DOCSLIB.ORG

On the Equilibrium of Heterogeneous Substances

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
On the Equilibrium of Heterogeneous Substances : TRANSACTIONS CONNECTICUT ACADEMY OF ARTS AND SCIENCES. VOX^XJJVIE III t7> NEW H AYEN PUBLISHED BY THE ACADEMY, 1874 to 1878. TulUr, Murehouse 4 Taylor, Printers, New Ha ———— CONTENTS. PAGE List of Additions to the Library,..,. v Art. I. —Report on the dredgings in the region of St. George's Banks, in 1872. By S. I. Smith and O. Harger. Plates 1 -8, 1 Art. IL—Descriptions op new and rare species of Hy- DROIDS from the NeW EnGLAND COAST. By S. F, Clark. Plates 9-10, 58 Art. III. On the Chondrodite from the Tilly-Foster IRON mine, Brewster, N. Y, By E. S. Dana, Plates 11-13, 67 Art. IV. On the Transcendental curves sin y sin iny=. a sin ic sin ??a; -|- ^''- By II. A. Newton and A. W. Philips. Plates 14-37, 97 Art. V. On the equilibrium of heterogeneous sub- stances. By J. W. Gibbs. First Part, 108 Art. VI. The Hydroids of the Pacific coast of the United States south of Vancouver Island, with a report upon those in the Museum of Yale Coixege. By S. F. Clark. Plates 38-41, 249 Art. VII. On the anatomy and habits of Nereis virens. By Y. M, Turnbull. Plates 42-44, 265 Art. VIII. Median and paired fins, a contribution to the history of vertebrate limbs. By J. K. Thacher, Plates 49-60, 281 Art. IX. Early stages op Hippa talpoida, with a note ON THE structure OF THE MANDIBLES AND MAXILLJE IN Hipp A and Remipes. By S. I. Smith. Plates 45-48, 311 Art. X. — On the equilibrium op heterogeneous sub- stances (concluded). By J. W. Gibbs, 343 OFFICERS OF THE ACADEMY. President, ELIAS LOOMIS. Vice-President, HUBERT A. NEWTON. /Secretary, OSCAR HARGER. Librarian, ADDISON VAN NAME. Treasurer, HENRY C. KINGSLEY. PtihlisJdng Committee, HUBERT A. NEWTON, ELIAS LOOMIS, GEORGE J. BRUSH, ADDISON E. VERRILL, CHESTER S. LYMAN, WILLIAM D. WHITNEY. Auditiiig Committee, HUBERT A. NEWTON, DANIEL C. EATON, HENRY T. BLAKE. V. On the Equilibrium of Heterogeneous Substances. Bt J. WlLLARD GiBBS. " Die Energie der Welt ist constant. Die Entropie der Welt strebt einera Maximum zu." CLAfsitrs.* The comprehension of the laws which govern any material system is greatly facilitated by considering the energy and entropy of the system in the various states of which it is capable. As the difference of the values of the energy for any two states represents the com- bined amount of work and heat received or yielded by the system when it is brought from one state to the other, and the difference of entropy is the limit of all the possible values of the integral / , [dQ denoting the element of the heat received from external sources, and t the temperature of the part of the system receiving it,) the varying values of the energy and entropy characterize in all that is essential the effects producible by the system in passing from one state to another. For by mechanical and theiTuodynamic con- trivances, supposed theoretically perfect, any supply of work and heat may be transformed into any other which does not differ from it either in the amount of work and heat taken together or in the value of the integral / . But it is not only in respect to the external relations of a system that its energy and entropy ai'e of predominant importance. As in the case of simply mechanical sys- tems, (such as are discussed in theoretical mechanics,) which are capable of only one kind of action upon external systems, viz., the perform- ance of mechanical work, the function which expresses the capability of the system for this kind of action also plays the leading part in the theory of equilibrium, the condition of equilibrium being that the variation of this function shall vanish, so in a thermodynamic system, (such as all material systems actually are,) which is capable of two different kinds of action upon external systems, the two functions which express the twofold capabilities of the system afford an almost equally simple criterion of equilibrium. *Pogg. Ann. Bd. cxxv (1865), S. 400; or Mechanische Warmetheorie, Abhand. ix., S. 44. : J. W. Gihhs—Equilibrium of Hetexogeneous Substances. 