Issue |
A&A
Volume 381, Number 2, JanuaryII 2002
|
|
---|---|---|
Page(s) | 539 - 559 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:20011447 | |
Published online | 15 January 2002 |
β–radioactive cosmic rays in a diffusion model: Test for a local bubble?
1
Laboratoire de Physique Théorique , 74941 Annecy–le–Vieux, France
2
Université de Savoie, 73011 Chambéry, France
Corresponding author: R. Taillet, taillet@lapp.in2p3.fr
Received:
7
August
2001
Accepted:
12
September
2001
In a previous analysis, Maurin et al. (2001) have constrained
several parameters of the cosmic ray diffusive
propagation (the diffusion
coefficient normalization K0 and its spectral index δ, the
halo
half-thickness L, the Alfvén velocity Va,
and the galactic wind Vc)
using stable nuclei.
In a second paper (Donato et al. 2002),
these parameters were
shown to reproduce the observed antiproton spectrum with no further
adjustment.
In the present paper, we extend the analysis to the β-radioactive
nuclei 10Be, 26Al and 36Cl.
These species will be shown to be particularly sensitive to the
properties of the local interstellar medium (lism).
As studies of the lism suggest that we live in an underdense
bubble
of extent 50–200 pc,
this local feature must be taken into account.
We present a modified version of our diffusion model which
describes the underdensity as a hole in the galactic disc;
we believe some of the formulæ presented here are new.
It is found that the presence of the bubble leads to a decrease in
the radioactive fluxes which can be approximated by a simple factor
where
is the
typical distance travelled by a radioactive nucleus before it decays.
We find that each of the radioactive nuclei independently points
towards a bubble of radius
100 pc.
If these nuclei are considered simultaneously, only models with a bubble
radius
60–100 pc are marginally consistent with
data. In particular, the standard case
pc is
disfavored.
Our main concern is about the consistency
of the currently available data, especially 26Al/27Al.
Key words: ISM: bubbles / galaxy: Solar neighbourhood
© ESO, 2002
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