the trends of extreme indices, their variation and interrelation between different indices. The perception study conducted in the same sites indicates that extreme rainfall events and change in rainfall amount and timing are well perceived by the local people.     

On the infrared opacity of sunspots

In the umbral atmosphere the depth dependence of the opacity due to the vibration rotation bands of various abundant molecules in the wavelength region 1 m to 10 m has been calculated. In the higher layers of the umbral atmosphere, the molecular opacity seems to dominate the opacity due to the negative hydrogen ion.     

The nature of velocity fields in quiescent prominences

It is shown that for certain definite conditions of symmetry imposed on the permitting magnetic field geometry for an isothermal case in Kippenhahn and Schlüter's (1957) model of a quiescent prominence, any irrotational velocity field would quickly get converted to rotational.     

The rotational motion in quiescent prominences

On the basis of Kippenhahn and Schlüter's magnetohydrostatic model of a quiescent prominence we have attempted to study the effect of a rotational velocity field in it. We find that a physically plausible solution is not possible in the vertical plane. A possibility, however, is shown in the horizontal plane, with certain assumptions to get equal velocity contours.     

On the mechanical response of saturated cemented materials—part II: Experimental investigation and numerical simulations

Results of experimental investigation and numerical simulations of the mechanical response of the saturated cemented materials are reported. Saturated as well as dry samples cored from commercially available fire bricks are used. The samples were tested in a triaxial rock cell at different initial confining pressures. The tests have been simulated using the constitutive framework proposed in Part I of this paper. The results both experimental and numerical, provide the evidence in support of the proposed stress decomposition, thereby questioning the validity of Terzaghi's principle for the considered class of materials.     

Energetic flare zones on the Sun

In this investigation, we have studied the latitudinal, longitudinal (northern and southern hemispheric) distributions based on 1737 major flares observed during solar cycles 19 and 20 (see subsequent paragraphs) and have arrrived at some interesting results which go to show that as far major flares are concerned latitudewise 11–20° belts, and longitudewise 5–8 places are most prolific in producing major flares in each hemisphere. During the above cycles at least 5 flare zones are present in each hemisphere. In fact these zones seem to produce more than 50% of the total number of energetic flares investigated by us and occupy only <4% area of the Sun.     

Stellar structures with constant local adiabatic index under extreme relativistic conditions

Stellar structures with a constant local adiabatic index Γ have been discussed under the extreme relativistic condition (dP/dρ=1, at the center of the configuration). The equation of state,Pαρ^Γ, where ρ _r is the rest-mass density leads to the relations, (i)ρ=AP ^1/Γ?P/(Γ?1) between energy density and pressure, and (ii)e=NP between internal energy density and pressure, where the constantN may be called local polytropic index. The local adiabatic index, Γ, is found to be related to the adiabatic index, γ, through a simple relation, Γ=γ(1+P/ρ). The maximum value of surface redshift comes out to be 0.614 when σ=(P/ρ)₀=0.6. The structure are bound for σ≤0.83 and the maximum value of the binding coefficient is 0.181 at σ=0.4. For bound structures the central redshift z₀≤8.24. The maximum mass of neutron star based upon such a model comes out to be 2.39M _⊙ (for σ=0.4) and the maximum size comes out to be 13.7 km (for σ=0.2).     

Study of Distribution and Asymmetry of Solar Active Prominences during Solar Cycle 23

In this article we present the results of a study of the spatial distribution and asymmetry of solar active prominences (SAP) for the period 1996 through 2007 (solar cycle 23). For more meaningful statistical analysis we analyzed the distribution and asymmetry of SAP in two subdivisions viz. Group1 (ADF, APR, DSF, CRN, CAP) and Group2 (AFS, ASR, BSD, BSL, DSD, SPY, LPS). The North – South (N – S) latitudinal distribution shows that the SAP events are most prolific in the 21° to 30° slice in the Northern and Southern Hemispheres; the East – West (E – W) longitudinal distribution study shows that the SAP events are most prolific (best observable) in the 81° to 90° slice in the Eastern and Western Hemispheres. It was found that the SAP activity during this cycle is low compared to previous solar cycles. The present study indicates that during the rising phase of the cycle the number of SAP events are roughly equal in the Northern and Southern Hemispheres. However, activity in the Southern Hemisphere has been dominant since 1999. Our statistical study shows that the N – S asymmetry is more significant then the E – W asymmetry.