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Multimedia Files in Support of the Voyager - Conditions At Edge Of Solar System Briefing

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Artist's concept of Voyager spacecraft. Credit: NASA › Link to Media Advisory
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Voyager data beamed back from their current location has lead to new computer models that show the edge of our solar system is not smooth, but filled with a turbulent sea of magnetic bubbles.

The finding suggests we need to revise our picture of this previously unexplored region so critical for understanding how cosmic rays are created and reach near-Earth space. Galactic cosmic rays are of concern for human space travel, in particular during the quiet periods called the solar minimum.

Speakers/Presenters

• Arik Posner, Voyager program scientist, Heliophysics Division, Science Mission Directorate, NASA Headquarters, Washington
• James F. Drake, Professor of Physics, University of Maryland, College Park
• Merav Opher, Assistant Professor, Astronomy Department, Boston University
• Eugene Parker, Professor Emeritus, Department of Physics, University of Chicago

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Visual: 1	› View larger Heliophysics is the science of the sun and its interactions with the earth and the solar system. An elaborate fleet of 26 spacecraft forms the Heliophysics System Observatory (HSO), which is shown in Visual 1. The HSO covers through observations the entire range of Heliophysics science from the solar interior to the upper atmosphere of the earth and beyond earth to the edge of the interstellar medium, more than three times the distance of the farthest planets from the sun. Credit: NASA
Visual: 2	› View larger The heliosphere is the word for the space filled by the sun’s outer atmosphere, the ionized and magnetized gas called the solar wind. Close to the sun up to the termination shock, the solar wind has a speed of a million miles per hour. At the termination shock, it slows down abruptly, feeling the influence of the interstellar medium that surrounds the heliosphere. The two Voyager spacecraft are in the nose region of the heliosheath, where the solar wind slows down further and eventually turns back towards the elongated heliotail. The heliosphere is shaped by the relative motions of the sun and the local interstellar medium. The boundaries of the heliosphere are dynamic, shaped by the relative pressures exerted by the solar wind and the interstellar gas. Credit: NASA
Visual: 3 › Download video This animation summarizes the new heliospheric scenario and the formation of the “sea” of bubbles in the heliosheath. The Sun’s magnetic field points toward the Sun in the Northern hemisphere and away from the Sun in the Southern (shown in red and blue). These oppositely pointing magnetic fields are separated by a layer of current called the heliospheric current sheet. Due to the tilt of the magnetic axis in relation to the axis of rotation of the Sun, the heliospheric current sheet flaps like a flag in the wind. The flapping current sheet separates regions of oppositely pointing magnetic field, called sectors. As the solar wind speed decreases past the termination shock, the sectors squeeze together, bringing regions of opposite magnetic field closer to each other. When the separation of sectors becomes very small, the sectored magnetic field breaks up into a sea of nested “magnetic bubbles” in a phenomenon called magnetic reconnection. The region of nested bubbles is carried by the solar wind to the north and south filling out the entire front region of the heliopause and the sector region in the heliosheath. Credit: NASA/Goddard Space Flight Center/CI Lab
Visual: 4	› View larger Artist's interpretation depicting“standard” old view of the heliosphere: the magnetic field lines in the heliosheath connect back to the Sun everywhere (Some field lines are shown in red and blue). In this view,scientists expected the heliopause, the boundary that separates where the solar wind dominates from where the interstellar wind dominates, to be smooth and the associated smooth magnetic field to shield us from the interstellar medium and galactic cosmic rays. Credit: NASA/Goddard Space Flight Center/CI Lab
Visual: 5	› View larger Artist's interpretation depicting the new view of the heliosphere. The heliosheath is filled with “magnetic bubbles” (shown in the red pattern) that fill out the region ahead of the heliopause. In this new view, the heliopause is not a continuous shield that separates the solar domain from the interstellar medium, but a porous membrane with fingers and indentations. Credit: NASA/Goddard Space Flight Center/CI Lab
Visual: 6 › Download video This animation shows the Voyager 2 observations of energetic electrons. Voyager 2 detected a dramatic drop of the flux of electrons as it left the sector region. The intense flux came back as soon as Voyager 2 was inside the sector region. Energetic particles have a hard time “navigating” through the sea of bubbles. The bubbles act like traps for these particles. When particles escape the sea of bubbles and access the field lines that connect back to the Sun, they quickly escape along the magnetic field lines, very much like entering a highway. These observations were the unexpected signature of the new scenario. Credit: NASA/Goddard Space Flight Center/CI Lab
Visual: 7 › Download video This animation depicts the effect of the new scenario on galactic cosmic rays. The heliospheric boundaries are very important in shielding the inner solar system from the galactic cosmic ray flux. The heliopause, the last region that separates us from the rest of the galaxy, acts more like a membrane that is permeable to galactic cosmic rays than a shield that deflects those energetic particles. The galactic cosmic rays slowly wander into the heliosphere and can get trapped in the sea of magnetic bubbles. Eventually they access the solar magnetic field lines that connect back to the sun, and can move quickly towards the sun and Earth. Credit: NASA/Goddard Space Flight Center/CI Lab

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