Bibcode
Martínez-Pillet, V.; Riethmüller, T. L.; Danilovic, S.; Pietarila, A.; Lagg, A.; Feller, A.; Solanki, S. K.; Jafarzadeh, S.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 549, id.A116, 19 pp.
Fecha de publicación:
1
2013
Revista
Número de citas
54
Número de citas referidas
46
Descripción
Aims: We aim to improve our picture of the low chromosphere in
the quiet-Sun internetwork by investigating the intensity, horizontal
velocity, size and lifetime variations of small bright points (BPs;
diameter smaller than 0.3 arcsec) observed in the Ca ii H 3968 Å
passband along with their magnetic field parameters, derived from
photospheric magnetograms. Methods: Several high-quality time
series of disc-centre, quiet-Sun observations from the Sunrise
balloon-borne solar telescope, with spatial resolution of around 100 km
on the solar surface, have been analysed to study the dynamics of BPs
observed in the Ca ii H passband and their dependence on the
photospheric vector magnetogram signal. Results: Parameters such
as horizontal velocity, diameter, intensity and lifetime histograms of
the isolated internetwork and magnetic Ca ii H BPs were determined. Mean
values were found to be 2.2 km s-1, 0.2 arcsec (≈150 km),
1.48 ⟨ ICa ⟩ and 673 s, respectively.
Interestingly, the brightness and the horizontal velocity of BPs are
anti-correlated. Large excursions (pulses) in horizontal velocity, up to
15 km s-1, are present in the trajectories of most BPs. These
could excite kink waves travelling into the chromosphere and possibly
the corona, which we estimate to carry an energy flux of 310 W
m-2, sufficient to heat the upper layers, although only
marginally. Conclusions: The stable observing conditions of
Sunrise and our technique for identifying and tracking BPs have allowed
us to determine reliable parameters of these features in the
internetwork. Thus we find, e.g., that they are considerably longer
lived than previously thought. The large velocities are also reliable,
and may excite kink waves. Although these wave are (marginally)
energetic enough to heat the quiet corona, we expect a large additional
contribution from larger magnetic elements populating the network and
partly also the internetwork.
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