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Author name code: henoux
ADS astronomy entries on 2022-09-14
author:"Henoux, Jean-Claude" 

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Title: Flare line impact polarization. Na D2 589 nm line polarization
    in the 2001 June 15 flare
Authors: Hénoux, J. C.; Karlický, M.
2013A&A...556A..95H    Altcode:
  Context. The impact polarization of optical chromospheric lines
  in solar flares is still being debated. For this reason, additional
  observations and improved flare atmosphere models are needed still. <BR
  /> Aims: The polarization-free telescope THEMIS used in multiline 2
  MulTiRaies (MTR) mode allows accurate simultaneous linear polarization
  measurements in various spectral lines. <BR /> Methods: In the 2001
  June 15 flare, Hα, Hβ, and Mg D2 lines linear impact polarization
  was reported as present in THEMIS 2 MTR observations. In this paper,
  THEMIS data analysis was extended to the Na D2 line. Sets of I ± U
  and I ± Q flare Stokes S 2D-spectra were corrected from dark-current,
  spectral-line curvature and from transmission differences. Then, we
  derived the linear polarization degree P and polarization orientation
  angle α 2D-spectra. No change in relative positioning could be found
  that would reduce the Stokes parameters U and Q values. No V and I
  crosstalks could explain our results either. <BR /> Results: The Na
  D2 line is linearly polarized with a polarization degree exceeding 5%
  at some locations. The polarization was found to be radial at outer
  ribbons edges, and tangential at their inner edges. This orientation
  change may be due to differences in electron distribution functions
  on the opposite borders of flare chromospheric ribbons. Electron beams
  propagating along magnetic field lines, together with return currents,
  could explain both radial and tangential polarization. At the inner
  ribbon edges, intensity profile-width enlargements and blueshifts
  in polarization profiles are observed. This suggests chromospheric
  evaporation. <P />Appendix A is available in electronic form at <A
  href="http://www.aanda.org">http://www.aanda.org</A>

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Title: Multi-wavelength analysis of the impact polarization of 2001
    June 15th solar flare .
Authors: Xu, Z.; Hénoux, J. C.
2007MmSAI..78...77X    Altcode:
  We report here the impact polarization of the Halpha , Hbeta and MgI
  (552.8 nm) lines during an M6.3 solar flare observed on 2001 June 15th
  with the THEMIS telescope in the multi-wavelength spectropolarimetric
  mode. Typical spectral intensity and polarization profiles are
  presented. All of these lines are linearly polarized and polarization
  degree vary 3% - 6% at line center. The directions of polarization
  are either parallel or perpendicular to the local transverse magnetic
  field, which are investigated by simultaneous observation of FeI
  (630.2 nm). The polarization islands are located at the edges of flare
  kernels. After eliminating scattering, Zeeman effect and intensity
  gradient, as possible origin of the observed polarization, this
  polarization is interpreted as due either to low energy proton beam
  or to the return current associated with electron beams.

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Title: First Results of Mg I (3p <SUP>1</SUP>P<SUB>1</SUB>-4d
    <SUP>1</SUP>D<SUB>2</SUB>) Line Linear Impact Polarization during
    the Solar Flare on 2001 June 15
Authors: Xu, Z.; Henoux, J. C.; Chambe, G.; Petrashen, A. G.; Fang, C.
2006ApJ...650.1193X    Altcode:
  The results of the analysis of the first spectropolarimetric
  observations of the 3p <SUP>1</SUP>P<SUB>1</SUB>-4d
  <SUP>1</SUP>D<SUB>2</SUB> Mg I line at 5528.4 Å made during a solar
  flare are presented in this paper. The line is found to be polarized
  with a polarization degree at the line center that reaches up to 3%
  and a direction of polarization nearly parallel to the local transverse
  magnetic field. After eliminating scattering, the Zeeman effect, and the
  intensity gradient as possible origins of the observed polarization,
  this polarization is interpreted as due either to a low-energy proton
  beam or to the return current associated with electron beams.

