solar probe: mission to the sun donald m. hassler/david j. mccomas southwest research institute

Solar Probe: Mission to the Sun

Donald M. Hassler/David J. McComasSouthwest Research Institute

2Don Hassler/Dave McComas (SwRI) Decadal Survey Presentation (Boulder, 17 April 2001)

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”.


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.


“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.


In-Situ Measurements

High 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


Direct In-situ measurements and tomographic imaging of Polar Plumes


The Hemispheric Imager’s 180 deg. FOV permits true tomographic

reconstruction of 3-D coronal structure and context for the in-situ package

A coronal fly-through is the ONLY way to reconstruct the 3-D coronal structure!


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.


Observations of the Sun’s Poles:Polar 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.


LEFT: An MDI full-disk magnetogram, reprojected to the pole. RIGHT: 32-minute averaged magnetogram.

Current measurements of the polar magnetic field are severely foreshortened and sensitivity-limited due to our perspective from the ecliptic plane. Magnetograms of the Sun’s polar region (above 60 deg.) are not sufficient to detect small scale flux concentrations or offsets in the large scale magnetic field.


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.


Solar Probe will solve fundamental mysteries related to the subsurface origins of the solar cycle.


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!


SCIENCE IMPACT:

• 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

Solar Probe is a mission of discovery -NOT incremental science!


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


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!

solar probe: mission to the sun donald m. hassler/david j. mccomas southwest research institute

Documents

distance of solar probe

solar surface

slow solar wind

production of solar

solar wind andestablish

minimum solar activitylocate

polar regions

polar coronal holes