Working of Earth’s Magnetic Field

The magnetic field of the Earth consists of magnetic fields coming from several sources both internal and external source. The external magnetic field of the Earth is mainly from the interaction between the solar wind and geomagnetic field. The solar wind can be described as the movement of particles particularly H+, Helium and electron which are traveling from the Sun to the Earth and interacting with the geomagnetic field. This interaction leads to pressure to the geomagnetic field creating a cavity called the magnetosphere.

The solar wind can force the geomagnetic field out of the way at the distances larger than 10 RE, closer to the earth the solar wind is deflected and it flows around the geomagnetic field. This interaction results in the outer boundary of the magnetosphere called as the magnetopause. On the night side it also forms a comet shape area called geomagnetictail or magnetotail which has diameter around 40 RE. Another boundary called the bow shock forms in front of the dayside of the magnetopause as result of the motion of the Earth in the solar wind. The region between the magnetopause and the bow shock is called the magnetosheath which has a significant role in reducing speed of the solar wind particles to sub-magnetosonic speeds relative to the Earth. The cleft or polar cusp is the region in which some penetration of the solar wind is allowed to enter the ionosphere causing the slight kink to the magnetopause. In the central part of the magneto tail, when the field lines of different direction are located in very short distance causing they eliminate each other, there is a narrow region with zero field called the neutral sheet.

The plasmasphere region in the magnetosphere protected from the interference of the solar wind leads to ring currents related with the motion of ions in which the positive and negative ions move in opposite directions on the closed field lines. Out side the boundary of plasmaphere called plasmapause, the plasma is strongly influenced by the solar wind’s interaction. A few very energetic particle of the solar wind can also be able to penetrate into magnetosphere forming what is well known as the radiation belt or Van Allen Belt as result of the motion of the particle in the geomagnetic field experiencing an electromagnetic force which forces them to move around the field lines and send back and fore from pole to pole. Significant numbers of very energetic particles of the solar wind are also able to penetrate into magnetosphere under special condition i.e. the large increases of the solar wind’s intensity due to solar flares. They can travel and penetrate to the Ionosphere causing the magnetic storms and aurora.

There is evident from the magnetic observatory record that the geomagnetic field has a regular daily variation in which the solar daily variation and lunar daily variation plays a significant contribution in this daily variation. The solar daily variation, S, has a period 24 h while the lunar daily variation has period near 25 hour. During 24 h period, the additional field, D or the disturbance variation, can present and affect the regular daily variation. The solar quiet day variations, Sq, is a term where the geomagnetic field has a daily variation without extreme variations and it depends on the latitude and the local time. The solar disturbance daily variation, SD which is part of D, also present in the days with small disturbance or normal days. So, all of them can be formulated by using their relation with the difference between the total field and the average field (∆F) as

D = ∆F-Sq-L

The geomagnetic field sometimes shows the evident of the irregular disturbances on the magnetogram. The interaction of the solar wind with the geomagnetic field is the main factor in creating the irregular disturbances. When the intensity of these disturbances is very large, they are called a magnetic storm. The magnetic storm consists of three phases : the initial, main and recovery phases. The initial phase can be recognized as a sudden change called a sudden commencement. During the main phase, the horizontal component of the geomagnetic field experiences reduction in its intensity. The recovery phase is process in which the horizontal component increases significantly towards the auroral zone.
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Biosphere Reserves

A biosphere reserve is an international conservation designation given by UNESCO under its Programme on Man and the Biosphere (MAB). The World Network of Biosphere Reserves is the collection of all 531 biosphere reserves in 105 countries (as of May, 2008).

According to “The Statutory Framework of the World Network of Biosphere Reserves,” biosphere reserves are created “to promote and demonstrate a balanced relationship between humans and the biosphere.” Under article 4, biosphere reserves must “encompass a mosaic of ecological systems,” and thus consist of combinations of terrestrial, coastal, or marine ecosystems.

Through appropriate zoning and management, the conservation of these ecosystems and their biodiversity is sought to be maintained.

The design of the reserve must include a legally protected core area, a buffer area where non-conservation activities are prohibited, and a transition zone where approved practices are permitted. This is done with regard for the sustainable use of natural resources for the benefit of local communities. This effort requires relevant research, monitoring, education and training.

All the above are tools for implementing Agenda 21, the Convention on Biological Diversity and other international agreements.

Map showing the World Network of Biosphere Reserves as of 2007. Note: transboundary sites have been redistributed among the concerned countries for the locator map, hence, have been counted multiple times.

