NASA’s TWINS Data Reveals Heated Particle Highway to Earth

By Mara Johnson-Groh
NASA’s Goddard Space Flight Center

Up in the night sky, above the auroras and below the Moon, there exists a heated superhighway. Instead of cars though, this transient highway funnels charged particles across hundreds of thousands of miles toward Earth for a few minutes before vanishing.

While we can’t see it with our eyes, scientists have recently discovered a new way to look at the entire transportation structure from afar for the first time using special particles called energetic neutral atoms. Ultimately, this could help scientists predict when dangerous effects of space weather might be headed towards Earth.

Data from NASA's TWINS and a computer model show how particles are funneled through Earth's magnetosphere.
Using data from NASA’s MMS and TWINS missions, scientists were able to map temporary highways hurtling particles towards Earth during stormy space weather conditions.
Credit: Amy Keesee/University of New Hampshire

The highway is temporarily created within Earth’s self-generated magnetic bubble, during periods of intense activity from the Sun, when the planet is bombarded with charged particles and radiation. The bubble protects the planet from most of the particles, but some sneak through and are funneled along towards Earth along a highway-like structure.

Since these particles can disrupt satellites and telecommunications in space and damage systems on Earth, scientists are keen to study how they are transported. However, charged particles have to be measured where they are – rather than being tracked with far-away observatories. This is like monitoring traffic by standing right on a highway instead of from a helicopter flying above – which makes it hard to get a full picture of the routes the vehicles travel.

As a result, scientists have only been able to glimpse snapshots of particles’ paths as satellites passed through the region.

But recently a group of scientists, led by Amy Keesee, a space physicist at the University of New Hampshire, decided to look at the highway in a new way. Using data from NASA’s Two Wide-angle Imaging Neutral-atom Spectrometers – TWINS – mission, which operated from 2008 to 2020, the scientists studied the region using energetic neutral atoms, or ENAs.

These particles are formed when a charged particle hits a neutral atom and loses its charge to the atom. Since it’s no longer charged, the particle is unbound from the magnetic fields it was previously confined to and goes streaming through space along a straight line. By measuring these particles, scientists can work back to see where the particle was created, providing an image of the region of charged particles. Scientists have previously used this technique to study the edge of the magnetic bubble created by the Sun.

Using near-Earth ENAs measured by TWINS, the scientists were able to create a complete map of the highway. They also verified their findings with data from NASA’s Magnetospheric Multiscale mission, which happened to fly through the region at the time. Together, this opens the door to observing these particle flows from far away, rather than needing to fly a spacecraft right through them. Such information could improve our real-time predictions of when charged particles are coming toward Earth.

The findings were published in a recent issue of Geophysical Research Letters.

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63 Years after Explorer 1, New Discoveries about the Van Allen Belts Continue

By Mara Johnson-Groh
NASA’s Goddard Space Flight Center

On January 31, 1958, the U.S. launched its first satellite: Explorer 1. Among its many achievements, Explorer 1 made the ground-breaking discovery of belts of charged particles encircling Earth.

Visualization of the two concentric donut-shaped Van Allen belts encircling Earth
Visualization of the Van Allen belts based on data from NASA’s SAMPEX mission. Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio

That discovery is still being studied today. 63 years on, scientists are still learning about these belts – now known as the Van Allen belts – and their effects on Earth and technology in space.

From 2012 to 2019, scientists used NASA’s Van Allen Probes to gather data from the dynamic region discovered by Explorer 1. While the mission is no longer operational, it left a treasure-trove of observations, which are continuing to reveal new things about the belts. In 2020, over 100 scientific papers were published in peer-reviewed international journals using Van Allen Probes data, often leading studies in conjunction with partner missions. Here are three surprising discoveries scientists have recently made about the Van Allen belts.

1) In addition to particles, space is filled with electromagnetic waves called plasma waves, which affect how charged particles in space move. Near Earth, one type of wave, called whistler chorus waves, bounces back and forth following magnetic field lines between Earth’s North and South poles. Observations from the Van Allen Probes and Arase missions recently showed that these waves can leave the equator and reach higher latitudes where they permanently knock particles out of the Van Allen belts – sending the particles out into space never to return.

2) In addition to removing charged particles from the belts, magnetic activity can also add in new particles. Van Allen Probes observations combined with data from a Los Alamos National Lab geosynchronous satellite and one of NASA’s THEMIS satellites showed how hot charged particles can be abruptly transported by magnetic activity across 400,000 miles, from distant regions under the influence of Earth’s magnetic field into the heart of the Van Allen belts.

