Search

Observations have shown a clear association of filament/prominence eruptions with the emergence of magnetic flux in or near filament channels. Magnetohydrodynamic (MHD) simulations have been employed to systematically study the conditions under which such eruptions occur. These simulations to date have modeled filament channels as 2D flux ropes or 3D uniformly sheared arcades. Here we present MHD simulations of flux emergence into a more realistic configuration consisting of a bipolar active region containing a line-tied 3D flux rope. We use the coronal flux-rope model of Titov et al. as the initial condition and drive our simulations by imposing boundary conditions extracted from a flux emergence simulation by Leake et al. We identify three mechanisms that determine the evolution of the system: (i) reconnection displacing footpoints of field lines overlying the coronal flux rope, (ii) changes of the ambient field due to the intrusion of new flux at the boundary, and (iii) interaction of the (axial) electric currents in the preexisting and newly emerging flux systems. The relative contributions and effects of these mechanisms depend on the properties of the preexisting and emerging flux systems. Here we focus on the location and orientation of the emerging flux relative to the coronal flux rope. Varying these parameters, we investigate under which conditions an eruption of the latter is triggered.

In this study we describe a series of MHD simulations covering the time period from 12 January 1999 to 19 September 2001 (Carrington Rotation 1945 to 1980). This interval coincided with: (1) the Sun’s approach toward solar maximum; and (2) Ulysses’ second descent to the southern polar regions, rapid latitude scan, and arrival into the northern polar regions. We focus on the evolution of several key parameters during this time, including the photospheric magnetic field, the computed coronal hole boundaries, the computed velocity profile near the Sun, and the plasma and magnetic field parameters at the location of Ulysses. The model results provide a global context for interpreting the often complex in situ measurements. We also present a heuristic explanation of stream dynamics to describe the morphology of interaction regions at solar maximum and contrast it with the picture that resulted from Ulysses’ first orbit, which occurred during more quiescent solar conditions. The simulation results described here are available at: http://sun.saic.com.Key words. Interplanetary physics (Interplanetary magnetic fields; solar wind plasma; sources of the solar wind)

We report the results of a multi-instrument, multi-technique, coordinated study of the solar eruptive event of 13 May 2005. We discuss the resultant Earth-directed (halo) coronal mass ejection (CME), and the effects on the terrestrial space environment and upper Earth atmosphere. The interplanetary CME (ICME) impacted the Earth’s magnetosphere and caused the most-intense geomagnetic storm of 2005 with a Disturbed Storm Time ( Dst) index reaching −263 nT at its peak. The terrestrial environment responded to the storm on a global scale. We have combined observations and measurements from coronal and interplanetary remote-sensing instruments, interplanetary and near-Earth in-situ measurements, remote-sensing observations and in-situ measurements of the terrestrial magnetosphere and ionosphere, along with coronal and heliospheric modelling. These analyses are used to trace the origin, development, propagation, terrestrial impact, and subsequent consequences of this event to obtain the most comprehensive view of a geo-effective solar eruption to date. This particular event is also part of a NASA-sponsored Living With a Star (LWS) study and an on-going US NSF-sponsored Solar, Heliospheric, and INterplanetary Environment (SHINE) community investigation. [ABSTRACT FROM AUTHOR]

The topology of the coronal magnetic field has a strong impact on the properties of the solar corona and presumably on the origin of the slow solar wind. To advance our understanding of this impact, we revisit the concept of so-called slip-back mapping and adapt it to determine open, closed, and disconnected flux systems that are formed in the solar corona by magnetic reconnection during a given time interval. In particular, the method we developed allows us to describe magnetic flux transfer between open and closed flux regions via so-called interchange reconnection with an unprecedented level of detail. We illustrate the application of this method to the analysis of the global MHD evolution of the solar corona driven by idealized differential rotation of the photospheric plasma. [ABSTRACT FROM AUTHOR]