109 CRITERIA OF EQUILIBRIUM AND STABILITY. The criterion of equilibi-ium for a material system which is isohited from all external influences may be expressed in either of the follow- ing entirely equivalent forms I. For the equilibrium of any isolated system it is necessary and sufficient that in all possible variations of the state of the system which do not alter its energy, the va.riatio7i of its entropy shall either vanish or be negative. If a denote the energy, and // the entropy of the system, and we use a subscript letter after, a variation to indicate a quantity of which the value is not to be varied, the condition of equilibrium may be written {^V)e ^0. (1) II. For the equilibrium of any isolated system it is necessary and sufficient that in all possible variations in the state of the system which do not alter its entropy, the variation of its energy shall either vanish or be positive. This condition may be written m,= 0. (2) That these two theorems are equivalent will appear from the con- sideration that it is always possible to increase both the energy and the entropy of the system, or to decrease both together, viz., by imparting heat to any part of the system or by taking it away. For, if condition (1) is not satisfied, there must be some variation in the state of the system for which S}j > and 6e =0; therefore, by diminishing both the energy and the entropy of the system in its varied state, we shall obtain a state for which (considered as a variation from the original state) dTf=iO and d"£<0; therefore condition (2) is not satisfied. Conversely, if condition (2) is not satisfied, there must be a variation in the state of the system for which d£< and St/z^ 0; hence there must also be one for which (J// de=iO and > ; therefore condition (1) is not satisfied. The equations which express the condition of equilibrium, as also its statement in words, are to be interpreted in accordance with the general usage in respect to difterential equations, that is, infinitesimals 110 tf. W. Gibbs — Equilibrium of Heterogeneous Substances. of higher orders than the fii-st relatively to tliose which express the amount of change of the system are to be neglected. But to distin- guish the different kinds of equilibrium in respect to stability, we must have regard to the absolute values of the variations. We will use A as the sign of variation in those equations which are to be con- strued strictly, i. e., in which infinitesimals of the higher orders are not to be neglected. With this understanding, we may express the necessary and sufficient conditions of the different kinds of equi- librium as follows;—for stable equilil)rium (•^;/),<0, i. e., (A6),^>0: (3) for neutral equilibrium there must be some variations in the state of the system for which (A//)^ = 0, i. e., {Af),^ = 0, (4) while in general {^V)e ^0, i.e., (Af),^^0; (5) and for unstable equilibrium there must be some variations for which (A;/),>0, (6) i. e., there must be some for which (^f),<0, (V) while in general (d7),^0,i.e., (c^f),^0. (8) In these criteria of equilibrium and stability, account is taken only oi })ossible variations. It is necessary to explain in what sense tliis is to be understood. In the first place, all variations in the state of the system which involve the transportation of any matter through any finite distance are of course to be excluded from consideration, although they may be capable of expression by infinitesimal varia- tions of quantities which perfectly determine the state of the system. For example, if the system contains two masses of the same sub- stance, not in contact, nor connected by other masses consisting of or containing the same substance or its components, an infinitesimal increase of the one mass with an equal decrease of the other is not to be considered as a possible variation in the state of the system. In addition to such cases of essential impossibility, if heat can pass by conduction or radiation from every part of the system to every other, only those variations are to be rejected as impossible, which involve changes which are prevented by passive forces or analogous resist- ances to change. But, if the system consist of parts between which there is supposed to be no thermal communication, it will be neces- sary to regard as impossible any diminution of the entropy of any of J. W. Gihhs—Equilihrium of Heterogeneous Substances. Ill these parts, as sueli a change can not take place without the passage of heat. This limitation may most conveniently l>e ai»plied to the second of the above forms of the condition of equilibrium, which will then become ri\ ?/', etc., denoting the entropies of the various parts between which there is no communication of heat. When the condition of equi- librium is thus expressed, the limitation in respect to the conduction of heat will need no farther consideration. In order to apply to any system the criteria of equilibrium which have been given, a knowledge is requisite of its passive forces or resistances to change, in so far, at least, as they are capable of pre- venting change. (Those passive forces which only retard change, like viscosity, need not be considered.) Such properties of a system ai-e in general easily recognized upon the most superficial knowledge of its nature.