3) Earth’s magnetic environment and the Van Allen belts are highly influenced by the Sun, particularly when it releases clouds of ionized gas called plasma, which can create hazardous space weather. Some stormy activity from the Sun can create an intense ring of current surrounding Earth. Understanding these currents is critical for predicting their adverse space weather effects on ground-based infrastructure. Using years of Van Allen Probes data, scientists can now accurately model the distribution of the ring current around Earth even during the most intense space weather storms.

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Research Highlights from NASA’s GOLD Mission

By Sarah Frazier
NASA’s Goddard Space Flight Center

A special collection of research in the Journal of Geophysical Research: Space Physics highlights the initial accomplishments of NASA’s GOLD mission. GOLD, short for Global-scale Observations of the Limb and Disk, is an ultraviolet imaging spectrograph that observes Earth from its vantage point on a commercial communications satellite in geostationary orbit.

Since beginning science operations in October 2018, GOLD has kept a constant eye on Earth’s dynamic upper atmosphere, watching changes in the Western Hemisphere, marked by changes in the temperature, composition and density of the gases in this region. 

A few highlights include:

    • Results on one source of airglow seen at night, which relies on electrons on Earth’s day side becoming ionized by sunlight, then being transported along magnetic field lines to the nightside, where they create visible airglow (Solomon, et al)
    • New evidence supporting the idea that the equatorial ionization anomaly appearing in the early morning — a prominent feature in the ionosphere with poorly-understood triggers that can disrupt radio signals — is linked to waves in the lower atmosphere (Laskar, et al)
    • New observations of planet-scale waves in the lower atmosphere that drive change in the ionosphere (Gan, et al & England, et al
    • Multi-instrument measurements of plasma bubbles — “empty” pockets in the ionosphere that can disrupt signals traveling through this region because of the sudden and unpredictable change in density — that suggest they are could be seeded by pressure waves traveling upwards from the lower atmosphere (Aa, et al)
    • Observations showing that plasma bubbles occur frequently at all of the longitudes covered by GOLD with different onset times, providing new information on the influence of the particular configuration of the geomagnetic field at these longitudes (Martinis, et al
    • Measurements of changes in the chemical composition of the thermosphere during the total solar eclipse of July 2, 2019, which give scientists an unprecedented hemisphere-wide look at how the reduction in solar radiation throughout an eclipse affects this part of the atmosphere (Aryal, et al


Read more research from the special collection on the Journal of Geophysical Research: Space Physics website, see an overview of early GOLD results from AGU’s Eos, and see more GOLD mission publications on the mission website.

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Mission to study space weather moves into formulation

By Sarah Frazier
NASA’s Goddard Space Flight Center

NASA will begin formulation of a new mission to study Earth’s dynamic interface to space: the upper atmosphere. This is a region that is constantly changing, influenced by Earth’s weather percolating up from below and space weather — in the form of solar energy and space plasma — streaming in from above. This new mission will provide the first systematic study of this region in our atmospheric backyard, providing the data needed to assess, and ultimately forecast, the phenomena that course through Earth’s upper atmosphere.

The new mission, called the Geospace Dynamics Constellation, or GDC, answers a call laid out in the most recent solar and space physics decadal survey for a mission to study how Earth’s atmosphere absorbs and responds to energy inputs. GDC is a mission within NASA’s Living With a Star program, focusing on fundamental heliophysics science and applications of that science to protecting human society and technology. On Sept. 8, 2020, GDC successfully completed the Key Decision Point – A review, or KDP-A, moving the project into Phase A, when the team works on concept and technology development that will support the mission. The GDC project management has been directed to NASA’s Goddard Space Flight Center. The target Launch Readiness Date is late 2027, and GDC mission timeline will be developed during Phase A.

Data visualization showing Earth with two bands of dense plasma near the equator, complex upper atmospheric winds, and Earth's magnetic field like a belt near the middle of the planet.
This data visualization combines models of ions, upper atmospheric winds, and Earth’s magnetic field, a few of the many overlapping conditions that feed into complex processes in Earth’s upper atmosphere. The upcoming Geospace Dynamics Constellation mission will study this region of Earth’s atmosphere and provide the first systematic view of this area. Credit: NASA’s Scientific Visualization Studio

GDC will study Earth’s upper atmosphere, where our planet’s near-space environment overlaps with our atmosphere and space weather effects can manifest — ranging from the scrambling of communications and navigation signals to satellite orbit disruptions and induced currents that can trigger power outages on Earth’s surface.

Using a distributed constellation of spacecraft working together to gather comprehensive observations from multiple vantage points, GDC will explore the fundamental physics of this region of near space, investigating the complex processes that transmit energy and momentum on scales ranging from seasonal to daily to minute by minute. The level of detail and resolution provided by GDC will give us an unprecedented understanding of the space environment surrounding our home planet. Understanding these processes will provide crucial information needed to understand, and ultimately predict, the variable nature of the space environment our satellites, signals, and astronauts must travel through — and give us new insights into the forces that shape our home planet and other worlds.

