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A Whole-Heliosphere View of the Solar Wind Hale Lecture American Astronomical Society 5/24/2010. Marcia Neugebauer University of Arizona. The Things that Happen to the Solar Wind After it Leaves the Sun. A Better Title:. The Complex Solar Atmosphere. - PowerPoint PPT Presentation
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A Whole-Heliosphere View of the Solar Wind
Hale LectureAmerican Astronomical Society
5/24/2010
Marcia NeugebauerUniversity of Arizona
A Better Title:
The Things that Happen to the Solar Wind After it Leaves the Sun
The Complex Solar Atmosphere
The Sun creates both slow and fast solar wind
But, it’s a complicated process
Model of open and closed field lines
(Wang et al., 2007)
The Source-Surface Model
(Cravens, 1997)
Major Processes in the Solar Wind
• Expansion• Collision• Reconnection• Pickup (mass loading)
• All of which leads to: – Turbulence– The interstellar medium
Expansion
First Adiabatic Invariant(Conservation of Magnetic Moment )
= mw2/2B T/B = constant
As B , expect T , and T||/ T
Magnetic moment versus distance
(Tu, 1988)
Magnetic Moment versus Distance from Sun
Tperp/Tpar vs βpar for protons < 600 /V km s
Contours of max growth rate inωcp
Proton cyclotron
Parallelfirehose
Mirror instability
Obliquefirehose
(Hellinger et al., 2009)
Proton Distribution functions
(Marsch et al., 1981)
Dis
tanc
e fr
om S
un -
->
Solar wind speed -->
The Strange Behavior of Alpha Particles
• Abundance highly variable• na/np = 0 - .03 in slow wind (~0 at HCS)• na/np = .04-.05 in fast wind• Greatly enhanced in CMEs (up to 0.40!)
• Hotter than protons• Ta/Tp = 4 to 6 in fast wind• Approaches isothermal in slow wind
• Faster than protons• Vap up to 100 km/s in fast wind • Vap -> 0 in dense, slow wind
• Anisotropic and double peaked
Vap vs Distance in Fast Wind
(Neugebauer et al., 1996)
Collision
Magnetized Plasmas Don’t Easily Mix
Note Boundaries Between Winds from Streamers & Coronal Holes
(Gosling et al., 1978)
Some Stream Interfaces are Stable over Many AU
Tangential discontinuities between plasmas fromdifferent sources
Also called the heliospheric current sheet
Heliospheric Current Sheets, Embedded in the Slow Wind, are Also Stable
Solar Maximum Solar MinimumDeclining Activity
Result of the Solar Dipole Tilt(Ballerina Skirt)
(Jokipii & Thomas, 1981)
Solar Rotation Creates Corotating Interaction Regions
(Pizzo, 1978)
Signatures of a CIR at
~5 AU
(Lazarus et al., 1999)
SI at density drop
HCS on Day 138
Coronal Mass Ejections
Interplanetary CMEs
(Richardson, 1997)
Interaction Regions at Solar Max and Min
Evolution of Interaction
regions from
1 to 60 AU
Formation of MIRs
(Wang & Richardson, 2003)
Ecliptic plane view of pileup out to 100 AU
Effect of GMIRs on Cosmic Rays
(Burlaga et al., 2003)
Anti-Correlation of Sunspots and Cosmic Rays
Reconnection
Petschek Reconnection Mechanism
(Gosling, 2005)
Reconnection Exhaust Fans
(Gosling, 2010)
Bifurcated structure
Opposite V//B
Decreased B, Increased V, T
Observed even for small angle changes
Created by turbulence?
Pickup
Pick-up is sometimes associated with
Mass Loading
Non-Solar Sources of Solar Wind Ions
• Atoms and ions– Interstellar medium– Dust– Comets– Planets
• Dust– Comets and Asteroids– Interstellar medium– Jupiter
The Pick-up Process
B
U
In solar-wind frame In inertial frame
Photoionization adds mass to wind.
Charge exchange creates fast neutral and slow ion.
Both processes provide drag on wind.
Proton Spectrum with Pickup Ions
(Gloeckler et al., 2001)
Inner Source of Pick-up Ions
(Gloeckler et al., 2001)
High-Energy Tails of H and He
(Gloeckler, 2003)
Effect of Pickup Ions on the Wind
• Photoionization adds mass • Charge exchange may conserve mass
– Results in a fast neutral atom and a slow ion
• Both processes result in:– Acceleration of slow ions up to Vsw – Drag– Hot ions with Vth Vsw
Slow-Down of Solar Wind due to Pick-up Ions
Turbulence
OGO 5Density fluctuations(Neugebauer, 1976)
f/fpg
Helios 2Field vector spectra
(Bruno & Carbone, 2005)
Power Spectra
2-D Simulation of MHD Turbulence
(Greco et al., 2010)
Field lines + Current density (gray shade)
Current sheets generated locally
Reconnection heats plasma
The End of the Road
(Approach to Alaska’s Bridge to Nowhere)
Interaction with the Interstellar Medium
Model of Outer Heliosphere
Anomalous Cosmic Rays at TS and in Heliosheath
(Courtesy A. Cummings, 2010)
“The Ribbon”
Summary
• A lot of interesting physics in the solar wind• Several unsolved issues
– Turbulent processes– Relaxation of anisotropic and multi-beams– Physics of high-energy tails– Acceleration of ACR– Prevalence of reconnection– Stability/sources of discontinuities
• Applications to many other astrophysical settings