Why the North Pole Is Really a South Pole (and Vice Versa)

If you go out hiking this weekend and somehow find yourself hopelessly lost in the wilderness, but suddenly remember you have a compass with you, you can use it to find north because the needle always points towards the Earth’s geographic north pole, which never changes… right?

Wrong, wrong, and wrong. And this video from MinutePhysics explains why.

(But still bring a compass with you. They do come in handy.)

See more videos from MinutePhysics here.

AR1654 is a Monster Sunspot. (And It’s Aiming Our Way.)

Active Region 1654 on the Sun’s western limb, seen by SDO on Jan. 11 (NASA/SDO/HMI team. Diagram by J. Major.)

Like an enormous cannon that is slowly turning its barrel toward us, the latest giant sunspot region AR1654 is steadily moving into position to face Earth, loaded with plenty of magnetic energy to create M-class flares — moderate-sized outbursts of solar energy that have the potential to cause brief radio blackouts on Earth and, at the very least, spark bright aurorae around the upper latitudes.

According to SpaceWeather.com, AR1654 “could be the sunspot that breaks the recent lengthy spell of calm space weather around our planet.”

The image above, captured by NASA’s Solar Dynamics Observatory earlier today, shows the structure of AR1654 upon the Sun’s photosphere — its light-emitting “surface” layer. Stretching many tens of thousands of miles, this magnetic solar blemish easily dwarfs our entire planet. And it’s not just a prediction that this sunspot will unleash a flare — it already has.

AR1654 came around the limb of the sun crackling with activity. Shortly after the probability of AR1654 releasing a flare was raised to 50% it did just that, letting loose with a burst of magnetic energy that was observed by SDO’s multi-channel cameras. Watch the video below:

Peaking at 9:11 UTC, this M1-class flare won’t have much more effect on Earth than perhaps some radio and GPS interference and maybe increased auroral activity. But AR1654 is still evolving and growing… and moving to face us.

In the meantime, solar astronomers and observatories like SDO are keeping an ever-watchful eye on this magnetic monster.

Keep up with the latest news here on Universe Today, on the SDO mission site and on spaceweather.com.

UPDATE 1/12: According to the NOAA, AR1654 has a 5% chance of producing an X-class flare, based on its current magnetic activity and alignment.

A sunspot is a magnetically active region on the sun that appears dark because it’s relatively cooler than the surrounding area—6,000ºF (3,300ºC) versus 10,000ºF (5,500º C). Sunspots are where solar flares are most likely to occur since the magnetic fields in these active regions can build up enough energy to break, releasing bursts of intense radiation into the solar system.

Navy Scientists Spot New Solar Structures

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There’s something new under the Sun… well, just above the Sun, actually. Scientists at the Naval Research Laboratory have spotted structures in the Sun’s super-hot corona that may shed some light on the way its magnetic fields evolve — especially near the edges of vast, wind-spewing coronal holes.

Coronal holes are regions where the Sun’s magnetic field doesn’t loop back down but rather streams outward into space. Appearing dark in images captured in ultraviolet wavelengths, these holes in the corona allow solar material to flow directly out into the solar system, in many cases doubling the normal rate of the solar wind.

Recently witnessed by NRL researchers using NASA’s SDO and STEREO solar-observing spacecraft, features called coronal cells exist at the boundaries of coronal holes and may be closely associated with their formation and behavior.

The coronal cells are plumes of magnetic activity that stream upward from the Sun, occurring in clusters. Likened to “candles on a birthday cake”, the incredibly hot (1 million K) plumes extend outwards, punching though the lower corona.

Seen near the center of the Sun’s disk, the cells appear structurally similar to granules — short-lived areas of rising and falling solar material on the Sun’s photosphere — but seen from an angle via STEREO, the cells were witnessed to be much larger, elongated and extending higher into the Sun’s atmosphere. For comparison, granules are typically about 1,000 km in diameter while the coronal cells have been measured at 30,000 km across.

“We think the coronal cells look like flames shooting up, like candles on a birthday cake,” said Neil Sheeley, a solar scientist at the Naval Research Laboratory in Washington, D.C. “When you see them from the side, they look like flames. When you look at them straight down they look like cells. And we had a great way of checking this out, because we could look at them from the top and from the side at the same time using observations from SDO, STEREO-A, and STEREO-B.”