Biosphere reserves are areas of terrestrial, coastal or marine ecosystems that are internationally recognised under the Man and Biosphere (MAB) Programme of the United Nations Educational, Scientific and Cultural Organisation (UNESCO).

They form an international network of sites, nominated by national governments, but designated by UNESCO. The first reserves were nominated as long ago as 1976. By 2001, a network of 393 reserves in 94 countries had been developed.

Biosphere reserves are an attempt to reconcile the problems of conserving biodiversity and biological resources, with sustainable use of natural resources for people. They have three main functions:
Conservation of biodiversity (ecosystems, species and genes).
Sustainable local economic and human development compatible with conservation needs.
Logistical support for environmental research and monitoring.

Each biosphere reserve ideally consists of one or more core areas, a buffer zone and a transition zone.

CORE AREAS:

The core areas are securely protected sites for conserving biological diversity, monitoring ecosystems, carrying out non-destructive research and low impact uses.

BUFFER ZONES:

This surrounds the core area and is used for co-operative activities which do not damage the ecology of the area.

TRANSITION AREAS:

An area containing agricultural activities and local communities, where interested parties work together to reconcile economic and conservation needs, while developing local resources in a sustainable way.

Biosphere reserves are unusual in having flexible boundaries, which are not legally defined. They are mostly managed by more than one owner or agency.

links:http://www.countrysideinfo.co.uk/biospher_reserves/biospher_reserves.htm

http://en.wikipedia.org/wiki/Biosphere_Reserve

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ROAD BUILDING AND THE ROMANS

When the Romans began their conquest of Celtic Britain in 43AD, they found a haphazard collection of roads and paths, most connecting local fields and hamlets, but also some longer distance trade routes (e.g.. along the North Downs in Kent, and the Icknield Way along the Chilterns into Norfolk).

The Roman administration, however, needed a better network of roads to connect its new towns and army posts and to speed the flow of both trade goods and troops. In building their network of roads the Romans mostly ignored the Celtic paths, partly because the Roman towns and forts were built on new sites away from the Celtic settlements. Click here to view the Roman Road network

The most vital priority was the movement of troops and supplies from the channel ports of Richborough, Dover, and Lympne to the military centres at London, Colchester, and the front-line legionary forts. The first frontier was set up along a road extending from Exeter to Lincoln, running through Bath, Gloucester, and Leicester. This was known as the Fosse Way, the first great Roman road in Britain. The Fosse Way has been largely adapted by modern highways.

The next military push established a new frontier between Lincoln and York, Wroxeter and Chester, and Gloucester and Caerleon. After these “front-line” roads had been established. The Romans turned their attention to expanding the network of minor roads within their new possessions, to better aid the flow of trade.

By 82AD the Romans had pushed north as far as a line between the Clyde and the Firth of Forth. During this campaign alone the army built over 60 forts and over 1200 miles of roads. The imperial posting service, used by Roman officials, maintained inns and relays of horses at intervals of 30 to 50 kilometres along the roads.

The minor roads (sometimes called “economic roads”) were also built by the Roman army to link economic centres, such as the Mendip lead mines and the Nene potteries, with administrative capitals like Silchester, and the coastal ports. At a best guess there were between 8000-10,000 miles of roads constructed during the first hundred years of Roman occupation. There was a third level of roads at the local level, connecting villas, temples, farms, and villages to larger roads and market towns. The full extent of this road building is apparent when you consider that according estimates by historians, no village or farm was more than 7 miles from a purpose-built road!

It is a fallacy to think that Roman roads are always straight. The Roman engineers were no fools – if there was a natural obstacle in the way, the road naturally deviated to go around it. The Romans had yet to invent front axle steering, so sharp corners where avoided.

That said, for the most part Roman roads were laid out in straight lines between sighting landmarks. Small hills were cut through, and wet ground covered by causeways, or timber embankments.

So, how did the Romans build these famous roads of theirs? The roads were literally highways, raised up on a cambered bank of material dug from roadside ditches. In general there were 3 layers. The first layer of large stones was covered by a second layer of smaller stones, then a top layer of gravel or small stones. Each layer varied in depth from 2-12 inches.

The choice of material depended upon what was locally available; in the chalk areas like the Wessex Downs a mix of chalk, flint, and gravel was used. The paved area was edged with upright stones to provide stability, and the major roads had ditches to each side, about 84 feet apart.

