2,103 research outputs found
Alterações de componentes do balanço de carbono e nutrientes em função da substituição do sistema de produção agrícola de corte e queima pelo corte e trituração/manejo de capoeira.
Production Systems for Sustainable Intensification: Integrating Productivity with Ecosystem Services
Radiative accretion shocks along nonuniform stellar magnetic fields in classical T Tauri stars
(abridged) AIMS. We investigate the dynamics and stability of post-shock
plasma streaming along nonuniform stellar magnetic fields at the impact region
of accretion columns. We study how the magnetic field configuration and
strength determine the structure, geometry, and location of the shock-heated
plasma. METHODS. We model the impact of an accretion stream onto the
chromosphere of a CTTS by 2D axisymmetric magnetohydrodynamic simulations. Our
model takes into account the gravity, the radiative cooling, and the
magnetic-field-oriented thermal conduction. RESULTS. The structure, stability,
and location of the shocked plasma strongly depend on the configuration and
strength of the magnetic field. For weak magnetic fields, a large component of
B may develop perpendicular to the stream at the base of the accretion column,
limiting the sinking of the shocked plasma into the chromosphere. An envelope
of dense and cold chromospheric material may also develop around the shocked
column. For strong magnetic fields, the field configuration determines the
position of the shock and its stand-off height. If the field is strongly
tapered close to the chromosphere, an oblique shock may form well above the
stellar surface. In general, a nonuniform magnetic field makes the distribution
of emission measure vs. temperature of the shocked plasma lower than in the
case of uniform magnetic field. CONCLUSIONS. The initial strength and
configuration of the magnetic field in the impact region of the stream are
expected to influence the chromospheric absorption and, therefore, the
observability of the shock-heated plasma in the X-ray band. The field strength
and configuration influence also the energy balance of the shocked plasma, its
emission measure at T > 1 MK being lower than expected for a uniform field. The
above effects contribute in underestimating the mass accretion rates derived in
the X-ray band.Comment: 11 pages, 11 Figures; accepted for publication on A&A. Version with
full resolution images can be found at
http://www.astropa.unipa.it/~orlando/PREPRINTS/sorlando_accretion_shocks.pd
Alterações nas emissões de gases traço em função da substituição do sistema de produção agrícola de corte/queima pelo de corte/trituração/manejo de capoeira.
Diversidade das unidades e dos produtores de derivados do leite em Nossa Senhora da Glória, semi-árido sergipano.
Diversidade das unidades e dos produtores de derivados do leite em Nossa Senhora da Glória, semi-árido sergipano.
bitstream/CPATC/19774/1/f_12_2007.pd
Disseminação e controle da resinose em troncos de cajueiro decepados para substituição de copa.
Ocorrencia e disseminacao da resinose em troncos de cajueiro e a acao protetora de dois fungicidas na reducao do processo de disseminacao.bitstream/CNPAT-2010/11953/1/Ct-017.pd
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