Watch for cracks in the magnetosphere
This week marked the vernal equinox. It is the time of the year when the length of daylight is exactly equal to the length of night. Except, on March 20, it wasn’t if you simply look up sunrise and sunset. Sunrise was at 7:12 a.m. and sunset was at 7:24 p.m. – a total of 12:12 hours of daylight. The difference is due to the definition of sunset and sunrise versus the definition of a day. The time assigned to sunrise is the moment the first part of the sun clears the virtual horizon at a particular occasion. Sunset is when the last visible part of the sun descends below the horizon. However, since the first part of the sun to clear the horizon is on the opposite side of the sun’s face, this time is a little longer due to the time it takes the sun to set or rise.
If you measure the time from when the sun first clears the horizon to the time it first touches the horizon, it would be exactly 12 hours.
At the equinoxes, the day is 12 hours long over the entire planet – from one pole to another. The website timeanddate.com provides graphical data for daylight hours at points around the planet and shows the variation in the length of daylight hours, along with twilight regions. It is an interesting site to explore.
In any case, the vernal equinox marks the point in the celestial cycles where daylight takes over and the days get longer by about four minutes and 20 seconds per day. It is the beginning of spring and if it would quit snowing, we might notice that.
The vernal and autumnal equinoxes are also the point in the year where cracks appear in the Earth’s magnetosphere. Our planet is a giant magnet with magnetic lines of force filling the space above us. If you have ever played with a magnet and iron filings, you would likely have seen the lines of force making up a magnetic field.
Our magnetosphere protects our planet. For the most part, it shepherds the cosmic debris spewed out by the sun around us.
Protons, electrons, ions, and other subatomic particles follow the lines of force, and are pushed north or south giving Earth a miss.
During a coronal mass ejection or CME, enough material is thrown off by the Sun to overwhelm our magnetosphere. This is when the material travels to the poles and descends into our upper atmosphere. The interaction of this space debris with the gases high up results in the Aurora Borealis and the Aurora Australis – the northern and southern lights.
Around the equinoxes, when our magnetosphere breaks down, auroras can form even if there isn’t a CME. Ordinary solar winds are capable of penetrating deep enough to react with nitrogen and oxygen molecules in the upper atmosphere. This past week has seen some pretty spectacular auroras around across the north. We might even see one in Prince George if the clouds go away.
The reason the cracks appear is a result of the cancellation of the magnetic field. Most people recognized two north poles on a magnet repel other as do two south poles.
A north and a south pole attract but, to a certain extent, they also cancel their mutual magnetic fields.
At the equinoxes, the north-south axis of Earth’s magnetic field is oriented perpendicular to the line between us and the Sun. This means Earth is effectively presenting the side of its magnet to the Sun. When this field is engaged with a magnetized solar wind, it causes the whole magnetosphere to shake or ring. And cracks appear allowing the solar wind through.
This is called the Russell-McPheron effect, named after the researchers who first described it in 1972. It is an annual variation in the Earth’s magnetosphere and explains why the auroras are more prominent around the equinoxes.
Cracks in the magnetosphere also result in disruptions in satellite communications which can lead to poor reception and scrambled signals
One final point about the magnetosphere – it helps to protect us from cosmic rays. These rays are high energy particles of unknown origin which appear to permeate much of space. Cosmic rays entering our atmosphere result in the formation of positrons and other sub-atomic particles which can have negative health impacts for living organisms.