APOD: Jupiter's Magnetic Field from Juno (2020 Feb 25)

[APOD Robot]

Jupiter's Magnetic Field from Juno

Explanation: How similar is Jupiter's magnetic field to Earth's? NASA's robotic Juno spacecraft has found that Jupiter's magnetic field is surprisingly complex, so that the Jovian world does not have single magnetic poles like our Earth. A snapshot of Jupiter's magnetic field at one moment in time, as animated from Juno data, appears in the featured video. Red and blue colors depict cloud-top regions of strong positive (south) and negative (north) magnetic fields, respectively. Surrounding the planet are imagined magnetic field lines. The first sequence of the animated video starts off by showing what appears to be a relatively normal dipole field, but soon a magnetic region now known as the Great Blue Spot rotates into view, which is not directly aligned with Jupiter's rotation poles. Further, in the second sequence, the illustrative animation takes us over one of Jupiter's spin poles where red magnetic hotspots are revealed to be extended and sometimes even annular. A better understanding of Jupiter's magnetic field may give clues toward a better understanding of Earth's enigmatic planetary magnetism.

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[Antony Rawlinson]

Intriguing. At first I thought it was suggesting that the Great Red Spot was the southern magnetic pole, but the text refers to the Great Blue Spot. Are they associated?

[orin stepanek]

? Confusing to me!

[Leon1949Green]

Same question as Antony Rawlinson.

[TheZuke!]

And I thought I was having a bad hair day!

[RJN]

Due to an inaccuracy in the text, the line

Surrounding the planet are imagined lines of constant magnetic field strength.

has been changed to

Surrounding the planet are imagined magnetic field lines.

on the main NASA APOD. I thank an emailer for pointing this out. I have taught undergraduate E&M but still did not think this through well enough when writing the text! I apologize for the oversight.
- RJN

PS: A magnetic field line extends in the direction that a magnetic charge (if it existed) would feel an acceleration due to the magnetic field.

[Boomer12k]

I am with Anthony.... Intriguing...It reminds me of the sun's... though the sun's is all over the place...

:---[===] *

[Fred the Cat]

Juno has uncovered the dawn of a bad hair day. Like our notorious leader, perhaps a hat is in order? No, that would just lead to an accusation of a cover-up.

[MarkBour]

Really amazing! ... I was expecting something simpler.

Wikipedia barely mentions this "Great Blue Spot", and that's probably a bad name to give it, since people who hear of it will likely start looking for a large blue spot on Jupiter's cloud tops ... and I may be wrong, but I don't think there is any visible cloud feature there.

From Wikipedia: https://en.wikipedia.org/wiki/Magnetosphere_of_Jupiter under the section "Internal magnetic field" ...

Jupiter's magnetic field rotates at the same speed as the region below its atmosphere, with a period of 9 h 55 m. No changes in its strength or structure had been observed since the first measurements were taken by the Pioneer spacecraft in the mid-1970s, until 2019. Analysis of observations from the Juno spacecraft show a small but measurable change from the planet's magnetic field observed during the Pioneer era. In particular, Jupiter has a region of strongly non-dipolar field, known as the "Great Blue Spot", near the equator. This may be roughly analogous to the Earth's South Atlantic Anomaly. This region shows signs of large secular variations.

So, this was the first I learned of the idea that Earth has a similar anomaly, and that this anomaly is a serious issue for operations in low Earth orbit. Kind of a "Bermuda Triangle" of nearby space. (It was possibly a cause factor in the destruction of the Japanese Hitomi satellite observatory.)

I wonder if Jupiter's magnetic field is jut as dynamic as Earth's. Will it be able to undergo magnetic reversals, like Earth does?

[BDanielMayfield]

So Jupiter is magnetically tri-polar?

[neufer]

So, this was the first I learned of the idea that Earth has a similar anomaly, and that this anomaly is a serious issue for operations in low Earth orbit. Kind of a "Bermuda Triangle" of nearby space. (It was possibly a cause factor in the destruction of the Japanese Hitomi satellite observatory.)

The South Atlantic Anomaly at an altitude of approximately 560 kilometers

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<<The South Atlantic Anomaly (SAA) is an area where the Earth's inner Van Allen radiation belt comes closest to the Earth's surface, dipping down to an altitude of 200 kilometres. This leads to an increased flux of energetic particles in this region and exposes orbiting satellites to higher-than-usual levels of radiation.

The effect is caused by the non-concentricity of the Earth and its magnetic dipole. The SAA is the near-Earth region where the Earth's magnetic field is weakest relative to an idealized Earth-centered dipole field.

The South Atlantic Anomaly is of great significance to astronomical satellites and other spacecraft that orbit the Earth at several hundred kilometers altitude; these orbits take satellites through the anomaly periodically, exposing them to several minutes of strong radiation, caused by the trapped protons in the inner Van Allen belt. The International Space Station, orbiting with an inclination of 51.6°, requires extra shielding to deal with this problem. The Hubble Space Telescope does not take observations while passing through the SAA. Astronauts are also affected by this region, which is said to be the cause of peculiar "shooting stars" (phosphenes) seen in the visual field of astronauts, an effect termed the cosmic ray visual phenomena. Passing through the South Atlantic Anomaly is thought to be the reason for the failures of the Globalstar network's satellites in 2007.