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Title: Multiwavelength analysis of the impact polarization of 2001
    June 15 solar flare
Authors: Xu, Z.; Henoux, J. C.; Chambe, G.; Fang, C.
2006cosp...36...49X    Altcode: 2006cosp.meet...49X
  The linear polarization of H alpha H beta and MgI lines have been
  found during the rise phase of soft X-ray emission of an M6 3 flare on
  June 15th 2001 observed by THEMIS telescopes in the multi-wavelength
  spectropolarimetric mode Here the linear polarization signals of MgI
  line 5528 A are reported for the first time The polarization of these
  three lines has a good spatial correspondence and is located at the
  edges of flare kernels The maximum polarization degree of H alpha and
  H beta lines can reach 4 - 6 at the line center and near line wings
  For MgI line the polarization degree can exceed 3 5 concentrating
  in the line center Polarization directions are not random but either
  parallel or perpendicular to the local transverse magnetic field in
  a large degree The origin of the observed short-time polarization is
  discussed here with respect to the bombardment on the solar atmosphere
  by low-energy protons or high-energy electrons associated with return
  current

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Title: Multiwavelength Analysis of the Impact Polarization of 2001
    June 15 Solar Flare
Authors: Xu, Z.; Hénoux, J. -C.; Chambe, G.; Karlický, M.; Fang, C.
2005ApJ...631..618X    Altcode:
  We report here on the temporal and spatial evolution of the
  impact polarization of the Hα and Hβ lines during an M6.3 solar
  flare observed on 2001 June 15 with the THEMIS telescope in the
  multiwavelength spectropolarimetric mode. Typical spectral intensity
  and polarization profiles are presented. Both lines are linearly
  polarized. The Hαline degree of polarization exceeds 4% at line
  center and in the near line wings. The Hβ line is also linearly
  polarized, with a degree of polarization reaching 6%. The directions
  of polarization are either parallel or perpendicular to the local
  transverse magnetic field (i.e., either radial or tangential because the
  transverse magnetic field is directed almost in the flare-to-disk center
  direction). However, contrary to Hα, the Hβ polarization direction
  is radial only. The Hα and Hβ polarization islands are located at the
  edges of flare kernels. Only for radial polarization are these islands
  cospatial. No Hβ polarization is found at the places where tangential
  Hα polarization is present. The origin of the observed polarization is
  discussed. Bombardment by low-energy protons or high-energy electrons
  associated with return currents can explain the radial polarization
  observed in the lowest flare kernel. The tangential Hα polarization
  observed in the surge near the upper flare location is interpreted
  as due to the electric current at the origin of the electromagnetic
  force that lifts the surge.

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Title: Information on particle acceleration and transport derived
    from solar flare spectropolarimetry
Authors: Xu, Z.; Hénoux, J. -C.; Chambe, G.; Karlický, M.; Fang, C.
2005AdSpR..35.1841X    Altcode:
  The hydrogen H α line has been found to be linearly polarized at
  some locations and times during a June 15th 2001 flare observed with
  THEMIS. This flare was accompanied by radio pulses and hard X-ray
  emission. Linear polarization is below the noise level in the flare
  kernels. However, it is present at the edges of these kernels, in
  the line center and near wings where the polarization degree exceeds
  4%. The directions of polarization are not random but close within
  ±15° to the tangential and radial directions. This polarization can
  be due either to electron beams and their associated return currents
  or to electron and proton beams.

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Title: Spectropolarimetric diagnostics of non-thermal particles in
    the solar chromosphere
Authors: Xu, Z.; Fang, C.; Henoux, J. -C.
2004cosp...35..278X    Altcode: 2004cosp.meet..278X
  Linear impact polarization of chromospheric lines has already
  been observed in the impulsive phase of solar flares, which
  can be interpreted as the results of the bombardment of an
  anisotropic non-thermal particle beam in the atmosphere. Using the
  spectropolarimetric observations of THEMIS, we have measured the
  degrees and the directions of the polarization from Hα and CaII
  8542 Stokes line profiles of Ellerman Bombs, bright points and faint
  flares, which occur mainly in the solar lower atmosphere. We attempt
  to explore the main characters of the non-thermal energetic particles
  from its effect on the impact linear polarization of the chromospheric
  lines. The existence of this polarization due to non-thermal particles
  can provide the evidence of reconnection in the solar lower atmosphere.

