SUNRISE
Science Requirements
Date:
13.02.2016
Author: Manfred Schüssler
Rev. :
0.0
Introduction
The scientific requirements for the SUNRISE
project result from the key questions that this
mission will address. This document starts
from these questions (which are described in
more detail and put into context in the
SUNRISE proposals) and connects them with
the types of data products that the instruments
should provide in order to find answers. The
corresponding prototypical observations define
the
more detailed requirements on the
instrument performance. No attempt is made to
provide an exhaustive catalogue of science
questions and possible observations. The aim
of this document is to give a list of
representative experiments that reasonably
covers the range of investigations foreseen for
SUNRISE. Once the requirements and the
resulting instrument designs are frozen in
(which will be rather soon), all science
experiments will have to be carried out within
these limits.
aims at the first continuous, quantitative
measurements of the magnetic structure of the
solar atmosphere on its intrinsic spatial and
temporal scales while simultaneously covering
the interaction with the local environment.
This context is crucially important: seemingly
isolated magnetic flux bundles connect with
other elements located some distance away, so
that both are part of a common dynamical
system. The UV spectrum in the range
200400 nm, which is not accessible from the
ground, is essential for studying the dynamics
of the upper solar photosphere and
chromosphere at unprecedented spatial
resolution. These measurements will directly
attack the following key scientific problems:
A) What are the origin and the properties of
the intermittent magnetic structure?
B) How does the magnetic field provide
energy to heat the upper solar atmosphere?
Science objectives
C) How is the magnetic field brought to and
removed from the solar surface?
The central aim of the Sunrise project is to
understand the structure and dynamics of the
magnetic field in the solar atmosphere. The
magnetic field is the source of solar activity,
controls the space environment of the Earth,
and causes the variability of solar irradiance,
which may be a significant driver of long-term
changes of the terrestrial climate. Interacting
with the convective flow field, the magnetic
field in the solar photosphere develops intense
field concentrations on scales below 100 km,
which are crucial for the dynamics and
energetics of the whole solar atmosphere.
Sunrise will provide an unwavering
diffraction-limited angular resolution of about
0.1 (70 km on the Sun) in the visible and
0.05 (35 km on the Sun) in the UV (at 200
nm) over a field of view that is large enough to
determine the local context and over a period
of time that is sufficiently long to study the
dynamical evolution. The Sunrise mission
D) How does the variable magnetic field
modify the solar brightness?
These questions are of fundamental
importance, not only for solar physics and for
understanding the influence of solar activity on
the human environment, but also for
astrophysics in general. The universe abounds
with objects that are dominated by
magnetohydrodynamical
and
plasma
processes, but of all astronomical objects only
the Sun offers the possibility to directly and
quantitatively investigate these processes with
sufficient resolution.
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SUNRISE
Science Requirements
Date:
13.02.2016
Author: Manfred Schüssler
Rev. :
0.0
General requirements
Accomplishing the science objectives requires
accurate measurements of the magnetic field
vector, of the plasma motions (both proper
motions obtained by local correlation tracking
and line-of-sight motions inferred from
Doppler shifts) and of the temperature with
high spatial, spectral and temporal resolution.
These measurements must encompass the
height range from the convection-dominated
deep photosphere to the magnetically
dominated chromosphere, so that the
instruments have to cover the visible and near
UV spectrum of the Sun. The (polarized)
spectral lines and the continuum encode the
information necessary to infer the physical
state of the plasma. Therefore, the required
methods are polarimetric spectroscopy as well
as (magnetic and intensity) imaging. The focalplane instrument package of Sunrise thus
consists of a scanning spectrograph/polarimeter, an imaging filtergraph, and a filter
magnetograph. The inversion procedures that
will be used to derive a maximum of physical
information from the spectroscopic measurements require precise data in order to operate
in a robust and reliable way. This implies that
precise, detailed spectra and filter images of
the Sun must be obtained at a variety of
wavelengths, and that the full state of
polarisation of the solar radiation (i.e., the
complete Stokes vector) has to be obtained in
order to determine the vector magnetic field.
evolutionary time scales of the local context
reach from minutes (granulation) over hours
(mesogranulation) to about a day (supergranulation).
The general requirements resulting from the
scientific objectives and the properties of the
physical system are summarized as follows:
The Sunrise instrumentation shall allow us to
The properties of the solar atmosphere define
the basic length and time scales that should be
accesible with Sunrise. Gravity sets the scale
height of about 100 km in the photosphere, its
characteristic scale for vertical variations of
pressure and density. Theoretical studies and
numerical simulations indicate that small-scale
photospheric magnetic flux concentrations
appear in a size range of roughly 50300 km,
containing significant dynamical substructure
on scales of a few tens of km.