Load more

Recommended publications
  • Severe Space Weather
    Severe Space Weather ThePerfect Solar Superstorm Solar storms in +,-. wreaked havoc on telegraph networks worldwide and produced auroras nearly to the equator. What would a recurrence do to our modern technological world? Daniel N. Baker & James L. Green SOHO / ESA / NASA / LASCO 28 February 2011 !"# $ %&'&!()*& SStormtorm llayoutayout FFeb.inddeb.indd 2288 111/30/101/30/10 88:09:37:09:37 AAMM DRAMATIC AURORAL DISPLAYS were seen over nearly the entire world on the night of August !"–!&, $"%&. In New York City, thousands watched “the heavens . arrayed in a drapery more gorgeous than they have been for years.” The aurora witnessed that Sunday night, The New York Times told its readers, “will be referred to hereafter among the events which occur but once or twice in a lifetime.” An even more spectacular aurora occurred on Septem- ber !, $"%&, and displays of remarkable brilliance, color, and duration continued around the world until Septem- ber #th. Auroras were seen nearly to the equator. Even after daybreak, when the auroras were no longer visible, disturbances in Earth’s magnetic fi eld were so powerful ROYAL ASTRONOMICAL SOCIETY / © PHOTO RESEARCHERS that magnetometer traces were driven off scale. Telegraph PRELUDE TO THE STORM British amateur astronomer Rich- networks around the globe experienced major disrup- ard Carrington sketched this enormous sunspot group on Sep- tions and outages, with some telegraphs being completely tember $, $()*. During his observations he witnessed two brilliant unusable for nearly " hours. In several regions, operators beads of light fl are up over the sunspots, and then disappear, in disconnected their systems from the batteries and sent a matter of ) minutes.
    [Show full text]
  • Wiki Template-1Eb7p59
    Wikipedia Reader https://en.wikipedia.org/wiki/Aurora Selected by Julie Madsen - Entry 10 1 Aurora From Wikipedia, the free encyclopedia An aurora, sometimes referred to as a polar lights or north- ern lights, is a natural light display in the sky, predominantly seen in the high latitude (Arctic and Antarctic) regions.[1] Au- roras are produced when the magnetosphere is sufficiently disturbed by the solar wind that the trajectories of charged particles in both solar wind and magnetospheric plasma, mainly in the form of electrons and protons, precipitate them into the upper atmosphere (ther- mosphere/exosphere), where their energy is lost. The resulting ion- ization and excitation of atmospheric constituents emits light of varying color and complexity. The form of the aurora, occur- ring within bands around both polar regions, is also dependent on the amount of acceleration imparted to the precipitating parti- cles. Precipitating protons generally produce optical emissions as incident hydrogen atoms after gaining electrons from the atmosphere. Proton Images of auroras from around the world, auroras are usually observed at including those with rarer red and blue lower latitudes.[2] lights Wikipedia Reader 2 May 1 2017 Contents 1 Occurrence of terrestrial auroras 1.1 Images 1.2 Visual forms and colors 1.3 Other auroral radiation 1.4 Aurora noise 2 Causes of auroras 2.1 Auroral particles 2.2 Auroras and the atmosphere 2.3 Auroras and the ionosphere 3 Interaction of the solar wind with Earth 3.1 Magnetosphere 4 Auroral particle acceleration 5 Auroral events of historical significance 6 Historical theories, superstition and mythology 7 Non-terrestrial auroras 8 See also 9 Notes 10 References 11 Further reading 12 External links Occurrence of terrestrial auroras Most auroras occur in a band known as the auroral zone,[3] which is typically 3° to 6° wide in latitude and between 10° and 20° from the geomagnetic poles at all local times (or longitudes), most clearly seen at night against a dark sky.
