Spp sweap nes_osa_oct2011

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Spp sweap nes_osa_oct2011

  1. 1. Kelly Korreck SWEAP Science and Operations Lead Smithsonian Astrophysical Observatory [email_address] Exploring the Sun Up Close: The Solar Wind Electron, Alphas, and Protons (SWEAP) Instrument Suite aboard Solar Probe Plus
  2. 2. Outline <ul><li>Solar Physics background and current unanswered questions </li></ul><ul><li>Solar Probe Plus Mission </li></ul><ul><li>What measurements do we need to solve solar mysteries? </li></ul><ul><li>SWEAP Instruments </li></ul><ul><li>SWEAP Technology Advancement </li></ul><ul><li>Summary </li></ul>
  3. 3. SOLAR PHYSICS BACKGROUND AND UNANSWERED QUESTIONS
  4. 5. Why is the Sun yellow? <ul><li>The surface of the Sun is hot because energy released through fusion in the solar core radiates and convects up to the surface </li></ul><ul><li>What is the spectrum of light from an object so hot it glows? </li></ul><ul><li>An ideal object without any intrinsic color emits light in a “Blackbody radiation curve” with a peak at one wavelength </li></ul><ul><li>Most of the solar surface is at 6000C </li></ul>
  5. 6. Is there anything above the surface?
  6. 7. THE SOLAR ATMOSPHERE <ul><li>The Solar Corona </li></ul>
  7. 8. How can you see the solar corona? <ul><li>The photosphere of the Sun is too bright to look for signatures of an atmosphere </li></ul><ul><li>We can use solar eclipses, when the Moon blocks the Sun, to search for anything beyond the disk </li></ul>
  8. 9. <ul><li>Astronomers have used solar eclipses to study the Moon and the Sun for thousands of years </li></ul><ul><li>Earliest recorded observations of eclipses date back to 6000BC </li></ul><ul><li>&quot;Astronomers Studying an Eclipse,&quot; a 1571 painting by Antoine Caron, oil on panel </li></ul>
  9. 10. Solar eclipse, as seen from the International Space Station over Turkey, March 2006
  10. 11. Druckmuller, Aniol, Rusin
  11. 12. SOLAR MYSTERIES <ul><li>Why so big? </li></ul>
  12. 13. The Scale Height Problem <ul><li>The scale height of an atmosphere is the distance in altitude you have to travel for the density to drop by a third </li></ul><ul><li>In a simple atmosphere with one temperature and one type of particle, there is a pretty simple relationship for the scale height of: </li></ul><ul><li>Using 6000 degrees C as a temperature and assuming the atmosphere is made of hydrogen then H = 175 km (110 miles) </li></ul><ul><li>Instead, from the eclipses the scale height is clearly like the radius of the Sun, or H = 695,500 km (430,000 miles) </li></ul><ul><li>We have a problem! The solar atmosphere is either: </li></ul><ul><ul><li>1000+ times hotter than the surface of the Sun </li></ul></ul><ul><ul><li>Made up of a new form of matter, 1000 times lighter than hydrogen </li></ul></ul>
  13. 14. New Matter or High Temperature? <ul><li>By 1905, scientists thought they had discovered a new form of matter, which they called “Coronium” </li></ul><ul><ul><li>A thousand times lighter than hydrogen </li></ul></ul><ul><ul><li>Only found in the atmosphere of the Sun </li></ul></ul><ul><ul><li>Other evidence (mysterious green lines), and a precedent… </li></ul></ul>
  14. 15. Evidence for a hot corona <ul><li>By the 1940s, we realized that the mysterious green lines were consistent with iron heated to millions of degrees </li></ul><ul><li>The interpretation was that the corona is extremely hot is slowly accepted </li></ul><ul><li>Today we can see this easily from space, by looking at x-rays from the Sun </li></ul>
  15. 16. Modern Images of the Hot Corona
  16. 17. Modern Artificial Eclipses
  17. 18. Going into the Eclipse Solar Probe Plus closest approach
  18. 19. SOLAR PROBE PLUS MISSION <ul><li>Mission to Touch the Sun </li></ul>
  19. 20. The Rationale for Solar Probe Plus is Five Decades Old <ul><li>Current study in line of studies dating back to “Simpson’s Committee” of the Space Science Board (National Academy of Sciences, 24 October 1958) </li></ul><ul><li>Why is the solar corona so much hotter than the photosphere? And how is the solar wind accelerated? </li></ul><ul><li>The answers to these questions can be obtained only through in-situ measurements of the solar wind down in the corona. </li></ul>