Tracing the course of Roman roads can be a fun activity. Large scale maps help, as does the excellent Ordnance Survey map of Roman Britain. Almost any straight stretch of road is a candidate, and often the roads follow parish boundaries or hedges.

The best-preserved examples of Roman roads in Britain today can be found at Wheeldale Moor (North Yorkshire), Holtye (Sussex), and Blackstone Edge (South Yorkshire). A clue to the existence of former Roman roads is the prefix “street”, as in Streatley, or Streatham.

After the fall of the Roman Empire the road system fell into a state of disrepair and by the end of the Middle Ages, there was in effect no road system in the country. The only routes available were unpaved tracks, muddy and impassable in winter and dusty and impassable in summer. Diversions around particularly poor stretches resulted in sinuous alignments. The state of the roads combined with the general lawlessness at the time meant only the determined or insane travelled them. Much the same as today .

Onward to Modern Road Building

The first change in this attitude came in 1555 when an Act of Parliament was passed imposing a duty on all parishes to maintain it’s roads. Also included in the Act was the creation of the position of a Surveyor of Highways. This was unpaid and under resourced though and when combined with the lack of technical skills it is no surprise that the post became distinctly unpopular and ineffective. Local peasants where given a bursary to “mend the ways”.

This lack of resources meant that the first major road was not established until the latter part of the seventeenth century. These roads were known as turnpike roads where the road user paid a toll. The first sections were known as the Great North Road and has since become the A1 trunk road. In the following century Turnpike Trusts were established to provide turnpike roads along major routes in the United kingdom. In this improved financial climate road building techniques evolved thanks to the work of pioneers such as Telford and Macadam. By about 1830 a system of well paved built roads existed such that the only constraints on road traffic and travel times were imposed by the nature of road vehicles.

The next improvement came about with the advent of the railways. With rapid transport between towns now possible, the turnpikes became uneconomical and whilst road building in towns continued apace the turnpike trusts collapsed. Legislation in the late 19th century set the scene for the current administrative arrangements for highway construction and maintenance but the technology remained primitive and empirical. Only in recent years has that situation improved to any extent and even now most road design is based on empirical relationships and experimental work.

The present situation is almost a complete reversal, with funding for new roads coming from the private sector. In exchange for building and maintaining the road the owners are paid a toll by the government for each vehicle using the road, a sort of modern turnpike system.

Terminology:

Road – derived from Ride or Rode
Street – Romans called roads Via Straeta which means a route or way
Pavement – From the Roman Pavimentum, the paving of the roads
Way – From the dark ages, i.e, Ridgeway tracks across escarpments
Holloway – A way eroded to form a hollow
Highway – Roads built on an elevated pavement for drainage
Byway – A way that is only accessible during the dry months across swamps and marshes
Carriageway – A way for carriages
Footway – A way by foot on either
Waterway – The first canals where known as waterways
Parkway – A landscaped way, usually associated with America who where the first to landscape the ways
Clearway – A way where no carriage may be left or may stop to obstruct the road

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Volcanic Activity at Llaima, Chile

SERNAGEOMIN reported that although observations of Llaima were inhibited by cloud cover on 2 July, incandescence from the 1-km-long lava flow on the W flank was observed. An overflight revealed cooled blocks at the end of the lava flow and a second lava flow (on the SW flank) about 150 m S of the first. The lava flows issued from the base of a pyroclastic cone in the main crater. Observers to the W witnessed an explosion from the summit that ejected material 1 km high. The material landed on the SW flank and up to 3.5 km away on the SE flank. Vapor plumes from the main crater were seen on 3 July. An overflight on the same day revealed that the lava flow on the W flank had advanced and generated a small lahar.

On 4 July, SERNAGEOMIN characterized the eruptive style as weakly Strombolian. A small explosion from the pyroclastic cone in the main crater produced an ash plume that rose 250-400 m and drifted 50 km SE. During 4-5 July, observers reported sporadic explosions and incandescence at the summit. Fine ashfall was reported in areas nearby. On 6 July, seismicity decreased to low levels. An overflight on 7 July revealed that the lava emission rate had decreased for both flows. The lava flow on the W flank was about 1.6 km long and the flow on the SW flank was about 2 km long. Bluish gas was emitted from the main crater.

Source: Servicio Nacional de Geología y Minería (SERNAGEOMIN) – “Reports provided courtesy of the Smithsonian’s Global Volcanism Program and the US Geological Survey’s Volcano Hazards Program.” News clip from Reuters.

originally posted by http://volcanoworld.wordpress.com/

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