    [Show full text]
  • GEOMAGNETISM -A HISTORICAL REVIEW Sashikanth Rapeti
    GEOMAGNETISM -A HISTORICAL REVIEW Sashikanth Rapeti To cite this version: Sashikanth Rapeti. GEOMAGNETISM -A HISTORICAL REVIEW. 2020. hal-02901860 HAL Id: hal-02901860 https://hal.archives-ouvertes.fr/hal-02901860 Preprint submitted on 17 Jul 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. GEOMAGNETISM – A HISTORICAL REVIEW R. Sashikanth Assistant Professor and Head of the Department Department of Physics and Space Sciences Gandhi Institute of Technology and Management, Gangapada, Bhubhaneshwar, Odisha, India. E-mail : [email protected], [email protected] [email protected], [email protected] Abstract : This specific paper addresses the historical events that had led in the current scenario, to the development of one of the most important fundamental research areas – Geomagnetism, which might even date back to probably millions of years embedded in the core scientific aspects of even ancient civilizations. The solar wind and its associated magnetic field have their source in the Sun and their interaction with the geo-magnetic field which extends into outer space has its origin inside the earth’s core. Needless to say, the contributions of many scientific researchers on the dynamics of upper, middle and lower atmospheres of the earth is really outstanding and remarkable, but certain important aspects appear to have been missed.
    [Show full text]
  • Olmsted 200 Bicentennial Notes About Olmsted Falls and Olmsted Township – First Farmed in 1814 and Settled in 1815 Issue 42 November 1, 2016
    Olmsted 200 Bicentennial Notes about Olmsted Falls and Olmsted Township – First Farmed in 1814 and Settled in 1815 Issue 42 November 1, 2016 Contents November Meteors Have Connection to Olmsted History 1 Sesquicentennial Coin Turns Up 7 Did Peltzes Move to California for Their Health? 8 Chestnut Grove Will Host Veterans Day Ceremony 10 Still to Come 11 November Meteors Have Connection to Olmsted History If the nighttime sky is dark enough and clear enough around the middle of November and you happen to see one or more meteors – or “shooting stars” – you might be witness to a portion of one of the best-known annual meteor showers. But maybe you didn’t know – until now – about that meteor shower’s connection to the family for whom Olmsted Falls and Olmsted Township, as well as North Olmsted, are named. Meteor showers occur when the Earth, in its orbit around the sun, encounters streams of particles. Those particles are left in the wake of comets in their trips from the edges of the solar system to close passes by the sun and then back to the outer realms. The Earth experiences several meteor showers of varied intensity each year. One of the best- known meteor showers is the Perseids, partly because they reliably provide an average of about one meteor each minute at their peak. It’s also partly because they occur in mid-August, when the weather is warm enough that it is comfortable for observers to stay outside for long periods NASA released this photo of the Leonids as in the middle of the night.
    [Show full text]
  • Between Two Empires: the Toronto Magnetic Observatory and American Science Before Confederation"
    Article "Between Two Empires: the Toronto Magnetic Observatory and American Science before Confederation" Gregory Good Scientia Canadensis: Canadian Journal of the History of Science, Technology and Medicine / Scientia Canadensis : revue canadienne d'histoire des sciences, des techniques et de la médecine , vol. 10, n° 1, (30) 1986, p. 34-52. Pour citer cet article, utiliser l'information suivante : URI: http://id.erudit.org/iderudit/800224ar DOI: 10.7202/800224ar Note : les règles d'écriture des références bibliographiques peuvent varier selon les différents domaines du savoir. Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y compris la reproduction) est assujettie à sa politique d'utilisation que vous pouvez consulter à l'URI https://apropos.erudit.org/fr/usagers/politique-dutilisation/ Érudit est un consortium interuniversitaire sans but lucratif composé de l'Université de Montréal, l'Université Laval et l'Université du Québec à Montréal. Il a pour mission la promotion et la valorisation de la recherche. Érudit offre des services d'édition numérique de documents scientifiques depuis 1998. Pour communiquer avec les responsables d'Érudit : [email protected] Document téléchargé le 14 février 2017 07:54 34 BETWEEN TWO EMPIRES: THE TORONTO MAGNETIC OBSERVATORY AND AMERICAN SCIENCE BEFORE CONFEDERATION* Gregory Good** (Received 20 November 1985. Revised/Accepted 19 May 1986) PERSPECTIVES ON THE TORONTO MAGNETIC OBSERVATORY The Magnetic Observatory was founded at Toronto in 1839 as part of the worldwide magnetic Crusade of the British Association for the Advancement of Science and the Royal Society of London.1 Although it was a focus of scientific research and of institutional development in Canada for decades, little attention has been given to it.
