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Voyager: Shock Waves in Deep Space

What exactly is the shock wave that Voyager 1 encountered earlier this year, a wave that is still propagating outward, according to new data from the craft? Researchers at the Jet Propulsion Laboratory refer to it as a ‘tsunami wave,’ a simile that reminds us of the devastating effects of roiled water as it encounters land following an earthquake or an impact in the ocean.

But in this case the cause is a coronal mass ejection (CME), in which the Sun heaves out a magnetic cloud of plasma from its surface, generating a pressure wave. As this JPL news release explains, the outgoing wave runs into charged particles in deep space — interstellar plasma — creating the disturbance. In all, Voyager 1 has experienced three of these shock waves, with the most recent first being observed in February of 2014 and still continuing.

The new data were presented on December 15 at the American Geophysical Union meeting in San Francisco by Don Gurnett (University of Iowa), who is quoted as saying “Most people would have thought the interstellar medium would have been smooth and quiet. But these shock waves seem to be more common than we thought.” Project scientist Ed Stone (Caltech) said the shock wave was causing the ionized interstellar gas to “‘sing’ or vibrate like a bell.”

“The density of the plasma is higher the farther Voyager goes,” Stone added. “Is that because the interstellar medium is denser as Voyager moves away from the heliosphere, or is it from the shock wave itself? We don’t know yet.”

You can hear the ‘singing’ that Stone describes in this JPL video, which includes a color-coded graph showing the frequency of the waves — this indicates the density of the plasma. Detection of the wave came through the spacecraft’s plasma instrument. Previous instances of the phenomenon occurred from October to November of 2012 and April to May of 2013. In fact, it was the shock wave in 2013 that helped scientists determine that Voyager 1 had left the heliosphere, the ‘bubble’ created by the solar wind that extends well past the outer planets. The plasma the spacecraft encountered then was forty times denser than any previously measured.

Voyager_wave

Image: The graphic above shows the frequency of the waves, an indication of the density of the plasma. Colors correspond to the intensity of the wave, with red being the loudest and blue the weakest. Credit: NASA/JPL.

Just how far out should these ‘tsunami waves’ be encountered? Gurnett, who is principal investigator for the plasma instrument on Voyager, thinks the waves may propagate out to twice the distance currently separating Voyager and the Sun. If that’s the case, we’ll be dealing with interesting plasma data as long as the Voyagers stay with us. Somewhere around 2025 is the likely endpoint of communications as the two probes run out of the power needed to transmit.

Ponder this: If it were not for loss of consumables, as seen in Voyager’s diminishing hydrazine and power levels, we could probably continue to track the craft for another century. As of this morning, Voyager 1 is 129.92 AU from the Sun, for a round-trip light time of over 36 hours.

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Comments on this entry are closed.

  • Stephen Urbanek December 17, 2014, 15:07

    What equipment is aboard the New Horizons spacecraft that will differ from what is on Voyager

  • ljk December 17, 2014, 17:28

    This article on what would have happened if Voyager 1 had been sent to Pluto instead of a Titan flyby in 1980 highlights what that venerable probe would have done as opposed to New Horizons:

    http://solarsystem.nasa.gov/news/display.cfm?News_ID=47674

    Here is an interesting discussion on why New Horizons will never catch up with Voyager 1:

    https://what-if.xkcd.com/38/

  • Marshall Eubanks December 17, 2014, 17:34

    They couldn’t fit a magnetometer in the New Horizon’s mass budget (!), so it doesn’t have one (!!!)*. However, it does have the “Plasma and high-energy particle spectrometer suite (PAM),” which can makes measurements such the one above. I haven’t heard anything about problems with it, so I assume its functional.

    Note that it will be 2045-2050 before NH reaches interstellar place and is able to make these sorts of measurements.

    * Neither does the Dawn spacecraft. It really should.

  • Space Audio December 17, 2014, 17:44

    Unfortunately, New Horizons doesn’t have a plasma wave receiver, so we won’t get similar data.

    Note that the signals we are reporting are by-products of the solar shock wave. We would be able to detect the shock wave directly as it passed, but would have to be very lucky to happen to be collecting data as it passed. These shock waves do not have a large radial extent and pass by in just a few minutes. After passing the heliopause, we were detecting local electron plasma oscillations driven by an electron beam heated at a distant shock. More recently (as I understand (computer guy, not a scientist)) we may be seeing radio waves produced as one of these shocks interacts with an extended region of denser plasma ahead of us. These signals may be a sign of a density feature we have yet to encounter.

