News Article | June 21, 2016
Earth's twin planet Venus is a blistering planet filled with streaks of acidic clouds, a runaway greenhouse effect and a surface hot enough to melt lead. This second planet from the sun is considered the closest semblance to our own planet because it is slightly smaller, but it's completely different. For instance, the atmosphere of Venus consists mainly of carbon dioxide, little nitrogen and small traces of sulfur oxide and other gases. Its atmosphere is much thicker than that of Earth and can reach pressures of more than 90 times that of our planet at sea level. It is also extremely dry, with a comparative abundance of water 100 times lower. But it wasn't always this way. Scientists believe that Venus once contained large amounts of water 4 billion years ago. However, as the planet heated up, much of the water evaporated into the atmosphere. They suspect that the planet's "electric wind" may have helped strip all the water out of the atmosphere. Astronomers have long been wondering whether all planets with atmospheres have an electric field generated by a layer of particles located in the ionosphere. But so far, in every planet that they looked, they have been unable to detect it. Their theory is that the electric field is just very, very weak. They even postulate that Earth's electric field is only at a range of 1 to 2 volts. The electric field of Venus, however, is quite enormous, says Glyn Collinson. "It's a monster lurking in the sky," says Collinson, who is a NASA scientist and lead author of a new paper that measures Venus' electric field. The planet's electric field is five times larger than that of Mars, Earth or Saturn's natural satellite Titan. Because it is so strong, scientists say the electric field produces its own "wind." It's very different from the gusts of air we experience, however, as it is more akin to solar wind - a stream of particles coming from the sun. Researchers say that when molecules of water go up into the atmosphere, light from the sun separates the water into hydrogen ions that easily escape and oxygen ions that are heavier. On Venus, the electric wind is so ferocious that it can accelerate these oxygen ions and cause them to escape the atmosphere. Co-author Professor Andrew Coates of the University College London Mullard Space Science Laboratory says the ions dragged away into space are lost forever, and that more than 100 metric tons of oxygen ions per year are actually removed from Venus. Collinson says although they do not know why the electric field is much stronger in Venus, they think its distance to the sun, as well as the ultraviolet sunlight being double in brightness, may be affecting it. The team used a large instrument aboard the European Space Agency's Venus Express to measure the planet's electric field. Details of the study are published in the journal Geophysical Research Letters on June 20. © 2016 Tech Times, All rights reserved. Do not reproduce without permission.
News Article | March 22, 2016
Jupiter has its own version of the Northern Lights, and it can be hundreds of times more energetic than the earthly phenomenon. For the first time, scientists have studied Jupiter’s X-ray aurora during a solar storm. They found that it was eight times brighter than usual under these conditions, and that its brightest spot “pulsed” more quickly—every 26 minutes as opposed to 45 minutes. The researchers don’t know exactly why this is, but ultimately understanding these kind of processes could help identify habitable planets elsewhere in the Universe. Here, the image on the left shows the aurora as a coronal mass ejection (solar flare) reached Jupiter in October 2011; the image on the right shows it two days later when the solar wind had subsided. As the aurora is made of X-rays—which are more energetic than the light in our aurora borealis—they’re not visible, but the brightness in the colouring is based on the data collected with NASA’s Chandra observatory. The study was published Tuesday in the Journal of Geophysical Research. William Dunn, a PhD student at University College London’s Mullard Space Science Laboratory and lead author, explained in a phone call that this research will help demystify the relationship between Jupiter’s massive magnetosphere (the area controlled by its magnetic field) and solar wind. “We have a vague idea of what’s going on between the Earth’s magnetic field and the solar wind, but we don’t really understand what happens elsewhere in the Solar System,” he explained. Jupiter is particularly interesting because its magnetic field and magnetosphere are very different from Earth’s. For a start, Jupiter is much bigger than Earth (and every other planet combined) and its magnetic field is magnitudes stronger. It also spins faster with a full rotation every 10 hours, as opposed to 24 hours, and is affected by volcanic material from the moon Io. As it’s so different to Earth, it could help inform which processes connecting Earth to the solar wind are shared among other celestial objects, and which may be unique. “Because Jupiter presents a very different set of circumstances, Jupiter and Earth kind of provide us with two benchmarks against which we can understand all these other places and all these other features across the Universe,” said Dunn. One reason this is particularly cool: We think magnetic fields are crucial to support complex life. The fact that Mars’s atmosphere was, we believe, stripped away by solar winds owing to its lack of a strong magnetic field, is a major reason many don’t expect it to host life anywhere near its surface. Knowing more about how magnetospheres relate to the Sun and solar winds could therefore inform our search for potentially habitable exoplanets. “By having a magnetic field, you get this protective boundary that prevents the solar wind sweeping away your atmosphere,” said Dunn. “And so understanding the signatures that are associated with that protective boundary, and that interaction with the Sun, will help us to understand how well-protected the planet is from the solar wind.” For now, the researchers don’t know exactly how the interplay between solar winds and Jupiter’s magnetosphere works, but given the effect of the solar storm on the aurora, they know there is a relationship there. Luckily for them, NASA’s Juno orbiter is scheduled to reach Jupiter in July, and one of its goals is to specifically investigate the gas giant’s magnetic field.
