This is an amazing video of Earth’s outer core surrounded by magnetic field lines during the ongoing or upcoming geomagnetic reversal.
To understand the video by J. Favre, A. Sheyko: The sphere is painted according to values of the radial component of the magnetic field B on the CMB (Core-Mantle Boundary): reds are where B points out of the Earth’s center, blues – inwards. The field lines are colored according to the direction of the magnetic field: orange color – outwards (the radial component of the field is opposite to the gravity), blue – inwards.
What is a geomagnetic reversal?
A geomagnetic reversal is a change in a planet’s magnetic field such that the positions of magnetic north and magnetic south are interchanged, while geographic north and geographic south remain the same.
The Earth’s field has alternated between periods of normal polarity, in which the direction of the field was the same as the present direction, and reverse polarity, in which the field was the opposite. These periods are called chrons.
The time spans of chrons are randomly distributed with most being between 0.1 and 1 million years with an average of 450,000 years. Most reversals are estimated to take between 1,000 and 10,000 years. The latest one, the Brunhes–Matuyama reversal, occurred 780,000 years ago, and may have happened very quickly, within a human lifetime.
A brief complete reversal, known as the Laschamp event, occurred only 41,000 years ago during the last glacial period. That reversal lasted only about 440 years with the actual change of polarity lasting around 250 years. During this change the strength of the magnetic field weakened to 5% of its present strength.