{"id":12611,"date":"2024-09-11T22:00:00","date_gmt":"2024-09-11T22:00:00","guid":{"rendered":"https:\/\/modernsciences.org\/staging\/4414\/?p=12611"},"modified":"2024-09-01T16:06:14","modified_gmt":"2024-09-01T16:06:14","slug":"2-solar-probes-are-helping-researchers-understand-what-phenomenon-powers-the-solar-wind","status":"publish","type":"post","link":"https:\/\/modernsciences.org\/staging\/4414\/2-solar-probes-are-helping-researchers-understand-what-phenomenon-powers-the-solar-wind\/","title":{"rendered":"2 solar probes are helping researchers understand what phenomenon powers the solar\u00a0wind"},"content":{"rendered":"\n
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\n This artist\u2019s rendition shows NASA\u2019s Parker Solar Probe approaching the Sun.\n Steve Gribben\/Johns Hopkins APL\/NASA via AP<\/a><\/span>\n <\/figcaption>\n <\/figure>\n\n Yeimy J. Rivera<\/a>, Smithsonian Institution<\/a><\/em>; Michael L. Stevens<\/a>, Smithsonian Institution<\/a><\/em>, and Samuel Badman<\/a>, Smithsonian Institution<\/a><\/em><\/span>\n\n

Our Sun drives a constant outward flow of plasma, or ionized gas, called the solar wind, which envelops our solar system. Outside of Earth\u2019s protective magnetosphere, the fastest solar wind rushes by<\/a> at speeds of over 310 miles (500 kilometers) per second. But researchers haven\u2019t been able to figure out how the wind gets enough energy to achieve that speed \u2013 until now. <\/p>\n\n

Our team<\/a> of heliophysicists<\/a> published a paper<\/a> in August 2024 that points to a new source of energy propelling the solar wind.<\/p>\n\n

Solar wind discovery<\/h2>\n\n

Physicist Eugene Parker predicted the solar wind\u2019s existence in 1958<\/a>. The Mariner spacecraft, headed to Venus, would confirm its existence<\/a> in 1962. <\/p>\n\n

Since the 1940s<\/a>, studies had shown that the Sun\u2019s corona, or solar atmosphere<\/a>, could heat up to very high temperatures \u2013 over 2 million degrees Fahrenheit<\/a> (or more than 1 million degrees Celsius). <\/p>\n\n

Parker\u2019s work suggested that this extreme temperature could create an outward thermal pressure strong enough to overcome gravity and cause the outer layer of the Sun\u2019s atmosphere to escape.<\/p>\n\n

Gaps in solar wind science quickly arose, however, as researchers took more and more detailed measurements of the solar wind near Earth. In particular, they found two problems with the fastest portion of the solar wind.<\/p>\n\n

For one, the solar wind continued to heat up after leaving the hot corona without explanation. And even with this added heat, the fastest wind still didn\u2019t have enough energy<\/a> for scientists to explain how it was able to accelerate to such high speeds.<\/p>\n\n

Both these observations meant that some extra energy source had to exist beyond Parker\u2019s models.<\/p>\n\n

\n \"A<\/a>\n
\n This artist\u2019s rendition shows the European Space Agency\u2019s Solar Orbiter orbiting the Sun.<\/span>\n NASA’s Goddard Space Flight Center Conceptual Image Lab<\/a><\/span>\n <\/figcaption>\n <\/figure>\n\n

Alfv\u00e9n waves<\/h2>\n\n

The Sun<\/a> and its solar wind are plasmas. Plasmas are like gases<\/a>, but all the particles in plasmas have a charge and respond to magnetic fields. <\/p>\n\n

Similar to how sound waves travel through the air and transport energy on Earth, plasmas have what are called Alfv\u00e9n waves moving through them. For decades, Alfv\u00e9n waves had been predicted<\/a> to affect the solar wind\u2019s dynamics and play an important role in transporting energy in the solar wind.<\/p>\n\n

However, scientists couldn\u2019t tell whether these waves were actually interacting with the solar wind directly or if they generated enough energy to power it. To answer these questions, they\u2019d have to measure the solar wind very close to the Sun. <\/p>\n\n

In 2018 and 2020, NASA and the European Space Agency launched their respective flagship missions: the Parker Solar Probe<\/a> and the Solar Orbiter<\/a>. Both missions carried the right instruments<\/a> to measure Alfv\u00e9n waves near the Sun.<\/p>\n\n

The Solar Orbiter ventures<\/a> between 1 astronomical unit, where the Earth is, and 0.3 astronomical units, a little closer to the Sun than Mercury. The Parker Solar Probe dives much deeper<\/a>. It gets as close as five solar diameters from the Sun, within the outer edges of the corona<\/a>. Each solar diameter is about 865,000 miles (1,400,000 kilometers).<\/p>\n\n

\n \"A<\/a>\n
\n NASA\u2019s Parker Solar Probe and ESA\u2019s Solar Orbiter missions measured the same stream of plasma flowing away from the Sun at different distances. Parker measured lots of magnetic waves near the edge of the corona \u2013 called the Alfv\u00e9n surface \u2013 while Solar Orbiter, located past the orbit of Venus, observed that the waves had disappeared and that their energy had been used to heat and accelerate the plasma.<\/span>\n Arya De Francesco<\/span><\/span>\n <\/figcaption>\n <\/figure>\n\n

With both these missions operating together, not only can researchers like us examine the solar wind close to the Sun, but we can also study how it changes between the point where Parker sees it and the point where the Solar Orbiter sees it.<\/p>\n\n

Magnetic switchbacks<\/h2>\n\n

In Parker\u2019s first close approach to the Sun, it observed that the solar wind<\/a> near the Sun was indeed abundant with Alfv\u00e9n waves<\/a>.<\/p>\n\n

Scientists used Parker to measure the solar wind\u2019s magnetic field. At some points they noticed the field lines \u2013 or lines of magnetic force \u2013 waved at such high amplitudes that they briefly reversed direction. Scientists called these phenomena magnetic switchbacks<\/a>. With Parker, they observed these energy-containing plasma fluctuations everywhere in the near-Sun solar wind.<\/p>\n\n

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