    The audio presented here is resampled to show the evolution of the signal over many months. For a small sample of the raw audio, see https://www.youtube.com/watch?v=CFklHHWbYrk

  • ProjectStudio December 17, 2014, 18:51

    For a bit now I’ve been wondering of a hybrid sail craft – combining a light and magnetic sail – might make a close pass by the sun for gravitational slingshot timed (requires a predictive capability) with a solar flare or CME event. The potential gain in kinetic energy should be enormous and, from the information in this article, it seems that the craft could ‘ride the wave’ of a mass ejection well beyond the heliopause.

  • NS December 18, 2014, 5:06

    If I understand correctly distance to the heliopause (and eventually to true interstellar space) varies drastically depending on direction. If those are the areas we want to explore we should aim directly for them by the quickest route possible e.g. that proposed for the Innovative Interstellar Explorer. The next launch window for the IIE (which requires a slingshot around Jupiter) is in 2026. Time to start developing it if we’re serious.

  • ljk December 22, 2014, 15:28

    Voyager 1 Detects ‘Tsunami’ Wave From Sun Still Going Strong Beyond the Heliopause

    By Leonidas Papadopoulos

    Having long ago completed its epic journey of exploration and discovery through the outer Solar System, NASA’s Voyager 1 is the spacecraft that keeps on going more than 37 years after it was launched, while having already taken on its new role as humanity’s first robotic emissary to the stars. This historic passage into interstellar space, which occurred in August 2012, was marked by a steep increase in the levels of cosmic rays coming from interstellar space as measured by Voyager 1’s onboard instruments, accompanied by a sudden drop in the number of solar wind particles that originated from the Sun.

    Yet, despite having exited the Sun’s magnetic sphere of influence, the spacecraft can still feel the effects of its activity. Ongoing measurements taken throughout 2014 show that a “tsunami wave,” which was generated by the Sun in February, is still flying through interstellar space, providing scientists with new insights about the physics of the interstellar medium.

    As described in a previous AmericaSpace article, the magnetosphere of the Sun, better known as the heliosphere, is a vast magnetic bubble that extends well beyond the planets of the Solar System. This realm is dominated by the outward flow of the solar wind—the steady stream of charged particles that is released by the Sun’s upper atmosphere at speeds that range between 400 and 800 km/second.

    Traversing interplanetary space along the magnetic field lines of our home star, the solar wind eventually slows down to subsonic speeds at a boundary called the termination shock, which is located between 84 and 94 Astronomical Units away from the Sun, until it is finally stopped altogether at the heliopause (the outer limits of the heliosphere) by the pressure of the stellar winds that stream through the interstellar medium.

    Full article here:

    http://www.americaspace.com/?p=73607

  • ljk February 24, 2015, 14:29

    Exploring The Solar System Through The Eyes Of Robotic Voyagers

    FEBRUARY 21, 2015 5:09 PM ET

    The Voyager spacecraft have revolutionized our understanding of our solar system since their launch in 1977. After decades of sending back data on our planetary neighbors, Voyager 1 and 2 are entering new territory: interstellar space.

    In a new book, The Interstellar Age: Inside The Forty-Year Voyager Mission, planetary scientist Jim Bell shares the amazing human stories behind the machines’ mission.

    “Voyagers are one of the grandest, most remarkable, incredible voyages of exploration that humans have ever taken,” Bell, president of the Planetary Society, tells NPR’s Arun Rath. “It just so happens that we’re taking that voyage through the eyes of robotic travelers.”

    The book goes behind the scenes into tense control room moments at NASA’s Jet Propulsion Lab, the compromises made in planning flyby encounters and the excitement of getting never-before-seen views of the cosmos. It’s also part personal memoir, as Bell explains how his own life is delicately intertwined with the Voyager mission.

    Full article here:

    http://www.npr.org/2015/02/21/387266477/exploring-the-solar-system-through-the-eyes-of-robotic-voyagers

    WSJ review of the book here:

    http://www.wsj.com/articles/book-review-the-interstellar-age-by-jim-bell-1424453386

  • ljk February 25, 2015, 9:47

    Review: The Interstellar Age

    One of the most remarkable planetary missions to date has been Voyager, providing up-close examinations of four outer planets and their moons, some never seen in that way before or since. Jeff Foust reviews a book by someone who had a cameo role on the mission that offers a very human story about these robotic explorers.