    [Show full text]
  • Denison Olmsted (1791-1859), Scientist, Teacher, Christian: a Biographical Study of the Connection Of
    AN ABSTRACT OF THE THESIS OF Gary Lee Schoepflin for the degree ofDoctor of Philosophy in General Science presented on June 17, 1977 Title:DENISON OLMSTED (1791-1859), SCIENTIST, TEACHER, CHRISTIAN: A BIOGRAPHICAL STUDY OF THE CONNECTION OF SCIENCE WITH RELIGION IN ANTEBELLUM AMERICA Redacted for Privacy Abstract approved: Danie JJ one s A biographical study of Denison Olmsted, focusing upon his own Christian world view and its connection with his various activities in science, supports the view that religion served as a significant factor in the promotion of science in America during this time period. Olmsted taught physics, meteorology and astronomy at Yale from 1826 to 1859, and from this position of influence, helped mold the minds and outlook of a new generation of scientists, of hundreds of students who came to Yale to obtain a liberal educa- tion, and of those members of society who attended his popular lectures.Olmsted's personal perspective was that science was God-ordained, that it would ever harmonize with religion, that it was indeed a means of hastening the glorious millennium. Olmsted lived in an era characterized by an unprecedented revivalism and emphasis upon evangelical Christianity. He graduated from Yale (1813) at a time when its president, Reverend Dr. Timothy Dwight, one of the most influential clergymen in New England, was at the height of his fame. Olmsted subsequently studied theology under Dwight, but before completing his prepara- tion for the ministry, Olmsted was appointed to a professorship of science at the University of North Carolina where he taught from 1818 until he was called to Yale in 1826.
    [Show full text]
  • George P. Merrill Collection, Circa 1800-1930 and Undated
    George P. Merrill Collection, circa 1800-1930 and undated Finding aid prepared by Smithsonian Institution Archives Smithsonian Institution Archives Washington, D.C. Contact us at [email protected] Table of Contents Collection Overview ........................................................................................................ 1 Administrative Information .............................................................................................. 1 Historical Note.................................................................................................................. 1 Descriptive Entry.............................................................................................................. 2 Names and Subjects ...................................................................................................... 3 Container Listing ............................................................................................................. 4 Series 1: PHOTOGRAPHS, CORRESPONDENCE AND RELATED MATERIAL CONCERNING INDIVIDUAL GEOLOGISTS AND SCIENTISTS, CIRCA 1800-1920................................................................................................................. 4 Series 2: PHOTOGRAPHS OF GROUPS OF GEOLOGISTS, SCIENTISTS AND SMITHSONIAN STAFF, CIRCA 1860-1930........................................................... 30 Series 3: PHOTOGRAPHS OF THE UNITED STATES GEOLOGICAL AND GEOGRAPHICAL SURVEY OF THE TERRITORIES (HAYDEN SURVEYS), CIRCA 1871-1877..............................................................................................................
