Generation and Life Cycle of Solar Spicules

Physical mechanism for the creation of solar spicules with three stages of their life cycle is investigated. It is assumed that at stage-I, the density hump is formed locally in the chromosphere in the presence of temperature gradients of electrons and ions along the z-axis. The density structure is accelerated in the vertical direction due to the thermal force ${\bf F}_{th} \propto \nabla n(x,y,t) \times (\nabla T_e + \nabla T_i)$. The magnitude of the upward acceleration depends on the steepness of the temperature gradients $\nabla T_j$ where $j=(e,i)$. The exact time-dependent 2D analytical solution of two fluid plasma equations is presented assuming that the exponentially decaying density structure is created in the xy plane and evolves in time as a step function $H(t)$ . The upward acceleration $a$ produced in this density structure is greater than the downward solar acceleration $g_\odot$. The vertical plasma velocity turns out to be the ramp function of time $R(t)$ whereas the source term for the density follows the delta function $\delta(t)$. In the transition region (TR), the temperature gradients are steeper and itupward acceleration increases in magnitude $g_\odot << a$ and density hump spends lesser time here. This is stage-II of its life cycle. In stage-III, the density structure enters the corona where the gradients of temperatures vanish and structure moves upward with almost constant speed which is slowly reduced to zero due to negative solar gravitational force because ${\bf a} \simeq - {\bf g}_\odot$. The estimates of height $H$ and life time $\tau_l$ of the spicule are in agreement with the observed values.Comment: 22 pages, 3 fig

Entanglement entropy of subtracted geometry black holes

We compute the entanglement entropy of minimally coupled scalar fields on subtracted geometry black hole backgrounds, focusing on the logarithmic corrections. We notice that matching between the entanglement entropy of original black holes and their subtracted counterparts is only at the order of the area term. The logarithmic correction term is not only different but also, in general, changes sign in the subtracted case. We apply Harrison transformations to the original black holes and find out the choice of the Harrison parameters for which the logarithmic corrections vanish.Comment: 15 page

Subtracted Geometry

In this thesis we study a special class of black hole geometries called subtracted geometries. Subtracted geometry black holes are obtained when one omits certain terms from the warp factor of the metric of general charged rotating black holes. The omission of these terms allows one to write the wave equation of the black hole in a completely separable way and one can explicitly see that the wave equation of a massless scalar field in this slightly altered background of a general multi-charged rotating black hole acquires an $SL(2,\mathbb{R}) \times \times SL(2,\mathbb{R}) \times SO(3)$ symmetry. The ”subtracted limit” is considered an appropriate limit for studying the internal structure of the non-subtracted black holes because new \u27subtracted\u27 black holes have the same horizon area and periodicity of the angular and time coordinates in the near horizon regions as the original black hole geometry it was constructed from. The new geometry is asymptotically conical and is physically similar to that of a black hole in an asymptotically confining box. We use the different nice properties of these geometries to understand various classically and quantum mechanically important features of general charged rotating black holes

Examining success factors: Entrepreneurial approaches in mountainous regions of Pakistan

Amongst the challenges faced by developing countries, one of the major challenges is the development of successful enterprises that not only helps its people but also contributes significantly in economic development of the country. This paper gauges the factors that contribute to the success of entrepreneurial activities. The focus is on the mountainous region, which faces many challenges. Ultimately, a framework of success has been proposed for consideration of policy makers. To measure the contribution of these factors a survey instrument has been used on a sample of 100 entrepreneurs in different sectors (mountainous region of Pakistan). The findings show the local perspective that entrepreneurs feel that these factors contribute significantly towards success. The eight factors used are advancement drive, achievement oriented, commitment, decision-making ability, managing risk, tenacity, networking, and optimism. Pakistan having a geographical importance in the region has the potential of growth and development, the unexplored natural resource, a trade route with China and potential trade route with Central Asian countries, diversified culture and tourism gives it an edge over other countries. The lack of effective policies and governance is the biggest problem Pakistan faces

Do effective risk management affect organizational performance

Due to globalization and intense competition, risks are increasing and risk management is becoming an integral part for the success of almost every organization, especially for the software development sector because of their high-risk projects, as the risks are associated with every development step of projects undertaken. The main purpose of this study is to report on the current practices of risk management in Pakistani software development sector. Based on the data, collected from 25 organizations working in software development sector, the results indicates that risk management practices are not widely used by the organization(s), moreover most of the organizations do not have documented risk management policy properly. Therefore, these organizations cannot deal with the risks systematically and sometimes face negative consequences for the non-systematic approaches. However, few companies have implemented certain risk management techniques and are enjoying high performance