{"id":22001,"date":"2021-12-15T17:32:10","date_gmt":"2021-12-15T11:47:10","guid":{"rendered":"https:\/\/www.revoscience.com\/en\/?p=22001"},"modified":"2021-12-15T17:32:14","modified_gmt":"2021-12-15T11:47:14","slug":"a-spacecraft-has-touched-the-sun-for-the-first-time","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/a-spacecraft-has-touched-the-sun-for-the-first-time\/","title":{"rendered":"A Spacecraft Has \u201cTouched\u201d the Sun for the First Time"},"content":{"rendered":"\n

NASA\u2019s Parker Solar Probe crossed into the sun\u2019s atmosphere on April 28, researchers report in\u00a0Physical Review Letters<\/em><\/strong><\/p>\n\n\n\n

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Credit: NASA \/ Johns Hopkins APL \/ Ben Smith<\/figcaption><\/figure>\n\n\n\n

COLLEGE PARK, MD<\/strong>\u00a0(APS)\u2014 On April 28, 2021, at 0933 UT (3:33 a.m. Eastern Daylight Time), NASA\u2019s Parker Solar Probe reached the sun\u2019s extended solar atmosphere, known as the corona, and spent five hours there. The spacecraft is the first to enter the outer boundaries of our sun.<\/p>\n\n\n\n

The results, published in Physical Review Letters<\/em><\/a>, were announced in a press conference at the American Geophysical Union Fall Meeting 2021 on December 14. The manuscript is open-access and freely available to download.<\/p>\n\n\n\n

\u201cThis marks the achievement of the primary objective of the Parker mission and a new era for understanding the physics of the corona,\u201d said Justin C. Kasper, the first author, Deputy Chief Technology Officer at BWX Technologies, and a professor at the University of Michigan. The mission is led by the Johns Hopkins University Applied Physics Laboratory (JHU\/APL).<\/p>\n\n\n\n

The probe made the first direct observations of what lies within the sun\u2019s atmosphere, measuring phenomena previously only estimated.<\/p>\n\n\n\n

The sun\u2019s outer edge begins at the Alfv\u00e9n critical surface: the point below which the sun and its gravitational and magnetic forces directly control the solar wind. Many scientists think that sudden reverses in the sun\u2019s magnetic field, called switchbacks, emerge from this area.<\/p>\n\n\n\n

\u201cThe concept of sending spacecraft into the magnetized atmosphere of the sun\u2014sufficiently close that the magnetic energy is greater than both ion and electron kinetic and thermal energy\u2014predated NASA itself,\u201d said Kasper.<\/p>\n\n\n\n

In 2018, NASA launched Parker Solar Probe with the goal of finally reaching the sun\u2019s corona and making humanity\u2019s first visit to a star.<\/p>\n\n\n\n

This past April, the probe spent five hours below the Alfv\u00e9n critical surface in direct contact with the sun\u2019s plasma. Below that surface, the pressure and energy of the sun\u2019s magnetic field were stronger than the pressure and energy of the particles. The spacecraft passed above and below the surface three separate times during its encounter. This is the first time a spacecraft has entered the solar corona and touched the atmosphere of the sun.<\/p>\n\n\n\n

Surprisingly, the researchers discovered that the Alfv\u00e9n critical surface is wrinkled. The data suggest that the largest and most distant wrinkle of the surface was produced by a pseudostreamer\u2014a large magnetic structure more than 40 degrees across, found back on the innermost visible face of the sun. It is not currently known why a pseudostreamer would push the Alfv\u00e9n critical surface away from the sun.<\/p>\n\n\n\n

Researchers noticed far fewer switchbacks below the Alfv\u00e9n critical surface than above it. The finding could mean that switchbacks do not form within the corona. Alternatively, low rates of magnetic reconnection on the sun\u2019s surface could have pumped less mass into the observed wind stream, resulting in fewer switchbacks.<\/p>\n\n\n\n

The probe also recorded some evidence of a potential power boost just inside the corona, which may point to unknown physics affecting heating and dissipation.<\/p>\n\n\n\n

\u201cWe have been observing the sun and its corona for decades, and we know there is interesting physics going on there to heat and accelerate the solar wind plasma. Still, we cannot tell precisely what that physics is,\u201d said Nour E. Raouafi, the Parker Solar Probe Project Scientist at JHU\/APL. \u201cWith Parker Solar Probe now flying into the magnetically-dominated corona, we will get the long-awaited insights into the inner workings of this mysterious region.\u201d<\/p>\n\n\n\n

The observations took place during Parker Solar Probe\u2019s eighth encounter with the sun. All data is publicly available in the NASA PSP archive. Several previous studies predicted the probe would first pass within the sun\u2019s boundaries in 2021.<\/p>\n\n\n\n

The fastest known object built by humans, Parker Solar Probe has made many new discoveries since its launch, including on explosions that create space weather<\/a> and the dangers of super-speedy dust<\/a>.<\/p>\n\n\n\n

The new findings suggest that direct observations by spacecraft have much to illuminate about the physics of coronal heating and solar wind formation. Having achieved its goal of touching the sun, Parker Solar Probe will now descend even deeper into the sun\u2019s atmosphere and linger for longer periods of time.<\/p>\n\n\n\n

According to Gary Zank, a co-investigator on the probe\u2019s Solar Wind Electrons Alphas and Protons (SWEAP) instrument and a member of the National Academy of Sciences, \u201cIt is hard to overstate the significance of both the event and the observations made by Parker Solar Probe. <\/p>\n\n\n\n

For over 50 years, since the dawn of the space age, the heliospheric community has grappled with the unanswered problem of how the solar corona is heated to well over a million degrees to drive the solar wind. The first measurements of the sub-Alfv\u00e9nic solar wind may represent the most major step forward in understanding the physics behind the acceleration of the solar wind since the formative model by Parker.\u201d<\/p>\n\n\n\n

\u201cThis event is what many heliophysicists have dreamed about for most of their careers!\u201d Zank added.<\/p>\n","protected":false},"excerpt":{"rendered":"

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