    [Show full text]
  • The Victorian Global Positioning System by Trudy E
    The Victorian Global Positioning System by Trudy E. Bell TARS GLEAMED OVERHEAD in a velvet-black With this vivid account, published immediately in the sky on a crisp October night in 1848 as six astrono- Cincinnati Observatory’s periodical The Sidereal Messen- mers entered the darkened dome of the three- ger, Mitchel affords an eyewitness’s glimpse into one of the year-old Cincinnati Observatory. Seating them- great untold stories in the histories of telegraphy, as- s selves around a table laden with several large tronomy, and geodesy: the telegraphic method of deter- batteries and clocks, Ormsby McKnight Mitchel, the mining longitudes. observatory’s director, was keenly aware of the moment’s Within a few short years, the telegraph had transformed historic significance. About 9 p.m., the men were joined by a both positional astronomy and geodesy. The telegraphic telegraph operator who, Mitchel wrote, method of determining longitudes held sway for eight decades not only in the . perfected the necessary arrange- United States but also in Europe—be- ments for communicating directly by ing replaced only in the 1920s by radio telegraph between the Cincinnati The telegraph (wireless) positioning techniques. Yet Observatory and the Philadelphia its history appears to have been largely [Central High School] Observatory. was as revolutionary overlooked, including in two recent At ten o’clock the way offices along for determining popular bestsellers on the measure- the line were closed, and the line of ment of longitude and on the telegraph.1 the telegraph given up to the use of longitude on land the astronomers. The novelty of the as the marine WHY A DEMAND FOR operations excited the deepest inter- chronometer was LONGITUDES? est among all who were present.
    [Show full text]
  • PART II. OTHER PUBLICATIONS of the ACADEMY MEMOIRS of the NATIONAL ACADEMY of SCIENCES -The Memoirs Are Monographs Published at Irregular Intervals
    PART II. OTHER PUBLICATIONS OF THE ACADEMY MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES -The Memoirs are monographs published at irregular intervals. Some volumes are comprised of a single monograph, while others consist of several separate papers relating to different branches of science. The Memoirs listed as "out of print" qare no longer available from the Academy,' but it is possible that some of these might still be obtained from the Superintendent of Documents, Government Printing Office, Washington, D. C., who sometimes has additional copies which are sold at cost. The Academy edition of the Memoirs is distributed free. CONTENTS VoLums I. 1866. Out of print 1. Reduction of the observations of fixed stars made by Joseph LePaute D'Agelet, at Paris, in 1783-1785, with a catalogue of the corresponding mean places, referred to the Equinox of 1800.0. BENJAMIN APTHORP GOULD. Read January 8, 1864. Pp. 1-261. 2. The Saturnian system. BZNJAMIN Pumcu. Read January 8, 1864. Pp. 263-86. 3. On the distribution of certain diseases in reference to hygienic choice of location for the cure of invalid soldiers. AUGUSTrUS A. GouLD. Read August 5, 1864. Pp. 287-90. 4. On shooting stars. H. A. NEWTON.- Read August 6, 1864. Pp. 291-312. 5. Rifled guns. W. H. C. BARTL*rT. Read August 25, 1865. Pp. 313-43. VoLums II. 1884 1. Report of the eclipse expedition to Caroline Island, May, 1883. Pp. 5-146. 2. Experimental determination of wave-lengths in the invisible prismatic spectrum. S. P. LANGIXY. April, 1883. 4 plates. Pp. 147-2.
    [Show full text]
  • Prof. E. Loomis on the Aurora of 1859. by ELIAS LOOMIS
    318 Prof. E. Loomis on the Aurora of 1859. ART. XXXVI.-On the great Auroml Exhibition of Aug. 28th to &pt. 4th, 1859, arid on Auroras generally.-8TH ARTICLE; by ELIAS LOOMIS, Professor of Natural Philosophy and As­ tronomy in Yale College. SINCE the publication of my seventh article on t11e great auroral exhibition of Aug. 28th to Sept 4th, 1859, I have received from Prof. Hansteen a copy of the observations made at Christiania, Norway, corresponding to those made at Hobarton, as given in this Journal, vol. xxxii, p 81. These observations are published in the Memoires del'Academie de Belgique, tome xx, pp. 103-116, and Bulletins de l'Academie Royale de Belgique, tome xxi, pp. 284-298. Observations of the Aurora at Ohristiania, Nortoay, lat. 59° 54', long. 10° 43' E. Magnetic dip in 1S59, 71° IS'. ~ . Day. Hour. Notic•• of Auror••. 1841. Mllrcb Iii, IOh Aurora. Mluch 22, Rllin. Mny 17, Rain. July 20. No lLurora visible. 1842. Feb. 18, 11-14 A urora faint. April II. 9-15 8light aurora. Faint arch at llih. April 12. 9-14 Rays and flllmes extendiug to the zenith. April 13. 9-13 Rays and flames. April 15. 11-15 Flaming aurora. July 2. 10 and 12 The bi/Har magnetometer was quite out of Reale. 1844. April 17, 9 Faint aurora. extending nearly to the zenith. 1846. Sept. 22, '1-15 Vehement flames o"er three· fourths of the heavens. Redtlish. Corona imperfect. 184'1. April 21, 11-14 Flaming and radiating aurora. Sept. 24, 7-10 Corona formed.
