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Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON SOLAR AND HELIOSPHERIC PHYSICS
307
ATST, FASR, and COSMO can make crucial measurements of coronal magnetic fields in the energyrelease particle-acceleration regions. SPP and Solar Orbiter would provide ideal complementary in situ
SEP/CME measurements close to the Sun and solar imaging (coronagraph, heliospheric imager, and HXR).
The minimum SEE mission evaluated by the CATE process included only FOXSI, ENASI, and UVCSII,
launched on a Taurus 3210. A EUVIS type of instrument and a WLC are part of Solar-C and Solar Orbiter,
respectively. GRIS requires more mass and power than the other instruments combined; flying it on ultralong-duration balloon flights at solar maximum should be investigated.
A two-instrument SEE mission (FOXSI and ENASI) was deemed by the CATE process to fit in the midscale line (less than $480 million), and it provides tremendous new science. One or more of these new
instruments, of appropriate size, would also be appropriate in an Explorer mission.
Regarding development status, a FOXSI instrument is scheduled for rocket flight in early 2012 and
the balloon-borne GRIPS (Gamma-Ray Imager/Polarimeter for Solar flares) payload is being developed for
a 2012 flight. UVCSII is based on proven SOHO UVCS technology. The ENASI instrument uses silicon
semiconductor detectors that have flown successfully on STEREO/IMPACT LET and STE instruments and
RHESSI modulation-grid imaging methods. EUVIS is based on the Hinode technology, and UVCSII is based
on UVCS on SOHO. A 10-m extendable boom will be flown on the NuSTAR SMEX mission (planned for
launch in 2012). 15
10.5.2.5 L5 Mission Concept
The L5 mission concept would place a spacecraft carrying imaging and in situ instruments in about
a 1-AU orbit near the L5 Lagrangian point (Figure 10.24). 16 From that location, the mission could make
major advances in helioseismology by probing for longitudinal variations in tachocline magnetic fields,
observe emerging active regions before they affect Earth, study CME evolution with stereoimaging and in
situ data, and make major advances in space weather forecasting. The spacecraft and payload could rely
on STEREO heritage. A Doppler magnetograph and UV spectrograph would be added.
An important science objective for L5 is to address the question, How does the solar dynamo drive
magnetic activity on the surface? Global helioseismology has had remarkable success in revealing the
Sun’s internal radial structure and internal rotation. However, global helioseismology does not resolve
longitudinal variations of the solar interior. Local helioseismic techniques (such as time-distance helioseismology) provide longitudinal information, but only in the upper third of the convection zone if viewed
from a single vantage point.
Calculations predict longitudinal variations as signatures of the magnetic field at the tachocline.
Simultaneous observations (Earth + L5) will detect both ends of long, deep, wave ray paths that penetrate
to the tachocline (see Figure 10.24). Combining L5 and near-Earth observations will probe variations over
a large longitude range. The relatively stable L5-Earth separation and increased solar-surface coverage
also enable improved measurements of rotational and meridional flows. Active longitudes and persistent
surface “hotspots” of magnetic activity are probably also associated with hotspots in the tachocline region
and require longitudinal resolution.
Another science objective concerns the question, Can helioseismology forecast strong flare activity?
Recent studies show that the strength and vorticity of subsurface flows around active regions are closely
15 This panel report was completed in late 2012. An update in June 2013 to the information above follows: FOXSI was launched
successfully in November 2012 from the White Sands Missile Range in New Mexico; GRIPS is now planned to have its first test
flight in September 2014; and NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) began its 2-year mission on June 13, 2012,
aboard a Pegasus XL rocket launched from Kwajalein Atoll in the Marshall Islands.
16 A. Vourlidas et al., Mission to the Sun-Earth L5 Lagrangian point: An Optimal Platform for Heliophysics and Space Weather
Research, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics), Paper 273.
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON SOLAR AND HELIOSPHERIC PHYSICS
307
ATST, FASR, and COSMO can make crucial measurements of coronal magnetic fields in the energyrelease particle-acceleration regions. SPP and Solar Orbiter would provide ideal complementary in situ
SEP/CME measurements close to the Sun and solar imaging (coronagraph, heliospheric imager, and HXR).
The minimum SEE mission evaluated by the CATE process included only FOXSI, ENASI, and UVCSII,
launched on a Taurus 3210. A EUVIS type of instrument and a WLC are part of Solar-C and Solar Orbiter,
respectively. GRIS requires more mass and power than the other instruments combined; flying it on ultralong-duration balloon flights at solar maximum should be investigated.
A two-instrument SEE mission (FOXSI and ENASI) was deemed by the CATE process to fit in the midscale line (less than $480 million), and it provides tremendous new science. One or more of these new
instruments, of appropriate size, would also be appropriate in an Explorer mission.
Regarding development status, a FOXSI instrument is scheduled for rocket flight in early 2012 and
the balloon-borne GRIPS (Gamma-Ray Imager/Polarimeter for Solar flares) payload is being developed for
a 2012 flight. UVCSII is based on proven SOHO UVCS technology. The ENASI instrument uses silicon
semiconductor detectors that have flown successfully on STEREO/IMPACT LET and STE instruments and
RHESSI modulation-grid imaging methods. EUVIS is based on the Hinode technology, and UVCSII is based
on UVCS on SOHO. A 10-m extendable boom will be flown on the NuSTAR SMEX mission (planned for
launch in 2012). 15
10.5.2.5 L5 Mission Concept
The L5 mission concept would place a spacecraft carrying imaging and in situ instruments in about
a 1-AU orbit near the L5 Lagrangian point (Figure 10.24). 16 From that location, the mission could make
major advances in helioseismology by probing for longitudinal variations in tachocline magnetic fields,
observe emerging active regions before they affect Earth, study CME evolution with stereoimaging and in
situ data, and make major advances in space weather forecasting. The spacecraft and payload could rely
on STEREO heritage. A Doppler magnetograph and UV spectrograph would be added.
An important science objective for L5 is to address the question, How does the solar dynamo drive
magnetic activity on the surface? Global helioseismology has had remarkable success in revealing the
Sun’s internal radial structure and internal rotation. However, global helioseismology does not resolve
longitudinal variations of the solar interior. Local helioseismic techniques (such as time-distance helioseismology) provide longitudinal information, but only in the upper third of the convection zone if viewed
from a single vantage point.
Calculations predict longitudinal variations as signatures of the magnetic field at the tachocline.
Simultaneous observations (Earth + L5) will detect both ends of long, deep, wave ray paths that penetrate
to the tachocline (see Figure 10.24). Combining L5 and near-Earth observations will probe variations over
a large longitude range. The relatively stable L5-Earth separation and increased solar-surface coverage
also enable improved measurements of rotational and meridional flows. Active longitudes and persistent
surface “hotspots” of magnetic activity are probably also associated with hotspots in the tachocline region
and require longitudinal resolution.
Another science objective concerns the question, Can helioseismology forecast strong flare activity?
Recent studies show that the strength and vorticity of subsurface flows around active regions are closely
15 This panel report was completed in late 2012. An update in June 2013 to the information above follows: FOXSI was launched
successfully in November 2012 from the White Sands Missile Range in New Mexico; GRIPS is now planned to have its first test
flight in September 2014; and NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) began its 2-year mission on June 13, 2012,
aboard a Pegasus XL rocket launched from Kwajalein Atoll in the Marshall Islands.
16 A. Vourlidas et al., Mission to the Sun-Earth L5 Lagrangian point: An Optimal Platform for Heliophysics and Space Weather
Research, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics), Paper 273.