Prediction of High-Energy Proton Hazards from CME Shocks:
Contributions from Ultraviolet Coronagraph Spectroscopy
The greatest hazard to astronauts and their equipment in interplanetary
space is believed to be relativistic protons produced by Coronal Mass
Ejections (CMEs) and Solar Flares.
This radiation hazard is produced by the CME shock as it propagates
through interplanetary space and at the sites of solar flares during
Ultraviolet Spectroscopy by
has revealed a means for: 1) detecting
and characterizing the CME shocks, which are believed to produce most
of the relativistic protons, and 2) characterizing the conditions
in the pre-CME corona (see
Raymond et al. , and
Such remote sensing combined with models of relativistic proton
acceleration and transport can be used to predict the levels and
production sites of the radiation.
Solar Flare/CME events observed in
October and November 2003 produced
highly elevated levels of relativistic protons for one to two days
after each event. Most of these protons are believed to have been
accelerated by the CME shock as it traveled at speeds up to
2000 km/second into interplanetary space, taking one to two days to
reach the vicinity of the Earth.
The CME characteristics near the Sun in the initial phases of the
event are the inputs needed for theoretical models that predict
the following one to two days of proton production including its
location and geometrical extent.
High-energy particles also are emitted on the Sun at the sites of
strong solar flares.
observations have shown that protons
and electrons are accelerated at different locations within flares
Lin et al. ).
Initial testing of predictions can utilize
satellite data and existing data from the SOHO
Ultraviolet Coronagraph Spectrometer (UVCS)
operated by the
Harvard-Smithsonian Center for Astrophysics
Kohl et al. ) in concert with ground-based
radio observations that help to identify the electron density at
the shock front
Mancuso & Raymond ).
Feasibility of next-generation instrumentation with greater capability
for such measurements has been established by Harvard-Smithsonian
during Medium Class Explorer Phase A studies.
Recent theoretical efforts have been devoted to modeling particle
(mainly proton) acceleration at CME-driven shocks and the subsequent
particle transport in the interplanetary medium (see, e.g.,
Li, Zank, and Rice ).
The spectroscopic measurements can determine the speed and Mach number
of the shock, the temperature and amount of associated plasma heating,
the handedness (chirality) of the associated magnetic field, and
inferred information about the local Alfven speed and associated
magnetic field strength. In addition to the production of relativistic
proton radiation, the same instrumentation can characterize fast solar
wind streams that are a known source of the energetic electron hazard.
This instrumentation determines the speed, densities, energetics and
particle abundances at the solar wind source regions.
The specific means by which the remote-sensing data will be used
as inputs and boundary conditions for the energetic particle codes
are described in more detail on
the following page.
Additional information about UVCS/SOHO and theoretical models of
relativistic proton production can be found at: