evolution of magnetic fields from the sun’s surface to the heliopause of one solar cycle nathan...
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![Page 1: Evolution of Magnetic Fields from the Sun’s Surface to the Heliopause of one Solar Cycle Nathan Schwadron, Boston University](https://reader036.vdocuments.mx/reader036/viewer/2022081520/5697c0251a28abf838cd55ad/html5/thumbnails/1.jpg)
Evolution of Magnetic Fields from the Sun’s Surface to the Heliopause of one Solar Cycle
Nathan Schwadron, Boston University
![Page 2: Evolution of Magnetic Fields from the Sun’s Surface to the Heliopause of one Solar Cycle Nathan Schwadron, Boston University](https://reader036.vdocuments.mx/reader036/viewer/2022081520/5697c0251a28abf838cd55ad/html5/thumbnails/2.jpg)
Outline
• Heliosphere’s Hale Cycle
• Possibilities for Reversing the Heliosphere’s
Magnetic Field
• The Role of CMEs in Field Evolution
• Observational Support
• Next Steps
• Conclusions
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The Helisphere’s Hale Cycle
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Evolving Magnetic
Flux
Wang et al., 2000
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Roughly factor x2 variationin Open Magnetic Flux
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QuestionsHow does the global
Field Reverse?
What causes variation in Open field strength?
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Interchange reconnection
(Media Diffusion)
Interchange reconnection conserves
open magnetic fluxProvides a means for
reversal of open magnetic flux without
changing the net quantity of flux
Fisk and Schwadron, 2001
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The Role of CMEs
CMEs move flux via interchange reconnection
CMEs temporarily add closed magnetic flux,
increasing |B|, particularly during solar
max
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Temporary Flux Addition by
CMEs
Black line shows the observed value of |B| at 1 AU from ACE/Wind
Red line shows simulated value of |B| at 1 AU using LASCO observed
CME rates
CME half-life 50 days
Model comparison validates open flux conservation during
CME ejections
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CMEs and the Hale Cycle
• CMEs generally have an orientation in agreement in with Hale’s law (Bothmer and Schwenn, Ann. Geophys., 1998)
• Is the flux opened by Interchange Reconnection sufficient for field reversal?
‣ Fopen = Open Flux ~1015 Wb
‣ FCME=CME flux ~1012 Wb
‣ freq = CME frequency ~ 3/day
‣ d = CME footpoint separation
‣ Number of Needed CMEs,
N =(Fopen/FCME)x(180o/d)
‣ Time required for field reversal,
T = N/freq ≈ 11 years
‣ Solve for footpoint separation
d > 5o
![Page 10: Evolution of Magnetic Fields from the Sun’s Surface to the Heliopause of one Solar Cycle Nathan Schwadron, Boston University](https://reader036.vdocuments.mx/reader036/viewer/2022081520/5697c0251a28abf838cd55ad/html5/thumbnails/10.jpg)
Owens et al., 2006
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Owens et al., 2006
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Confirmation from Suprathermal Electron
Observations• Does Interchange
Reconnection open fields primarily in one or both legs of the CME
• Answer: One
85%
15%
Crooker et al., 2006
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Disconnection?
• Disconnection across the helmet streamer is another process that leads to the reduction of open flux
• This may be balanced by the addition of flux by CMEs
• It is difficult to differentiate between disconnection and the effects of large-scale interchange reconnection (flux addition, then I.C.)
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Long-Term Evolution
• Evidence of Open Flux Conservation over Large Timescales (Svalgaard and Cliver, 2007)
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Outer Heliosphere Implications
New Outer Heliosphere Current Layer
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Next Steps• Is the Open Magnetic Flux of the Heliosphere
Conserved?‣ Recent Ulysses results may suggest disagreement with Source
surface models after the field reversal?
‣ SHINE session: Svalgaard, Murphy, Arge invited speakers
• Essential at this stage that energetic particle and magnetic field models take into account flux conservation
‣ The Earth-Moon-Mars Radiation Environment Model is designed to couple EP models w/evolving MHD results of the global solar wind
‣ Approach is to develop a mesh in which node lines follow magnetic field lines
‣ Starightforward to use the code framework to understand implications of footpoint motions for the magnetic field over the solar cycle.
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Conclusions
• Coronal Mass Ejections may control the heliospheric Hale Cycle
‣ Changes in |B| through temporary buildup of open flux‣ Movement of open flux through Interchange Reconnection‣ Reversal of the Heliospheric Magnetic Field
• Next Steps‣ Is the Open Magnetic Flux of the Heliosphere Conserved?
- On what timescales and why - fundamental to solar dynamo
‣ Investigate detailed implications for energetic particles (EMMREM) and outer heliosphere configuration
- Utilize EPs to probe global structure (requires coupling between EP models and MHD/field models)
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Temporary Flux Addition due to CMES
Observed
CME freq
Modeled
Owens and Crooker, JGR, 2006
•CME flux half-life ~40-55 days
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Solar Butterfly Diagram
Hathaway, 2003
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