Orbiting ‘Magnetism to Light Converter’ Maps Earth’s Magnetic Field

Three identical satellites of ESA Swarm mission will move into separate polar orbits to blanket the planet with high-precision magnetic measurements. Illustrations: ESA

The European Space Agency’s Swarm expedition was launched from the Plesetsk Cosmodrome on 22 November, on a mission to study how the Earth’s magnetic field and ionosphere vary in time and space. It started sending back data four days later.

The mission consists of three identical satellites launched into separate polar orbits that will let them sheathe the Earth in a web of magnetic measurement. Swarm will gauge the direction and strength of the planet’s magnetic field more precisely than ever before, using instruments up to five times as sensitive as those deployed on the Danish Øersted (launched 1999) and German CHAMP (2000) satellites. These measurements will return data on every part of the Earth, from the dynamo at the planet's core to the workings of the ionosphere and magnetosphere. It may even, perhaps, explain more about the magnetic “soft spot” that hovers over the South Atlantic (and might presage one of the periodic reversals in the Earth’s magnetic polarity).

Each Swarm spacecraft looks like an elongated horseshoe crab, with a solar-cell-covered carapace and a rapier of a tail. Once unfolded, the tail is a tubular, 4.3-meter-long, carbon-fiber-reinforced polymer boom. It’s manufactured without any magnetic components, because it is carries some of the most advanced magnetic-field-measurement instruments yet built.

Illustrations: ESA

About halfway down the boom is an optical bench that couples a three-axis star-tracking telescope with a Vector Field Magnetometer (VFM)—a highly sensitive device for measuring the intensity and orientation of magnetic lines of flux. Overall, the assembly (devised by researchers at the Danish Technical University) is accurate to within about 0.5 nanotesla (0.5 x 10-9 T) in field strength and 0.1 degrees in satellite attitude. The VFM, which is the satellite’s primary instrument, will measure not only the direction and strength of the surrounding magnetic field, but also plot it against positions confirmed by the three-way star-sight.

At the end of the boom is a new design—the Absolute Scalar Magnetometer, (ASM) built by CEA-Leti (Grenoble, France), with scientific support from the Institut de Physique du Globe de Paris and financing and logistics from the Centre National d’Etudes Spatiales (CNES), the French national space agency.

The ASM’s nominal role is to understudy the VFM, helping to keep the vector instrument calibrated. What it actually offers, say the designers, goes a lot farther. (For a collection of papers on ASM’s design, see this CNES library.)

The device uses low-density helium as its sensor, and exploits the Zeeman effect—the splitting of the element’s emission-spectrum lines in a magnetic field.

To measure this spread, the ASM first applies radio frequency energy to lift electrons from their ground state to a metastable intermediate energy level (actually, one of three levels, since the Earth’s magnetic field splits this level into three levels, depending on the combined spins of the atom and its electrons).

Then a linearly polarized laser beam further pumps electrons to an even higher, though very short-lived, excited state. In one-tenth of a microsecond, the electrons drop back into one of the metastable levels, giving off photons and creating three closely grouped spectral lines (clustering at around 1083 nanometers wavelength in the infrared). The gap between the lines is proportional to the ambient magnetic field.

The instrument incorporates a number of refinements. To maintain accuracy, the designers had to maintain a constant relationship between the stimulating laser beam and the applied magnetic fields. By using a beam that’s polarized linearly rather than (as in previous designs) circularly, the designers were ab keep the system aligned by adjusting the direction of polarization rather than the direction of beam propagation—and it’s much easier to change polarization than to move the laser. In the ASM, non-magnetic piezoelectric motors control the orientations of the RF coils.

The net result is that the Absolute Scalar Magnetometer is about ten times as sensitive as the Vector Field Magnetometer, with a maximum error of less than 65 picotesla (65 x 10-12 T). By comparison, that’s about one millionth of the Earth’s surface magnetic field, which ranges from about 30 to 60 microtesla (30-60 x 10-6 T), and about one one-hundred-millionth the magnetic field strength of a common household refrigerator magnet (5 x 10-3 T). The precision should be better than 1 picotesla, and the noise levels are low, better than 1 pT / (Hz)1/2.

Also, the ASM uses three orthogonal sets of RF coils. The device is able to report how much of the scalar field is projected along each of these axes…so, voila, the scalar magnetometer can also function as a vector magnetometer, although at a lower sampling rate and with reduced accuracy. Among other experiments, the Swarm mission will test whether the understudy ASM might be ready to step out from backstage and take on the starring role of the VFM.



ORIGINAL: IEEE Spectrum
By Douglas McCormick
Posted 16 Dec 2013 

Modified 18 Dec. 2013 to include correct launch site at Plesetsk.