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Title: What have we learned on non-thermal particle acceleration
    and transport by optical spectropolarimetry
Authors: Hénoux, J. -C.; Karlicky, M.; Xu, Z.; Fang, C.
2004cosp...35..647H    Altcode: 2004cosp.meet..647H
  Most of the information on non-thermal particles is derived from
  hard X-ray, gamma-ray or radio observations. Optical spectroscopic
  polarimetry provides complementary information on the particle nature
  and velocity distributions. Information is also provided on their
  propagation conditions at chromospheric level. We will report here
  on the information derived from measurements of the impact linear
  polarization made in the Halpha and Hbeta lines with the French-Italian
  solar telescope THEMIS.

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Title: First detection of return currents in solar flares by
    spectropolarimetry with THEMIS
Authors: Hénoux, J. -C.; Karlický, M.
2003A&A...407.1103H    Altcode:
  Using THEMIS French-Italien telescope with the MTR mode, the Hydrogen
  Hα and Hβ lines have been observed to be linearly polarized up to a
  few percent by impact during the impulsive phase of two solar flares
  associated with high-frequency radio pulses. Two privileged directions
  of linear polarization are present, respectively radial (in the disk
  center to flare direction) and tangential (perpendicular to the radial
  direction). This 90 degree change in the linear polarization direction
  is interpreted as due to the chromospheric return current generated
  by the penetration of a non-thermal electron beam into the chromosphere.

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Title: Impact Polarization: A Diagnostic Test for Non-thermal
    Particles at Chromospheric Level During Solar Flares
Authors: Hénoux, J. C.; Vogt, E.; Sahal-Bréchot, S.; Karlichký,
   M.; Feautrier, N.; Fárník, F.; Chambe, G.; Balanca, C.
2003ASPC..307..480H    Altcode:
  No abstract at ADS

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Title: Is it possible to accelerate ions in collapsing magnetic traps?
Authors: Somov, B. V.; Hénoux, J. -C.; Bogachev, S. A.
2002AdSpR..30...55S    Altcode:
  A coronal hard X-ray source observed by Yohkoh during solar flares
  can be interpreted under assumption that a fast plasma outflow from a
  reconnecting current sheet creates a shock wave above loops of strong
  magnetic field. Since the HXR source is located in the upstream side,
  rather than in the downstream side of the shock, this provides a new
  opportunity of particle acceleration — the two-step acceleration
  of electrons and ions. The first step is acceleration by the strong
  electric field present inside the current sheet. The second step is fast
  'adiabatic heating' inside the collapsing magnetic trap. We demonstrate
  some possibilities of ion acceleration in collapsing traps.

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Title: Impact polarization as a diagnostic for non-thermal particles
    in solar flares
Authors: Vogt, E.; Sahal-Bréchot, S.; Hénoux, J. -C.
2002ESASP.477..191V    Altcode: 2002scsw.conf..191V
  Observations of linear polarization of lines (mainly Hα) during solar
  flares have been reported. The orientation (predominantly radial) and
  magnitude of the Hα polarization (about 5%) suggest an interpretation
  as impact polarization by low energy (&lt;200 keV) non-thermal protons,
  which are not accessible by more direct diagnostic observations,
  such as hard X-rays (for non-thermal electrons) or gamma-ray lines
  (for high energy protons, above a few MeV) which will be observed by
  the HESSI spacecraft, soon to be launched by NASA. Impact polarization
  observations could thus provide useful complementary data for the study
  of accelerated particles in flares. However, observations in a single
  line such as Hα can give at best an order of magnitude estimate
  of the accelerated protons number flux, so multiline polarimetric
  observations, as can be done by the franco-italian THEMIS telescope,
  are highly desirable.

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Title: Impact Hα line polarization and return current
Authors: Karlický, M.; Hénoux, J. C.
2002A&A...383..713K    Altcode:
  Electron beams, bombarding the dense chromospheric layers during
  solar flares, carry electric currents which need to be neutralized by
  so-called return currents. Return currents are formed by background
  plasma electrons having an anisotropic velocity distribution. Thus
  they can generate impact Hα line polarization. First, a numerical
  method of computation of the impact Hα line polarization for an
  arbitrary electron distribution function is presented. Then the
  polarization due to return current electrons associated with beam
  electrons is computed. For low electron beam fluxes, the return
  current is low and the polarization is only due to the electron beam,
  i.e. it is perpendicular to the electron beam direction and it reaches
  -8.0%. Increasing the return current and the beam flux leads to a
  change of orientation of the polarization by 90<SUP>deg</SUP> and
  the polarization degree can even reach a maximum of +22.4%. But this
  change and the maximum of the polarization require very high electron
  beam fluxes of 1.79 x 10<SUP>12</SUP> and 4.8 x 10<SUP>12</SUP>
  ergs cm<SUP>-2</SUP> s<SUP>-1</SUP>, respectively. Therefore plasma
  processes, which can reduce the high-energy flux requirement for the
  polarization change observations, are briefly discussed.

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Title: Solar Flares: White Light
Authors: Hénoux, J.
2000eaa..bookE2296H    Altcode:
  Characteristics of white light solar flares...

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Title: Hα Polarization during a Well-observed Solar Flare: Proton
    Energetics and Implications for Particle Acceleration Processes
Authors: Emslie, A. Gordon; Miller, James A.; Vogt, Etienne; Hénoux,
   Jean-Claude; Sahal-Bréchot, Sylvie
2000ApJ...542..513E    Altcode:
  Observations of polarization of chromospheric lines in solar flares
  can constrain the energy flux in accelerated protons. In this paper
  we analyze recently reported observations of Hα linear polarization
  obtained during a rather well observed flare on 1989 June 20. Modeling
  of the magnitude and orientation of the Hα polarization provides
  a constraint on the flux of low energy (&gt;~200 keV) protons,
  while simultaneous gamma-ray and hard X-ray observations provide
  constraints on the fluxes of &gt;~10 MeV protons and &gt;~50 keV
  electrons, respectively. These, plus information on the energetics of
  the low-temperature and high-temperature thermal emissions, permit
  evaluation of both the absolute and relative roles of electrons
  and protons in the flare energy budget. We find that accelerated
  protons with energies &gt;~200 keV can contain a significant portion
  of the total energy released during the flare, consistent with a steep
  extrapolation of the proton spectrum to such relatively low energies. We
  discuss these results in light of a unified electron/proton stochastic
  particle acceleration model and show that the energetics are indeed
  consistent with this large proton energy content.

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Title: Diagnostics of non-thermal processes in chromospheric
    flares --- IV. Limb flare spectra for an atmosphere bombarded by an
    electron beam
Authors: Fang, C.; Hénoux, J. -C.; Ding, M. D.
2000A&A...360..702F    Altcode:
  Hα, Lyα, Lyβ, CaII K and λ8542 Å line profiles have been computed
  for limb flares with height distributions of temperatures as given by
  the semi- empirical models F<SUB>1</SUB> and F<SUB>2</SUB>, by including
  the non-thermal collisional excitation and ionization of hydrogen and
  of ionized calcium that results from electron bombardment. In agreement
  with observations, the computed profiles of the hydrogen lines are very
  broad, especially at the height where the source function reaches its
  maximum. Non-thermal effects are less pronounced for CaII lines.

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Title: Hα Polarization Observations and Flare Energetics
Authors: Emslie, A. G.; Miller, J. A.; Vogt, E.; Hénoux, J. -C.;
   Sahal-Bréchot, S.
2000SPD....31.0253E    Altcode: 2000BAAS...32..820E
  Observations of polarization of chromospheric lines in solar flares
  can constrain the proton energy flux during the flare. In this paper,
  we analyze recently-reported observations of Hα linear polarization
  obtained during a rather well-observed flare on 1989 June 20. Modeling
  of the magnitude and orientation of the Hα polarization provides
  a constraint on the flux of low energy ( ~ 0.2 MeV) protons, while
  simultaneous gamma-ray and hard X-ray observations provide the fluxes
  of ~ 10 MeV protons, and ~ 50 keV electrons, respectively. These,
  plus information on the energetics of the low-temperature and
  high-temperature thermal emissions, permit evaluation of the relative
  role of electrons and protons in exciting the flare plasma. We find
  that above about 200 keV, accelerated protons significantly dominate
  the flare energy budget, overwhelming electrons by at least two
  orders of magnitude. We discuss these results in light of a unified
  electron/proton stochastic particle acceleration model, and show
  that the energetics are indeed consistent with the broad range of
  observational data. This work was supported by NASA's Office of Space
  Science and by an NSF/CNRS International Collaboration Award.

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Title: On the origin of solar white-light flares
Authors: Gan, W. Q.; Hénoux, J. C.; Fang, C.
2000A&A...354..691G    Altcode:
  Using the Hα line intensity as a constraint, we study the role of
  a chromospheric condensation and the role of non-thermal effects in
  producing the continuum enhancement of white-light flares. Within
  an acceptable range of Hα line intensities and electron energy
  flux, it is shown that neither a chromospheric condensation nor
  non-thermal effects alone can directly explain the observed continuum
  enhancement. The hybrid role of both chromospheric condensation and
  non-thermal effects can only lead to a Balmer jump, but still not to a
  significant continuum intensity increase between 4000 and 7000 Ä. A
  possible picture is discussed, that is, the Balmer jump is directly
  produced by the association of a chromospheric condensation and of
  non-thermal effects, while the continuum enhancement between 4000 and
  7000 Ä, is indirectly produced by the condensation and the non-thermal
  effects via radiative heating to the deeper photospheric layers.

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Title: Optical View of Particle Acceleration and Complementarity
    with HESSI
Authors: Hénoux, J. -C.
2000ASPC..206...27H    Altcode: 2000hesp.conf...27H
  No abstract at ADS

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Title: Generation and Interaction of Electric Currents in the Quiet
    Photospheric Network
Authors: Somov, B. V.; Hénoux, J. C.
1999ESASP.448..659S    Altcode: 1999ESPM....9..659S; 1999mfsp.conf..659S
  No abstract at ADS

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Title: Acceleration Of Photoelectrons In A Return-Current Electric
    Field And Ha Polarization
Authors: Karlický, Marian; Hénoux, Jean-Claude
1999ESASP.446..369K    Altcode: 1999soho....8..369K
  Chromospheric hydrogen Balmer Ha and Hb lines have been found to be
  linearly polarized in the gradual phase of some solar flares. This
  impact polarization is believed to be caused by low energy protons
  (E&lt; 200 keV). However, we still must examine if low energy electrons
  (E&lt; 200 eV) with an anisotropic velocity distribution function, if
  presents, could also generate impact polarisation . In a recent paper
  by H noux and Karlicky (1999), the evolution, in chromospheric layers,
  of the ve-locity distribution function of high energy photoelectrons
  produced by flare X-ray irradiation, was studied. A significant
  anisotropy was found. However, due to the dominance of local electrons
  in the line formation process, the resulting impact polarization
  was one order of magnitude lower than ob-served. In this paper,
  we look for the change of the photoelectrons anisotropy that could
  result from the pre-sence of a return-current electric field. A 1-D
  test particle code is used for computating both the re-turn-current
  electric field generated by monoenergetic electron beams in flaring
  chromospheric layers and the evolution of the photoelectron distribution
  function. Using a 100 keV electron beam with a density of 2 and the MAVH
  flare atmosphere, it is found that, at chromospheric level, low-energy
  photoelectrons (E at 150 eV), produced by flare X-ray irradiation, can
  be accelerated by the return-current electric field. This acceleration
  is very sensi-tive to the exact density and temperature profile of the
  solar atmosphere and the resulting effect as generation of impact Ha
  polarization is discussed.

