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Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON SOLAR AND HELIOSPHERIC PHYSICS
295
10.4.6.3 Science Goals for the Interface Region Imaging Spectrograph
IRIS is a small Explorer scheduled for launch in June 2013 for a 2-year prime mission. The IRIS science goals focus on three themes of broad importance in solar and plasma physics, space weather, and
astrophysics, aiming to understand how internal convective flows power atmospheric activity:
• Which types of nonthermal energy dominate in the chromosphere and beyond (SHP action 2a)?
• How does the chromosphere regulate mass and energy supply to the corona and heliosphere (SHP
actions 2a and 2b)?
• How do magnetic flux and matter rise through the lower atmosphere, and what role does flux
emergence play in flares and mass ejections (SHP actions 2a, 2b, and 3a)?
10.4.6.4 Goals for the Heliophysics Systems Observatory
The Heliophysics Systems Observatory (Table 10.2) will provide unique opportunities to observe solar
and interplanetary activity and heliosphere-interstellar interactions evolve over a new solar cycle. 9 Since
February 2011 and continuing through 2019, STEREO and near-Earth observatories (SDO, Hinode, SOHO,
and ground-based facilities) have combined to provide a 360° view of the Sun. This total-Sun view can
observe far-side active regions emerge and develop and can observe far-side flares and CMEs that often
cause near-Earth solar-particle events. The solar origins of Earth-directed CMEs and flares will be observed
with ultra-high precision by SDO, which delivers continuous measurements of the photospheric vector
magnetic field and of coronal XUV structure. In addition, STEREO and near-Earth spacecraft (ACE, Wind,
SOHO, and GOES) now provide broad longitudinal coverage of solar wind, pickup ions, CMEs, shocks,
SEPs, and radio bursts, enabling greatly improved nowcasts and forecasts of the interplanetary environment. Simultaneously, the Voyagers traverse the heliosheath, and IBEX maps the outer heliosphere and
samples interstellar flows.
An important goal enabled by the HSO is the comprehensive study of solar activity and explosive
events. SOHO, ACE, and GOES studies show that about 10 percent of the CME kinetic energy often goes
into accelerated particles. Uncertainties arise from limitations of knowledge of CME geometries and singlepoint sampling of particle intensities. STEREO and near-Earth spacecraft have enabled multipoint observations of cycle-24 SEP events, which indicate surprisingly broad longitudinal SEP distributions. Combined
multipoint in situ and stereoscopic solar and CME studies by STEREO, SOHO, and SDO (to be augmented
with radial coverage by Solar Orbiter and SPP) will provide more precise measurements of CME evolution,
shock-acceleration efficiency, and its controlling properties (SHP actions 3a-c).
On a related note, recent SDO observations show near-simultaneous closely connected “sympathetic”
eruptions over broad regions of the Sun (§10.3.3), which complicate eruption forecasts from active regions
that may, somehow, be triggered remotely. Coordinated observations by SDO, STEREO, and other 1-AU
resources during 2013-2019 (with 360° solar viewing) may reveal the nature of those connections.
The launch of the Fermi astrophysical observatory supplements RHESSI solar gamma-ray observations
of eruptive events with extended temporal and energy coverage (to about 300 MeV). Combining those with
STEREO and near-Earth SEP coverage can determine the escape efficiency of flare-accelerated particles
from large solar eruptions (SHP action 3b).
9 J.G. Luhmann et al., Extended Missions: Engines of Heliophysics System Science, white paper submitted to the Decadal Strategy
for Solar and Space Physics (Heliophysics), Paper 167; C.W. Smith et al., The Case for Continued, Multi-Point Measurements in
Space Science, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics), Paper 246; M.H. Israel et
al., The Effect of the Heliosphere on Galactic and Anomalous Cosmic Rays, white paper submitted to the Decadal Strategy for Solar
and Space Physics (Heliophysics), Paper 116.
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON SOLAR AND HELIOSPHERIC PHYSICS
295
10.4.6.3 Science Goals for the Interface Region Imaging Spectrograph
IRIS is a small Explorer scheduled for launch in June 2013 for a 2-year prime mission. The IRIS science goals focus on three themes of broad importance in solar and plasma physics, space weather, and
astrophysics, aiming to understand how internal convective flows power atmospheric activity:
• Which types of nonthermal energy dominate in the chromosphere and beyond (SHP action 2a)?
• How does the chromosphere regulate mass and energy supply to the corona and heliosphere (SHP
actions 2a and 2b)?
• How do magnetic flux and matter rise through the lower atmosphere, and what role does flux
emergence play in flares and mass ejections (SHP actions 2a, 2b, and 3a)?
10.4.6.4 Goals for the Heliophysics Systems Observatory
The Heliophysics Systems Observatory (Table 10.2) will provide unique opportunities to observe solar
and interplanetary activity and heliosphere-interstellar interactions evolve over a new solar cycle. 9 Since
February 2011 and continuing through 2019, STEREO and near-Earth observatories (SDO, Hinode, SOHO,
and ground-based facilities) have combined to provide a 360° view of the Sun. This total-Sun view can
observe far-side active regions emerge and develop and can observe far-side flares and CMEs that often
cause near-Earth solar-particle events. The solar origins of Earth-directed CMEs and flares will be observed
with ultra-high precision by SDO, which delivers continuous measurements of the photospheric vector
magnetic field and of coronal XUV structure. In addition, STEREO and near-Earth spacecraft (ACE, Wind,
SOHO, and GOES) now provide broad longitudinal coverage of solar wind, pickup ions, CMEs, shocks,
SEPs, and radio bursts, enabling greatly improved nowcasts and forecasts of the interplanetary environment. Simultaneously, the Voyagers traverse the heliosheath, and IBEX maps the outer heliosphere and
samples interstellar flows.
An important goal enabled by the HSO is the comprehensive study of solar activity and explosive
events. SOHO, ACE, and GOES studies show that about 10 percent of the CME kinetic energy often goes
into accelerated particles. Uncertainties arise from limitations of knowledge of CME geometries and singlepoint sampling of particle intensities. STEREO and near-Earth spacecraft have enabled multipoint observations of cycle-24 SEP events, which indicate surprisingly broad longitudinal SEP distributions. Combined
multipoint in situ and stereoscopic solar and CME studies by STEREO, SOHO, and SDO (to be augmented
with radial coverage by Solar Orbiter and SPP) will provide more precise measurements of CME evolution,
shock-acceleration efficiency, and its controlling properties (SHP actions 3a-c).
On a related note, recent SDO observations show near-simultaneous closely connected “sympathetic”
eruptions over broad regions of the Sun (§10.3.3), which complicate eruption forecasts from active regions
that may, somehow, be triggered remotely. Coordinated observations by SDO, STEREO, and other 1-AU
resources during 2013-2019 (with 360° solar viewing) may reveal the nature of those connections.
The launch of the Fermi astrophysical observatory supplements RHESSI solar gamma-ray observations
of eruptive events with extended temporal and energy coverage (to about 300 MeV). Combining those with
STEREO and near-Earth SEP coverage can determine the escape efficiency of flare-accelerated particles
from large solar eruptions (SHP action 3b).
9 J.G. Luhmann et al., Extended Missions: Engines of Heliophysics System Science, white paper submitted to the Decadal Strategy
for Solar and Space Physics (Heliophysics), Paper 167; C.W. Smith et al., The Case for Continued, Multi-Point Measurements in
Space Science, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics), Paper 246; M.H. Israel et
al., The Effect of the Heliosphere on Galactic and Anomalous Cosmic Rays, white paper submitted to the Decadal Strategy for Solar
and Space Physics (Heliophysics), Paper 116.