Modeling coronal magnetic field using spherical geometry: cases with several active regions

The magnetic fields in the solar atmosphere structure the plasma, store free magnetic energy and produce a wide variety of active solar phenomena, like flare and coronal mass ejections(CMEs). The distribution and strength of magnetic fields are routinely measured in the solar surface(photosphere). Therefore, there is considerable interest in accurately modeling the 3D structure of the coronal magnetic field using photospheric vector magnetograms. Knowledge of the 3D structure of magnetic field lines also help us to interpret other coronal observations, e.g., EUV images of the radiating coronal plasma. Nonlinear force-free field (NLFFF) models are thought to be viable tools for those task. Usually those models use Cartesian geometry. However, the spherical nature of the solar surface cannot be neglected when the field of view is large. In this work, we model the coronal magnetic field above multiple active regions using NLFFF extrapolation code using vector magnetograph data from the Synoptic Optical Long-term Investigations of the Sun survey (SOLIS)/ Vector Spectromagnetograph (VSM) as a boundary conditions. We compare projections of the resulting magnetic field lines solutions with their respective coronal EUV-images from the Atmospheric Imaging Assembly (SDO/AIA) observed on October 11, 2011 and November 13, 2012. This study has found that the NLFFF model in spherical geometry reconstructs the magnetic configurations for several active regions which agrees with observations. During October 11, 2011 observation, there are substantial number of trans-equatorial loops carrying electric current.Comment: 3 Figures, Submitted to Astrophysics and Space Science Journa

Review on Cell Reprogramming: Methods and Applications

Cellular differentiation and development appears as a unidirectional process to specific cell fates irreversibly. Once differentiated, mature cells seems permanently locked into the differentiated state and unable to return to pluripotent stem cell state. However, using cell reprogramming methods it is possible to do reversal cell fate from a mature differentiated state to an undifferentiated state or directly to that of progenitors or mature cells of a different cell type. This is due to the resetting of the somatic cell specific epigenotype to the pluripotential cell specific epigenotype. Different methods are used to reprogram somatic cells into pluripotent cells. Among which are somatic cell nuclear transfer, cell fusion, genetic integration of cells extracts into chromatin and direct reprogramming using transcription factor integration. These methods result in morphological and molecular changes because of modification in chromatin and gene expression. The integration of the genome can be performed by the help of viral and non-viral vectors which have great variability the integration efficiency. Reprogrammed induced Pluripotent stem cells (iPS) and the recent induced endodermal cells are a few cell types to mention. Though these cells have numerous limitation in cell transplantation therapy but are promising cell for diseases modeling, drug discovery and bio-artificial organ synthesis. The major problems observed is retaining somatic cell genetic memory. Generally it is possible to reprogram personalized cells using different methods so that it can be patient specific. Keywords: pluripotent, reprogramming, stem cell, transcription factors, vectors.

Magnetic Connectivity between Active Regions 10987, 10988, and 10989 by Means of Nonlinear Force-Free Field Extrapolation

Extrapolation codes for modelling the magnetic field in the corona in cartesian geometry do not take the curvature of the Sun's surface into account and can only be applied to relatively small areas, \textit{e.g.}, a single active region. We apply a method for nonlinear force-free coronal magnetic field modelling of photospheric vector magnetograms in spherical geometry which allows us to study the connectivity between multi-active regions. We use vector magnetograph data from the Synoptic Optical Long-term Investigations of the Sun survey (SOLIS)/Vector Spectromagnetograph(VSM) to model the coronal magnetic field, where we study three neighbouring magnetically connected active regions (ARs: 10987, 10988, 10989) observed on 28, 29, and 30 March 2008, respectively. We compare the magnetic field topologies and the magnetic energy densities and study the connectivities between the active regions(ARs). We have studied the time evolution of magnetic field over the period of three days and found no major changes in topologies as there was no major eruption event. From this study we have concluded that active regions are much more connected magnetically than the electric current.Comment: Solar Physic

Coronal Magnetic Field Structure and Evolution for Flaring AR 11117 and its Surroundings

In this study, photospheric vector magnetograms obtained with the Synoptic Optical Long-term Investigations of the Sun survey (SOLIS), are used as boundary conditions to model the three-dimensional nonlinear force-free (NLFF) coronal magnetic fields as a sequence of nonlinear force-free equilibria in spherical geometry. We study the coronal magnetic field structure inside active regions and its temporal evolution. We compare the magnetic field configuration obtained from NLFF extrapolation before and after flaring event in active region (AR) 11117 and its surroundings observed on 27 October 2010. We compare the magnetic field topologies and the magnetic energy densities and study the connectivities between AR 11117 and its surroundings. During the investigated time period, we estimate the change in free magnetic energy from before to after the flare to be 1.74x10^{32}erg which represents about 13.5% of nonlinear force-free magnetic energy before the flare. In this study, we find that electric currents from AR 11117 to its surroundings were disrupted after the flare.Comment: 14 pages, 14 figures, Accepted by Solar Physics Journa

