Tag Archives: magnetosphere

Solar Storms Cause Enormous X-Ray Aurorae On Jupiter

Everything is bigger on Jupiter, and that includes aurorae, also known as northern or southern lights. Now, a study of Jovinian aurorae coinciding with the arrival of a solar storm has, for the first time, witnessed X-ray aurorae that outshine those on Earth hundreds of times.

Aurorae result from interactions between the solar wind and a planet’s magnetic field. Charged particles pushed out by the Sun disturb magnetospheric plasma. The shape of the magnetic field funnels these particles towards the north and south magnetic poles. When these charged particles encounter the upper atmosphere, they excite the atoms and molecules they encounter, leading to spectacular light shows.

Jupiter is five times Earth’s distance from the Sun, so it experiences a weakened solar wind. On the other hand, its enormous magnetic field dwarfs that of the Earth. Even when the Sun is not particularly active, this can lead to impressive aurorae, which made astronomerswonder what would happen when a major solar storm sent its charged particles straight towards Jupiter.

“There’s a constant power struggle between the solar wind and Jupiter’s magnetosphere, said William Dunn, a Ph.D. student at University College London, in a statement. We want to understand this interaction and what effect it has on the planet. By studying how the aurora changes, we can discover more about the region of space controlled by Jupiter’s magnetic field, and if or how this is influenced by the Sun. Understanding this relationship is important for the countless magnetic objects across the galaxy, including exoplanets, brown dwarfs and neutron stars.”

X-ray emissions viewed by the Chandra space telescope overlaid on Hubble telescope photographs of Jupiter during and after the arrival of a powerful coronal mass ejection. Joseph DePasquale, Smithsonian Astrophysical Observatory Chandra X-ray Center

In the Journal of Geophysical Research Space Physics, Dunn described observations of a coronal mass ejection (CME) that hit Jupiter in October 2011. Despite the delay in analyzing what occurred, the paper is well timed. The Juno spacecraft will arrive at Jupiter in July, having been launched not long before the storms investigated in this paper occurred.

Among Juno’s many goals is the study of Jupiter’s magnetosphere, andDunn’s work will give its operators ideas on what to look for.

Dunn’s study follows the discovery of X-ray emissions on Jupiter in the 1980s, followed by the identification in 2002 of a polar X-ray hotspot. The impact of the solar wind particleshugely accelerated by Jupiter’s magnetic fieldon the atmosphere is so powerful, it causes the release of X-rays that are visible from the Chandra X-ray telescope in Earth orbit.

With the arrival of the CME, the X-rays became eight times as powerful as previous observations, and the hotspot’s pulsing sped upfrom a period of 45 minutes to 26 minutes.

There has been debate as to whether the ions that cause the X-ray discharge comeinitiallyfrom the solar wind, or if they were previously part of the magnetosphere disturbed by an increase in wind strength. By measuring the dominant frequencies of the X-rays, Dunn found strong evidence of sulfur, which is common in Jupiter’s atmosphere. However, he detected enough carbon to suggest some of the ions came from the solar wind, of which carbon is a major component.

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Read more: http://www.iflscience.com/space/jupiters-enormous-x-ray-auroras-revealed

Venus Has Massive Planet-Sized Explosions of Weather

Let’s face it: news about weather on Venus is never going going to be pleasant. Not only does the surface temperature remain a constant 900º F (480º C) with atmospheric pressure about 90 times higher than on Earth, but it rains sulfuric acid and snows metal.  We haven’t even been able to send a probe that lasts more than a couple hours. Not exactly a great vacation spot. 

Researchers have now discovered that Venus is exposed to extremely massive weather explosions, sometimes multiple times per day. The announcement comes from first author Glyn Collinson at NASA’s Goddard Space Flight Center and was published in the Journal of Geophysical Research.

Collinson et al. analyzed information gathered by the European Space Agency’s Venus Express orbiter, which studies the dynamics and chemistry of the Venusian atmosphere.  Venus is subjected to hot flow anomalies (HFAs), and these massive explosions of weather are actually larger than the planet itself. Solar wind, traveling a million miles per hour, doesn’t always move straight away from the sun. Sometimes it becomes tangled in itself and remains in contact with a planet’s bow shock (the point where the wind’s speed drops from contact with fields surrounding the planet) to create a powerful projection of hot plasma known as an HFA.

Credit: NASA

Large HFAs also occur near Earth, but our magnetosphere (the area of space surrounding our planet controlled by our magnetic field) shields us from any ill effects. In fact, the charged particles from the solar wind are responsible for creating aurorae, which are extremely pretty. When solar wind hits an HFA at Earth, the magnetosphere is strong enough to actually deflect the wind, even back toward the sun.

Venus, possessing only a tiny magnetosphere, isn’t as lucky. It has an ionosphere, which doesn’t really have much to offer in the way of protection against solar wind. When solar wind hits an HFA at Venus, it is much closer to the surface than the ones at Earth. The force could act like a vacuum and pull layers of the ionosphere away from the planet, potentially rendering it completely defenseless. 

Though Venus is basically an uninhabitable wasteland, there is a lot we can use to compare it to Earth. Understanding how space weather affects Venus differently than Earth is a great way to learn about our own magnetosphere and how essential it is for life to exist on this planet. Researchers will also explore how planetary formation proceeded so differently that Earth would have the capability to support life while Venus does not.

Photo credit: NASA/Collinson

Read more: http://www.iflscience.com/space/venus-has-massive-planet-sized-explosions-weather