Long-period EUV pulsations, recently discovered to be common in active regions, are understood to be the coronal manifestation of thermal nonequilibrium (TNE). The active regions previously studied with EIT/Solar and Heliospheric Observatory and AIA/SDO indicated that long-period intensity pulsations are localized in only one or two loop bundles. The basic idea of this study is to understand why. For this purpose, we tested the response of different loop systems, using different magnetic configurations, to different stratifications and strengths of the heating. We present an extensive parameter-space study using 1D hydrodynamic simulations (1020 in total) and conclude that the occurrence of TNE requires specific combinations of parameters. Our study shows that the TNE cycles are confined to specific ranges in parameter space. This naturally explains why only some loops undergo constant periodic pulsations over several days: since the loop geometry and the heating properties generally vary from one loop to another in an active region, only the ones in which these parameters are compatible exhibit TNE cycles. Furthermore, these parameters (heating and geometry) are likely to vary significantly over the duration of a cycle, which potentially limits the possibilities of periodic behavior. This study also confirms that long-period intensity pulsations and coronal rain are two aspects of the same phenomenon: both phenomena can occur for similar heating conditions and can appear simultaneously in the simulations. [ABSTRACT FROM AUTHOR]

In solar coronal loops, thermal non-equilibrium (TNE) is a phenomenon that can occur when the heating is both highly stratified and quasi-constant. Unambiguous observational identification of TNE would thus permit us to strongly constrain heating scenarios. While TNE is currently the standard interpretation of coronal rain, the long-term periodic evolution predicted by simulations has never been observed. However, the detection of long-period intensity pulsations (periods of several hours) has been recently reported with the Solar and Heliospheric Observatory/EIT, and this phenomenon appears to be very common in loops. Moreover, the three intensity-pulsation events that we recently studied with the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA) show strong evidence for TNE in warm loops. In this paper, a realistic loop geometry from linear force-free field (LFFF) extrapolations is used as input to 1D hydrodynamic simulations. Our simulations show that, for the present loop geometry, the heating has to be asymmetrical to produce TNE. We analyze in detail one particular simulation that reproduces the average thermal behavior of one of the pulsating loop bundle observed with AIA. We compare the properties of this simulation with those deduced from the observations. The magnetic topology of the LFFF extrapolations points to the presence of sites of preferred reconnection at one footpoint, supporting the presence of asymmetric heating. In addition, we can reproduce the temporal large-scale intensity properties of the pulsating loops. This simulation further strengthens the interpretation of the observed pulsations as signatures of TNE. This consequently provides important information on the heating localization and timescale for these loops. [ABSTRACT FROM AUTHOR]

We present a study on particle acceleration in the low corona associated with the expansion and acceleration of coronal mass ejections (CMEs). Because CME expansion regions low in the corona are effective accelerators over a finite spatial region, we show that there is a rigidity regime where particles effectively diffuse away and escape from the acceleration sites using analytic solutions to the Parker transport equation. This leads to the formation of broken power-law distributions. Based on our analytic solutions, we find a natural ordering of the break energy and second power-law slope (above the break energy) as a function of the scattering characteristics. These relations provide testable predictions for the particle acceleration from low in the corona. Our initial analysis of solar energetic particle observations suggests a range of shock compression ratios and rigidity dependencies that give rise to the solar energetic particle (SEP) events studied. The wide range of characteristics inferred suggests competing mechanisms at work in SEP acceleration. Thus, CME expansion and acceleration in the low corona may naturally give rise to rapid particle acceleration and broken power-law distributions in large SEP events. [ABSTRACT FROM AUTHOR]

Seven different models are applied to the same problem of simulating the Sun's coronal magnetic field during the solar eclipse on 2015 March 20. All of the models are non-potential, allowing for free magnetic energy, but the associated electric currents are developed in significantly different ways. This is not a direct comparison of the coronal modelling techniques, in that the different models also use different photospheric boundary conditions, reflecting the range of approaches currently used in the community. Despite the significant differences, the results show broad agreement in the overall magnetic topology. Among those models with significant volume currents in much of the corona, there is general agreement that the ratio of total to potential magnetic energy should be approximately 1.4. However, there are significant differences in the electric current distributions; while static extrapolations are best able to reproduce active regions, they are unable to recover sheared magnetic fields in filament channels using currently available vector magnetogram data. By contrast, time-evolving simulations can recover the filament channel fields at the expense of not matching the observed vector magnetic fields within active regions. We suggest that, at present, the best approach may be a hybrid model using static extrapolations but with additional energization informed by simplified evolution models. This is demonstrated by one of the models.

