Solar Probe: Mission to the Sun

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Solar Probe Mission to the Sun

• Donald M. Hassler/David J. McComas
• Southwest Research Institute

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Why Solar Probe?

• Solar Probe is the single most important mission
  for the solar and heliospheric community to make
  breakthrough discovery science in the next
  decade!
• Why?
• Solar Probe is the last great flyby mission of
  discovery, providing the next great advance in
  understanding our star!
• A coronal fly-through is the ONLY way to make
  conclusive measurements to determine uniquely
  what heats the corona and accelerates the solar
  wind,... and solve the mysteries of the critical
  region where the solar wind is born.

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Solar Probe Science Objectives

• Group 1 Objectives
• Determine the acceleration processes and find
  the source regions of the fast and slow solar
  wind at maximum and minimum solar activity
• Locate the source and trace the flow of energy
  that heats the corona
• Construct the three-dimensional coronal density
  configuration from pole to pole and determine the
  subsurface flow pattern, the structure of the
  polar magnetic field, and their relationship with
  the overlying corona and
• Identify the acceleration mechanisms and locate
  the source regions of energetic particles, and
  determine the role of plasma waves and turbulence
  in the production of solar wind and energetic
  particles.
• Group 2 Objectives
• Investigate dust rings and particulates in the
  near-Sun environment
• Determine the outflow of atoms from the Sun and
  their relationship to the solar wind and
• Establish the relationship between remote
  sensing, near-Earth observations at 1 AU and
  plasma structures near the Sun.
• Group 3 Objectives
• Determine the role of x-ray microflares in the
  dynamics of the corona and
• Probe nuclear processes near the solar surface
  from measurements of solar gamma rays and slow
  neutrons.

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High-speed Solar Wind Acceleration

• This plot shows the flow speed above polar
  coronal holes and indicates that the solar wind
  acceleration is relatively rapid, reaching
  velocities of the terminal speeds of about 800
  km/s well below a distance of 10 RS. SOHO
  measurements have placed the velocities on the
  order of 100 to 150 km/s as maximal, at a
  distance of 2 to 3 RS. Solar Probe will cross
  the polar regions at 7 RS and if the coronal
  holes extend down to 30 degrees latitude at the
  time of its passage, it will extend the distance
  of Solar Probe down to 5 RS in the high-speed
  region. Solar Probe will cross the equatorial
  region at 4 RS, a distance believed to be inside
  the subsonic point.

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In-Situ MeasurementsHigh time resolution,
synchronized plasma, energetic particle, and
field measurements, including mass resolved ion
distribution functions, will resolve

• solar wind heating and acceleration
• macroscopic coronal structure and composition
• fine scale spatial structures
• plasma and magnetic structures in the helmet
  streamer belt
• plume/interplume structure

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Direct In-situ measurements and tomographic
imaging of Polar Plumes
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A coronal fly-through is the ONLY way to
reconstruct the 3-D coronal structure!
The Hemispheric Imagers 180 deg. FOV permits
true tomographic reconstruction of 3-D coronal
structure and context for the in-situ package
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Reconstructed image of the heliosphere out to 1.5
AU, derived by tomographic reconstruction from
HELIOS photometer data. Solar Probe will permit
reconstruction of the corona and inner
heliosphere with 1,000 times better spatial
resolution.
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Observations of the Suns PolesPolar Magnetic
Field

• Solar Probe magnetograph will provide the first
  high resolution maps and time series evolution
  studies of the polar magnetic field.
• Solar Probe magnetograms will be the highest
  resolution magnetograms of the photosphere ever
  obtained.

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Current measurements of the polar magnetic field
are severely foreshortened and sensitivity-limited
due to our perspective from the ecliptic plane.
Magnetograms of the Suns polar region (above 60
deg.) are not sufficient to detect small scale
flux concentrations or offsets in the large scale
magnetic field.
LEFT An MDI full-disk magnetogram, reprojected
to the pole. RIGHT 32-minute averaged
magnetogram.
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Solar Probe will provide important constraints on
theories of the Solar Dynamo

• The poloidal component of the magnetic field, a
  key ingredient to the dynamo mechanism, is
  predicted to be strongest at the poles.
• Models suggest that transport of magnetic flux by
  meridional circulation is crucial for the solar
  cycle and the operation of the dynamo, because it
  couples toroidal and poloidal field components,
  and links the surface field to the shear layer at
  the base of the convection zone.

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Solar Probe will solve fundamental mysteries
related to the subsurface origins of the solar
cycle.
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Solar Probe will provide EUV imaging of the
corona and solar surface with a resolution 10
times higher than TRACE.
Ultra-high (35 km) resolution images of the
corona and solar surface, including the poles!
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SCIENCE IMPACT
Solar Probe is a mission of discovery - NOT
incremental science!

• Dramatic exploration of new territory in the
  solar system
• Comparable to the first planetary flybys
• ONLY way to determine uniquely what heats the
  corona and accelerates the solar wind

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Solar Probe Status/Update (1)

• Solar Probe was on track!!!
• mature mission concept that has undergone years
  of design optimization
• within budget and below initial projected cost
• NASA ready to make instrument team selections -
  project ready to undertake mission
• extended study phase at minimal cost to NASA
  reduces overall risk and total mission cost

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Solar Probe Status/Update (2)

• SP is in jeopardy of cancellation under the
  current presidential budget.
• The Solar Probe mission, slated to be NASA's
  first voyage to a star, was not determined to be
  a near-term budget priority for NASA, and is not
  funded in the FY 2002 budget. In the event that
  the Solar Probe is assigned a high priority by
  the solar and space physics science community,
  the mission could be funded out of the resources
  planned for other solar and space physics
  programs. - OSS White Paper on Presidential
  Budget (9 April 2001)
• SP is the single most important mission for the
  solar and heliospheric community to make
  breakthrough, discovery science!
• The findings of the Decadal Survey Panel can make
  a difference!