Magnetically charged particles at night, the joy of astronomers


Europe's planned solar time forecast mission, L5, will be the first to provide real-time data 24 hours a day, seven days a week, in addition to Earth's orbit, to help protect sensitive storm infrastructure potential.

It's a quiet day at the Met Office Operations Center in Exeter. The center occupies only a small corner in the gigantic hall occupied by dozens of meteorologists working for the UK National Weather Service. Large screens display complex weather patterns on all walls. In the space weather prediction corner, two scientists are leaning over a series of graphs and a series of satellite images capturing the solar disk in various colors. A small sunspot, a darker area on the surface of the Sun, indicating reduced temperature due to changes in the magnetic field, is visible in the sphere of fire.

"We use images from Soho, the Solar and Heliospheric Observatory, located near the so-called Lagrange 1 (L1), which lies on the direct line between Earth and Sun at a distance of about a million miles from Earth. "Says Catherine Burnett, manager of the Met Office space weather program. "This is the closest observation we have received from the sun. When a sunspot moves to the central region of the image, it is when we have to be on high alert, as it can produce a coronal mass ejection that can reach Earth. "

Coronal mass ejection (CME) is an explosion of plasma and magnetically charged particles from the solar corona, the outer atmosphere of the sun. CMEs can happen when magnetic fields distorted in sunspots, also called active regions, break down. Today's weather forecasters can not predict with certainty when a CME will occur. Once they realize that a very active region is heading toward the center of the Sun's vision in the Sun, they issue warnings to governments, infrastructure operators and other parts of the Earth that may be affected by a possible geomagnetic storm.

It takes the CME one to four days to reach Earth. The more powerful the CME, the faster it travels. "The problem is that when we look at L1, we are looking directly at the Sun and therefore it is very difficult to say how quickly the CME is going in our direction," says Burnett. "Furthermore, until we hit the L1 spacecraft, we do not know if it would cause any problems on Earth.

"If the orientation of the magnetic poles of the CME is the same as that of Earth, the two magnetic fields repel each other and the impacts will be minimal," he explains. "If the magnetic fields have an opposite orientation, they will engage and the CME's energy will be transferred to Earth's magnetic field and cause a magnetic storm. We only get this information when the CME arrives at the Soho spacecraft. "

In 1989, a powerful geomagnetic storm caused a nine-hour power outage in the Canadian province of Quebec, which affected six million people.

The interaction of the CME's highly energetic particles with particles in the Earth's atmosphere could break satellite links and knock down communications and navigation systems such as GPS. Such a rupture could wreak havoc on the transportation industry, but it would also affect infrastructure that depends on GPS for the weather. Aircraft could have problems with high-frequency radio communication, which would cause problems, especially on high latitude routes.

The potential impacts of a powerful geomagnetic storm on Earth are such that in 2011 the UK government added a severe space weather to the National Risk Register along with other natural hazards such as volcanic eruptions, floods, bad weather, low air quality, forest fires and earthquakes.

In 2012, a huge CME lost the Earth with a margin of only nine days. The event, which was recorded by NASA's Stereo A spacecraft, was as powerful as the most intense geomagnetic storm ever recorded, the so-called Carrington event in 1859. If the CME 2012 had hit Earth, it could have caused a rupture before the Olympics. Games in London.

To improve their predictions, scientists use data from Earth-based telescopes as well as those provided by some of Sun's scientific observation missions operated by NASA and ESA. Images of NASA's Stereo A probe are of particular interest. The spacecraft orbits around the Sun and is currently at a 90-degree angle from the Sun-Earth line. Predictors use data from Stereo A to get a view of the Sun side that is turning to Earth. The images allow them to see and monitor the sunspots before they are visible from point L1 through Soho.

When a CME explodes toward Earth, the side view allows predictors to better calculate the velocity of the plasma cloud's displacement. They can better predict when the CME will reach Earth, but also, because the more powerful CMEs travel faster, they can better estimate the intensity of the event.

However, the Stereo A is in the convenient position only temporarily – and the mission is already ten years away from its planned duration.

The UK Met Office therefore joined forces with the European Space Agency (ESA) to develop a mission that would provide a view similar to that of Stereo A, but with constant access to data.

The L5 mission, named after Lagrange point 5, where it would be located, could join the global fleet of space weather forecast in 2025 if approved by the ministerial council of ESA member states later this year.

The Lagrange points, named after the eighteenth-century Italian astronomer Joseph-Louis Lagrange, are five points in relation to every two large bodies in orbit where the gravitational forces of the two objects cancel each other out. This means that a third object placed on one of the five Lagrange points would remain in a stable position relative to the two bodies.

The L5 is located about 149 million kilometers from Earth and the Sun, forming an equilateral triangle with them and crawls behind the Earth in its orbit around the Sun.

"Our society is increasingly dependent on the assets we have in space. If the capacity of these assets were lost, people would notice immediately.

According to Jussi Luntama, the head of the ESA Space Climate Office, the L5 mission, if approved, will be the first operational mission out of Earth's orbit. Contact with the spacecraft will be maintained 24 hours a day, 7 days a week, and the data will be accessible almost in real time, which has never been done before. All other probes that travel to deep space are scientific missions that allow only the download of data at convenient times.

