NASA's Juno finds Jupiter's solar wind defence relies on richer plasma waves than Earth's

First reported 29 Oct, 12:26 UTCSource: ScienceDaily + 1 moreLast editorial activity 29 Oct, 12:26 UTCWrite a comment ↓

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According to ScienceDaily, NASA’s Juno spacecraft has identified a layered defence Jupiter uses against the solar wind, built from plasma waves and shock regions that are more intricate than those seen at Earth. The study, led by scientists at the University of Iowa, may also help researchers understand the powerful shock waves produced by exploding stars.

How Juno measured the planet's defence

Using measurements from Juno, researchers found that Jupiter relies on plasma waves with several frequencies to slow and heat incoming particles from the Sun. These frequencies, known as harmonics, form a wave pattern more elaborate than the one typically observed at Earth.

Jayasri Joseph, a postdoctoral researcher at Iowa's Department of Physics and Astronomy and the study's corresponding author, compared the effect to music: a chord of several notes sounds richer than a single note, and plasma waves carrying multiple frequencies can act on incoming particles in more involved ways.

Why Jupiter's bow shock behaves differently

Earth's bow shock draws mainly on plasma waves concentrated around one frequency. Jupiter's bow shock, by contrast, passes energy to a larger number of particles, heating them and reducing their speed. Joseph said this makes the planet's approach especially effective, since several frequencies allow more particles in the solar wind to be heated and slowed.

The solar wind is a continuous stream of electrically charged particles released by the Sun, travelling at great speed and often faster than sound moves through the surrounding plasma. When it meets a planet with a magnetic field, it reaches a boundary known as the bow shock, which at Earth helps steer much of the flow around the planet.

An additional line of defence

The researchers also identified a further difference. Before incoming particles reach Jupiter's main bow shock, they can run into smaller shock structures called shocklets, which add a layer of protection outside the main boundary.

Open questions

How much do the shocklets contribute to Jupiter's protection compared with the main bow shock?

Key facts

NASA’s Juno spacecraft has found that Jupiter defends itself against the solar wind with a complex system of powerful plasma waves and several shock regions.

Led by scientists at the University of Iowa, the study offers the most detailed observations so far of Jupiter’s bow shock, an invisible boundary where particles from the Sun meet the planet’s magnetic environment.