  20. 21. The Spacecraft SPC SPAN-A FIELDS WISPR SPAN-B ISIS
  21. 22. SPP Instrument Suites <ul><li>Electromagnetic Fields (FIELDS) Investigation </li></ul><ul><ul><li>PI. S. Bale, University of California Space Sciences Laboratory, Berkeley, CA </li></ul></ul><ul><li>Integrated Science Investigation of the Sun Energetic Particle Instruments (ISIS-EPI), </li></ul><ul><ul><li>PI. D. McComas, South West Research Institution, San Antonio, TX </li></ul></ul><ul><li>Solar Wind Electrons Alphas and Protons (SWEAP) Investigation </li></ul><ul><ul><li>PI. J. Kasper, Smithsonian Astrophysical Observatory, Cambridge, MA </li></ul></ul><ul><li>Wide field Imager for Solar Probe (WISPR) </li></ul><ul><ul><li>PI. R. Howard Naval Research Laboratory, Washington, DC </li></ul></ul><ul><li>Heliospheric Origins with Solar Probe Plus - Observatory Scientist (HeliOSPP) </li></ul><ul><ul><li>PI. M. Velli, Jet Propulsion Laboratory, Pasadena, CA </li></ul></ul><ul><li>SPP Participation </li></ul><ul><li>31 institutions participate in SPP science teams </li></ul><ul><ul><li>23 in the US, 8 foreign </li></ul></ul><ul><ul><li>17 educational, 5 non-profit, 8 government labs </li></ul></ul><ul><li>106 science team members </li></ul><ul><ul><li>69 PIs and Co-Is </li></ul></ul><ul><ul><li>37 additional scientists </li></ul></ul><ul><ul><li>Next generation graduate students and post-docs </li></ul></ul>
  22. 24. Final Orbit Near-Sun Trajectory
  23. 25. MEASUREMENTS NEEDED
  24. 26. FIELDS Measurements Magnetic measurements that hints at the heating of the solar corona and acceleration of the solar wind Bruno & Carbone 2006
  25. 27. ISIS Energetic Particle Suite <ul><li>Energetic Particle are produced in flaring active regions on the Sun as well as in shocks between the Sun and Earth. </li></ul><ul><li>These particles are hazardous to our space assets. </li></ul><ul><li>The acceleration mechanisms of these high energy particles are of interest throughout astronomy and physics. </li></ul>ISIS EPI-Lo EPI-Hi
  26. 28. Wide field Imager for Solar Probe <ul><li>Imaging </li></ul><ul><ul><li>The Solar Wind Structures and Fluctuations Directly. </li></ul></ul><ul><ul><li>CME and Shock Propagation and Evolution and Their Connection to the Site of Production of SEPs. </li></ul></ul><ul><li>Provides the Links Between the </li></ul><ul><ul><li>Solar Wind Structure and SPP in-situ Instruments </li></ul></ul><ul><ul><li>Solar Orbiter and Solar Probe Plus Missions </li></ul></ul>Characteristic Value Image Type White Light Broadband Aperture and Focal Length 3.78 cm diameter, 1.78 cm focal length Spatial Resolution 6.25 arc min Maximum Cadence – Full Frame <2 min Sensor APS – new design Format 2K x 2K, 10 µ square
  27. 29. Overview of STEREO’s Heliospheric Imager
  28. 30. WISPR Observations <ul><li>Images over an encounter used to determine large scale structure, inverted to produce electron density profile </li></ul><ul><li>High time resolution images used to study variable structures near the spacecraft: shocks, streams, reconnection exhausts, turbulence </li></ul>Polar Wind
  29. 31. SWEAP INSTRUMENT SUITE <ul><li>Electrons, Alphas and Protons </li></ul>
  30. 32. The Role of SWEAP <ul><li>SWEAP makes detailed measurements of the electrons, alpha-particles (fully ionized helium), and protons (fully ionized hydrogen) that make up 99% of the solar corona and solar wind </li></ul><ul><li>SWEAP observations map out the number of particles moving at different velocities. These maps are then used to determine, e.g.: </li></ul><ul><ul><li>Velocities, densities, temperatures, anisotropies </li></ul></ul><ul><ul><li>Electron temperature, anisotropy, heat flux </li></ul></ul><ul><ul><li>Interactions between particles and electromagnetic waves </li></ul></ul>