Watch a video below of cells made from images acquired by STEREO-B… note how their elongated structure becomes evident as the cells rotate closer to the Sun’s limb.

NRL researchers also noted that the coronal cells appeared when adjacent coronal holes closed and disappeared when the holes opened, suggesting that the holes and cells share the same magnetic structure. In addition, the coronal cells were seen to disappear when a solar filament would erupt nearby, being “extinguished” as the cooler strand of solar material moved across them. Once the filament passed, the cells reformed — again, indicating a direct magnetic association.

The coronal cells were also identified in earlier images from ESA and NASA’s SOHO and Japan’s Hinode spacecraft.

It’s hoped that further study of these candle-like structures will lead to more knowledge of our star’s complex magnetic field and the effects it has on space weather and geomagnetic activity experienced here on Earth.

Read the press release from the Naval Research Laboratory here, and on NASA’s STEREO site here.

How the Moon Became Magnetized

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It’s been a mystery ever since the Apollo astronauts brought back samples of lunar rocks in the early 1970s. Some of the rocks had magnetic properties, especially one collected by geologist Harrison “Jack” Schmitt. But how could this happen? The Moon has no magnetosphere, and most previously accepted theories state that it never did. Yet here we have these moon rocks with undeniable magnetic properties… there was definitely something missing in our understanding of Earth’s satellite.

Now a team of researchers at the University of California, Santa Cruz thinks they may have cracked this enigmatic magnetic mystery.

In order for a world to have a magnetic field, it needs to have a molten core. Earth has a multi-layered molten core, in which heat from the interior layer drives motion within the iron-rich outer layer, creating a magnetic field that extends far out into space. Without a magnetosphere Earth would have been left exposed to the solar wind and life as we know it could may never have developed.

Apollo 17 lunar rock sample

Simply put, Earth’s magnetic field is crucial to life… and it can imbue rocks with magnetic properties that are sensitive to the planet-wide field.

But the Moon is much smaller than Earth, and has no molten core, at least not anymore… or so it was once believed. Research of data from the seismic instruments left on the lunar surface during Apollo EVAs recently revealed that the Moon may in fact still have a partially-liquid core, and based on a paper published in the November 10 issue of Nature by Christina Dwyer, a graduate student in Earth and planetary sciences at the University of California, Santa Cruz, and her co-authors Francis Nimmo at UCSC and David Stevenson at the California Institute of Technology, this small liquid core may once have been able to produce a lunar magnetic field after all.

The Moon orbits on its axis at such a rate that the same side always faces Earth, but it also has a slight wobble in the alignment of its axis (as does Earth.) This wobble is called precession. Precession was stronger due to tidal forces when the Moon was closer to Earth early in its history. Dwyer et al. suggest that the Moon’s precession could have literally “stirred” its liquid core, since the surrounding solid mantle would have moved at a different rate.

This stirring effect – arising from the mechanical motions of the Moon’s rotation and precession, not internal convection – could have created a dynamo effect, resulting in a magnetic field.

This field may have persisted for some time but it couldn’t last forever, the team said. As the Moon gradually moved further away from Earth the precession rate slowed, bringing the stirring process – and the dynamo – to a halt.

“The further out the moon moves, the slower the stirring, and at a certain point the lunar dynamo shuts off,” said Christina Dwyer.

Still, the team’s model provides a basis for how such a dynamo could have existed, possibly for as long as a billion years. This would have been long enough to form rocks that would still exhibit some magnetic properties to this day.

The team admits that more paleomagnetic research is needed to know for sure if their proposed core/mantle interaction would have created the right kind of movements within the liquid core to create a lunar dynamo.

“Only certain types of fluid motions give rise to magnetic dynamos,” Dwyer said. “We calculated the power that’s available to drive the dynamo and the magnetic field strengths that could be generated. But we really need the dynamo experts to take this model to the next level of detail and see if it works.”

In other words, they’re still working towards a theory of lunar magnetism that really sticks.

 

Read the article by Tim Stephens on the UCSC website.