Parker Solar Probe: Diving into the solar atmosphere | Science| In-depth reporting on science and technology | DW | 09.08.2018
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Parker Solar Probe

Parker Solar Probe: Diving into the solar atmosphere

The Parker Solar Probe is designed to unveil a great secret of the sun. To do so, it must travel closer to our star than any other spacecraft before it to collect data in a hellish environment.

For decades, solar researchers have been searching for an explanation for a mysterious phenomenon: how is it possible that the atmosphere of the sun is up to five hundred times hotter than its surface? In the atmosphere around the sun, known as the Sun's 'corona,' temperatures of several million degrees Celsius prevail. But the visible surface below it, from which the corona gets its heat, is only about 5800 degrees.

The incredible, unparalleled heat of the corona is a central question in solar physics. Scientists suspect the underlying mechanism probably also holds relevance for the formation of the so-called solar winds.

Hellish conditions

Our Sun is a glowing hot ball of gas from which matter constantly escapes into space - this is known as 'solar wind.' It flows out of the hot corona, and consists mainly of ionized hydrogen, electrons and protons.

This electrically charged particle stream also blows toward the Earth, where it meets the Earth's magnetic field. It acts as a protective shield and, for the most part, keeps the particle shower away from our planet.

Explosive processes in the Sun, such as coronary mass ejections and sudden radiation bursts - called 'flares' - can cause turbulence and transform the uniformly flowing solar wind into a storm.

With a flare, the intensity of 'x-rays' often increases by more than a thousand times. Those are high-energy protons and electrons. That radiation reaches us unhindered after just eight minutes. While the particle streams reach Earth 10 to 30 minutes later.

In a coronary mass ejection, the Sun hurls huge clouds of electrically charged gas into space. These clouds can have a mass of several tens of billions of tons and reach a speed of over 2000 kilometers per second!

The explosive mass ejections cause shock waves within the constantly flowing solar wind, comparable to the supersonic bang of an aircraft.

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Earth in the line of fire

If these shock waves hit Earth, the particles from the Sun can overcome Earth's protective shield with their powerful speed, penetrating its magnetic field.

This means strong solar storms can cause enormous damage. They influence the structure of electromagnetic waves and interfere with mobile radio and satellite navigation.

On March 13th, 1989, a nine-hour power outage occurred in Quebec, Canada. Millions of people were without electricity. A violent solar storm had induced strong currents in the overhead lines and caused transformers to burn through.

The electrically charged particles from the sun can decelerate satellites and even shorten their lifetime by destroying electronic components.

Electronics and satellite technologies are playing an increasingly important role in our lives. Now more than ever, it's important to predict such solar storms. But before this can be done, the researchers must understand how solar storms form.

Space probe to unveil secrets

It is hoped the Parker Solar Probe can fill the gaps in our understanding; showing us how the solar atmosphere is heated and how the particles of the solar wind are accelerated.

Solar physicists have already developed different theories in answer to these questions. Only in March this year an international team led by Samuel D.T. Grant published anarticle in the renowned journal "Nature Physics".

In this paper, the researchers propose that the heating takes place via plasma waves in the transition layer between the surface and the corona of the sun. Other theories attribute the heating of the corona to processes in the Sun's magnetic field, such as the sudden fusion of magnetic field loops.

The Parker Solar Probe is designed to collect data for the first time in the region where the solar wind is generated. To do this, the satellite must approach our central star like no other probe before it. The spaceship has to dive into the corona of the sun and get as close as six million kilometers to the fiery red-hot ball of gas. 

Long journey to the sun

For decades, solar physicists have dreamt about sending satellites into the corona of the sun. In 1958, the year NASA was founded, such a mission was put on the agenda. But it would be decades before the necessary technologies were developed to protect the space probes from the extreme radiation and the enormous heat in the solar corona.

It will be a few more years before the Parker Solar Probe can explore this hellish region at close range. The probe's success is contingent on the help of Venus. After all, braking is not easy when flying a spaceship into the inner solar system. Therefore, the research probe must fly past Venus seven times. During each of these so-called 'swing-by' maneuvers, it transfers some energy to the planet. It slows down, changes its course and continues to advance towards the sun.

After the last fly-by in November 2024, the Parker Solar Probe will finally reach the speed at which it can approach the Sun by only six million kilometres. It will then fly through the solar atmosphere at a speed of 200 kilometres per second. That's approximately 30 times faster than the speed at which the International Space Station currently travels through space. With its four scientific instruments, it is to measure the particles buzzing around and the magnetic fields of our star.

Three times, the spacecraft is scheduled to fly into the vicinity of the Sun and give us completely new insights into its turbulent processes. Once off the ground, the Parker Solar Probe will be the fastest spaceship ever launched by humans.

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