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Stellar Winds and their Interaction with the Interstellar Medium

Stellar Winds and their Interaction with the Interstellar Medium. OUTLINE Astrospheric and Heliospheric Evolution Associated with Solar/Stellar Wind Evolution Intro to Basic Heliospheric Structure How Can We Detect Stellar Winds and/or Astrospheres?

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Stellar Winds and their Interaction with the Interstellar Medium

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  1. Stellar Winds and their Interaction with the Interstellar Medium • OUTLINE • Astrospheric and Heliospheric Evolution Associated with Solar/Stellar Wind Evolution • Intro to Basic Heliospheric Structure • How Can We Detect Stellar Winds and/or Astrospheres? • Inferring Wind Evolution from Astrospheric Absorption • Planetary Implications for Wind Evolution • Astrospheric and Heliospheric Evolution Associated with ISM Variability (Linsky) Brian E. Wood (Naval Research Laboratory) Jeffrey L. Linsky (JILA, University of Colorado) Neutrals interact through simple charge exchange processes (e.g., Ho+H+→H++Ho)

  2. Neutral Diagnostics of the Outer Heliosphere BISM Bow Shock? Heliopause VISM Termination Shock Solar Wind “Post-TS Neutralized Pick-Up Ions” Tail Schwadron et al. 2011, ApJ, 731, 56

  3. Neutral Diagnostics of the Outer Heliosphere BISM Bow Shock? Heliopause VISM Termination Shock Solar Wind “The Ribbon,” presumably where BISM n=0 “Post-TS Neutralized Pick-Up Ions” Tail Schwadron et al. 2011, ApJ, 731, 56 Schwadron et al. 2011, ApJ, 731, 56

  4. Neutral Diagnostics of the Outer Heliosphere Linsky & Wood 1996, ApJ, 463, 254 Cen “Hydrogen Wall,” or “Post-BS Neutralized ISM” BISM Bow Shock? Heliopause VISM Termination Shock Solar Wind “The Ribbon,” presumably where BISM n=0 “Post-TS Neutralized Pick-Up Ions” Tail Schwadron et al. 2011, ApJ, 731, 56 Schwadron et al. 2011, ApJ, 731, 56

  5. Neutral Diagnostics of the Outer Heliosphere Linsky & Wood 1996, ApJ, 463, 254 Wood et al. 2007, ApJ, 657, 609 Cen “Hydrogen Wall,” or “Post-BS Neutralized ISM” 1Ori “Post-TS Neutralized Bulk Solar Wind” BISM Bow Shock? Heliopause VISM Termination Shock Solar Wind “The Ribbon,” presumably where BISM n=0 “Post-TS Neutralized Pick-Up Ions” Tail Schwadron et al. 2011, ApJ, 731, 56 Schwadron et al. 2011, ApJ, 731, 56

  6. Astrosphere Images Young Star (LL Ori) Red Supergiant (Mira) Pulsar Massive Hot Star Red Supergiant (Betelgeuse) But unfortunately we cannot detect the astrosphere of a Sun-like star like this!

  7. Spectroscopic Diagnostics of Stellar Winds HD151515 (O7 II) C IV Mg II

  8. Methods for Detecting and Studying the Solar Wind Aurora Comet tails Direct spacecraft measurement Coronal imaging ACE (Advanced Composition Explorer)

  9. Evolution of the Solar X-ray and EUVFLux Ribas et al. 2005, ApJ, 622, 680

  10. The Case for a Very Strong Wind for the Young Sun The young Sun would have been much more coronally active, with higher coronal densities, so one would intuitively expect a stronger wind. Aside from the quiescent wind, the stronger and more frequent flares of the young Sun should by themselves lead to a massive CME-dominated wind. Example: Due to CMEs alone, Drake et al. (2013) predict Ṁ=150 Ṁʘ for the 500 Myr old solar analog 1UMa. Conclusion: There is every reason to believe the solar wind must have been much stronger in the past. Drake et al. 2013, ApJ, 764, 170

