Earth’s geographic and magnetic axes are oriented at a slight angle to each other

fateme alaie Q8W2r2aCmaw unsplash
fateme alaie Q8W2r2aCmaw unsplash

The Earth’s geographic axis is inclined at an angle of about 23.5° with respect to the orbital plane. 

The Earth’s magnetic field is also tilted at an angle but the reason for this tilt is not fully understood. how are earth’s geographic and magnetic axes oriented relative to each other?

There are hypotheses that one or more solar eruptions occurred in 1859, 1866, or 1872,

 which could have tilted the north polarity axis by about 6 degrees from where it had been before its polarity reversal in 1800.

 However, evidence remains inconclusive. 

Another hypothesis is that the Earth’s magnetic field could have been tilted by a collision with a celestial body such as an asteroid or comet. 

A third hypothesis proposes that the tilt may have been caused by the gravitational pull of Saturn. 

This last hypothesis is supported by calculations which show that 

if Saturn had been nearby to the Earth in 1859 and had passed near the north pole at around the same time,

 there would have been a stronger than normal gravitational pull and it is possible that this could explain why we see a tilt of about 6 degrees at present.

The Earth’s orientation of its geographic axis is 23.5° with respect to the orbital plane.

 The gravitational pull of the Sun acts upon matter on Earth to produce a magnetic field

 that deflects incoming stellar radiation by an angle equal to the angle between the Sun 

 our orbital plane. Because of this, our magnetic field inclines at an angle of 23.5° with respect to the orbital plane (see image).

The Earth’s orbital inclination (also called the obliquity of the ecliptic) is currently 23.5° with respect to

 the orbital plane (roughly 2° less than its precession period of 25,761.09 solar revolutions; see infobox at right).

 Its precession period is near 25,761.09 years (11.78 years in excess of the spin period), 

corresponding to an angular interval of about 4 radians (approximately 37 minutes of arc) in its rotational period (see infobox at left).

During its precession, the Earth’s obliquity is slightly changed by at least approximately 0.3° or 1.0° on either side of this value, 

so it is unlikely that the Earth’s obliquity at present has remained unchanged during the past 4 million years. 

The obliquity of the ecliptic has probably not changed by more than 0.05° since at least 2 million years ago, 

due to secular changes in solar activity, plate tectonics and other factors over that period. 

The last time the obliquity drifted more than 0.2° was approximately 250 thousand years ago (averaged over some 800 thousand years).

As the Earth orbits around the Sun, configurations of its orbital plane and of the spin axis of the 

Earth produce patterns in the distribution of day and night. 

The configuration that had existed for 4 million years prior to 2008 was called “the precessional cycle”, which resulted 

 one side of the Earth being summer, while its other side was winter.

 Because this cycle is so long, it has made it easier for people to determine ancient alignments. 

Furthermore, as discussed below, many ancient cultures have been aware of this precessional cycle.

In 2008 the tilt changed from 23.4° to 23.5°, causing the precessional cycle to change from the summer hemisphere to winter.

The obliquity of the ecliptic changes only slightly over time, but it does change.

 For example, there is a period of 1-1/3 precession cycles between pairs of oppositions—

that is, approximately 18000 years between rounds of dates on which the Sun crosses the ecliptic through nearly exactly opposite points. 

This means that two reversals can occur in that interval, or one longer reversal can occur after only about 12 reversals.

 At present, however, Earth has not done this since 1859 (and may not do so for some thousands of years). 

At the end of this time, the obliquity will be 23° 26′ 35″.

A more frequent and smaller cycle (1 precession cycle in 371 years) is the Chandler wobble. 

This also changes the declination by about 0.2° per year, with an amplitude of about 3° in a period of a few decades. 

A second less-regular effect is due to axial precession due to the Moon 

which speeds up slightly during perigee and slows down slightly during apogee 

with a cycle time of 18.6 years and a change of about 0.08° over that period.

The tilt of the Earth’s axis with respect to the Sun is known as the obliquity of the ecliptic.

 It is currently 23° 26′. Its precession cycle has two components, one slow component which has a period of 25,761.09 years, 

 another that is about twice as fast but which takes about 11 years less to complete one cycle. 


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