The PAMELA experiment, while passing through the SAA, detected antiproton levels that were orders of magnitude higher than expected. This suggests the Van Allen belt confines antiparticles produced by the interaction of the Earth's upper atmosphere with cosmic rays.

NASA has reported that modern laptops have crashed when Space Shuttle flights passed through the anomaly. In October 2012, the SpaceX CRS-1 Dragon spacecraft attached to the International Space Station experienced a transient problem as it passed through the anomaly.

The SAA is believed to have started a series of events leading to the destruction of the Hitomi, Japan's most powerful X-ray observatory. The anomaly transiently disabled a direction-finding mechanism, causing the satellite to rely solely on gyroscopes that were not working properly, after which it spun itself apart.>>

[maumau]

Are the open lines actually open, or do they just continue out of the field of view of the illustration?

[neufer]

Are the open lines actually open, or do they just continue out of the field of view of the illustration?

An artist's concept of a magnetosphere, where plasmasphere (7) refers to the plasma torus and sheet

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<<At the opposite side of [Jupiter], the solar wind stretches Jupiter's magnetic field lines into a long, trailing magnetotail, which sometimes extends well beyond the orbit of Saturn. The structure of Jupiter's magnetotail is similar to Earth's. It consists of two lobes (blue areas in the figure), with the magnetic field in the southern lobe pointing toward Jupiter, and that in the northern lobe pointing away from it. The lobes are separated by a thin layer of plasma called the tail current sheet (orange layer in the middle).>>

[Chris Peterson]

Are the open lines actually open, or do they just continue out of the field of view of the illustration?

Field lines can't be truly open. But keep in mind that field lines aren't physical things, just visualization tools for the field. And Jupiter is not an isolated magnet in the middle of an empty universe, so the shape of the field becomes complex when it interacts with other magnetic fields.

[neufer]

Are the open lines actually open, or do they just continue out of the field of view of the illustration?

Field lines can't be truly open.

• If you have enough GUTs they can:

<<One of the defining advances in quantum theory was Paul Dirac's work on developing a relativistic quantum electromagnetism. Before his formulation, the presence of electric charge was simply "inserted" into the equations of quantum mechanics (QM), but in 1931 Dirac showed that a discrete charge naturally "falls out" of QM. That is to say, we can maintain the form of Maxwell's equations and still have magnetic charges.

Quantum mechanics dictates that angular momentum is quantized in units of ħ, so therefore the product q_eq_m must also be quantized. This means that if even a single magnetic monopole existed in the universe, and the form of Maxwell's equations is valid, all electric charges would then be quantized.

GUTs [grand unified theories] lead to compact U(1) gauge groups, so they explain charge quantization in a way that seems logically independent from magnetic monopoles. However, the explanation is essentially the same, because in any GUT that breaks down into a U(1) gauge group at long distances, there are magnetic monopoles.>>

[Chris Peterson]

Are the open lines actually open, or do they just continue out of the field of view of the illustration?

Field lines can't be truly open.

• If you have enough GUTs they can:

<<One of the defining advances in quantum theory was Paul Dirac's work on developing a relativistic quantum electromagnetism. Before his formulation, the presence of electric charge was simply "inserted" into the equations of quantum mechanics (QM), but in 1931 Dirac showed that a discrete charge naturally "falls out" of QM. That is to say, we can maintain the form of Maxwell's equations and still have magnetic charges.

Quantum mechanics dictates that angular momentum is quantized in units of ħ, so therefore the product q_eq_m must also be quantized. This means that if even a single magnetic monopole existed in the universe, and the form of Maxwell's equations is valid, all electric charges would then be quantized.

GUTs [grand unified theories] lead to compact U(1) gauge groups, so they explain charge quantization in a way that seems logically independent from magnetic monopoles. However, the explanation is essentially the same, because in any GUT that breaks down into a U(1) gauge group at long distances, there are magnetic monopoles.>>

Yup. I'm not holding my breath for monopoles, though.

[neufer]

Field lines can't be truly open.

• If you have enough GUTs they can:

<<One of the defining advances in quantum theory was Paul Dirac's work on developing a relativistic quantum electromagnetism. Before his formulation, the presence of electric charge was simply "inserted" into the equations of quantum mechanics (QM), but in 1931 Dirac showed that a discrete charge naturally "falls out" of QM. That is to say, we can maintain the form of Maxwell's equations and still have magnetic charges. Quantum mechanics dictates that angular momentum is quantized in units of ħ, so therefore the product q_eq_m must also be quantized. This means that if even a single magnetic monopole existed in the universe, and the form of Maxwell's equations is valid, all electric charges would then be quantized. GUTs [grand unified theories] lead to compact U(1) gauge groups, so they explain charge quantization in a way that seems logically independent from magnetic monopoles. However, the explanation is essentially the same, because in any GUT that breaks down into a U(1) gauge group at long distances, there are magnetic monopoles.>>

Yup. I'm not holding my breath for monopoles, though.

Click to play embedded YouTube video.

Gyroscopically balanced monorail (1909)

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