The Solar Wind: ACE, Ulysses, Genesis, STEREO

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The Solar WindACE, Ulysses, Genesis, STEREO
Ulysses

• Ruth Skoug
• LASSO Workshop
• July 2008

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The Solar Wind

• In the19th century, associations were made
  between
• Solar flares (visible)
• Magnetic storms and aurora
• Implies there is something between the Sun and
  the Earth which transfers solar energy to the
  Earth (and other planets)
• 1930s Chapman Ferraro postulate that
  geomagnetic storms are caused by solar wind
  plasma
• But think that the solar wind is intermittent
• Evidence for continuous solar wind from comet
  tails (1950s)

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Comet Hale-Bopp http//www.solarviews.com/eng/co
met.htm (Courtesy John Laborde) This image of
comet Hale-Bopp was taken by John Laborde with
his home designed and built, 8.8" f/3.7 Wright
Schmidt Camera. The picture was taken at the
Tierra Del Sol Observatory site in San Diego
County with a 25 minute exposure on Kodak PPF400
film.
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Comet West (1975) http//www.solarviews.com/eng/
comet.htm This
photograph was taken by amateur astronomer John
Loborde on March 9, 1976. This picture shows two
distinct tails. The thin blue plasma tail is made
up of gases and the broad white tail is made up
of microscopic dust particles. (Courtesy John
Laborde)
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• Ion tail
• Solar wind pressure.
• Always points away from the sun.
• Ions picked up by solar wind.
• Dust tail and hydrogen envelope
• Light pressure.
• Material on lagging orbits.

http//www.solarviews.com/eng/comet.htm
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The Solar Wind

• 1958 Parker develops a theoretical model of a
  continuous solar wind
• Corona is so hot that particles are not
  gravitationally bound
• First direct observation from spacecraft by
  Mariner 2 (1962)
• Shows a continuous solar wind

From Neugebauer Snyder, 1966
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Eclipse 7/11/1991 From Mauna Kea
http//antwrp.gsfc.nasa.gov/apod/ap990716.html
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The Solar Wind

• Photosphere the visible sun. 5800 K
• Corona visible during solar eclipse. 1,000,000
  K
• Local Interstellar Medium 10,000 K
• The corona expands naturally because of
• High pressure in corona
• Low pressure in interstellar medium
• The solar corona expanding into space is called
  the solar wind
• Spacecraft have measured solar wind beyond Pluto
• Voyager 1 2 have crossed the termination
  shock and entered the heliosheath

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The Solar Wind

• Flow of ionized plasma from the Sun
• Extension of the solar corona
• 95 H, 5 He
• Speed range 2001000 km/s
• average 400 km/s ( a million miles/hour!)
• Density lt1100 particles/cc
• average 7 particles/cc
• Carries a weak magnetic field
• 5 nT (1/10,000 of Earths field)

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The Solar Wind

• The solar wind varies on many time scales
• Years
• 11 year solar cycle
• Days - hours
• fast streams
• slow streams
• coronal mass ejections (CMEs)
• Hours - seconds
• waves
• shocks
• interactions

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Spiral magnetic fields The Garden Sprinkler
effect
http//www-istp.gsfc.nasa.gov/istp/outreach/theret
ohere.html
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Smooth Spiral is only an average.
Real data local interplanetary field measured
by a spacecraft shows fluctuations
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Solar Wind Types

• Different origins, composition, speeds, etc.
• Fast solar wind
• gt 500 km/s
• From coronal holes
• Major type at the poles
• Slow solar wind
• lt 500 km/s
• Major type in the ecliptic
• Coronal mass ejections
• Transient events, can have high or low speed
• Distinguished by shock waves, low temperatures,
  enhanced alpha particle densities, bi-directional
  electron beams
• Responsible for most large geomagnetic storms

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EIT images courtesy of the SOHO EIT
team http//sohowww.nascom.nasa.gov/
SOHO EIT 284 Å
Feb 3, 2002
Mar 2, 2002
Jan 8, 2002
Solar rotation 27 days
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Coronal Mass Ejection
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Los Alamos Solar Wind Detectors
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Electrostatic Analyzer for Detecting Charged
Particles (Curved Plate Analyzer)
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Electrostatic Analyzer for Detecting Charged
Particles (Curved Plate Analyzer)
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Electrostatic Analyzer for Detecting Charged
Particles (Curved Plate Analyzer)
Particles with slightly less energy Still make it
through
Particles with slightly more energy Still make it
through
For a fixed voltage on the analyzer plates,
particles are accepted over a range of
energies ?E.
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Electrostatic Analyzer for Detecting Charged
Particles (Curved Plate Analyzer)
Electrostatic analyzers have an energy-angle
skewing. Detector designers try to minimize this.
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Solar Wind Measurements

• LANL designs and builds electrostatic analyzers
  to measure ions and electrons
• Have flown on many spacecraft
• Vela, IMP, ISEE, Ulysses, ACE, Genesis
• Collaborations with SNL, JPL

Ion detector
Electron detector
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Ion Detectors Solar wind ions come from a narrow
range of angles. Consider the flow direction, and
the thermal spread.
Genesis Ion Monitor (GIM)
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Electron Detectors Solar wind electrons come
from all directions in space!
Ulysses, ACE, Genesis electron monitors
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ions
Arrow gives spacecraft spin axis, which roughly
points to the Sun
electrons
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Our detectors dont select particles by Energy,
they select by Energy/Charge
Electric field between the plates is E Vo/Dgap
Force on a charge q in an electric field E is F
q E
F qVo/Dgap mv2/R Solve for Vo Vo (Dgap
mv2)/(qR) Vo 2 (Dgap/R)(mv2 /2)/q
Energy/Charge!
Newtons 2nd law F ma
Acceleration for an object in uniform circular
motion (v is speed) a v2/R
Kinetic Energy of motion Ke mv2 /2
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Vo 2 (Dgap/R)(mv2 /2)/q

