Astronomy and Astrophysics – Astrophysics
Scientific paper
Aug 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003a%26a...406..735v&link_type=abstract
Astronomy and Astrophysics, v.406, p.735-740 (2003)
Astronomy and Astrophysics
Astrophysics
16
Instabilities, Sun: Particle Emission, Turbulence
Scientific paper
A simple analytical theory of Alfvén waves amplified by streaming solar energetic particles (SEPs) is studied. It is pointed out that a finite time-integrated net flux of energetic protons has to pass each point in space before we can expect Alfvén waves to be significantly modified by the streaming instability. The time-integrated net proton flux needed for the time-integrated wave growth rate (or wave growth, for short) to exceed unity is evaluated. Assuming that protons stream much faster than the waves, we evaluate the wave growth as a function of position and wavenumber for a specified proton injection energy spectrum, dN/dE. The wave growth is found to be proportional to vp dN/dE, where v and p are the particle speed and momentum, and to the local Alfvén speed VA. Thus, maximum wave growth is achieved at the location of maximum VA (at a few solar radii), and the minimum value of dN/dE required for the wave growth to exceed unity there is a few times 1032/vp protons per unit solid angle (in coordinate space) at the solar surface. If dN/dE is below this value, test-particle theory is a valid description of particle transport and acceleration. The value is not exceeded (above 1 MeV energies) in small gradual SEP events having peak 1-MeV proton intensities below ~ 10 protons (cm2 sr s MeV)-1 at 1 AU. The spatial and momentum dependence of the wave growth can also be used to estimate the maximum emission strength of a moving proton source in the interplanetary medium. For a strong source moving through the solar wind at constant super-Alfvénic speed, the number of escaping particles per unit time and flux-tube cross section is approximately constant in time, predicting a plateau-type time-intensity profile observed ahead of the source. The model reproduces observations of streaming-limited intensities at energies around 10 MeV and explains the double peaked injection profiles observed in large SEP events.
No associations
LandOfFree
On the generation of Alfvén waves by solar energetic particles does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with On the generation of Alfvén waves by solar energetic particles, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and On the generation of Alfvén waves by solar energetic particles will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1662727