Solar eruptions are the main driver of space-weather disturbances at the Earth. Extreme events are of particular interest, not only because of the scientific challenges they pose, but also because of their possible societal consequences. Here we present a magnetohydrodynamic (MHD) simulation of the 14 July 2000 "Bastille Day" eruption, which produced a very strong geomagnetic storm. After constructing a "thermodynamic" MHD model of the corona and solar wind, we insert a magnetically stable flux rope along the polarity inversion line of the eruption's source region and initiate the eruption by boundary flows. More than 10 33 ergs of magnetic energy are released in the eruption within a few minutes, driving a flare, an EUV wave, and a coronal mass ejection (CME) that travels in the outer corona at ≈1500 km s -1 , close to the observed speed. We then propagate the CME to Earth, using a heliospheric MHD code. Our simulation thus provides the opportunity to test how well in situ observations of extreme events are matched if the eruption is initiated from a stable magnetic-equilibrium state. We find that the flux-rope center is very similar in character to the observed magnetic cloud, but arrives ≈8.5 hours later and ≈ 15° too far to the North, with field strengths that are too weak by a factor of ≈ 1.6. The front of the flux rope is highly distorted, exhibiting localized magnetic-field concentrations as it passes 1 AU. We discuss these properties with regard to the development of space-weather predictions based on MHD simulations of solar eruptions.

Introduction: Greek physician Oribasius from Pergamum (today's Bergama in western Turkey) (c. 320-400) was one of the most important physicians and personalities of his time., The Life and Career: Oribasisus studied medicine at Alexandria. Although he was the personal physician and friend of the Roman emperor Julian the Apostate, and a very important political figure of that period, he has been remembered as a most important medical writer and historian of medicine., Medical Writing: His major work, written in 70 books (only 25 of these survived), was the "Collectiones Medicae" which contains massive compilation of excerpts (epitomai) from the writings of older medical writers of the ancient world. Later on, he produced the "Synopsis for Eustathius" (Synopseos ad Eustathium) for his son Eustathius, who was also a physician. Oribasius dedicated a large work to his friend, the philosopher Eunapius: "Libri ad Eunapium", a kind of medical encyclopaedia in four volumes with a collection of easily procured medicines compiled for laymen. Several more of his writings are known to have been entirely lost. The works of Oribasius were translated in Latin as early as the fifth century, and later, in the medieval times his books were published in Europe (the "Synopsis for Eustathius" was published in 1554), while the critical edition of his works translated from Greek texts was published in Germany in 1926-1933., Commentary and Conclusion: The special importance of the Oribasius' works is that they have preserved a number of excerpts from many medical authors of antiquity whose writings would otherwise have been lost. Besides, these extracts (epitomai) were not entirely verbatim, they were looked upon critically and sorted out in an encyclopaedic manner. Because of that Oribasius is rightly considered to be the first writer of a medical encyclopaedia in the history of medicine.

Prof. dr Borivoje Gradojevic was one of the greatest figures of our medicine, and one of the pioneers and founders of orthopedic surgery in our country. He was the first professor of orthopedic surgery in Serbia ie. the professor of Belgrade Faculty of Medicine. Beside well education and professional skills dr Gradojevic published the numerous scientific papers and he published the first textbook of orthopedics in this country. Unfortunately, his professional career was brutally interrupted in 1945, when he was forced to retire and moved from Medical faculty, together with other professors in these times. This resulted in enormous regression--fall in academic community, and our health care system and country also.

Introduction: Thin rubber gloves were used for the first time in the history of medicine at the end of 1889. On the occasion of the 120th anniversary of that event at the end of 2009, the great importance of that discovery for the development of surgery in general should be emphasized once again. The surgical gloves were invented and introduced by a famous American surgeon Dr. William Halsted from Johs Hopkins Hospital in Baltimore (USA). DR. WILLIAM HALSTED AND MISS CAROLINE HAMPTON: This significant innovation actually occured thanks to the romance between Dr. W. Halsted and his scrub nurse Miss Caroline Hampton, later his wife, Mrs C. Halsted. According to the antiseptic practice of that hospital the hands of the operating personnel had to be desinfected in mercuric chloride which damaged the skin of nurse Caroline who developed a bad case of dermatitis, and because of that she considered abandoning the hospital. This prompted Dr. Halsted to contract Goodyear Rubber Company to produce thin rubber gloves to protect Caroline's hands and to keep her in his vicinity. They proved to be very satisfactory and soon Dr. Halsted's assistants too began to wear sterilized rubber gloves routinely., Commentary and Conclusion: Although it was not until later that the importance of rubber gloves in preventing infection was realized these "gloves of love" soon entered into general surgical practice and proved to be of the greatest importance for the development of asepsis and aseptic surgical work.