Fox Dives Headfirst Into Snow | North America

A red fox pinpoints field mice buried deep beneath the snow, using his sensitive hearing and the magnetic field of the North Pole to plot his trajectory. 

ORIGINAL: Discovery 
Nov 19, 2013 

Sun's magnetic field about to flip

ORIGINAL: ABC
Ian O'Neill
Thursday, 8 August 2013
Discovery News

As the Sun approaches solar max the magnetic field is at its most stressed (NASA/SDO)

Every 11 years or so, the Sun does something quite profound - its magnetic field completely swaps polarity. This event occurs at the peak of the solar cycle, heralding the mid-point and the most active phase of Solar Cycle 24.

"It looks like we're no more than three to four months away from a complete field reversal," says solar physicist Todd Hoeksema of Stanford University. "This change will have ripple effects throughout the solar system."

Solar astronomers have been keeping a close eye on the magnetic conditions in the lowest regions of the Sun's atmosphere, measuring its magnetic field strength and direction.

"The Sun's polar magnetic fields weaken, go to zero, and then emerge again with the opposite polarity. This is a regular part of the solar cycle," says solar physicist Phil Scherrer, also of Stanford University.

Hoeksema and Scherrer work at Stanford's Wilcox Solar Observatory, one of the few observatories on the planet that is capable of acquiring solar magnetograms.

Wilcox has been monitoring the Sun's polarity since 1976, seeing in three "grand reversals" from three solar cycles. This will be its fourth and excitement is mounting, especially as we're only a few months away from complete reversal.

The solar cycle ebbs and flows over an approximate 11-year period. From "solar minimum" to "solar maximum," our nearest star's internal magnetic field gets wound up by the Sun's differential rotation. Differential rotation means that the Sun rotates faster at the equator than it does at the poles, dragging the magnetic field - like an elastic band - that is embedded in the superheated plasma.

As the Sun approaches solar max (as it is now) the magnetic field is at its most stressed, causing magnetic arcs to be forced from the solar interior and into the lower corona.

It is during this period that space weather is at its most ferocious, creating beautiful aurorae at the Earth's poles caused by an intensified solar wind blasting energetic particles into the Earth's magnetosphere.

This is also a period of intensified flare and coronal mass ejection (CME) activity, potentially damaging satellites and interfering with communications on the ground.

A visible marker of the progression of the solar cycle is the appearance of sunspots - dark blemishes in the Sun's photosphere, marking the location of active regions and potential sites of magnetic eruptions.

Tipping point

So, as we experience solar maximum, the Sun's interior reaches a tipping point in its magnetic polarity, signified by a magnetic field weakening.

When the field does switch polarity, it's not just a local event. The Sun's magnetic field projects from the Sun and sweeps throughout the Sun's environment - the heliosphere. As the field flips inside the Sun, so does the interplanetary magnetic field, causing the magnetic field and associated electric "current sheet" to ripple and warp.

Although the underlying reasons for the solar cycle are yet to be understood, Hoeksema and Scherrer know what's going to happen next.

"The Sun's north pole has already changed sign, while the south pole is racing to catch up," says Scherrer. "Soon, however, both poles will be reversed, and the second half of Solar Max will be underway."

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Dramatic solar tsunamis reveal magnetic secrets in sun's corona

ORIGINAL: LATimes

By Amina Khan

July 12, 2013

This image from the Solar Dynamics Observatory shows the "quiet corona" and upper transition region of the sun. A study tracking solar tsunamis through the sun's plasma shows that the quiet corona may not be so quiet after all. (Solar Dynamics Observatory / NASA)

If tsunamis on Earth don’t seem terrifying enough, imagine the power of such a monstrous wave on the sun -- bigger, faster and made of searing plasma. Scientists have spotted two solar tsunamis that have allowed them to accurately measure the sun's magnetic field. The results, published by the journal Solar Physics, should help researchers better understand the makeup of the sun’s "quiet corona" and help predict when coronal mass ejections threaten Earth.

Solar tsunamis, spotted initially in 1997, are caused when a coronal mass ejection is hurled from the sun out into space. The eruption of charged matter pushes the surrounding plasma outward, sending out a circular wave that can travel 620 miles per second and cover half the sun’s surface in an hour, said study lead author David Long, a solar physicist at University College London.

Using NASA’s Solar Dynamics Observatory and the Japanese Hinode spacecraft, the researchers managed to capture two solar tsunamis in action, rising about 43,500 miles high and speeding along at roughly 250 miles per second. Having data from both spacecraft was key. Using NASA’s spacecraft, they tracked the tsunami by watching the ultraviolet light given off as the wave progressed. Using data from the Japanese spacecraft, they determined the density of the matter it was traveling through.

