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195 Å image – behind

SECCHI Extreme Ultraviolet Imager (EUVI). In Space Weather, you get ahead by being behind. 24 March 2008. 195 Å image – Sun- Earth line – SOHO / EIT image. 195 Å image – ahead. 195 Å image – behind. Suggested Plan C Place Solar-C at L5. Solar-C. Sun.

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195 Å image – behind

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  1. SECCHI Extreme Ultraviolet Imager (EUVI) In Space Weather, you get ahead by being behind. 24 March 2008 195 Å image – Sun- Earth line – SOHO/ EIT image 195 Å image – ahead 195 Å image – behind

  2. Suggested Plan C Place Solar-C at L5 Solar-C Sun Separation varies from ~60 to more than 90 deg from the Sun-Earth line Earth

  3. L5 Mission Science Joseph M. Davila NASA Goddard Space Flight Center December 2008

  4. Science Objectives (1) • Understand the origin of magnetic fields in the Sun • Nearly stable 2-point helioseismology over a long observing periods provides optimum observing – questionable, large continuous telemetry needed, out-of-ecliptic observation desirable, NEED TO TALK TO HELIOSEISMOLOGISTS • Long, uninterrupted observing periods give excellent frequency resolution of the relevant wave modes • Observation of the Tachocline region over solar cycle (or a large fraction thereof) • 3D photospheric field – accurate 3D field even in weak regions by triangulation validates vector field measurement methods • Photospheric and/or chromospheric field measurement possible depending on science and instumental ability • LAST 2 POINTS IMPORTANT FOR SPACE WEATHER, DISCUSSION: L4 OR L5 FOR B?

  5. Science Objectives (2) • Understand the 3D coronal structure and magnetic FIELDS of active regions – REDUNDANT WITH CURRENT STEREO MISSION • Determine the structure of active region fields: SPACECRAFT AT L5 AND SUN-EARTH LINE TOO FAR APART? • Triangulation of magnetic loops provides independent measure of coronal magnetic field to compare with extrapolations • How is energy stored in the active region magnetic field? • How are CMEs initiated in active regions • Transients and CMEs are imaged all the time • Constant view of Sun-Earth directed CMEs to study geoeffectiveness • Optimum observing position to overcome the occulter and Thomson surface limitations of Earth-based instrument • CIR: NEXT GENERATION HI IS SUGGESTED HERE

  6. Science Objectives (3) – NOT A STRONG JUSTIFICATION FOR L5 • How does the magnetic field of the Sun connect to the Heliosphere? • Increased surface angular coverage to improve heliospheric models • Magnetic field measurements over 75% of the solar surface (approaching 100% if one STEREO is operating) – STEREO MISSION DOES NOT HAVE A MAGNETOGRAPH! • Activity observation over 75% of Sun • How is open flux destroyed on the Sun to maintain the nearly steady state solar field strength? • How are structures observed in the IPM related to solar structure? • What is the origin of interplanetary turbulence? • What is the origin of the FIP effect, and what height does it occur? – NO NEED FOR L5 • Use composition to trace IPM structures back to solar surface

  7. Science Objectives (4) • What is the 3D structure of the corona near the Sun? • Routine tomography will provide 3D pictures of the solar streamer structure, and how it relates to the heliospheric current sheet. • How is energy released in a flare – YES, BUT WANT STEREO OBSERVATIONS • How do loop top sources relate to puzzling RHESSI footpoint results? – L5 IS ONLY ADVANTAGIOUS WITH STEREO OBSERVATIONS • Height information for critical flare emissions • Stereo observation of reconnecting flare regions • Flare structure in 3D • How are particles accelerated near the Sun? and how do they propagate to 1AU? • What is the structure of shocks in the low corona? • What is the site of particle acceleration, and what controls the acceleration process?

  8. L5 Mission Approach • No overlap with ALL existing or planned missions • And at the same time COMPLEMENTS all existing missions

  9. Proposed Instrumentation • High resolution vector magnetograph • High resolution coronal soft x-ray or EUV imager • High cadence UV-EUV spectrometer • High resolution white light coronagraph • Solar wind ions with composition and electrons • Energetic ions with composition • Magnetometer

  10. L5 Orbit • L5 provides quasi stable orbit • Earth-sun-sc angle varies from about 40 to 90 degrees • About 1 AU from Sun • Insertion time 1-2 yrs Earth Sun L5 Equipotentials

  11. Data Downlink Capability • STEREO demonstrates a minimum using X-band • Transmission rate of order 480 kbps • Contacts are 5 hours long • Total downlink varies from 5 to 7 gigabits/day • Using 30 m dish • The total downlink can be improved by increasing any of these parameters

  12. The External Environment • SDO – high time and spatial resolution from geosynchronous Earth orbit, magnetograph and coronal imaging • Solar Orbiter – out of the ecliptic (~30 deg) observation from ~25 Rsun • Solar Probe – in ecliptic observation, in-situ instruments and coronal imager with multiple passes to 10 Rsun • STEREO (Extended Mission?) – 45 degree drift/2 years, 135 degrees from Earth in 2013, directly behind Sun in 2015

  13. Suggested Plan C Place Solar-C at L5 Solar-C Sun Separation varies from ~60 to more than 90 deg from the Sun-Earth line Earth

  14. Overcomes Thomson Surface Problem for CME Observation Earth CME Direction Earth Sun

  15. Technical Issues to Consider • Injection into L5 orbit – tradeoff between fast arrival time, propulsion mass, and instrument mass – INVESTIGATE TRADE SPACE; NEED SPECS ON POSSIBLE INSTRUMENT PARAMETERS • Maintenance of the orbit • Optimize telemetry and ground system • Once-a-day upload of ops plan

  16. NRL Ideas/Instruments for Science at L5 • SEP (particle instruments, coronagraph): rescue lost science of STEREO - central meridian at L1 is western for L5, characterize shock front, evolution of active region producing multiple events (take out longitudinal variation), early phases of CMEs • EUV spectrograph off-limb, coronal electron profiles above the limb, spectroscopy at L5, particle measurements at L1, suprathermal distributions of ions and electrons, L1 context instruments, space weather predictive power, solar flares (standard model) • Irradiance (predictive power) (zone plates are small and light) • Advanced HI – image CIRs and CMEs better as well as solar wind • Particle instrumentation? • EUV/X-ray imaging • Chromospheric/coronal magnetic field measurements • Gamma ray spectroscopy (different viewpoints)? • Remote observation sensing of CME magnetic field, synergy with MWA/LWA • NRL proposed modification of L5 (slow moving spacecraft)

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