Review of solar energetic particle models

Solar Energetic Particle (SEP) events are interesting from a scientific perspective as they are the product of a broad set of physical processes from the corona out through the extent of the heliosphere, and provide insight into processes of particle acceleration and transport that are widely applicable in astrophysics. From the operations perspective, SEP events pose a radiation hazard for aviation, electronics in space, and human space exploration, in particular for missions outside of the Earth’s protective magnetosphere including to the Moon and Mars. Thus, it is critical to improve the scientific understanding of SEP events and use this understanding to develop and improve SEP forecasting capabilities to support operations. Many SEP models exist or are in development using a wide variety of approaches and with differing goals. These include computationally intensive physics-based models, fast and light empirical models, machine learning-based models, and mixed-model approaches. The aim of this paper is to summarize all of the SEP models currently developed in the scientific community, including a description of model approach, inputs and outputs, free parameters, and any published validations or comparisons with data.</p

Estrus characteristics, ovarian response to synchronization hormones, and fertility of crossbred dairy heifers managed under a semi-intensive system

This study aimed to characterize estrus sign/s which best predict the time of ovulation and determine ovarian responses to different&nbsp; synchronization protocols and conception rates to fixed-time artificial insemination in Boran*Holstein crossbred heifers. In the first part of the study, twenty-seven heifers were observed for estrus signs (from induced and natural) and the relationship of various estrus signs with ovulation time was evaluated by using ultrasonography. In the second part, 91 Boran*Holstein crossbred heifers were randomly grouped into three groups. Group one heifers (n=28) received 100μg gonadotropin-releasing hormone (GnRH) on day zero (D0), 500μg&nbsp; prostaglandin F2α (PGF2α) on day 7 and 100μg of GnRH on day 9. Group 2 heifers (n=32) were treated as group one but additionally&nbsp; received progesterone as controlled internal drug release (CIDR). Group three heifers (n=31) were treated as those in group 2 but without injection with GnRH on day 0. In all the 3 groups’ insemination was made at 19h of the second GnRH. The results showed that irrespective of estrus source type (induced or natural), score for standing to be mounted, mounting other heifers, and non-receptive mount by other heifers showed a strong positive correlation with ovulation time (r=0.67, P&lt;0.05). Standing estrus duration, and time elapsed from standing estrus to ovulation were shorter (P&lt;0.05) in induced estrus. The conception rate was 39.3% in synchronized ovulation in the absence of CIDR. The conception rate in timed insemination was 56.3% when ovulation was synchronized by combining CIDR, PGF2α, and GnRH. In conclusion injection of GnRH on day zero together with treatment with CIDR improved ovulation rate, the number of new corpus luteum, and conception rate. Heifers that ovulated within the first 24h after timed insemination had a higher (P&lt;0.05) conception rate than heifers ovulated after 24h of timed insemination. Cycling heifers at day zero had a greater (P&lt;0.05) conception rate than non-cycling

Nonlinear force-free field extrapolation in spherical geometry: improved boundary data treatment applied to a SOLIS/VSM vector magnetogram

Routine measurements of the solar magnetic field are mainly carried out in the photosphere. Therefore, one has to infer the field strength in the higher layers of the solar atmosphere from the measured photospheric field based on the assumption that the corona is force-free. Meanwhile, those measured data are inconsistent with the above force-free assumption. Therefore, one has to apply some transformations to these data before nonlinear force-free extrapolation codes can be applied. Extrapolation codes in cartesian geometry for modelling the magnetic field in the corona do not take the curvature of the Sun's surface into account and can only be applied to relatively small areas, e.g., a single active region. Here we apply a method for nonlinear force-free coronal magnetic field modelling and preprocessing of photospheric vector magnetograms in spherical geometry using the optimization procedure.We solve the nonlinear force-free field equations by minimizing a functional in spherical coordinates over a restricted area of the Sun. We extend the functional by an additional term, which allows to incorporate measurement error and treat regions with lacking observational data. We use vector magnetograph data from the Synoptic Optical Long-term Investigations of the Sun survey (SOLIS) to model the coronal magnetic field. We study two neighbouring magnetically connected active regions observed on May 15 2009. For vector magnetograms with variable measurement precision and randomly scattered data gaps (e.g., SOLIS/VSM) the new code yields field models which satisfy the solenoidal and force-free condition significantly better as it allows deviations between the extrapolated boundary field and observed boundary data within measurement errors. Data gaps are assigned to an infinite error. We extend this new scheme to spherical geometry and apply it for the first time to real data.Comment: Accepted on Astronomy and Astrophysic