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  • richardmitnick 8:45 am on September 17, 2019 Permalink | Reply
    Tags: "Explainer: what happens when magnetic north and true north align?", Agonic lines, Angle of declination, Geographic north, Magnetic North,   

    From CSIROscope: “Explainer: what happens when magnetic north and true north align?” 

    CSIRO bloc

    From CSIROscope

    17 September 2019
    Paul Wilkes

    1
    Very rarely, depending on where you are in the world, your compass can actually point to true north. Image: Shutterstock

    At some point in recent weeks, a once-in-a-lifetime event happened for people at Greenwich in the United Kingdom.

    Magnetic compasses at the historic London area, known as the home of the Prime Meridian, were said to have pointed directly at the north geographic pole for the first time in 360 years.

    This means that, for someone at Greenwich, magnetic north (the direction in which a compass needle points) would have been in exact alignment with geographic north.

    Geographic north (also called “true north”) is the direction towards the fixed point we call the North Pole.

    Magnetic north is the direction towards the north magnetic pole, which is a wandering point where the Earth’s magnetic field goes vertically down into the planet.

    The north magnetic pole is currently about 400km south of the north geographic pole, but can move to about 1,000km away.

    2
    The lines of the Earth’s magnetic field come vertically out of the Earth at the south magnetic pole and go vertically down into the Earth at the north magnetic pole. Image: Nasky/Shutterstock

    How do the norths align?

    Magnetic north and geographic north align when the so-called “angle of declination”, the difference between the two norths at a particular location, is 0°.

    Declination is the angle in the horizontal plane between magnetic north and geographic north. It changes with time and geographic location.

    On a map of the Earth, lines along which there is zero declination are called agonic lines. Agonic lines follow variable paths depending on time variation in the Earth’s magnetic field.

    3
    The declination angle varies between -90° and +90°.

    Currently, zero declination is occurring in some parts of Western Australia, and will likely move westward in coming years.

    That said, it’s hard to predict exactly when an area will have zero declination. This is because the rate of change is slow and current models of the Earth’s magnetic field only cover a few years, and are updated at roughly five-year intervals.

    At some locations, alignment between magnetic north and geographic north is very unlikely at any time, based on predictions.

    4
    Locations on this 2019 map with a green contour line have zero declination. Lines along which declination is zero are called agonic lines.

    The ever-changing magnetic poles

    Most compasses point towards Earth’s north magnetic pole, which is usually in a different place to the north geographic pole. The location of the magnetic poles is constantly changing.

    Earth’s magnetic poles exist because of its magnetic field, which is produced by electric currents in the liquid part of its core. This magnetic field is defined by intensity and two angles, inclination and declination.

    The relationship between geographic location and declination is something people using magnetic compasses have to consider. Declination is the reason a compass reading for north in one location is different to a reading for north in another, especially if there is considerable distance between both locations.

    Bush walkers have to be mindful of declination. In Perth, declination is currently close to 0° but in eastern Australia it can be up to 12°. This difference can be significant. If a bush walker following a magnetic compass disregards the local value of declination, they may walk in the wrong direction.

    The polarity of Earth’s magnetic poles has also changed over time and has undergone pole reversals. This was significant as we learnt more about plate tectonics in the 1960s, because it linked the idea of seafloor spreading from mid-ocean ridges to magnetic pole reversals.

    Geographic north

    Geographic north, perhaps the more straightforward of the two, is the direction that points straight at the North Pole from any location on Earth.

    When flying an aircraft from A to B, we use directions based on geographic north. This is because we have accurate geographic locations for places and need to follow precise routes between them, usually trying to minimise fuel use by taking the shortest route. All GPS navigation uses geographic location.

    Geographic coordinates, latitude and longitude, are defined relative to Earth’s spheroidal shape. The geographic poles are at latitudes of 90°N (North Pole) and 90°S (South Pole), whereas the Equator is at 0°.

    An alignment at Greenwich

    For hundreds of years, declination at Greenwich was negative, meaning compass needles were pointing west of true north.

