Como Os Animais Usam O Campo Magnético Para Navegação, Durante As Migrações?

Magnetic compass adjustaments.

Adjustment of the compass is the arranging of magnetic and soft iron correctors about the binnacle so that their effects are equal and opposite to the effects of the magnetic material in the ship, thus reducing the deviations and eliminating the sectors of sluggishness and unsteadiness.

Magnetic Compass Adjuster

https://www.agulhamagnetica.com/

Cool!! This is the Han Dynasty Compass.

Extreme Science: Launching Sounding Rockets from The Arctic

This winter, our scientists and engineers traveled to the world’s northernmost civilian town to launch rockets equipped with cutting-edge scientific instruments.

This is the beginning of a 14-month-long campaign to study a particular region of Earth’s magnetic field — which means launching near the poles. What’s it like to launch a science rocket in these extreme conditions?

Our planet is protected by a natural magnetic field that deflects most of the particles that flow out from the Sun — the solar wind — away from our atmosphere. But near the north and south poles, two oddities in Earth’s magnetic field funnel these solar particles directly into our atmosphere. These regions are the polar cusps, and it turns out they’re the ideal spot for studying how our atmosphere interacts with space.

The scientists of the Grand Challenge Initiative — Cusp are using sounding rockets to do their research. Sounding rockets are suborbital rockets that launch to a few hundred miles in altitude, spending a few minutes in space before falling back to Earth. That means sounding rockets can carry sensitive instruments above our atmosphere to study the Sun, other stars and even distant galaxies.

They also fly directly through some of the most interesting regions of Earth’s atmosphere, and that’s what scientists are taking advantage of for their Grand Challenge experiments.

One of the ideal rocket ranges for cusp science is in Ny-Ålesund, Svalbard, off the coast of Norway and within the Arctic circle. Because of its far northward position, each morning Svalbard passes directly under Earth’s magnetic cusp.

But launching in this extreme, remote environment puts another set of challenges on the mission teams. These launches need to happen during the winter, when Svalbard experiences 24/7 darkness because of Earth’s axial tilt. The launch teams can go months without seeing the Sun.

Like for all rocket launches, the science teams have to wait for the right weather conditions to launch. Because they’re studying upper atmospheric processes, some of these teams also have to wait for other science conditions, like active auroras. Auroras are created when charged particles collide with Earth’s atmosphere — often triggered by solar storms or changes in the solar wind — and they’re related to many of the upper-atmospheric processes that scientists want to study near the magnetic cusp.

But even before launch, the extreme conditions make launching rockets a tricky business — it’s so cold that the rockets must be encased in styrofoam before launch to protect them from the low temperatures and potential precipitation.

When all is finally ready, an alarm sounds throughout the town of Ny-Ålesund to alert residents to the impending launch. And then it’s up, up and away! This photo shows the launch of the twin VISIONS-2 sounding rockets on Dec. 7, 2018 from Ny-Ålesund.

These rockets are designed to break up during flight — so after launch comes clean-up. The launch teams track where debris lands so that they can retrieve the pieces later.

The next launch of the Grand Challenge Initiative is AZURE, launching from Andøya Space Center in Norway in March 2019.

 For even more about what it’s like to launch science rockets in extreme conditions, check out one scientist’s notes from the field: https://go.nasa.gov/2QzyjR4

For updates on the Grand Challenge Initiative and other sounding rocket flights, visit nasa.gov/soundingrockets or follow along with NASA Wallops and NASA heliophysics on Twitter and Facebook.

@NASA_Wallops | NASA’s Wallops Flight Facility | @NASASun | NASA Sun Science

Farewell to the Van Allen Probes

After seven years of studying the radiation around Earth, the Van Allen Probes spacecraft have retired.

Originally slated for a two-year mission, these two spacecraft studied Earth’s radiation belts — giant, donut-shaped clouds of particles surrounding Earth — for nearly seven years. The mission team used the last of their propellant this year to place the spacecraft into a lower orbit that will eventually decay, allowing the Van Allen Probes to re-enter and burn up in Earth’s atmosphere.

Earth’s radiation belts exist because energized charged particles from the Sun and other sources in space become trapped in our planet’s huge magnetic field, creating vast regions around Earth that teem with radiation. This is one of the harshest environments in space — and the Van Allen Probes survived more than three times longer than planned orbiting through this intense region.

The shape, size and intensity of the radiation belts change, meaning that satellites — like those used for telecommunications and GPS — can be bombarded with a sudden influx of radiation. The Van Allen Probes shed new light on what invisible forces drive these changes — like waves of charged particles and electromagnetic fields driven by the Sun, called space weather. 

Here are a few scientific highlights from the Van Allen Probes — from the early days of the mission to earlier this year:

The Van Allen belts were first discovered in 1958, and for decades, scientists thought there were only two concentric belts. But, days after the Van Allen Probes launched, scientists discovered that during times of intense solar activity, a third belt can form.

The belts are composed of charged particles and electromagnetic fields and can be energized by different types of plasma waves. One type, called electrostatic double layers, appear as short blips of enhanced electric field. During one observing period, Probe B saw 7,000 such blips repeatedly pass over the spacecraft in a single minute!

During big space weather storms, which are ultimately caused by activity on the Sun, ions — electrically charged atoms or molecules — can be pushed deep into Earth’s magnetosphere. These particles carry electromagnetic currents that circle around the planet and can dramatically distort Earth’s magnetic field.

Across space, fluctuating electric and magnetic fields can create what are known as plasma waves. These waves intensify during space weather storms and can accelerate particles to incredible speeds. The Van Allen Probes found that one type of plasma wave known as hiss can contribute greatly to the loss of electrons from the belts.

The Van Allen belts are composed of electrons and ions with a range of energies. In 2015, research from the Van Allen Probes found that, unlike the outer belt, there were no electrons with energies greater than a million electron volts in the inner belt.

Plasma waves known as whistler chorus waves are also common in our near-Earth environment. These waves can travel parallel or at an angle to the local magnetic field. The Van Allen Probes demonstrated the two types of waves cannot be present simultaneously, resulting in greater radiation belt particle scattering in certain areas.

Very low frequency chorus waves, another variety of plasma waves, can pump up the energy of electrons to millions of electronvolts. During storm conditions, the Van Allen Probes found these waves can hugely increase the energy of particles in the belts in just a few hours.  

Scientists often use computer simulation models to understand the physics behind certain phenomena. A model simulating particles in the Van Allen belts helped scientists understand how particles can be lost, replenished and trapped by Earth’s magnetic field.

The Van Allen Probes observed several cases of extremely energetic ions speeding toward Earth. Research found that these ions’ acceleration was connected to their electric charge and not to their mass.

The Sun emits faster and slower gusts of charged particles called the solar wind. Since the Sun rotates, these gusts — the fast wind — reach Earth periodically. Changes in these gusts cause the extent of the region of cold ionized gas around Earth — the plasmasphere — to shrink. Data from the Van Allen Probes showed that such changes in the plasmasphere fluctuated at the same rate as the solar rotation — every 27 days.

Though the mission has ended, scientists will use data from the Van Allen Probes for years to come. See the latest Van Allen Probes science at nasa.gov/vanallen.

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