284 research outputs found
The determination of shock ramp width using the noncoplanar magnetic field component
We determine a simple expression for the ramp width of a collisionless fast
shock, based upon the relationship between the noncoplanar and main magnetic
field components. By comparing this predicted width with that measured during
an observation of a shock, the shock velocity can be determined from a single
spacecraft. For a range of low-Mach, low-beta bow shock observations made by
the ISEE-1 and -2 spacecraft, ramp widths determined from two-spacecraft
comparison and from this noncoplanar component relationship agree within 30%.
When two-spacecraft measurements are not available or are inefficient, this
technique provides a reasonable estimation of scale size for low-Mach shocks.Comment: 6 pages, LaTeX (aguplus + agutex);
packages:amsmath,times,graphicx,float, psfrag,verbatim; 3 postscript figures
called by the file; submitted to Geophys. Res. Let
Coherent Emission from Magnetars
It is proposed that magnetospheric currents above the surfaces of magnetars
radiate coherent emission in analogy to pulsars. Scaling the magnetospheric
parameters suggests that the coherent emission from magnetars would emerge in
the infra-red or optical
Pick-up ion dynamics at the structured quasi-perpendicular shock
We study the pickup ion dynamics and mechanism of multiple reflection and
acceleration at the structured quasi-perpendicular supercritical shock. The
motion of the pickup ions in the shock is studied analytically and numerically
using the test particle analysis in the model shock front. The analysis shows
that slow pickup ions may be accelerated at the shock ramp to high energies.
The maximum ion energy is determined by the fine structure of the
electro-magnetic field at the shock ramp and decreases when the angle between
magnetic field and shock normal decreases. Evolution of pickup ion distribution
across the nearly-perpendicular shock and pickup ion spectrum is also studied
by direct numerical analysis.Comment: LaTeX (elsart.cls), packages: times,amsmath,amssymb; 15 pages + 13
figures (GIF). To appear in Planetary and Space Science
On convergence of the ChPT HFF expansion for one loop contribution to meson production in NN collisions
We consider the application of heavy fermion formalism based chiral
perturbation theory to meson production in nucleon-nucleon collisions. It is
shown that for one loop contributions the heavy fermion formalism expansion
corrections for the nucleon propagator produce infinite series of correction
terms which are of the same momentum power order. This destroys the one-to-one
correspondence between the perturbative and small momentum expansion and thus
negates the application of any finite order heavy fermion formalism chiral
perturbation theory to the reactions.Comment: 13 pages, 3figure
- …