“In both of these events we were just in the right place — wasn’t too close, wasn’t too far away,” Long said.

That’s because as the tsunami spreads outward somewhat like a ripple, it gets distorted by the material it passes through. It will travel faster in denser areas and slower in less dense ones, Long said, because in dense areas the molecules are tightly packed together and can quickly relay the wave along. In sparser areas there might be a slight delay before one molecule runs into the next. The resulting raggedy circles showed that the wave was running through patchy star stuff rather than a smooth, homogeneous medium.

Together, this information allowed the scientists to determine what the density, and the magnetic field, looked like in the less active areas of the sun’s atmosphere known as the quiet corona.

"The fact that it gets deformed means that there are variations in the magnetic field of the solar atmosphere, which was very interesting," Long said. "There’s a lot more going on there than we originally thought."

Understanding a solar tsunami could also help scientists better predict the arrival of a coronal mass ejection. If such a burst of charged particles reaches Earth, it can wreak havoc on the globe’s power, electronics and navigation systems.

"If a coronal mass ejection is coming straight at you, it’s very difficult to measure its speed; it’s very difficult to measure how powerful it is," Long said. "So we are hoping that by looking at these waves, we’d be able to tell something about coronal mass ejections, which would be very useful for space weather forecasting."

amina.khan@latimes.com

Chemical bond discovered that only exists in space

ORIGINAL: New Scientist

New type of atomic bond can't be observed on Earth(Image: Stocktrek Images/Getty Images)

There's a new bond in town, and this secret agent works best in extreme situations.

The bond, of the chemical variety, occurs in the presence of very strong magnetic fields, such as those found around ultra-dense white dwarf stars. Its discovery not only demonstrates the existence of an unfamiliar and exotic type of chemistry, it may also give insight into the behaviours of these mysterious stellar bodies.

White dwarfs are the remnant cores of low-mass stars that have exhausted all their fuel. They are thought to be the final state for most of the stars in our galaxy. Though they have masses comparable to that of our sun, white dwarfs only occupy the same amount of space as a small planet like Earth, making them incredibly dense.

They also exhibit super-strong magnetic fields on the order of 100,000 tesla – 10 billion times greater than Earth's magnetic field, and 10 million times greater than that of an average refrigerator magnet. This intense field can affect the behaviour of the electrons that make up chemical bonds.

Exclusion principle

On Earth, atoms usually bond either covalently, by sharing electrons with neighbouring atoms, or ionically, via electrostatic attractions created by the transferral of electrons.

The electrons that give rise to these bonds are governed by the Pauli exclusion principle: two cannot occupy the same quantum state simultaneously. To avoid this scenario, electrons in bonds normally pair up in couples of opposing spin. But under the intense magnetic field of a white dwarf, "this spin interacts with the external field, acting like a little magnet," says lead author Kai Lange at the University of Oslo in Norway.

As a result, the spins of both electrons align with the external field, forcing one of the electrons to move into a different position known as an anti-bonding orbital. Normally, this would spell the end of any chemical bonds. "In a normal molecule these anti-bonding orbitals are not occupied by electrons," says Lange. "If they are occupied, the atoms are no longer bound together and the molecule breaks apart."

Unfamiliar chemistry

Lange and his colleagues wondered if things might be different around white dwarfs. "Chemistry and molecular physics become very different in the presence of a strong magnetic field," says Erik Tellgren, Lange's colleague. "Even very simple systems behave in exotic and unfamiliar ways compared to what we are used to under normal conditions."

With this in mind, the researchers used quantum chemical simulations to model chemical bonding in hydrogen and helium atoms in the magnetic field of a white dwarf. In both cases, the atoms were drawn into strongly bonded pairs.

Because the electrons in these bonded atoms occupied anti-bonding orbitals – which is forbidden in both types of known chemical bond – the researchers say this is a new type of bond. They have dubbed it "perpendicular paramagnetic bonding".

The work shows that "molecules that don't exist under normal conditions can exist in a sufficiently large magnetic field," says Lange.

David Clary of the University of Oxford, who was not involved in the study, called the research "excellent", adding that "the results show that a magnetic field can stabilise molecules".

Reading the stars

Although the authors say that replicating the new bonds on Earth isn't feasible, the finding highlights how molecular chemistry may change in the presence of extreme conditions.

"I think there are probably other weird or unfamiliar types of bonding to be discovered," says Tellgren.