Ozeke L.G.,University of Alberta |
Mann I.R.,University of Alberta |
Murphy K.R.,University of Alberta |
Jonathan Rae I.,University of Alberta |
And 2 more authors.
Journal of Geophysical Research: Space Physics | Year: 2014
We present analytic expressions for ULF wave-derived radiation belt radial diffusion coefficients, as a function of L and Kp, which can easily be incorporated into global radiation belt transport models. The diffusion coefficients are derived from statistical representations of ULF wave power, electric field power mapped from ground magnetometer data, and compressional magnetic field power from in situ measurements. We show that the overall electric and magnetic diffusion coefficients are to a good approximation both independent of energy. We present example 1-D radial diffusion results from simulations driven by CRRES-observed time-dependent energy spectra at the outer boundary, under the action of radial diffusion driven by the new ULF wave radial diffusion coefficients and with empirical chorus wave loss terms (as a function of energy, Kp and L). There is excellent agreement between the differential flux produced by the 1-D, Kp-driven, radial diffusion model and CRRES observations of differential electron flux at 0.976 MeV - even though the model does not include the effects of local internal acceleration sources. Our results highlight not only the importance of correct specification of radial diffusion coefficients for developing accurate models but also show significant promise for belt specification based on relatively simple models driven by solar wind parameters such as solar wind speed or geomagnetic indices such as Kp. Key Points Analytic expressions for the radial diffusion coefficients are presented The coefficients do not dependent on energy or wave m value The electric field diffusion coefficient dominates over the magnetic ©2014. The Authors.
Lovejoy S.,McGill University |
Muller J.-P.,Mullard Space Science Laboratory |
Boisvert J.P.,McGill University
Geophysical Research Letters | Year: 2014
Terrestrial atmospheric and oceanic spectra show drastic transitions at τw ≈ 10 days and τow ≈ 1 year, respectively; this has been theorized as the lifetime of planetary-scale structures. For wind and temperature, the forms of the low- and high-frequency parts of the spectra (macroweather and weather) as well as the τw can be theoretically estimated, the latter depending notably on the solar-induced turbulent energy flux. We extend the theory to other planets and test it using Viking lander and reanalysis data from Mars. When the Martian spectra are scaled by the theoretical amount, they agree very well with their terrestrial atmospheric counterparts. We discuss the implications for understanding planetary fluid dynamical systems. Key Points Mars has weather/macroweather transition very similar to Earth'sWe can calculate the transition scale from first principlesLander, Mars reanalysis, and terrestrial data agree ©2014. American Geophysical Union. All Rights Reserved.
Kaviraj S.,Imperial College London |
Kaviraj S.,Mullard Space Science Laboratory |
Kaviraj S.,University of Oxford
Monthly Notices of the Royal Astronomical Society | Year: 2010
We explore the properties of 'peculiar' early-type galaxies (ETGs) in the local Universe that show (faint) morphological signatures of recent interactions such as tidal tails, shells and dust lanes. Standard-depth (∼51-s exposure) multicolour galaxy images from the Sloan Digital Sky Survey (SDSS) are combined with the significantly (∼2 mag) deeper monochromatic images from the public SDSS Stripe82 to extract, through careful visual inspection, a robust sample of nearby (z < 0.05), luminous (Mr < -20.5) ETGs, including a subset of ∼70 peculiar systems. ∼18 per cent of ETGs exhibit signs of disturbed morphologies (e.g. shells), while ∼7 per cent show evidence of dust lanes and patches. An analysis of optical emission-line ratios indicates that the fraction of peculiar ETGs that are Seyferts or LINERs (19.4 per cent) is twice the corresponding values in their relaxed counterparts (10.1 per cent). LINER-like emission is the dominant type of nebular activity in all ETG classes, plausibly driven by stellar photoionization associated with recent star formation. An analysis of ultraviolet-optical colours indicates that, regardless of the luminosity range being considered, the fraction of peculiar ETGs that have experienced star formation in the last Gyr is a factor of ∼1.5 higher than that in their relaxed counterparts. The spectrophotometric results strongly suggest that the interactions that produce the morphological peculiarities also induce low-level recent star formation which, based on the recent literature, are likely to contribute a few per cent of the stellar mass over the last ∼1 Gyr. Peculiar ETGs preferentially inhabit low-density environments (outskirts of clusters, groups or the field), either due to high peculiar velocities in clusters making merging unlikely or because shell systems are disrupted through frequent interactions within a cluster crossing time. The catalogue of galaxies that forms the basis of this paper can be obtained at http://www.mssl.ucl.ac.uk/~ska/stripe82/skavirajstripe82.dat or on request from the author. © 2010 The Author. Journal compilation © 2010 RAS.