Ly. cap alpha. and H. cap alpha. emission by superthermal proton beams

Journal Article · Thu Aug 01 04:00:00 EDT 1985 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/163371· OSTI ID:5266215

Canfield, R C; Chang, C

We investigate nonthermal Doppler shifted Ly..cap alpha.. and H..cap alpha.. emission as a diagnostic of beams of 10 keV--10 MeV protons in the chromosphere during flares. We determine the steady state excitation and ionization balance of the proton beam, taking into account radiative and collisional interactions with a uniform pure hydrogen 10% ionized model chromosphere. We find that, from the point of view of generating Ly..cap alpha.. and H..cap alpha.. wing emission, the dominant processes throughout the energy range of interest are charge exchange and collisional excitation and ionization. We use a Coulomb collision model to describe the stopping of the beam particles. We analytically compute nonthermal Ly..cap alpha.. and H..cap alpha.. wing profiles of the Doppler-shifted emission from a purely vertical beam, for monoenergetic, power-law, and thermal input proton spectra. Assuming a total input proton energy flux comparable to the electron energy flux commonly inferred for large flares, we find Ly..cap alpha.. wing intensities orders of magnitude larger than observed active region or flare values, but H..cap alpha.. wing intensities somewhat smaller than typical nonflaring values. We show that the Ly..cap alpha.. emission is much more sensitive to the mean input proton energy than to the proton energy spectrum. Finally, we derive characteristic time scales for departures from the equilibrium assumed, and show that these range from 10/sup -6/ to 10/sup 4/ s, depending on input energy and beam flux. Hence, we conclude that over a wide range of values of mean proton energy and beam parameters, Doppler shifted nonthermal Ly..cap alpha.. emission is a useful observational diagnostic of the presence of 10 keV--10 MeV superthermal proton beams in the chromosphere.

• Research Organization: Center for Astrophysics and Space Sciences; and Department of Physics, University of California, San Diego
• OSTI ID: 5266215
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 295:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
BALMER LINES
BEAMS
CHROMOSPHERE
EMISSION SPECTRA
LINE WIDTHS
LYMAN LINES
MAIN SEQUENCE STARS
NUCLEON BEAMS
PARTICLE BEAMS
PROTON BEAMS
SOLAR ACTIVITY
SOLAR ATMOSPHERE
SOLAR FLARES
SPECTRA
STARS
STEADY-STATE CONDITIONS
SUN