    At the time of writing this article I used an online calculator to discover that, at the Greenwich Observatory, the Earth’s magnetic field currently has a declination just above zero, about +0.011°.

    The average rate of change in the area is about 0.19° per year, which at Greenwich’s latitude represents about 20km per year. This means next year, locations about 20km west of Greenwich will have zero declination.

    It’s impossible to say how long compasses at Greenwich will now point east of true north.

    Regardless, an alignment after 360 years at the home of the Prime Meridian is undoubtedly a once-in-a-lifetime occurrence.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    SKA/ASKAP radio telescope at the Murchison Radio-astronomy Observatory (MRO) in Mid West region of Western Australia

    So what can we expect these new radio projects to discover? We have no idea, but history tells us that they are almost certain to deliver some major surprises.

    Making these new discoveries may not be so simple. Gone are the days when astronomers could just notice something odd as they browse their tables and graphs.

    Nowadays, astronomers are more likely to be distilling their answers from carefully-posed queries to databases containing petabytes of data. Human brains are just not up to the job of making unexpected discoveries in these circumstances, and instead we will need to develop “learning machines” to help us discover the unexpected.

    With the right tools and careful insight, who knows what we might find.

    CSIRO campus

    CSIRO, the Commonwealth Scientific and Industrial Research Organisation, is Australia’s national science agency and one of the largest and most diverse research agencies in the world.

     
  • richardmitnick 8:41 am on May 22, 2019 Permalink | Reply
    Tags: Earth has its own magnetic field., , Lancaster University, Magnetic North, , , Reports that the magnetic north pole has started moving swiftly at 50km (31 miles) per year   

    From Lancaster University via EarthSky: “Magnetic north is shifting fast. What’ll happen to the northern lights?” 

    lancaster-u-uk-bloc

    From Lancaster University

    via

    1

    EarthSky

    May 22, 2019
    Nathan Case,
    Lancaster University

    As magnetic north shifts increasingly away from the geologic north pole – towards Siberia – studies suggest the northern lights could move with it.

    1
    Northern lights over Lake Lappajärvi in Finland. Image via Santeri Viinamäki.

    Like most planets in our solar system, the Earth has its own magnetic field. Thanks to its largely molten iron core, our planet is in fact a bit like a bar magnet.

    3

    It has a north and south magnetic pole, separate from the geographic poles, with a field connecting the two. This field protects our planet from radiation and is responsible for creating the northern and southern lights – spectacular events that are only visible near the magnetic poles.

    However, with reports that the magnetic north pole has started moving swiftly at 50km (31 miles) per year – and may soon be over Siberia – it has long been unclear whether the northern lights will move too. Now a new study, published in Geophysical Research Letters, has come up with an answer.

    Our planetary magnetic field has many advantages. For over 2,000 years, travellers have been able to use it to navigate across the globe. Some animals even seem to be able to find their way thanks to the magnetic field. But, more importantly than that, our geomagnetic field helps protect all life on Earth.

    Earth’s magnetic field extends hundreds of thousands of kilometers out from the center of our planet – stretching right out into interplanetary space, forming what scientists call a “magnetosphere”.

    Magnetosphere of Earth, original bitmap from NASA. SVG rendering by Aaron Kaase

    This magnetosphere helps to deflect solar radiation and cosmic rays, preventing the destruction of our atmosphere. This protective magnetic bubble isn’t perfect though, and some solar matter and energy can transfer into our magnetosphere. As it is then funneled into the poles by the field, it results in the spectacular displays of the northern lights.

    A wandering pole

    Since Earth’s magnetic field is created by its moving, molten iron core, its poles aren’t stationary and they wander independently of one another. In fact, since its first formal discovery in 1831, the north magnetic pole has travelled over 1,240 miles (2,000 km) from the Boothia Peninsula in the far north of Canada to high in the Arctic Sea. This wandering has generally been quite slow, around 9km (6 mi) a year, allowing scientists to easily keep track of its position. But since the turn of the century, this speed has increased to 30 miles (50 km) a year. The south magnetic pole is also moving, though at a much slower rate (6-9 miles, or 10-15 km a year).