    [Show full text]
  • Aurora (Astronomy)
    Aurora (astronomy) From Wikipedia, the free encyclopedia "Aurora Borealis" redirects here. For other uses, see Aurora Borealis (disambiguation). "Aurora Australis" redirects here. For the ship, see Aurora Australis (icebreaker). For the book, see Aurora Australis (book). "Northern lights" redirects here. For the novel, see Northern Lights (novel). For other uses, see Aurora (disambiguation). The aurora borealis shines above Bear Lake Red and green aurora in Fairbanks, Alaska Northern lights with very rare blue light over Moskosel, Lapland in Sweden Northern lights over Malmesjaur, Moskosel, Lapland, Sweden Aurora australis in Antarctica False color DMSP image looking down from 850 km altitude showing discrete aurora (yellow) north of Scandinavia. Clouds and fog are blue. An aurora (plural: auroras or aurorae) is a natural light display in the sky particularly in the high latitude (Arctic and Antarctic) regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere (thermosphere). The charged particles originate in the magnetosphere and solar wind and are directed by the Earth's magnetic field into the atmosphere. Aurora is classified as diffuse or discrete aurora. Most aurora occur in a band known as the auroral zone[1][2] which is typically 3° to 6° in latitudinal extent and at all local times or longitudes. The auroral zone is typically 10° to 20° from the magnetic pole defined by the axis of the Earth's magnetic dipole. During ageomagnetic storm, the auroral zone will expand to lower latitudes. The diffuse aurora is a featureless glow in the sky which may not be visible to the naked eye even on a dark night and defines the extent of the auroral zone.
    [Show full text]
  • South American Auroral Reports During the Carrington Storm Hisashi Hayakawa1,2,3,4* , José R
    Hayakawa et al. Earth, Planets and Space (2020) 72:122 https://doi.org/10.1186/s40623-020-01249-4 EXPRESS LETTER Open Access South American auroral reports during the Carrington storm Hisashi Hayakawa1,2,3,4* , José R. Ribeiro5 , Yusuke Ebihara6,7 , Ana P. Correia5 and Mitsuru Sôma8 Abstract The importance of the investigation of magnetic superstorms is not limited to academic interest, because these superstorms can cause catastrophic impact on the modern civilisation due to our increasing dependency on techno- logical infrastructure. In this context, the Carrington storm in September 1859 is considered as a benchmark of obser- vational history owing to its magnetic disturbance and equatorial extent of the auroral oval. So far, several recent auroral reports at that time have been published but those reports are mainly derived from the Northern Hemi- sphere. In this study, we analyse datable auroral reports from South America and its vicinity, assess the auroral extent using philological and astrometric approaches, identify the auroral visibility at 17.3° magnetic latitude and further poleward and reconstruct the equatorial boundary of the auroral oval to be 25.1°− 0.5° in invariant latitude. Interest- ingly, brighter and more colourful auroral displays were reported in the South American± sector than in the Northern Hemisphere. This north–south asymmetry is presumably associated with variations of their magnetic longitude and the weaker magnetic feld over South America compared to the magnetic conjugate point and the increased amount of magnetospheric electron precipitation into the upper atmosphere. These results attest that the magnitude of the Carrington storm indicates that its extent falls within the range of other superstorms, such as those that occurred in May 1921 and February 1872, in terms of the equatorial boundary of the auroral oval.
    [Show full text]