The first children's hospital in Serbia, as an exclusive paediatric intitution, was founded in a deserted military barrack in Studenieka Street, near the Military Hospital, in January 1919. The founder was Dr. Katherine MacPhail, a young Scottish lady doctor, who came to Serbia for the first time in January 1915, with the first "Scottish Women's Hospital". After that, she worked as a volunteer during the First World War in France and on the Thessalonica Front. In the spring of 1919, the hospital was given an open pavilion in Topcider, which worked only during the summer months till 1924. In November 1919, the hospital was moved to a new building in Knez Milos Street, and then named The Anglo-Serbian Children's Hospital. In February 1920, a new annex, called "Villa Bravacić", was opened in Dubrovnik, which was active till 1922. In this hospital, the first Training School for Serbian Nurses was opened in 1921, and in February of that year, the hospital moved into its new permanent house in Visegradska Street, where it had 70 beds, three wards with a modern operating theatre, outpatients' department, X-ray outfit and a pharmacy. Because of much better working conditions, the Children's Surgical Department of the General State Hospital headed by Dr. Dimitrije Jovcić, later a professor of the Faculty of Medicine in Belgrade, was accommodated in this hospital from 1923 to 1931. Apart from him, in this hospital, there used to work a number of young Serbian physicians and several of them later became professors of the Belgrade Faculty of Medicine. The hospital worked till 1934, when it was closed, the building was sold and from that money Dr. MacPhail built a new Anglo-Yugoslav Children's Hospital for Tuberculosis of Bones and Joints in Sremska Kamenica.

Introduction: The medicine had been practiced in ancient Egypt since the earliest, prehistoric days, many millenia before Christ, and was quite developed in later periods. This is evident from the sceletal findings, surgical instruments found in tombs, wall printings, the reliefs and inscriptions, and most of all, from the sparse written material known as medical papyri. However, there were not many physicians from that time whose names had been recorded. The earliest physician in ancient Egypt known by name was Imhotep. WHO WAS IMHOTEP?: Imhotep lived and worked during the time of the 3rd Dynasty of Old Kingdom and served under the pharaoh Djoser (reigned 2667-2648 BC) as his vizier or chief minister, high priest, chief builder and carpenter. He obviously was an Egyptian polymath, a learned man and scribe and was credited with many inventions., Builder: As one of the highest officials of the pharaoh Djoser Imhotep is credited with designing and building of the famous Step Pyramid of Djoser at Saqqarah, near the old Egyptian capital of Memphis. Imhotep is also credited with inventing the method of stone-dressed building and using of columns in architecture and is considered to be the first architect in history known by name., Physician: It is believed that, as the high priest, Imhotel also served as the nation's chief physician in his time. As the builder of the Step Pyramid, and as a physician, he also had to take medical care of thousands of workers engaged in that great project. He is also credited with being the founder of Egyptian medicine and with being the author of the so-called Smith papirus containing a collection of 48 specimen clinical records with detailed accurate record of the features and treatment of various injuries. As such he emerges as the first physician of ancient Egypt known by name and, at the same time, as the first physician known by name in written history of the world. GOD: As Imhotep was considered by Egyptian people as the "inventor of healing", soon after the death, he was worshiped as a demigod, and 2000 years later he was elevated to the position of a god of medicine and healing. His cult reached its zenith during Greco-Roman times when he was identified with the Greek god of medicine Asclepius., Conclusion: Imhotep was a real historic person from the period of the 3rd Dynasty of Old Kingdom (2686-2637 BC) and he served under the pharaoh Djoser as his vizier and high priest. Obviously, he was a very capable and many-sided man who is believed to be the designer and builder of the so-called Step Pyramid of Djoser at Saqqarah and of several other buildings. Apart from that he was believed by his people to be the "inventor of healing" and is considered to be the practicing physician at his time and the author of the famous Smith papirus. As such he is considered to be the first physician known by name in written history of the world. He was one of only two mortals ever to be accorded divining status after death.