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Title: Physics of Thin Flux Tubes in a Partially Ionized Atmosphere
Authors: Hénoux, J. -C.; Somov, B. V.
1999ASPC..184...55H    Altcode:
  We discuss basic features of the thin magnetic flux-tube generation by
  vortex-type motions of the weakly ionized plasma near the temperature
  minimum in the solar atmosphere.

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Title: Observations of linear polarization in the H_alpha line during
    two solar flares
Authors: Vogt, Etienne; Hénoux, Jean-Claude
1999A&A...349..283V    Altcode:
  Two chromospheric flares were observed in Meudon using an H_alpha
  flare polarimeter on 17() th July 1982 and 20() th June 1989. A
  careful reduction of the data sets has been done in order to remove
  the false polarization signals induced by atmospheric turbulence. In
  each event, linear polarization directed towards the disk center with a
  polarization degree of the order of 5% is detected. This polarization is
  correlated in time with the maximum of soft X-ray emission. One event
  also shows polarization parallel to the solar limb at the moment of
  maximum hard X-ray emission but with a poor signal to noise ratio. We
  interpret this polarization as impact polarization, resulting from the
  excitation of hydrogen atoms by anisotropic particles. The tangential
  polarization could be due to a beam of energetic electrons moving
  vertically. However, the best candidates to explain both tangential
  and radial polarization are beams of energetic protons with an energy
  below 100 keV entering into the chromosphere. The variation of the
  polarization direction could result from a modification of the magnetic
  topology during the flare.

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Title: A spectropolarimetric estimate of energy deposition into the
    chromosphere during solar flares
Authors: Kazantsev, S. A.; Karlicky, M.; Petrashen', A. G.; Hénoux,
   J. -C.
1999ARep...43..340K    Altcode:
  The dependence of the degree of polarization of Hα and Hβ emission in
  the solar chromosphere during solar flares on the energy of an incident
  proton beam is calculated assuming that the origin of the observed
  linear polarization is collisional. Estimates of the lower boundary
  for the energy of the proton beam are obtained using a model for the
  kinetics of the propagation of fast protons inside solar-flare magnetic
  loops together with spectropolarimetric Hα and Hβ observations.

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Title: Velocity distribution function anisotropy of soft X-ray
    generated photoelectrons and resulting Hα polarization in solar
    flares
Authors: Hénoux, J. -C.; Karlický, M.
1999A&A...341..896H    Altcode:
  Soft X-rays irradiation of the solar atmosphere during solar
  flares generates photoelectrons which have an anisotropic velocity
  distribution. Using a 1-D test particle code, the anisotropy of the
  photoelectrons velocity distribution is derived, and the maximum
  degree of linear polarization in the hydrogen Hα and Hβ lines that
  photoelectrons could generate by impact is estimated. Over a band
  pass of 0.75 and 0.5 Angstroms, the net polarization degree expected
  in both lines is predicted not to exceed 0.2%. Therefore, soft X-ray
  irradiation cannot explain the one order of magnitude higher degree
  of linear polarization observed in solar flares.

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Title: Impact polarization of the Hα line during solar flares
Authors: Vogt, E.; Hénoux, J. -C.; Sahal-Bréchot, S.
1999ASSL..243..431V    Altcode: 1999sopo.conf..431V
  No abstract at ADS

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Title: The NOAA AR 6718 magnetic field extrapolation with localized
    current filaments.
Authors: Karlický, M.; Démoulin, P.; Aulanier, G.; van
   Driel-Gesztelyi, L.; Hénoux, J. C.; Jirička, K.
1999joso.proc...97K    Altcode:
  The 3-D extrapolation of magnetic field lines of the July 11, 1991
  Kitt Peak magnetogram shows a differential magnetic field shear in
  the NOAA 6718 active region. A new combined extrapolation technique,
  which includes localized current filaments is suggested and applied in
  modelling of this shear. First, the potential field extrapolation is
  made and then force-free current paths for several current filaments
  in specific positions are computed. It is shown that with the electric
  current increase the localized magnetic field shear is increasing. The
  total electric current in 16 current filaments is considered up to
  1.2×10<SUP>12</SUP>A.

