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World Magnetic Declination

For the first time in several centuries, compasses in Greenwich will point at true north

Compasses in Greenwich will be pointing towards the true north for the first time. This coincidence of magnetism and time has not occurred for almost 360 years. It is set to occur in the coming fortnight and it is a reminder of the fact that magnetic north pole of Earth is constantly wandering, unlike Earth’s geographic north pole. 

The angular difference between the geographic and magnetic meridian at any place is known as magnetic declination. Although this difference does not affect the normal citizens in a significant way, this disparity can last for a long time. For almost a hundred years in the United Kingdom, the compass needles have been pointing to west of actual north since the magnetic declination has been negative. 

This is not permanent. The agonic, an invisible line which joins the north and south magnetic poles of Earth which also represents the zero declination has been shifting in the western direction at a rate of nearly 20 kilometres or 12 miles every year

If this rate continues, it will be passing through Greenwich in this month which is the site of the Greenwich Royal Observatory thus creating a historic occurrence. Ciaran Beggan, geomagnetism researcher at British Geological Survey said that in the month of September, the agonic will meet zero longitudes at Greenwich. Since the creation of the Observatory, this is the first time that geomagnetic and geographic coordinate systems will be coinciding at this place. 

The Royal Observatory was founded at the decree of King Charles II in 1675. It is a coincidence that compasses in Greenwich due to zero declination also pointed towards true north. From that time, the agonic has been shifting as Earth’s magnetic north pole has been varying in its position due to changes in the molten outer core. 

Beggan said that the agonic will continue to pass across the United Kingdom for the next 15-20 years. So this phenomenon is expected to continue beyond circumstantial synchronicity of this September. By 2040, compasses will most probably point east of true north. Beyond this scientists cannot provide any prediction as it is difficult to estimate the future magnetic movements. Beggan said that currently, it is not possible to predict how the magnetic field will change in the time span of several decades. For 360 more years in the United Kingdom, the compass may point towards the east of the true north direction. 

Earth’s Magnetic Field Reversal Took Three Times Longer Than Thought

Earth’s magnetic field reversal takes much longer time than we thought

Human beings could not record the last time reversal of the magnetic poles of Earth occurred. However now with the help of the flow of ancient lava, it is possible for the scientists to estimate the duration of this phenomenon. 

A group of scientists used volcanic records for studying the last magnetic field reversal that occurred almost 780,000 years ago. They found that this reversal might have taken much longer duration than what was expected by scientists previously. The paper has been published in Science Advances journal

In the last 2.5 million years, the magnetic field of Earth reversed dozens of times, when north turned to the south and vice versa. It is known to the scientists that the last reversal occurred in the time of Stone Age but they have fewer details about the duration of the reversal and when it might occur next. 

Scientists relied on the lava flow sequences which erupted near to the last reversal for estimating its duration. With the help of this method, scientists estimated that it went on for 22000 years which is indeed quite longer than the past estimates of 1000 to 10000 years. 

Bradley Singer, a geoscience professor at the University of Wisconsin-Madison and the study’s lead author said the last reversal was quite complex which started within the outer core of the Earth. When he was performing studies on a Chilean volcano in 1993, he stumbled on a sequence of the lava which had partially recorded the process of reversal. In an effort to date the lava, Singer observed weird magnetic field directions in the lava flow sequences. These are some of the rarest records and Singer is one of the few scientists to date them. So this incident led to his life-long career goal to understand and explain the timings of the reversals of the magnetic field. 

Reversals occur when the iron molecules in the outer spinning core of the Earth start to move in the opposite direction as the surrounding iron molecules around them. With an increase in numbers, the magnetic field present in the core of the Earth is offset by the molecules. As a result, the magnetic field of our planet gets weaker. John Tarduno, a geophysics professor at the University of Rochester said that this kind of duration of the reversal would weaken the protection of Earth from solar radiations.

Additional effects might include genetic mutations or extinctions when the exposure to UV Sunrays increases. Increasing Sun particles entering Earth would disrupt communication systems, GPS and other satellite-based communication. 

Reports of a magnetic field in direction of Canadian Arctic to Siberia has started discussions over if the next field reversal is imminent and what effect would it have on life. Singer said that there is very less evidence that the decrease in field strength or shifting in the north pole’s position would mean a reversal in polarity in the coming 2000 years. Volcanic records are the best type of records of a particular place and time. 

Journal Reference: Science Advances journal

Mini Sun

Researchers recreate mini sun for studying solar winds and plasma burps

The stars in our universe have a magnetic field that interacts with the winds which they produce including our sun. As a result of the collaboration between the Sun’s magnetic field and the solar wind leads to the formation of a heliospheric magnetic field like a spiralling structure known as the Parker spiral. This spiral is important for administering the plasma processes that source the solar wind.

According to a new study at the University of Wisconsin-Madison, the physicists have reported the creation of a mini sun like a laboratory model of the Parker spiral system based on the idea of rotating plasma magnetosphere and measurement of the global structure and dynamic behaviour. The study has been published in Nature Physics.

Physicists have access to this Big Red Ball, which is a three-meter wide hollow sphere which contains different probes and a strong magnet at the centre. The helium gas is siphoned and ionized to create plasma and then an applied electric field alongside the magnetic field which copies the ideal case of spinning plasma and the electromagnetic fields of the sun. Estimations can be taken at numerous points inside the bass which enables physicists to study the solar phenomena in three dimensions.

They have an option to replicate the Parker Spiral, a magnetic field which covers the entire solar system, the magnetic field transmits straight out of the sun. From there onwards, the solar wind dynamics take over and haul the magnetic field into a spiral.

A graduate student in the Physics department at UW-Madison, Ethan Peterson said that the satellite measurements are pretty consistent with the Parker Spiral model, only at one point at a time and so can never make simultaneous and map it on a large scale map. The plasma from the sun’s plasma burps fuel up the slow solar winds.

The speed of light and magnetic field are probed and the data has mapped a region where plasma is moving fast enough and where the plasma could break off and eject radially. The ejections have been spotted by satellites and no one knows the reason as to what drives them. They found similar burps in the experiment and found out how they developed.

The work has shown that understanding fundamental physics of these processes is possible through laboratory experiments and the Big Red Ball being funded as a National User Facility allows scientists to study the physics of solar winds. The Earthbound experiments can not replace satellite missions like the Parker Solar Probe which was launched in August 2018 can reach the Alfven surface and can even dip below it. It is expected to provide direct measurements of the solar wind.

Journal Reference: Nature Physics