Energetic and Suprathermal Particle: Transport and Source in the Inner Heliosphere

George C. Ho

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The Johns Hopkins University Applied Physics Laboratory

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Two-class Picture (Old Picture)

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Reames (1995)

• Wild et al. (1963)
• Lin (1970)
• Pallavacini et al. (1974)
• Kahler et al. (1978)
• Mason et al. (1984; 1986)
• Cane et al. (1986; 1988; 1991)
• Reames 1988; 1995; 1999)

1. Shock Acceleration

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2. Flare Acceleration

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Liu et al. 2013

Drake et al. 2012

Flare Acceleration

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• Electron rich
• Enhanced ³He, Fe
• Last for hours
• Flare associated
• Impulsive X-ray

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Need Solar Orbiter,

PSP to disentangle transport effects from injection effects.

Illustration of the effect of transport on particles

Wibberenz & Cane, 2006

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Transport to 1 AU

Scatter free?

Some Scattering? (λ > 0.3 AU)

Lots of Scattering? (λ < 0.1 AU)

Scattering λ dependent on time

And location?

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Transport Effects�

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• Common energy organizes better than velocity
• Maybe rigidity is better

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Mason et al. 2012

May 22-23, 2021

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Ho et al., 2022

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Blue: 1AU

Red: Ulysses (see above)

How does the Sun fill the heliosphere with energetic particles?

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Note how the decay phases are all very similar.

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This indicates that a large 'reservoir' of energetic particles that fills the heliosphere is being depleted at the same rate everywhere.

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How is it filled?

Why does it empty in lockstep?

Measurements close to Sun!

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McKibben et al., 2003

Tracer Elements in Energetic Particles: ³He ions -- where do they come from?�

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When a CME driven shock event occurs, the suprathermal ³He is accelerated into the energetic particle range

Mason et al., 1999; Cohen et al., 1999

CME figure from Reames et al., 1996

Desai et al., 2001

CME speed vs. Particle intensity

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Kahler, JGR, 2001

What is being accelerated?

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• Solar Wind & SEP have different composition

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Mewaldt et al., ASR, 2002; Desai et al., ApJ, 588, 1149, 2003

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Heavy ion enhancements seen in solar energetic particles (Mason et al., 2004).

Could be due to wave-particle interactions.

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But not these!?!

Mason et al., 2004

Dependence of solar energetic particle fluences �on suprathermal seed-particle densities�

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Mewaldt et al., AIP Conf Proc 1500, 2012

Kahler & Vourlidas, 2014

SEP and Suprathermal Correlations

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Consistency of four representative sets of data points from both suprathermal ions (H & He) and energies (lo & hi), and four time periods plotted at mid longitude ranges for all 201 SEP events.

All SEP events

Kahler et al., (2018) recently studied NOAA list of > 10 pfu >10 MeV events and found:

• B field correlations are not significant for any conditions;
• Significant correlations between SEP peak and 1 AU suprathermal intensities;

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Suggests suprathermal seeds may be the primary factor and CME shock secondary

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Suprathermal in the Interplanetary Medium

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Solar Cycle Progression

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Solar ENAs (Mewaldt et al., 2009)

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Solar ENAs (Mason et al., 2021)

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