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

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

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?

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

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

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.

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).

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

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

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

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

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

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

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

j~r-5.29

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.

Impulsive SEP Event at Various Radial Distances Red circles: 1-hr ACE/ULEIS 0.55 MeV/n He intensity for the May 1, 2001 3He-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

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

Heating at 0.3 AU Gershman et al. [2012]

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

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

Solar Orbiter EPD Suite

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)

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.

SEP Longitudal Alignment Study (SPP/SOLO Radial aligned)

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°

IMF Alignment Opportunities

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

Gómez-Herrero et al., 2015

SPP and Solar Orbiter Radial Study

Radial and Longitudal Study (#2)

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

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

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

Shock acceleration theories provide a rough framework for particle acceleration 1970-80s, 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

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

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

Remote Sensing of Suprathermal Ions at the Corona

Kappa Distribution Laming et al., ApJ, 2013

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

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

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