STREAMING-LIMITED INTENSITIES OF SOLAR ENERGETIC PARTICLES ON THE INTENSITY PLATEAU
Abstract
We examine the energy spectra of H, He, O, and Fe ions on the temporal intensity plateau region in large solar energetic-particle (SEP) events, where intensities may be ''streaming limited.'' Upstream of shock waves near the Sun, equilibrium may occur when outwardly streaming protons amplify resonant Alfven waves that then scatter subsequent protons sufficiently to reduce the streaming. In the largest SEP events, the so-called ground-level events (GLEs), we find proton energy spectra that are peaked near {approx}10 MeV with the energy of similar peaks decreasing for heavier ions and for smaller events. These spectra contrast sharply with spectra near the time of shock passage which rise monotonically above the plateau spectra with decreasing energy. We suggest that strong suppression of upstream ion intensities near {approx}1 MeV amu{sup -1} on the plateau occurs when those ions resonate with waves amplified earlier by streaming protons of {approx}10 MeV and above. GLEs with much lower intensities of 10-100 MeV protons on the plateau show spectra of ions that rise monotonically toward low energies with no peaking and no suppression of low-energy ions. Wave amplification by streaming protons and the pitch-angle dependence of the resonance condition are essential factors in our understanding ofmore »
- Authors:
-
- Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742 (United States)
- Publication Date:
- OSTI Identifier:
- 21471270
- Resource Type:
- Journal Article
- Journal Name:
- Astrophysical Journal
- Additional Journal Information:
- Journal Volume: 723; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/723/2/1286; Journal ID: ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALFVEN WAVES; ENERGY SPECTRA; HEAVY IONS; HELIUM IONS; HYDROGEN IONS; ION WAVES; IRON IONS; MEV RANGE; OXYGEN IONS; PROTONS; SHOCK WAVES; SOLAR CORONA; SOLAR RADIATION; SUN; ATMOSPHERES; BARYONS; CHARGED PARTICLES; ELEMENTARY PARTICLES; ENERGY RANGE; FERMIONS; HADRONS; HYDROMAGNETIC WAVES; IONS; MAIN SEQUENCE STARS; NUCLEONS; PLASMA WAVES; RADIATIONS; SOLAR ATMOSPHERE; SPECTRA; STARS; STELLAR ATMOSPHERES; STELLAR CORONAE; STELLAR RADIATION
Citation Formats
Reames, Donald V, and Ng, Chee K., E-mail: dvreames@umd.ed, E-mail: cng2@gmu.ed. STREAMING-LIMITED INTENSITIES OF SOLAR ENERGETIC PARTICLES ON THE INTENSITY PLATEAU. United States: N. p., 2010.
Web. doi:10.1088/0004-637X/723/2/1286.
Reames, Donald V, & Ng, Chee K., E-mail: dvreames@umd.ed, E-mail: cng2@gmu.ed. STREAMING-LIMITED INTENSITIES OF SOLAR ENERGETIC PARTICLES ON THE INTENSITY PLATEAU. United States. https://doi.org/10.1088/0004-637X/723/2/1286
Reames, Donald V, and Ng, Chee K., E-mail: dvreames@umd.ed, E-mail: cng2@gmu.ed. 2010.
"STREAMING-LIMITED INTENSITIES OF SOLAR ENERGETIC PARTICLES ON THE INTENSITY PLATEAU". United States. https://doi.org/10.1088/0004-637X/723/2/1286.
@article{osti_21471270,
title = {STREAMING-LIMITED INTENSITIES OF SOLAR ENERGETIC PARTICLES ON THE INTENSITY PLATEAU},
author = {Reames, Donald V and Ng, Chee K., E-mail: dvreames@umd.ed, E-mail: cng2@gmu.ed},
abstractNote = {We examine the energy spectra of H, He, O, and Fe ions on the temporal intensity plateau region in large solar energetic-particle (SEP) events, where intensities may be ''streaming limited.'' Upstream of shock waves near the Sun, equilibrium may occur when outwardly streaming protons amplify resonant Alfven waves that then scatter subsequent protons sufficiently to reduce the streaming. In the largest SEP events, the so-called ground-level events (GLEs), we find proton energy spectra that are peaked near {approx}10 MeV with the energy of similar peaks decreasing for heavier ions and for smaller events. These spectra contrast sharply with spectra near the time of shock passage which rise monotonically above the plateau spectra with decreasing energy. We suggest that strong suppression of upstream ion intensities near {approx}1 MeV amu{sup -1} on the plateau occurs when those ions resonate with waves amplified earlier by streaming protons of {approx}10 MeV and above. GLEs with much lower intensities of 10-100 MeV protons on the plateau show spectra of ions that rise monotonically toward low energies with no peaking and no suppression of low-energy ions. Wave amplification by streaming protons and the pitch-angle dependence of the resonance condition are essential factors in our understanding of the limiting behavior.},
doi = {10.1088/0004-637X/723/2/1286},
url = {https://www.osti.gov/biblio/21471270},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 723,
place = {United States},
year = {Wed Nov 10 00:00:00 EST 2010},
month = {Wed Nov 10 00:00:00 EST 2010}
}