    This rapid wandering of the north magnetic pole has caused some problems for scientists and navigators alike. Computer models of where the north magnetic pole might be in the future have become seriously outdated, making accurate compass-based navigation difficult. Although GPS does work, it can sometimes be unreliable in the polar regions. In fact, the pole is moving so quickly that scientists responsible for mapping the Earth’s magnetic field were recently forced to update their model much earlier than expected.

    Will the aurora move?

    The aurora generally form in an oval about the magnetic poles, and so if those poles move, it stands to reason that the aurora might too. With predictions suggesting that the north pole will soon be approaching northern Siberia, what effect might that have on the aurora?

    The northern lights are currently mostly visible from northern Europe, Canada and the northern U.S. If, however, they shifted north, across the geographic pole, following the north magnetic pole, then that could well change. Instead, the northern lights would become more visible from Siberia and northern Russia and less visible from the much more densely populated U.S./Canadian border.

    Fortunately, for those aurora hunters in the northern hemisphere, it seems as though this might not actually be the case. A recent study made a computer model of the aurora and the Earth’s magnetic poles based on data dating back to 1965. It showed that rather than following the magnetic poles, the aurora follows the “geomagnetic poles” instead. There’s only a small difference between these two types of poles – but it’s an important one.

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    Magnetic versus geomagnetic poles. Image via Wikipedia.

    The magnetic poles are the points on the Earth’s surface where a compass needle points downwards or upwards, vertically. They aren’t necessarily connected and drawing a line between these points, through the Earth, would not necessarily cross its center. Therefore, to make better models over time, scientists assume that the Earth is like a bar magnet at its center, creating poles that are exactly opposite each other – “antipodal”. This means that if we drew a line between these points, the line would cross directly through the Earth’s center. At the points where that line crosses the Earth’s surface, we have the geomagnetic poles.

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    Positions of the north magnetic pole (red) and the geomagnetic pole (blue) between 1900 and 2020. Image via British Geological Survey.

    The geomagnetic poles are a kind of reliable, averaged out version of the magnetic poles, which move erratically all the time. Because of that, it turns out they aren’t moving anywhere near as fast as the magnetic north pole is. And since the aurora seems to follow the more averaged version of the magnetic field, it means that the northern lights aren’t moving that fast either. It seems as though the aurora are staying where they are – at least for now.

    We already know that the magnetic pole moves. Both poles have wandered ever since the Earth existed. In fact, the poles even flip over, with north becoming south and south becoming north. These magnetic reversals have occurred throughout history, every 450,000 years or so on average. The last reversal occurred 780,000 years ago meaning we could be due for a reversal soon.

    So rest assured that a wandering pole, even a fast one, shouldn’t cause too many problems – except for those scientists whose job it is to model it.

    Bottom line: Studies suggest that the northern lights could move as the Earth’s magnetic north pole heads towards Siberia.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    lancaster-u-uk-campus

    Lancaster University (legally the University of Lancaster) is a collegiate public research university in Lancaster, Lancashire, England. The university was established by Royal Charter in 1964, one of several new universities created in the 1960s.

    The university was initially based in St Leonard’s Gate in the city centre, before moving in 1968 to a purpose-built 300 acres (120 ha) campus at Bailrigg, 4 km (2.5 mi) to the south. The campus buildings are arranged around a central walkway known as the Spine, which is connected to a central plaza, named Alexandra Square in honour of its first chancellor, Princess Alexandra.

    Lancaster is one of only six collegiate universities in the UK; the colleges are weakly autonomous. The eight undergraduate colleges are named after places in the historic county of Lancashire, and each have their own campus residence blocks, common rooms, administration staff and bar.

    Lancaster is ranked in the top ten in all three national league tables, and received a Gold rating in the Government’s inaugural (2017) Teaching Excellence Framework. In 2018 it was awarded University of the Year by The Times and Sunday Times Good University Guide, and achieved its highest ever national ranking of 6th place within the guide’s national table. The annual income of the institution for 2016–17 was £267.0 million of which £37.7 million was from research grants and contracts, with an expenditure of £268.7 million.

     
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