plasma-chemistry-2017-keynote

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Page 13
Journal of Biotechnology and Phytochemistry
Volume 1, Issue 2
Notes:
Plasma Chemistry 2017
November 13-14, 2017 Paris, France
5th International Conference on
PLASMA CHEMISTRY AND
PLASMA PROCESSING
Véronique Bommier, J Biot Phyt 2017
The anisotropic Debye Shielding as visible in
sunspot photosphere
Recent measurements, that now allow 3D mapping
of the solar magnetic field vector, as well as past
astrophysics literature, coincide about the surprising
feature that thevertical gradient of themagnetic field |dBz/
dz|, which is found about 3 G/km, is not compensated
for by the horizontal gradient |dBx/dx + dBy/dy|, which
is found about 0.3 G/km only, in sunspot photosphere.
The departure from zero of their combination to form
divB is much larger than the estimated measurement
uncertainties. A test of the observational result will be
presented. I assign this feature to a plasma effect, the
Debye shielding, but anisotropic as in plasma located at
the surface of a star. The horizontal Froude number is
found to be on the order of a few 1e-
2. The solar photosphere plasma is however dominated
by neutral hydrogen atoms, whose density is on the
order of 1e16 atoms per cubic centimetre, whereas
the electron density is about 1e12 electrons per cubic
centimetre only. Thus the magnetization remains small.
I will present how the Debye shielding when anisotropic
is able to explain how the gravity, which makes the
velocities anisotropic by strong stratification, thus makes
the shielding anisotropic, which results in an apparent
magnetic flux non-conservation for the magnetic field
created by the moving charges. Interesting experimental
results in an also anisotropic plasma, also displaying
measured non-zero divB, are available in the literature
(Gekelman et al., 2012, ApJ, 753, 131 and Gekelman et
al., 2016, Phys. Scr. 91, 054002).
Biography
Véronique Bommier, born in 1954, is "ancienne eleve" of the "Ecole Normale
Superieure de Jeunes Filles". She was formed about quantum mechanics by Pr
Cohen-Tannoudji at the "Ecole Normale Superieure". After her thesis about the
magnetic field measurement by interpretation of the hanle effect observed in the He
I D3 line of solar prominences, she participated to the preparation and development
of the observations with the French-Italian THEMIS telescope. She was formed
in radiactive transfer by Pr Egidio Landi Degl'Innocenti (Florence University),
who developed also a Zeeman effect inversion code UNNOFIT, that V. Bommier
generalized to the scan of active and quiet regions and unresolved magnetic
structures. Thus, she is now an expert on all magnetic field measurements in all the
various solar regions. She then applied to space data from the HINODE/SOT/SP
and recently SDO/HMI satellites, the methods developed on THEMIS about active
and quiet region magnetic field mapping.
Véronique Bommier
LESIA, Paris Observatory, France