The
corresponding
dynamical
time
scale
(horizontal sound travel time through the
magnetic element) is 530 s, while the
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
resolve the atmospheric structure down to
the intrinsic scale of magnetic elements,
(30100 km);

resolve and cover the evolutionary history
of the small-scale magnetic structure
with a time resolution of a few seconds
and uninterrupted measurements lasting
for hours;

determine the 3D (horizontal and height)
distribution of the thermodynamic state,
magnetic field vector, and flow velocity;

image the Sun simultaneously in radiation
coming from a number of photospheric
and chromospheric layers.
SUNRISE
Science Requirements
Date:
13.02.2016
Author: Manfred Schüssler
Rev. :
0.0
Prototypical experiments
and required data types
In this section, the basic scientific problems are
broken down to more specific questions and
then connected to prototypical observations
and data types. Specific requirements for the
respective experiments are indicated. The data
types and the specifications of the data form
the basis for the instruments requirements
given in the following section.
mesogranulation) and the difference between
network and intranetwork regions.
 magnetic images (vector field)
 LOS velocity images
 intensity images (visible continuum,
for local correlation tracking)
 Stokes spectra (rapid scans in small
subfields of a few arcsecs)
A) Magneto-convection: What are
the origin and the properties of the
intermittent magnetic structure ?
A3: What are the properties and the origin of
the fine structure in sunspot umbrae and
penumbrae ?
A1: How do small-scale magnetic flux
concentrations form, evolve, and decay ?
Determine the fine structure of the magnetic
field, velocity and temperature in penumbral
filaments and umbral dots. Follow the
temporal evolution of the different types of
structures. Requires very high spatial
(0.050.1) and temporal reso-lution (15 s
for imaging, 510 s for spectra) in limited
fields (1010).
Determine the temporal evolution of the
photospheric magnetic field, flow velocity, and
radiation intensity with very high spatial resolution (0.050.1) and high cadence (25 s)
over moderately large areas (2020) in the
quiet photosphere, in the network, and in plage
regions.
 Stokes spectra (fixed slit or short scans
in small subfields)
 magnetic images (vector field)
 LOS velocity images
 intensity images (covering a range of
heights)
 magnetic images (vector field)
 Stokes spectra (rapid scans in small
subfields of a few arcsecs)
 line-of-sight (LOS) velocity images
 intensity images (brightness contrasts
in the visible & UV; horizontal
velocity by local correlation tracking)
B) Chromospheric dynamics:
How does the magnetic field
provide energy to heat the
upper solar atmosphere ?
A2: How much magnetic flux is generated by
local dynamo action on the granulation scale ?
Determine the budget of magnetic flux
(emergence and cancellation rate, average
amount of unsigned flux) in very quiet regions.
Relate to the granular velocity field. Requires
highest spatial resolution to capture very small
bipolar structures. A large field of view
(5050) is necessary for reliable statistics
and to cover variations on larger scales (e.g.,
B1: What is the contribution of waves and
shock dissipation to chromospheric heating ?
Detect (M)HD waves and shocks; connect the
photospheric input to the chromospheric
reaction (e.g., brightening): measure the
variability of magnetic field and LOS velocity
in the photosphere; compare with simultaneous
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SUNRISE
Science Requirements
Date:
13.02.2016
Author: Manfred Schüssler
Rev. :
0.0
 spectral profiles of a chromospheric
line (detection of reconnection jets)
velocity and intensity measurements in the
chromosphere. Requires high spatial resolution
(0.10.2) and rapid cadence (15 s for
imaging, 510 s for spectra).
B4: What are the solar limb profiles of faculae
and spicules ?
 Stokes spectra (photosphere) and
profiles of a chromospheric line
(fixed slit location or short scans)
 intensity images (chromospheric lines
and UV continuum for rapid variability
and shock detection)
 magnetic and velocity images
(for context information)
Determine the structure of dynamic chromospheric features above the limb. Determine the
Sun´s intrinsic limb profile and its disturbance
by faculae. Requires very high spatial
resolution (0.050.1) for faculae and high
resolution (0.10.2) in a chromospheric line
for spicules.
 intensity images (continuum bands
in the visible and the UV)
 spectral line profiles in a
chromospheric line (rapid scans with
slit perpendicular to the limb)
B2: How much do magnetic elements contribute to chromospheric heating outside the
network ?
Clarify the relationship between photospheric
magnetic structure and chromospheric
brightenings at very high spatial resolution
(0.050.1) in quiet regions (inter-network).
C) Active regions: How is the
magnetic flux brought to and
removed from the surface ?
 magnetic images (vector field)
 intensity images (in strong lines and
UV continuum)
 spectral line profiles in a
chromospheric line
 LOS velocity images
C1: Which are the properties of newly
emerging flux ?
