1. Measurements of Suprathermal Ions in the Inner Heliosphere from Solar Probe Plus and Solar Orbiter
George C. Ho
SPP SWT
September 14-15th, 2016

2. Barely Explored Energy Range
Bulk plasma (~keV)
Typically measure by solar wind instrument
Energetic particle (~100s keV)
Typically measure by particle instrument
Suprathermal (~10s keV)
Gap between two measurement technique
Suprathermal
Mewaldt et al., 2001

3. The interplanetary particle population at 1 AU
The solar wind and suprathermal tail have grossly similar composition, but is the energetic particle seed population from the bulk plasma or the suprathermal tail?
The details point to suprathermal tail as the source.
seed particles
from here?
or here?

4. The mystery of huge heavy ion (Fe) variations in intensity
Peak intensities in shock events vary over a range of ~104
not explained by CME speed
not explained by shock acceleration models
not explained by solar wind number density which does not change nearly as much
Many researchers have suggested important role of suprathermal seed population
Mason et al., AIP CP781, 2005

5. Energetic particle intensities roughly correlate with CME speeds BUT where do the variations come from?
a general correlation but with a huge range of intensities for the same CME speed – what causes that?
10,000

6. Tracer Elements in Energetic Particles: 3He ions -- where do they come from?
Mason et al., 1999; Cohen et al., 1999
CME figure from Reames et al., 1996
When a CME driven shock event occurs, the suprathermal 3He is accelerated into the energetic particle range
Example: a large SEP event with 3He with same time profile as 4He, enhanced ~7x over solar wind.
This is seen in many events.

7. Sources of Suprathermals
Inner heliospheric material sources (circles), and physical mechanisms (rectangles) that produce energetic particle populations in the inner heliosphere. Except for flare sources at the Sun, the energetic particle seeds are from the suprathermal interplanetary ion pool which has many contributors that vary in both location and time (Mason et al. 2005).

8. Barely Explored Population
If the ubiquitous quiet-time suprathermal tails observed at 1 AU and beyond extend close to the Sun, they will carry critical information about turbulence mechanisms in the solar wind, and the tails will be a important part of the suprathermal heavy ion pool in the inner heliosphere. SIS will map the upper energy portion of these tails, their spatial and temporal dependence, and their rollovers which carry information about the source mechanisms

9. SPP to disentangle transport effects from injection effects.
Illustration of the effect of transport on particles
Need Solar Orbiter,
SPP to disentangle transport effects from injection effects.
Kallenrode & Wibberenz, 1991

10. At 1 AU temporal profiles have suffered significant modification due to transport effects.
Expect much clearer picture close to the Sun.
But this also requires higher time resolution for in-situ payload. 10

11. Helios and IMP 8 Comparison (Lario et al., 2006)

12. Helios and IMP 8 Comparison (Lario et al., 2006)

13. MSGR, ACE, Stereo Peak Intensities
Peak Intensity:
MSRG: ~5x104 pf
ACE: ~1x104 pf
Stereo A: ~6x103pf
Scale: Rn
n: -1.8 (-1.3)

14. MESSENGER and ACE/STEREO (Lario et al., 2013)

15. j~r-5.29

16. Large SEP Event at Various Radial Distances
Red circles in both panels: 1-hr ACE/ULEIS 0.55 MeV/n He intensity for the April 15, 2001 event period. Solid lines: calculated intensities using an improved version of the numerical model of Li et al., (2005) at different radial distances.

17. Impulsive SEP Event at Various Radial Distances
Red circles: 1-hr ACE/ULEIS 0.55 MeV/n He intensity for the May 1, He-rich event period. Solid curves: intensities calculated with the same model as previous slide but with 1/5 the interplanetary turbulence level. Filled blue circles on 0.05 AU trace are time tics <1 min apart

18. MESSENGER FIPS Heavy Ion Measurements
Gershman et al. [2012]

19. Heating at 0.3 AU
Gershman et al. [2012]

20. SPP Particle Instruments
SWEAP SPAN-A (ion and electron
ISʘIS EPI-Lo FM Wedge Assembly
August Solar Probe Plus Tag-Up

21. Solar Orbiter Spacecraft
10 instrument suite: 4 in-situ; 6 remote

22. Solar Orbiter EPD Suite

23. Solar Orbiter EPD/SIS EPD is now being delivered (DRB: September 2016)
He histograms with TOF-1
m/sigma-m:
A telescope: 73.6
B telescope: 74.5
EPD is now being delivered (DRB: September 2016)
SIS has direct heritage from ACE/ULEIS
SIS measures all elements from helium to ion and samples trans-iron elements
8 keV/nuc – 10 MeV/nuc (Oxygen)

24. Synergistic Observations
(1) radially aligned cases where one mission samples solar wind and turbulence on plasma samples that then move past the other spacecraft;
(2) Parker spiral alignments where both spacecraft are on a single field line and energetic particles move from one to the other and;
(3) quadrature alignments where Solar Orbiter observes the lower corona with remote sensing instruments and then the plasma from this region moves past Solar Probe.
In addition, even when not aligned, in surveying the suprathermal ion pool two-point measurements by SIS on Solar Orbiter and SPP will greatly help separate temporal and spatial properties of the pool.

25. SEP Longitudal Alignment Study (SPP/SOLO Radial aligned)

26. Lario et al. [ApJ, 2006]
27-37 MeV protons
ϕ0=-10.9° k=1.20 rad-2
σ=36°
ϕ0=-18.0° k=0.63 rad-2 σ=51°
ϕ0=-14.5° k=0.77 rad-2 σ=46°

27. IMF Alignment Opportunities

28. SEP Wide Longitudal Alignment Study (SPP/SOLO Same R)

29. Gómez-Herrero et al., 2015

30. SPP and Solar Orbiter Radial Study

31. Radial and Longitudal Study (#2)

33. Need to analyze not only particles, but all signatures!
(After all, this is 'multi-waveband Observations')

34. Mission Design Nominal launch in October 2018 NASA-provided launcher
First perihelion is reached 3.5 years after launch
Minimum perihelion at 0.28 AU
Operating orbit has a 168 days period

35. Mission Design (continue)
Resonant orbit with Venus
7 years nominal mission at 25° inclination
Extended mission will reach 33°

36. Shock acceleration theories provide a rough framework for particle acceleration
s, analytic, steady-state Diffusive Shock Acceleration (DSA) models (Axford, Fisk & Lee, etc) predicted particle energy spectra, but measured spectral slopes & shock compression ratios were poorly correlated, contrary to theoretical expectations
recent numerical of DSA addresses evolution of shock and energetic particles, including heavy ion composition for nominal cases, but no detailed closure between theory and observations
Li, Zank, and Rice, 2005

37. Correlation between shock parameters and particle signatures
ISEE-3 observations
van Nes et al. [1984]
ACE observations
Ho et al. [2005]

38. Abundances of common ions show correlation with ambient suprathermal population that is NOT predicted in DSA
The spectral index and energy dependence of the Fe/O ratioof the ambient population show significant correlation with the spectral index at the shock -- simple diffusive theory would say they are totally unrelated
Desai et al., ApJ, 611, 1156, 2004

39. Remote Sensing of Suprathermal Ions at the Corona

40. Kappa Distribution
Laming et al., ApJ, 2013

41. Stimulated Lyα Profiles
Rs=1.8
Rs=2.1
Rs=2.5
Rs=3.5
Laming et al., ApJ, 2013

42. Heating of Ions at CME-driven Shock
Mancuso et al., A&A, 2002

43. UVCS Observations before and after Shock Passage
Mancuso et al., A&A, 2002