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Title: Coronal Abundances
Authors: Fludra, A.; Saba, J. L. R.; Henoux, J. -C.; Murphy, R. J.;
   Reames, D. V.; Lemen, J. R.; Strong, K. T.; Sylwester, J.; Widing,
   K. G.
1999mfs..conf...89F    Altcode:
  Flare X-Ray Measurements from BCS Calcium Abundance Fe/H and Fe/Ca
  Abundance Relative Abundances of Ar. Ca. and Fe in Flares Factors
  Affecting Abundance Determinations from X-Ray Spectra FCS Abundances
  FCS Active-Region Abundances Abundance Variability in Active Regions
  Impact of Resonance Scattering Assessment of FCS Active-Region Abundance
  Results FCS Flare Abundance Studies Coronal CI/S and Ar/S Measurements
  Dem Studies of Flare Abuncances Determination of Solar Abundances
  by Solar Flare γ-Ray Spectrometry γ-Ray Spectral Analysis γ-Ray
  Results Solar Energetic Particles Major Proton Events CIR Events from
  Coronal Holes Impulsive Flare Events Theory of Abundance Fractionation
  Gravitational Settling Pressure Gradient and Stationary Diffusion
  Ion-Neutral Separation Due to Currents Ion-Neutral Separation Due to
  Electromagnetic Forces Discussion Summary

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Title: Multi-Wavelength Analysis of the Flare on 2 October 1993
Authors: Fang, C.; Tang, Y. H.; Hénoux, J. -C.; Huang, Y. R.; Ding,
   M. D.; Sakurai, T.
1998SoPh..182..163F    Altcode:
  By use of Yohkoh hard X-ray flux and soft X-ray images, and of vector
  magnetograms and 2D spectral observations, a 1N/C6.5 flare observed on
  2 October 1993 is analysed in detail. Evidence is provided not only
  morphologically but also quantitatively that the dynamics at kernels
  A and C of the flare in the impulsive phase were controlled mainly by
  electron beam bombardment, while the heating of kernel B is mainly due
  to heat conduction. By plotting the energy gradient of the electron
  energy flux as a function of energy for the various spectral indexes
  observed during the flare, the acceleration mechanism is found to be
  such that there is a constant energy E<SUB>0</SUB>, close to 20 keV,
  for which the electron flux d F<SUB>1</SUB>/dE is constant. It is shown
  that such a conclusion can be reached more directly by using the photon
  flux, which in that case must be constant for E=E<SUB>0</SUB>, whatever
  the value of the power index. This result implies also that the electron
  spectrum is represented by a power law and that the X-ray photons are
  produced in a thick target. Instantaneous momentum balance is shown to
  exist between the upflowing soft X-ray-emitting and the downflowing
  Hα- emitting plasma at the kernels of the flare. The observed Hα
  red asymmetry is well reproduced by the non-LTE computation, with the
  down-moving condensation included. The observation of the magnetic
  field suggests that the flare was triggered probably by magnetic
  flux emergence.

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Title: Spectropolarimetric studies of H<SUB> alpha </SUB> emission
in "solar moustaches": Observations and calculation of the Stokes
    parameters
Authors: Kazantsev, S. A.; Firstova, N. M.; Kashapova, L. K.; Bulatov,
   A. V.; Petrashen', A. G.; Henoux, J. -C.
1998ARep...42..702K    Altcode:
  The results of spectropolarimetric observations of three solar
  `moustaches' carried out on the Large Vacuum Solar Telescope of
  Baikal Observatory of the Institute of Solar-Terrestrial Physics are
  presented. The observed degree of polarization varies from 2-13%. The
  direction of the plane of polarization for a moustache with moderate
  intensity is tangential, and is radial for the weakest moustache. In
  the brightest moustache, the plane of polarization is close to radial
  at the line center, and is tangential in the wings.