Determine magnetic field, velocity, and
thermal structure at flux emergence sites of
young active regions. Requires high spatial
resolution (0.10.2), high cadence (5 s for
imaging, 510 s for spectra) and a large field
of view (5050).
B3: How important are magnetic footpoint
motions and reconnection for the energetics of
the chromosphere ?
 magnetic images (vector field)
 Stokes spectra in small sub-fields
harboring flux emergence
 LOS velocity images
 intensity images (covering both
photosphere and chromosphere)
Determine build-up of magnetic energy
through footpoint motions and its release by
reconnection and/or current sheet dissipation.
Measure displacement of magnetic footpoints
in the photosphere and relate to chromospheric
brightenings with highest possible spatial
resolution (0.050.1) and rapid cadence
(25s) over small (1010) to medium-sized
(2020) areas in the network and in plage
regions.
C2: How is magnetic flux removed from the
solar surface ?
Study flux cancellation events in quiet and
active regions (e.g., near magnetically neutral
lines). Look for signatures of reconnection
events (oppositely directed plasma jets, local
brightenings). Requires very high spatial
resolution (0.050.1), high cadence (5 s for
 magnetic images (vector field)
 intensity images (in the UV for
chromospheric response; in the visible
for local correlation tracking)
 LOS velocity images
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SUNRISE
Science Requirements
Date:
13.02.2016
Author: Manfred Schüssler
Rev. :
0.0
(network, inter-network). The requirements are
similar to those of task D1.
imaging, 510 s for spectra) and a large field
of view (5050).
 intensity images (visible, UV).
 magnetic images (vector field)
 magnetic images (vector field)
 Stokes spectra and chromospheric line
profiles (scans at cancellation sites)
 LOS velocity images
 Intensity images (covering both
photosphere and chromosphere)
D3: How are irradiance variations in the UV
connected with the magnetic structure ?
Relate chromospheric brightenings in the UV
to the photospheric magnetic flux distribution.
Requires very high spatial resolution
(0.050.1) and moderate cadence (510 s)
over large areas (5050) covering quiet Sun,
network, and plage regions.
C3: What is the flux budget of active regions ?
How much small-scale flux is ‘recycled’ ?
Determine the temporal evolution of the total
(unsigned) magnetic flux of active regions on
small and on large scales.
 Magnetic images (vector field)
 intensity images (chromospheric lines,
UV)
 profiles of a chromospheric line
(large scans)
 scans of Stokes spectra (spatial resolution 0.2), field of view covering a
whole active region (50100)
 magnetic images (vector field)
 intensity images (visible & UV, for
context information)
D) Solar irradiance: How does the
variable magnetic field modify the
solar brightness ?
D1: How does the intensity contrast of
magnetic elements depend on their size ?
Measure the brightness of magnetic elements
(and their surroundings) as functions of
wavelength, magnetic field and location on the
solar disk at very high spatial resolution
(0.050.1) and moderate cadence (1020 s)
over large areas (5050) covering quiet Sun,
network, and plage regions.
 magnetic images (vector field)
 intensity images (continuum)
D2: What is the contribution of the network
fields to the variation of total irradiance ?
Determine the brightness in the visible and the
UV as a function of magnetic fill fraction.
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SUNRISE
Science Requirements
Date:
13.02.2016
Author: Manfred Schüssler
Rev. :
0.0
on the magnetic, velocity and temperature
structure. Such inversion of the data and the
requirements from the science experiments
lead to the following list of requirements:
Instrument requirements
The prototypical science experiments sketched
above constitute the basis for the requirements
on the instrumentation for Sunrise. Three
types of data products have to be provided:
SUPOS-1: Signal-to-noise ratio of S/N
>1000 and a corresponding polarimetric
precision to detect weak polarisation
signals. The noise level for polarimetric
measurements must be N<103 of the
continuum intensity (N~104 in weak-field
intranetwork regions)
1. Spectral profiles of all four Stokes
parameters in a photospheric line and
intensity profiles of chromospheric
and photospheric lines.
SUPOS-2: Spectral resolving power of
>250,000 in the visible to obtain detailed
spectral line profiles and reliable inversion
results. In the UV, a resolution of TBD is
sufficient.
2. Images of the vector magnetic field
and the line-of-sight velocity field in
a photospheric line.
3. Intensity images covering the height
range between low photosphere and
middle chromosphere.
SUPOS-3: Simultaneous measurements of at
least one chromospheric line (preferably
Mg h/k at 279 nm) and photospheric lines.