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Comet NEOWISE Seen in an Aurora-Filled Sky

Comet NEOWISE is visible in a sky filled with purple and green aurora
Image: Copyright Donna Lach, used with permission

Comet NEOWISE is visible in an aurora-filled sky in this photo by Aurorasaurus Ambassador Donna Lach. The photo was taken early on July 14, 2020, in western Manitoba, Canada. The purple ribbon-like structure to the left is STEVE, an aurora-related phenomenon discovered with the help of citizen scientists working with the Aurorasaurus project. The bright streak near the top of the image is a meteor.

Read more on nasa.gov.

NASA’s STEREO Sees Comet NEOWISE

By Sarah Frazier
NASA’s Goddard Space Flight Center

Comet NEOWISE appears as a streak against a starry background

This image of comet NEOWISE was captured by NASA’s Solar and Terrestrial Relations Observatory, or STEREO, on June 24, 2020, as the comet approached the Sun. The comet was visible in the field of view of STEREO’s Heliospheric Imager because of a special observing campaign: STEREO underwent a 180-degree roll on June 24 in order to observe the star Betelgeuse, whose brightness variations over the past several months have intrigued scientists. This image has been processed to increase contrast.

Credit: NASA/STEREO/William Thompson

Download additional imagery from NASA Goddard’s Scientific Visualization Studio.

Dancing the Lunar Transit

By Sarah Frazier
NASA’s Goddard Space Flight Center

On March 6, 2019, our Solar Dynamics Observatory, or SDO, witnessed a lunar transit — where both the Sun and Moon displayed a little odd behavior.

First, there was the transit itself. A lunar transit occurs when the Moon passes between SDO and the Sun, blocking the satellite’s view. But instead of appearing on one side of the frame and disappearing on the other, the Moon seemed to pause and double back partway through crossing the Sun. No, the Moon didn’t suddenly change directions in space: This is an optical illusion, a trick of perspective.

Illustration of the relative motion of the Moon and SDO during the lunar transit
NASA’s Solar Dynamics Observatory spotted a lunar transit just as it began the transition to the dusk phase of its orbit, leading to the Moon’s apparent pause and change of direction during the transit. This animation (with orbits to scale) illustrates the movement of the Moon, its shadow and SDO. Credits: NASA/SDO

Here’s how it happened: SDO is in orbit around Earth. When the transit started, the satellite was moving crosswise between the Sun and Earth, nearly perpendicular to the line between them, faster than the Moon. But during the transit, SDO started the dusk phase of its orbit — when it’s traveling around towards the night side of Earth, moving almost directly away from the Sun — but no longer making any progress horizontally to the Sun. The Moon, however, continued to move perpendicular to the Sun and thus could “overtake” SDO. From SDO’s perspective, the Moon appeared to move in the opposite direction.

The second, subtler part of this celestial dance seemed to come from the Sun itself. If you look closely, you may notice the Sun seems to wiggle a bit, side-to-side and up and down, during the transit. That’s another result of SDO’s perspective, though in a different way.

SDO relies on solar limb sensors to keep its view steady and focused on the Sun. These limb sensors consist of four light sensors arranged in a square. To keep the Sun exactly centered in its telescopes, SDO is trained to move as needed to keep all four sensors measuring the same amount of light.

But when the Moon covers part of the Sun, the amount of light measured by some of the sensors drops. This makes SDO think it’s not pointed directly at the Sun, which would cause SDO to repoint — unless that function gets overridden.

Since SDO’s fine guidance system wouldn’t be much use during a lunar transit regardless, the mission team commands the spacecraft to disregard limb sensor data at the beginning of such transits. This loss of fine guidance accounts for some of the Sun’s apparent movement: SDO is now pointing at a general Sun-ward spot in space, instead of keeping its view steady using the much more accurate limb sensors.

The other factor behind the apparently wiggly Sun is temperature. SDO’s instruments are designed to work in the full glare of the Sun’s light and heat. When the Moon’s shadow passes over the spacecraft, the instruments quickly cool in the vacuum of space and start to bend and flex. The flexing of the front part of the telescope can make it look like the image is moving around in the frame.

SDO’s operators use strategically-placed heaters onboard the spacecraft to minimize this flexing as much as possible and to get back to providing science-quality data — images that are focused, centered and steady — as quickly as possible.

You can see and download SDO’s data — science-quality and otherwise — at sdo.gsfc.nasa.gov/data.