Introduction: 90 years ago, on November 26th, 1917, died Dr. Elsie Inglis, one of the greatest heroines of the First World War, founder and driving force of the famous "Scottish Women's Hospitals", and one of the most interesting persons in the history of medicine in general, and especially in Serbia where she and her hospitals were of the greatest help in the most difficult times., Childhood and Education: Elsie Maud Inglis was born in India in 1864, in a Scottish family which in 1878 moved back to Scotland where Elsie studied medicine and graduated from the Edinburgh University in 1899. Medical practice and Women's Movement (1894-1914) Dr. E. Inglis worked in Edinburgh, where in 1904. She opened a small hospital for women and children called "The Hospice", which was staffed only by women. She was also very active in the Women's Movement (the so-called suffragettes), fighting for the women's rights and for the Vote. From 1906 until 1914 she was Honorary Secretary of the Scottish Federation of Women's Suffrage Societies. THE FIRST WORLD WAR-THE SCOTTISH WOMEN'S HOSPITALS: After the outbreak of the Great War in August, 1914. Dr. E. Inglis immediately organised, through her Federation, the so-called "Scottish Women's Hospitals" (SWH), on the whole 13 of them, which worked through the war in France, Belgium, Serbia, Greece (Macedonia), and Russia (Romania). SERBIA, 1915: In.January, 1915 the first Unit of the SWH arrived to Kragujevac, and.soon three more hospitals came to Serbian towns of Valjevo, Lazarevac and Mladenovac. In May 1915 Dr. E. Inglis herself came to Serbia. In October, 1915, when the great offensive of the Central Powers began, all these hospitals were evacuated to Krusevac, where they undertook the task of nursing 900 Serbian wounded at the "Csar Lazar" military hospital. Dr. Inglis and the majority of her staff refused to evacuate any further and stayed with their Serb patients. In November, 1915 they became prisoners of war, but continued to treat their patients until February, 1916 when they were repatriated. RUSSIA, 1916-1917: Back home, Dr. E. Inglis formed a new large SWH Unit, which, headed by herself sailed for Russia in August, 1916, and soon joined the so-called Yugoslav Volunteer Division, consisting mainly of Serbs, fighting on the Dobrudja front. After heavy losses and many retreats the remainder of this division, together with the SWH were evacuated back to England, to Newcastle, where Dr. E. Inglis, who was already seriously ill, died, on November 26th, 1917. She was later buried in Edinburgh, with full military honours., Epilogue: High honours were bestowed posthumously on Dr. E. Inglis both by Great Britain and Serbia, and now, 90 years after her death, we should remember her with deep gratitude and respect for all she did for our people in the most difficult times of its history.

The Scottish Women's Hospitals (SWH), a unique health institution in the history of medicine, staffed entirely by women, was founded soon after the outbreak of the First World War, August 12, 1914 in Edinburgh, by the National Union of Women's Suffrage Societies. The founder and the main driving force behind this organisation was Dr. Elsie Inglis (1864-1917). Although her proposition to the British War Office had been rejected, she offered her services to the Allies (France, Belgium, Russia and Serbia). The first 200 bed SWH unit was sent to France in November 1914, and soon after followed other units, so at the end there were 13 very well equipped SWH units working in the various theatres of war in Belgium, Serbia, Russia, Rumania and Greece. The first unit of SWH came to Serbia in early January 1915, and was located at Kragujevac. Soon after, three other SWH units arrived to Serbia and were stationed at Mladenovac, Valjevo and Lazarevac. It was an enormous help to Serbia, full of wounded and sick people, due to the dreadful typhus epidemic which was devastating the country. A large SWH unit, attached to the Southern Slav Volunteer Division, had worked on the Dobrudja front, and there were three hospitals and a special transport unit on the Salonika Front, which were all engaged in the treatment of Serbian wounded soldiers until the end of the First World War. Two other SWH units, located in France, were treating the Serbian refugees. Serving bravely and honorably on the various theatres of war, the legendary Scottish Women's Hospitals made enormous contributions to the allied war efforts, and helped Serbian people a great deal.