Data product 1. is provided by the spectrograph/polarimeter (SUPOS: Sunrise Polarimetric Spectrograph), a slit spectrograph with
a polarimetric and a diagnostic channel. The
magnetograph IMaX yields data of type 2,
while the filtergraph/imager (SUFI: Sunrise
Filter Imager) will provide the intensity
images of the third data type. The (fixed)
properties of the Sunrise telescope,
particularly the 1 m diameter of the primary
and the wavelength dependence of the
atmospheric transmission in the stratosphere,
fix the maximally achievable spatial resolution
to about 0.1 in the visible (400 nm) and about
0.05 at the shortest available wavelength of
about 200 nm. At least one instrument (the
FG) must be designed to reach the optimum
spatial resolution. Since the main mirror will
probably not be polished to diffraction limit at
200 nm, image reconstruction (Phase Diversity) will have to be applied to FG images.
SUPOS-4: Mitigation of the effect of intensity
variations on the polarisation
measurement. Intrinsic evolution of solar
features requires that the polarimetric
measurement technique be insensitive to
intensity changes of the image. This
demands either rapid sampling of the
polarisation (a fraction of a second for
0.1% accuracy) and/or a dual-beam
measurement system.
SUPOS-5: Cadence: a full Stokes measurement sequence reaching the values for S/N
and N given in SP-1 must be completed in
a time shorter than 510 s to avoid
blurring by the intrinsic motion and
internal dynamics of magnetic features.
Within this time, a S/N of TBD must be
reached in the dark core of the chromospheric line observed in the diagnostic
channel.
Spectrograph/Polarimeter (SUPOS)
SUPOS-6: Slit length at least of 50 (better
100) to cover a full active region.
The instrument has to provide detailed profiles
of all four Stokes parameters in a photospheric
line (polarimetric channel)
and intensity
profiles in a chromospheric line (preferably
Mg h/k). The profiles shall be used to obtain
detailed high-resolution diagnostic information
SUPOS-7: Scan mode: precise and repeatable
rastering is required for time series and for
covering extended regions on the Sun.
6
SUNRISE
Science Requirements
IMaX-1: IMaX-1: S/N ratio (Q,U,V) of
1000 at the nominal mode (vector field
with 4 seconds per wavelength point).
Variable cadence modes to achieve lower
(faster cadence) or higher (slower cadence)
S/N ratios to study rapidly evolving strong
field features or weak fields.
Filtergraph / Imager (SUFI)
SUFI has to provide 2D intensity maps in 46
wavelength bands. These maps will serve also
as context images SUPOS. The science
requirements for are:
IMaX-2:
SUFI-1:
S/N ratio >200 to detect subtle
brightness variations relevant for the
variability of irradiance.
Spectral resolution > 50,000.
IMaX-3: 4 wavelength positions within the
spectral line plus one continuum in
nominal mode.
SUFI-2:
Wavelength bands in the visible
and UV spectral regions to cover various
heights in the photosphere and
chromosphere.
IMaX-4: The total integrating time for the
4+1 wavelength positions in nominal mode
shall be < 20 s. For faster cadence,
observations with only 2 wavelength
points shall be used. This cadence shall be
between 5 to 10 seconds (for S/N between
500 and 1000 respectively) in vector mode
and of 2 to 5 seconds in longitudinal mode
(for the same S/N values).
SUFI-3:
Spectral bandwidth smaller than 1
nm in order to separate photospheric
(continuum) and chromospheric (cores of
strong spectral lines) contributions.
SUFI-4:
Provisions to achieve diffractionlimited resolution at 200 nm: application
of the Phase Diversity method and a
sufficiently small pixel size for critical
sampling (<0.025).
SUFI-5:
Date:
13.02.2016
Author: Manfred Schüssler
Rev. :
0.0
IMaX-5: Mitigation of the effect of intensity
crosstalk into the polarization images due
to residual image jittering to achieve the
S/N given in IMaX-1.
Field of view at least 5050.
IMaX-6:
SUFI-6:
Image cadence 5 s for the full field
of view. Provision for read-out of subfields
(windowing) of 1020 side length with
a more rapid cadence of 12 s.
FOV of 1 arcmin.
IMaX-7: Provisions to measure the short
exposure optical transfer function over the
isoplanatic patch (as set by the telescope
and instrument performance).
Imaging Magnetograph eXperiment
(IMaX)
The instrument shall provide near diffraction
limited sets of images of the four Stokes
parameters (I,Q,U,V) taken within a
photospheric spectral line (vector mode).
Image sets comprising only Stokes I and V
(longitudinal mode) and interlaced continuum
images shall also be available. IMaX data will
allow to study the temporal evolution of the
surface magnetic fields and provide context
data for SUPOS and SUFI. The science
requirements are:
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