    Monday, February 23, 2015

    http://www.thespacereview.com/article/2697/1

  • ljk February 25, 2015, 9:49

    NASA Voyager 1 & 2 Owners’ Workshop Manual: 1977 onwards (including Pioneer 10 & 11) Hardcover

    Coming out on August 15, 2015

    by Christopher Riley (Author)

    ISBN-13: 978-0857337757 ISBN-10: 0857337750

    Some more details here:

    http://www.amazon.com/NASA-Voyager-Owners-Workshop-Manual/dp/0857337750/ref=sr_1_3?s=books&ie=UTF8&qid=1424871109&sr=1-3&keywords=voyager+1

  • ljk March 15, 2015, 19:54

    40 years and counting: the team behind Voyager’s space odyssey

    In 1977, Voyager 1 and 2 started their one-way journey across our galaxy, travelling a million miles a day. Jonathan Margolis meets the dedicated team keeping the craft moving.

    Sunday 15 March 2015 04.00 EDT

    On a chilly March morning, Steve Howard, aged 65, is at work in his office on the northern edge of Pasadena, California. Two computer screens are squeezed on to his corner desk along with family photos, a tissue box and tins of Altoids Curiously Strong Peppermints. The office is in a quiet business park by a workaday main road. Next to it is a McDonald’s, where people linger for hours over a $1 coffee, seemingly to keep warm. Over the road there’s a scruffier burger joint, Jim’s, with an M missing from its sign – and, visible from Howard’s window, a landscaping supplies yard.

    Full article here:

    http://www.theguardian.com/science/2015/mar/15/voyager-1-and-2-space-journey-nasa

    To quote:

    Engineers are not given to emotion, but the romance of this incredible voyage of discovery has, by their own account, kept the ageing mission team together. Even latecomers, who were at school when Voyager was launched, have been working on the same mission for 30 years and more. “I’m in my mid-50s and treat the craft like my ageing parents,” says Suzy Dodd, who was 16 at launch, joined as a graduate student and whose card now proclaims surely one of the cooler job titles in science: Project manager, Voyager Interstellar Mission.

    “You treat them with a certain amount of reverence; you know they’re stately spacecraft, venerable senior citizens, and you want to do everything possible for them to have a healthy lifetime,” she says. “You need to help them a bit because things have failed and you want to be careful other things don’t. Most of the engineers here have dedicated their career to this project. They have turned down opportunities for promotions and other things because they like Voyager so much they want to stay with it.”

    It is clear talking to Voyager staff that they genuinely love their spacecraft, even though most were too young to see them before they flew, and it is more than possible that the older ones will have died before the Voyagers bleep their last. But as engineers, they have mixed feelings about the most famous aspect of that romance, the “golden record” that each craft carries. This is a gold-covered copper LP, packed with a needle and cartridge (plus instructions), and containing, in groove form, 115 photos from Earth, a selection of natural sounds from surf to whales, music from a variety of cultures and eras (the modern west is represented by Chuck Berry’s “Johnny B Goode”) and spoken greetings in 55 languages, from Akkadian, spoken in Sumer about 6,000 years ago, to Welsh.

    Carl Sagan, who had the initial idea for the record, wrote in the 1970s: “The spacecraft will be encountered and the record played only if there are advanced spacefaring civilisations in interstellar space. But the launching of this bottle into the cosmic ocean says something very hopeful about life on this planet.” Sagan’s son Nick, then an infant, now a science-fiction novelist and screenwriter (his credits include Star Trek episodes), recorded the English message: “Hello from the children of planet Earth.” But one sure to make many tear up is the Mandarin: “Hope everyone’s well. We are thinking about you all. Please come here to visit when you have time.” (The messages are on the Voyager website, http://voyager.jpl.nasa.gov).

    Voyager’s mission controllers are less starry-eyed than Sagan about the golden records. You sense some feel that it was too much of a bow to religious sentiment. Steve Howard is one of the more positive on the record question. “Even though Earth may not be here, some intelligent being could pick it up and detect it. I would say that many of the civilisations are much more advanced and would detect something like that and simply go in and decipher it,” he says.

    Suzy Dodd’s view is more typical of the team’s. “I think it’s a great idea to get humans and mankind thinking what-ifs. Let’s send a picture of ourselves vintage 1977 and put it on a spacecraft and send it out there forever. I think it’s done to connect us to the spacecraft more than for an alien running into it. I’m of the opinion that space is very empty and the chances of something finding it are remote. But that doesn’t diminish the fact that we’ve got a little time capsule out there travelling through space and now orbiting around in our galaxy. And that’s us.”