• Solar Wind is 95 H and 5 He
• He has 4 times the mass of H
• He has 2 times the charge of H
• If both H and He move at the same speed v,
• then He has 2 times the Energy/Charge

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Genesis Ion Monitor Data
Protons alphas
1 2 3 45 (keV)
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Genesis Ion Monitor Data
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Solar Wind Data
Suprathermal electron pitch angle distribution
Proton Density
Proton Temperature
Solar Wind Speed
He/H Density Ratio
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Advanced Composition Explorer (ACE)

• Designed to measure elemental, isotopic, and
  charge state composition of solar system material
• LANL provided plasma instrument
• Launched in August, 1997
• Halo orbit about the L1 point
• Approximately 1 hour upstream of the Earth
• Continuous real-time solar wind monitor

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Advanced Composition Explorer (ACE)
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• ACE provides real time solar wind observations
• One hour warning for Earth-directed events

http//www.swpc.noaa.gov/ace/index.html
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Unusually high speed solar wind -- October 2003
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Unusually high speed solar wind -- October 2003
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• Suprathermal electrons move through the solar
  wind
• 100 1000 eV
• Typically aligned with the magnetic field
  direction
• Plot shows pitch angle, which is the angle
  between the magnetic field direction and the
  particle travel direction

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Electrons at 100 eV - 1000 eV move through the
solar wind
Transient Solar Burst Time of arrival is
delayed for slower particles
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Genesis Solar Wind Sample Return

• Launched August, 2001
• Returned to Earth Sept 2004

• Place a spacecraft in the solar wind
• Expose ultra-pure materials to collect solar wind
  (2 years)
• Use LANL ion and electron monitors and logic to
  characterize solar wind in real time and deploy
  appropriate collectors
• Return embedded solar wind samples to Earth
• Analyze samples with state-of-the-art laboratory
  equipment

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• GENESIS A NASA DISCOVERY MISSION to
• Expose nearly 3 m2 of collector materials to the
  solar wind
• And return samples to Earth for analysis
• Materials include
• Ultrapure Si, Ge, CVD diamond, and Al Au on
  sapphire.
• Collectors assembled in a class 10 cleanroom.
• Analysis of returned samples will be done by
  mass spectrometry
• AMS, SIMS, RIMS, and neutron activation analysis.
  
• Key Measurement objectives
• 17O/16O, 18O/16O to an accuracy of ?0.1,
• 15N/14N, 13C/12C, noble gas isotope ratios,
• 14C, Li, Be, B composition,
• Other heavier element and
• isotope abundances.

Photo courtesy JSC, JPL.
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Launch August 8, 2001 L1 Orbit Insertion
November 16, 2001 Begin Solar Wind Collection
December 3, 2001
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Genesis Solar Wind Concentrator

• Increases solar wind fluence by a factor of 20
• Uses a large electrostatic mirror
• H rejection controlled by ion monitor
• Improves measurement of oxygen isotopes
• Unique instrument!
• Designed and built at LANL

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Genesis Autonomous Solar Wind Identification
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Genesis Regime Selection Example
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Ulysses

• First observations of the solar wind out of the
  ecliptic plane, over the poles of the Sun
• Heliographic latitudes of 080
• Study differences between fast and slow solar
  wind
• Determine latitudinal and radial dependence of
  solar wind
• LANL provided plasma instrument
• Launched in 1990
• Observations over a complete solar cycle
• Currently in 3rd solar orbit

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Solar Wind Speed Over the Poles Ulysses
McComas et al., 1998
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Solar Cycle
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Solar Min vs. Solar Max Ulysses
McComas, D. J., et al., 2001
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Solar Min vs. Solar Max Ulysses
McComas et al., Geophys. Res. Lett., 27, 2437,
2000
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Solar Cycle
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Solar Cycle
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STEREO

• Solar TErestrial RElations Observatory
• Two nearly identical satellites
• One ahead of Earth in its orbit
• One trailing behind Earth in its orbit

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STEREO

• Provide the first-ever stereoscopic measurements
  to study the Sun and the nature of coronal mass
  ejections (CMEs)
• Scientific Objectives
• Understand the causes and mechanisms of CME
  initiation
• Characterize the propagation of CMEs through the
  heliosphere
• Discover the mechanisms and sites of energetic
  particle acceleration in the low corona and the
  interplanetary medium
• Improve the determination of the structure of the
  ambient solar wind
• Launched Oct 25, 2006

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STEREO Instruments

• Instruments include
• coronagraphs (SECCHI)
• wave detectors (S/WAVES)
• magnetometers (IMPACT)
• enegetic particle detectors (IMPACT)
• plasma detectors (PLASTIC)

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Artists conception of STEREO observing a solar
flare
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In-situ STEREO science
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In-situ STEREO science
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STEREO sees the Sun
EUV light Orange 304 Å Blue 171 Å Yellow
284 Å Green 195 Å
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STEREO sees a CME
Jan 24, 2007
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STEREO sees a solar eclipse
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3D Coronal Hole
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3D Active Region
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Summary

• Variations in the Sun and the solar wind can have
  important impacts on humans and technological
  systems
• LANL has long been, and continues to be, involved
  in solar wind measurements
• Designing and building instruments
• Science data analysis
• On-board autonomous algorithms
• Science highlights
• Solar wind variations with latitude
• Study of solar wind evolution from multi-point
  measurements
• Determination of topology from electron
  measurements
• CME identification the possibility of
  forecasting events

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• ACE provides real time solar wind observations
• One hour warning for Earth-directed events

http//www.swpc.noaa.gov/ace/index.html