Such work will also help to further our knowledge of astrophysical objects like white dwarfs. By understanding how matter behaves around these objects, it may be possible to interpret their observed spectra more easily and accurately, and to better unravel what is happening in their atmospheres.

Journal reference: Science, DOI: 10.1126/science.1219703

Huge 'Solar Tornado' Twists Across Sun's Surface in New Video

ORIGINAL: Space

SPACE.com Staff

Date: 29 March 2012 Time: 07:00 AM ET

NASA's Solar Dynamics Observatory spacecraft observed a "tornado" as wide as five Earths raging on the sun's surface on Sept. 25, 2011. This sequence of photos follows the tornado over 2 1/2 hours.

CREDIT: NASA/SDO/AIA/Aberystwyth University/Li/Morgan/Leonard

A NASA spacecraft has captured video of a massive solar "tornado" five times wider than the Earth twisting its way across the surface of the sun.

NASA's Solar Dynamics Observatory (SDO) looked on as the huge, swirling storm raged on Sept. 25, 2011, spinning solar gas at speeds up to 186,000 mph (300,000 kph), researchers said. Here on Earth, tornado wind speeds top out at around 300 mph (483 kph).

"This is perhaps the first time that such a huge solar tornado is filmed by an imager," Xing Li of Aberystwyth University in Wales, who analyzed the SDO footage, said in a statement. "Previously, much smaller solar tornadoes were found by the [NASA/European Space Agency] SOHO satellite. But they were not filmed."

Li and other researchers will present a movie of the tornado Thursday (March 29) at the 2012 National Astronomy Meeting in Manchester, the United Kingdom.

SDO's instruments saw gases as hot as 3.6 million degrees Fahrenheit (2 million degrees Celsius) rise from a dense solar structure called a prominence, then travel about 124,000 miles (200,000 kilometers) along a spiral path into the upper solar atmosphere, researchers said.

Unlike Earth's tornados, which are driven by wind, solar twisters are shaped by our star's powerful magnetic field. They often occur in concert with violent explosions of solar plasma known as coronal mass ejections, or CMEs. Some researchers think the tornados may help trigger CMEs, which can streak through space at several million miles per hour.

CMEs that hit Earth can wreak havoc on our planet, causing temporary disruptions in GPS signals, radio communications and power grids. They also typically supercharge the dazzling light shows near Earth's poles known as the northern and southern lights.

The $850 million SDO spacecraft, which launched in February 2010, is the first in a fleet of NASA efforts to study our sun. The probe's five-year mission is the cornerstone of a NASA science program called Living with a Star, which aims to help researchers better understand aspects of the sun-Earth system that affect our lives and society.

The sun is currently in an active period of its 11-year weather cycle. The current cycle is known as Solar Cycle 24 and will peak in 2013.

Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

La NASA encuentra portales ocultos en el campo magnético de la Tierra

ORIGINAL: Alt1040

Miguel Jorge ( Perfil )

4 de julio, 2012, 14:26

Así lo asegurado la NASA , confirmando que el científico Jack Scudder, de la Universidad de Lowa, ha encontrado portales ocultos en el campo magnético de la Tierra que se abren y cierran decenas de veces al día, en ocasiones, manteniéndose abiertos durante largos períodos de tiempo.

Según el científico, estos portales crean un camino ininterrumpido que va desde nuestro propio planeta a la atmósfera del Sol a 150.000 km de distancia. Denominados como puntos-X, estarían localizados a unas pocas decenas de miles de kilómetros de la Tierra.

Los portales se crean a través de un proceso de reconexión magnética en la que las líneas de fuerza magnética de ambos cuerpos celestes se mezclan y entrecruzan por el espacio creando estos puntos-X.

Según Scudder:

Los portales son invisibles, inestables y difíciles de alcanzar, se abren y cierran sin previo aviso. En el momento en el que se abren, sin embargo, son capaces de transportar las partículas energéticas a gran velocidad en la atmósfera del Sol a la Tierra, provocando tormentar geomagnéticas.

¿Y cómo consiguió localizarlos? Scudder utilizó los datos de la sonda espacial de la NASA, Themis, y las de la ESA, siguiendo las pistas que se encuentran en los datos de la nave Polar que ha estado estudiando la magnetosfera de la Tierra a finales de los 90:

Utilizando los datos de Polar, hemos encontrado cinco combinaciones simples de campo magnético y mediciones de partículas energéticas que nos dicen cuando nos hemos encontrado con un punto-X. Una sola nave, bien instrumentada, puede hacer estas mediciones.

A partir de aquí la NASA ha anunciado que prepara una nave que se utilizará alrededor de la Tierra que pueda rodear los portales para observar cómo funcionan. Una misión que se iniciará en el 2014.