The EPD/Suprathermal Ion Spectrograph (SIS) For Solar Orbiter

The Suprathermal Ion Spectrograph (SIS) for the Solar Orbiter spacecraft
J.
1
Köhler ,
R. F.
1
Wimmer-Schweingruber ,
2
Mason ,
G. M.
2
3
G. C. Ho , J. R-Pacheco
K.
2
Tyagi ,
H.
2
Seifert ,
1IEAP,
Christian-Albrechts-University Kiel, Germany,
2Johns Hopkins University Applied Physics Laboratory, United States
3Space Research Group/University of Alcalá
Abstract
Instrument concept
The SIS instrument is part of the Energetic Particle Detector (EPD) suite for the
Solar Orbiter spacecraft. The EPD will provide a full range of measurements for
energetic electrons, energetic protons, and energetic heavy ions, where SIS will
provide observations of He-Fe for an energy range from just above the solar wind
up to several MeV/nucleon. SIS identifies particle species and energy by time-offlight by energy technique, and is based on the ACE/ULEIS design. Particles are
detected when they pass through the entrance foil and deposit their energy in one
solid state detector pixel at the back of the instrument. When the ion passes
through the entrance, mid, and detectorfoils secondary electrons are emitted,
accelerated to ~1 kV, and directed via isochronous mirrors onto microchannel plate
stacks to provide a time-off-light measurement. The very high mass resolution of
m/σm ~ 50 will allow SIS to measure particle populations with 3He/4He ratios down
to <1%
• Particles are detected when they pass through the entrance foil and trigger
one of the SSD pixels in the array at the back
• Secondary electrons are emitted when the ion passes the entrance, middle
and detector foils
• The electrons are accelerated up to ~ 1kV and directed via electrostatic
mirrors onto microchannel plates (MCP)
• The Start-1, Start-2 and Stop signals provide two independent time-of-flight
measurements (flight paths length 21.0 and 11.2 cm)
• Particle speed is obtained from the velocity measurement: v = l/t.
• The SSD measures the residual energy, E, of the ion
• The energy E, time-of-flight t, and known flight path in the telescope l, are
combined to give the particle mass m  2 E (t / l ) 2
The Suprathermal Ion Spectrograph (SIS) is a sensor that is part of the
Energetic Particle Detector (EPD) suite for the Solar Orbiter Spacecraft. The
EPD suite’s sensors are designed to provide the full range of measurements
for energetic electrons, energetic protons, and energetic heavy ions.
• SIS has large geometry factor for studying the ambient suprathermal
populations
• Door closes to limit aperture during high intensity periods
• Electrostatic mirrors give precise secondary electron time required for high
mass resolution
SIS has one sunward
looking and one rearward
facing telescope sharing a
single electronics box;
mounted on –y panel of
Solar Orbiter in the
permanent shade of the
sunshield.
SIS as a part of the EPD suite
SIS provides composition measurements for He-Fe from the suprathermal
range up through ~10 MeV/nucleon, with protons, electrons, and higher
energies covered by other sensors in the Energetic Particle Detector (EPD)
Suite (Pacheco et al. 2008).
Science Objectives
Suprathermal ion studies on Solar Orbiter:
Key Relevant Science Goals from the "Red Book":
2.3 How do solar eruptions produce energetic particle
radiation that fills the heliosphere?
• How and where are energetic particles accelerated at the Sun?
• How are energetic particles released from their sources and
distributed in space and time?
• What are the seed populations for energetic particles?
Acceleration - seed population?
Material in coronal
loops? (high T, Ferich?)
Ions encountering
shock?
Bulk solar wind?
“Flare” particles?
Suprathermal ions? -- what
properties?
Adapted from Marty Lee, ApJS, 158, 2005
Oxygen fluence at 1 AU from
solar wind through galactic
cosmic ray energy range. SIS
energy range for heavy ions
is shown as filled red box. SIS
covers the suprathermal
energy range and the
principal energy ranges for
impulsive SEPs, shocks, etc.
(Fluence figure adapted from
Mewaldt et al., 2001).
• telescope high resolution design based on ACE/ULEIS
• high heritage electronics design based on current projects
• meets or exceeds all Solar Orbiter requirements for energy range, mass
resolution
EPD fields of view in the spacecraft frame of reference. Mean Parker spiral
direction is marked as a black star. The two shaded areas correspond to the
variability of the field at 1 AU in a slow-wind stream (green) and at 0.225 AU in a
fast stream (gray).
There are many important sources of suprathermals -- not just solar wind:
• Solar wind suprathermal tail
• Pick up ions
• Remnant material from
...Impulsive SEPs
...CIRs
...Shock events
...Bow shocks
 SIS will determine the constituents and properties of the unexplored
suprathermal ion pool within 1 AU
 SIS will provide the critical link between the energetic particles and the bulk
solar wind measurements
 SIS will probe the energy range where differences in solar wind and energetic
particle composition begin, in order to explore the reason for these
differences
 Impulsive events will be detected primarily by SIS, since most produce
particles of energy ~1 MeV/nucleon or less
 SIS will provide observational data for magnetic connection to reconnection
sites low in the corona
 SIS will provide the low energy SEP spectral segment required to identify
“breaks” in the large SEP event particle spectra observed by LET and HET
 SIS will provide high time resolution CME-shock associated energetic particle
spectra close to or even within the acceleration site
...Inner source
… others?
Contact:
Dr. Jan Köhler
Institute of Experimental and Applied Physics
Christian-Albechts-Universität zu Kiel
Leibnizstr. 11, 24118 Kiel, Germany
Tel.: +49-431-880-3944
Fax: +49-431-880-3968
koehler@physik.uni-kiel.de
www.ieap.uni-kiel.de/et
Poster download:
Suprathermal Ion Spectograph for Solar Orbiter mission
• SIS is an ESA facility instrument
• SIS is a portion of the Energetic Particle Detector suite, Dr. Javier R.-Pacheco, Univ
of Alcalá, PI
• SIS is to be provided by Christian-Albrechts Univ., Kiel, in collaboration with the
Johns Hopkins Univ./Applied Physics Laboratory
• Dr. R. F. Wimmer-Schweingruber is the SIS PI