  31. 33. Overview – SWEAP Suite <ul><li>SWEAP Consists of Two Instruments (SPC & SPAN) and an Electronics Module (SWEM) </li></ul><ul><li>SPC – Solar Probe Cup </li></ul><ul><ul><li>Sun-viewing Faraday Cup </li></ul></ul><ul><li>SPAN – Solar Probe Analyzers </li></ul><ul><ul><li>SPAN-A, ion and electron electrostatic analyzers (ESAs) on ram-side of spacecraft bus </li></ul></ul><ul><ul><li>SPAN-B, electron ESA on anti-ram size of spacecraft bus </li></ul></ul><ul><li>SWEM – SWEAP Electronics Module (not shown) </li></ul><ul><ul><li>Single electrical interface to SPP, distributes power, commands instruments, formats and buffers data products, interfaces with FIELDS </li></ul></ul>SPAN-B SPC Ram Direction SPAN-A
  32. 34. Overview – SWEAP Science (1/4) <ul><li>Objective 1: Trace the flow of energy that heats and accelerates the solar corona and solar wind. </li></ul><ul><ul><li>How is magnetic energy converted into heating ions and electrons? </li></ul></ul><ul><ul><li>How does thermal and kinetic energy of plasma change with distance? </li></ul></ul>NASA/SDO/AIA Reconnection? Wave/Turbulence? Hinode/XRT
  33. 35. Overview – SWEAP Science (2/4) SPP SPP Hinode/SOT G-band bright points SUMER/SOHO Helios & Ulysses UVCS/SOHO Undamped (WKB) waves Damped (non-WKB)waves
  34. 36. Overview – SWEAP Science (3/4) <ul><li>Objective 2: Determine the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind. </li></ul><ul><ul><li>What is the fraction of closed magnetic field lines? </li></ul></ul><ul><ul><li>How do solar wind sources evolve with time? </li></ul></ul><ul><ul><li>How does coronal structure evolve into the solar wind? </li></ul></ul>
  35. 37. Overview – SWEAP Science (4/4) <ul><li>Objective 3: Explore mechanisms that accelerate and transport energetic particles. </li></ul><ul><ul><li>What are the roles of shocks, reconnection, waves, and turbulence in the acceleration of energetic particles? </li></ul></ul><ul><ul><li>What are the source populations and physical conditions necessary for energetic particle acceleration? </li></ul></ul>NASA/SDO/AIA Flare and corona mass ejection
  36. 38. WHAT SWEAP MEASUREMENTS DO WE NEED TO SOLVE SOLAR MYSTERIES? <ul><li>Data Needed </li></ul>
  37. 39. Kinetic Physics <ul><li>We are driven by two main questions and puzzling observations </li></ul><ul><ul><li>Why is the solar corona so hot? </li></ul></ul><ul><ul><ul><li>Plasma in corona 100-1000x hotter than photosphere (apparently violating 2 nd law of thermodynamics) </li></ul></ul></ul><ul><ul><ul><li>Temperature anisotropies (10-100x hotter in one direction than another) </li></ul></ul></ul><ul><ul><li>How is the solar wind accelerated so efficiently? </li></ul></ul><ul><ul><ul><li>Too much mass escaping at too high a speed </li></ul></ul></ul><ul><li>Why are these questions so hard to answer? </li></ul><ul><ul><li>Kinetic physics f(time, space, velocity) is needed, but we do not understand it well - 7 dimensions! </li></ul></ul><ul><ul><li>We cannot make the needed measurements remotely, we cannot reproduce the environment in a laboratory, and we cannot simulate it on a computer </li></ul></ul><ul><li>What can Solar Probe Plus do? </li></ul><ul><ul><li>Enter the corona and make direct observations </li></ul></ul><ul><ul><li>Capture the particle distributions and electromagnetic field fluctuations with high precision and cadence to get to the kinetic physics </li></ul></ul>
  38. 40. Background: Physics of a Classical Gas <ul><li>It is too difficult to describe the motion of every single particle in a gas or plasma, so we adopt statistical approaches </li></ul><ul><li>If there are many collisions, then the distribution of particles with speed follows a Bell Curve </li></ul><ul><li>However, in the Solar Wind, there are very few collisions. </li></ul><ul><ul><li>Leading to Temperature anisotropies and wave propagation and instabilities </li></ul></ul>A gas of particles Maxwell-Boltzmann distribution (the Bell Curve) Relative number of particles Speed