"Let's have a continuous radio connection with the satellite," said Luntama E & T. "We will use the three ground stations of the ESA network of European space tracking (Estrak) that have antennas of 35 meters in diameter to maintain the telemetry download link with the L5 spacecraft. This will be the biggest challenge to ensure there are no gaps in the data. "

NASA will provide ground support stations, said Luntama, and the data will be available to American and European meteorologists.

ESA hopes to reduce the cost of the mission by reusing the technology developed for previous scientific missions, such as Solar Orbiter, due to be launched in 2020.

The two-ton L5 spacecraft will carry four remote sensing instruments to observe the Sun and the solar corona, as well as instruments to monitor the cosmic radiation around the satellite.

"The coronagraph will allow us to see if there are any potentially dangerous eruptions and CMEs," says Luntama. "So we have a heliospheric imager, which is a camera that monitors the space between the Sun and the Earth and allows us to monitor the spread of the CMEs so we can give a more precise warning about when the impacts of space weather will begin. the Earth and how serious the impact will be. "

The spacecraft will also carry a magnetograph that can remotely measure the magnetic field of the solar disk, which will allow meteorologists to produce accurate numerical models to predict the characteristics of CMEs. The final optical instrument is an extreme ultraviolet that shows the active regions of the part of the Sun that is not yet facing the Earth but will do so in about five days.

It is expected that the mission will be launched just as the regular cycle of the Sun reaches its next maximum. The Sun goes through regular cycles of 11 years, during which its activity increases and decreases in a somewhat predictable way. During the solar minimum, the Sun produces only a relatively low number of sunspots and CMEs, while during the maximum the risk of a powerful event is much greater.

The previous cycle, Burnett says, was unusually quiet, but that does not mean the next cycle will also be quiet. The problem is that many new satellites have risen during the last ten years during the period of low activity, and many others, developed in the time of the silent Sun, are expected to be launched in the next few years.

"I would hope that at some point Sun's activity will return to the levels we have seen in the past and we would see more CMEs and more space weather problems for modern technology," says Burnett. "The problem is that when we developed many of these technologies, we did not plan a bad space climate."

In addition to disrupting signal transmission, protons of very high energy from cosmic radiation can damage the spacecraft electronics and cause anomalies. In severe cases, such events may render the satellite completely inoperable. Operators can protect against damage, with satellites designed with robust shielding. When advised in advance, they can turn off the spacecraft and keep it off until the electromagnetic storm disappears.

"Our society is increasingly dependent on the assets we have in space," says Luntama. "The use of satellites, whether satellite communications or satellite navigation, or satellite monitoring of the environment and weather forecast, may be invisible to ordinary people, but if the capacity of these assets is lost, people will immediately notice."

While the disruption of satellite operations itself could not be avoided, entities that depend on such services, such as airlines or maritime traffic operators, could at least take precautions, he adds.

In addition to the geomagnetic storms resulting from the CMEs, more background solar wind will flow to Earth during a more active cycle, exposing the spacecraft orbiting Earth to higher levels of corrosive radiation.

According to Burnett, the prediction of space time is decades behind terrestrial meteorology. What space meteorologists need to improve their models and begin to catch up with terrestrial meteorology is more data. "Our understanding of the Sun is far from being as advanced as our understanding of the Earth," she says. "We do not have a unique model that takes what is happening in the Sun, transfer it through the inner solar system and show it interacting with our magnetic field and atmosphere so we can tell what would be impacted, at what time and what location. "

Burnett says the L5 spacecraft is only the first step. Space weather forecasters would like to take advantage of the current boom in Earth observation satellites that are rapidly proliferating through Earth's low orbit. "Any satellite that is flying and has room for an extra payload could carry a small sensor that would measure the radiation environment in which the satellite is installed. This environment is changing all the time and if we could inform operators about the high activity period, they could operate their satellites more efficiently. "


Types of space weather

Solar wind: A stream of charged charged particles originating from the solar corona. The particles flow continuously, but their temperature, density and velocity vary. The solar wind can reach speeds of up to 900 km / s and can reach up to one million degrees Celsius (° C). During solar maximum, the intensity of the solar wind tends to be higher.

Solar flares: Release of the electromagnetic energy of the Sun in the form of light and X-rays. X-rays, which would be harmful to living organisms, are intercepted by the atmosphere before reaching Earth's surface, but may cause short-term interruptions in radio communications and satellite signals. The effects usually pass within 30 minutes to 3 hours. Solar eruptions usually precede coronal mass ejections.

Coronal mass ejections (CMEs): massive eruptions of plasma and magnetically charged particles from the solar corona. The magnetic field carried by the CMEs is much stronger than the background solar wind. CMEs travel from the Sun at speeds between 250 and 300 km / s. The most powerful can reach the Earth within 18 hours. If the CME magnetic field is opposite the Earth's orientation, the CME would cause a magnetic storm that would last for several days.

Geomagnetic Storms: Disturbances of the earth's magnetic field caused by a sudden increase in the flow of the solar wind. The direction of the magnetic field of the solar wind has to be opposite to the Earth's magnetic field for the rupture to occur. The largest storms are associated with CMEs.

Aurora Borealis: The effects of ionization of the upper atmosphere caused by interaction with solar wind particles.

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