  11. The Case for a Relatively Weak Wind for the Young Sun Solar activity varies significantly over the course of its activity cycle, but: Voyager has observed little variation from the canonical solar mass loss rate of Ṁʘ=2×10-14 Mʘ/yr. There is no strong correlation between solar X-ray flux and mass loss rate. Conclusion: Perhaps the solar wind is relatively constant over time. Cohen 2011, MNRAS, 417, 2592

  12. astrospheric absorption heliospheric absorption

  13. Models of the  Cen Astrosphere Ṁ=0.2 Ṁ⊙ Ṁ=0.5 Ṁ⊙ Ṁ=1.0 Ṁ⊙ Ṁ=2.0 Ṁ⊙

  14. Astrospheric Absorption Predictions for  Cen Wood et al. 2001, ApJ, 547, L49

  15. Wood et al. 2002, ApJ, 574, 412

  16. Astrospheric Models The εEri astrosphere is comparable in size to the full moon in the night sky!

  17. The New1UMa Measurement • 1UMa and 3 other young Sun analogs observed by HST in 2012. • Only 1UMa provided an astrospheric detection. • 1UMa (G1.5 V) is a 500 Myr solar analog. • The absorption suggests a mass loss rate of only 0.5 Ṁʘ (Wood et al. 2014, ApJ, 781, L33).

  18. List of Astrospheric Measurements

  19. Mass Loss/X-ray Relation Red: Solar-like GK main sequence stars Green: M dwarfs ṀFX1.340.18 Wood et al. 2014, ApJ, 781, L33

  20. Is Magnetic Topology Inhibiting the Winds of Young, Active Stars? Rice & Strassmeier 2001, A&A, 377, 264

  21. Wind Evolution for a Sun-like Star Ṁt-2.330.55

  22. Evolution of the Martian Atmosphere Mars 4 Gyr ago Mars Today

  23. What Role do Magnetospheres Play in Atmospheric Evolution? Earth is protected by a “magnetosphere,” but Mars is not! Lundin 2001, Science, 291, 1909

  24. Stellar Wind Erosion of a “Hot Jupiter” This is just an artist’s conception of a stellar wind eroding a planetary atmosphere, but Ly absorption from such an eroding atmosphere may have actually been detected for the transiting exoplanet HD 209458b (Vidal-Madjar et al. 2003, Nature, 422, 143; Linsky et al. 2010, ApJ, 717, 1291).

  25. The Faint Young Sun Problem (FYSP)(first defined by Sagan & Mullen 1972, Science, 177, 52) Bahcall et al. 2001, ApJ, 555, 990

  26. Could the FYSP be Resolved by a More Massive Young Sun? Sackmann & Boothroyd 2003, ApJ, 583, 1084

  27. Mass Lost due to Solar Wind Inferred from Astrospheric Measurements

  28. Could a Stronger Wind for the Young Sun Explain the FYSP Via Cosmic Ray Cooling? Shaviv 2003, JGR, 108, 1437

  29. SUMMARY • Currently the only way to study the astrospheres and winds of solar-like stars is through astrospheric Lyαabsorption observed by HST. • Analysis of the astrospheric absorption suggests that for solar-like GK dwarfs, mass loss and activity are correlated such that ṀFX1.340.18. • However, this relation does not extend to high activity levels (FX>106 ergs cm-2 s-1), possibly indicating a fundamental change in magnetic structure for more active stars. • The mass-loss/activity relation described above suggests that mass loss decreases with time as Ṁt-2.330.55. However, the apparent high activity cutoff means that this mass loss evolution law doesn’t extend to times earlier than t~0.7 Gyr. • Despite the higher mass loss rates predicted for the young Sun by our mass loss evolution law, the total mass lost by the Sun in its lifetime is still insignificant, so this stronger young wind can’t directly solve the Faint Young Sun problem, though there is speculation that it could indirectly via cosmic ray attenuation. • The existence of generally stronger winds at younger stellar ages makes it more likely that solar/stellar wind erosion plays an important role in the evolution of planetary atmospheres.

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