  39. 41. SWEAP Measurements <ul><li>SWEAP measures velocity distribution functions </li></ul><ul><li>Need to determine velocity (speed and direction) , density , and temperature of the solar wind. </li></ul><ul><li>Why not just fly an anemometer and a weather vane? </li></ul><ul><li>Because the solar wind is not in equilibrium </li></ul><ul><ul><li>Relative densities change </li></ul></ul><ul><ul><li>Species have different velocities </li></ul></ul><ul><ul><li>Species have different temperatures </li></ul></ul><ul><ul><li>Temperature can be hard to define </li></ul></ul><ul><li>A SWEAP measurement is a map of the number of electrons, alphas, and protons as a function of direction and energy </li></ul>Speed # of Particles density velocity (speed and direction) temperature Hydrogen (protons) Helium (alphas)
  40. 42. SPC Operating Principle HV Grid Four collector plates HV Waveform AC-Coupled Current Convert signal to voltage and amplify Measure amplitude with digital lock-in amplifier Move on to next energy window
  41. 43. SPAN Operating Principle <ul><li>All three electrostatic analyzers in SPAN begin with top hat hemispherical analyzers </li></ul><ul><ul><li>Voltage across pair of deflector plates selects elevation angle </li></ul></ul><ul><ul><li>Voltage across pair of curved plates selects energy/charge </li></ul></ul><ul><li>Anodes arranged in a ring determine the azimuth angle of each particle </li></ul><ul><li>Counters record flux of particles as a function of energy/charge, elevation, and azimuth </li></ul>Symmetry axis Deflectors Curved Plates
  42. 44. SWEAP TECHNOLOGY ADVANCEMENTS <ul><li>Solar Research in the Laboratory </li></ul>
  43. 45. The Faraday Cup on Voyager I & II Star Trek: The Motion Picture
  44. 46. Faraday Cups <ul><li>More than 20 Faraday cups built by members of the SWEAP team have flown on a variety of spacecraft in a wide range of environments </li></ul><ul><ul><li>e.g. Wind, Voyager, SOLRAD A-B, Pioneer 6-7 </li></ul></ul><ul><li>How do we build this to survive close to the Sun? </li></ul><ul><li>How do we know we got it right? </li></ul>
  45. 47. SPC Technology Advancement <ul><li>Mission: Bring Solar Probe Cup to TRL6 </li></ul><ul><li>Driving Requirement </li></ul><ul><ul><li>TRL 6=Show instrument operates in the thermal and particle environment of solar encounters </li></ul></ul><ul><li>Key Development Milestones </li></ul><ul><ul><li>High temperature/high solar intensity material testing in solar furnace </li></ul></ul><ul><ul><li>Exposure of SPC thermal test model in solar furnace </li></ul></ul><ul><ul><li>Exposure to simulated solar photon and particle environments </li></ul></ul><ul><li>Experimental Practices </li></ul><ul><ul><li>Use multiple facilities for measurement of materials properties </li></ul></ul><ul><ul><li>Use multiple facilities for solar simulator </li></ul></ul>
  46. 49. You can clearly see the furnace from the highway.
  47. 50. Solar Furnace The control room we were in where you steer the mirrors The laboratory with the vacuum chamber The focusing parabola The mirrors The “iris”: a pair of doors that open and close to adjust the amount of sunlight that hits the chamber
  48. 51. This is the view from the operations center. At the moment the mirrors are all stowed pointing straight forward.
  49. 52. In this example, the center 32 mirrors have just been commanded to move from standby to projecting the Sun onto the focusing parabola. As the mirrors tilt downward, the Sun shines into the window of the control center and then to the center of the parabola. The light is bright but not dangerous because we are not at any kind of focus. This entire sequence of images took place in less than 60 seconds.
  50. 53. Summary <ul><li>There are outstanding mysteries about our Sun </li></ul><ul><ul><li>Why is the corona so hot? </li></ul></ul><ul><ul><li>Why is the solar wind so fast? </li></ul></ul><ul><li>The Solar Probe Plus mission will enter the atmosphere of our Sun in 2018 </li></ul><ul><ul><li>Using measurements ranging from white light images to proton distribution functions, we will help answer the outstanding solar mysteries. </li></ul></ul><ul><ul><li>Follow our adventure! </li></ul></ul><ul><ul><li>http://twitter.com/TheSWEAPLife </li></ul></ul>

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