Hydrogen and the Abundances of Elements in Gradual Solar Energetic-Particle Events. (arXiv:1902.03208v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Reames_D/0/1/0/all/0/1">Donald V. Reames</a>
Despite its dominance, hydrogen has been largely ignored in studies of the
abundance patterns of the chemical elements in gradual solar energetic-particle
(SEP) events; those neglected abundances show a surprising new pattern of
behavior. Abundance enhancements of elements with 2 <= Z <= 56, relative to
coronal abundances, show power-law dependence, versus their average
mass-to-charge ratio A/Q, that varies from event to event and with time during
events; the ion charge states Q depend upon the source plasma temperature T.
For most gradual SEP events, shock waves have accelerated ambient coronal
material with T < 2 MK to produce a decreasing power-laws in A/Q; here the
proton abundances agree rather well with the power-law fits extrapolated from
elements with Z >= 6 at A/Q > 2 down to hydrogen at A/Q = 1. Thus the
abundances of the elements with Z >= 6 fairly accurately predict the observed
abundance of H, at a similar velocity, in most SEPs. However, for those gradual
SEP events where ion enhancements follow positive powers of A/Q, especially
those with T > 2 MK where shock waves have reaccelerated residual suprathermal
ions from previous impulsive SEP events, pro-ton abundances commonly exceed the
extrapolated expectation, usually by a factor of order 10. This is a new and
unexpected pattern of behavior that is unique to the abun-dances of protons.
This proton behavior is a signature that can help distinguish the presence or
absence of shock acceleration when Fe-rich impulsive material is observed.
Despite its dominance, hydrogen has been largely ignored in studies of the
abundance patterns of the chemical elements in gradual solar energetic-particle
(SEP) events; those neglected abundances show a surprising new pattern of
behavior. Abundance enhancements of elements with 2 <= Z <= 56, relative to
coronal abundances, show power-law dependence, versus their average
mass-to-charge ratio A/Q, that varies from event to event and with time during
events; the ion charge states Q depend upon the source plasma temperature T.
For most gradual SEP events, shock waves have accelerated ambient coronal
material with T < 2 MK to produce a decreasing power-laws in A/Q; here the
proton abundances agree rather well with the power-law fits extrapolated from
elements with Z >= 6 at A/Q > 2 down to hydrogen at A/Q = 1. Thus the
abundances of the elements with Z >= 6 fairly accurately predict the observed
abundance of H, at a similar velocity, in most SEPs. However, for those gradual
SEP events where ion enhancements follow positive powers of A/Q, especially
those with T > 2 MK where shock waves have reaccelerated residual suprathermal
ions from previous impulsive SEP events, pro-ton abundances commonly exceed the
extrapolated expectation, usually by a factor of order 10. This is a new and
unexpected pattern of behavior that is unique to the abun-dances of protons.
This proton behavior is a signature that can help distinguish the presence or
absence of shock acceleration when Fe-rich impulsive material is observed.
http://arxiv.org/icons/sfx.gif