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Title: A possible mechanism for the Hα broad wings emission of
    Ellerman bombs
Authors: Henoux, J. -C.; Fang, C.; Ding, M. D.
1998A&A...337..294H    Altcode:
  In this paper, the non-thermal emission of Lyalpha , Lybeta and Hα
  lines generated through charge exchange by protons accelerated in
  the low chromosphere and moving with a small pitch angle around an
  horizontal magnetic field has been computed. Computations have been
  done for observations made at the center of the solar disk, i.e. in a
  situation where the solar magnetic field is perpendicular to the line
  of sight, for non zero pitch angles. In such conditions, the photons
  emitted through charge exchange are Doppler shifted symmetrically in
  both wings of the lines. The Hα far line wing intensities increase
  significantly, making possible to reproduce the characteristics of
  the spectra of Ellerman bombs. Thus it is proposed that a proton beam
  accelerated in the low chromosphere, and losing its energy there,
  is a viable candidate for explaining the observed EB spectra.

---------------------------------------------------------
Title: Spectropolarimetric studies of H<SUB> alpha </SUB> emission in
"solar moustaches": Energy of the excited electron beam
Authors: Kazantsev, S. A.; Firstova, N. M.; Petrashen', A. G.; Henoux,
   J. =C.
1998ARep...42..707K    Altcode:
  Spectropolarimetric observations of the Hα emission of `solar
  moustaches' are used to estimate the energy of the beam of electrons
  that is assumed to give rise to the observed polarization during
  its shock excitation of an ensemble of hydrogen atoms in the solar
  chromosphere.

---------------------------------------------------------
Title: FIP Fractionation: Theory
Authors: Hénoux, Jean-Claude
1998SSRv...85..215H    Altcode:
  In this review, the main models of ion-neutral frationation leading to
  an enhancement of the low FIP to high FIP abundance ratio in the corona
  or in the solar wind, are presented. Models based on diffusion parallel
  to the magnetic field are discussed; they are highly dependent on the
  boundary conditions. The magnetic field, that naturally separates ions
  from neutrals moving perpendicular to the field lines direction, when
  the ion-neutral frequency becomes lower than the ion gyrofrequency,
  is expected to play an active role in the ion-neutral separation. It
  is then suggested that ion-neutral fractionation is linked to the
  formation of the solar chromosphere, i.e. in magnetic flux-tubes at
  a temperature between 4000 and 6000 K.

---------------------------------------------------------
Title: Line profiles in moustaches produced by an impacting energetic
    particle beam
Authors: Ding, M. D.; Henoux, J. -C.; Fang, C.
1998A&A...332..761D    Altcode:
  The Hα line profile in moustaches is characterized by enhanced wings
  and a deep central absorption. We explore the possibility that such a
  profile may be due to the effect of energetic particles bombarding the
  atmosphere. Computations show that the characteristics of moustache
  line profiles can be qualitatively reproduced in two extreme cases,
  either injection from the corona of high energy particles (ga 60 keV
  electrons or ga 3 MeV protons) or injection in a low-lying site, in
  middle chromosphere or deeper, of less energetic particles ( ~ 20 keV
  electrons or ~ 400 keV protons). The requirements on the energy and on
  the depth of the injection site of energetic particles are reduced in
  the case of observations close to the solar limb. The role of protons
  of energies below 1 MeV is slightly less significant than that of
  deka-keV electrons in the case of a high particle injection site,
  but such protons remain to be viable candidates in the case of lower
  particle injection sites and of observations at larger heliocentric
  angles. Observations at various wavelengths are needed to find which
  of these hypotheses is convenient for explaining a given event.

---------------------------------------------------------
Title: Non-thermal hydrogen line emission caused by an oblique
    incident proton beam through charge exchange
Authors: Zhao, X.; Fang, C.; Henoux, J. -C.
1998A&A...330..351Z    Altcode:
  In this paper, formulae are given for computing the non-thermal emission
  of superthermal hydrogen atoms generated through charge exchange by
  the bombardment of the solar atmosphere by an oblique incident proton
  beam with a given pitch angle. Specifically, we discuss the non-thermal
  emission of hydrogen in Lyalpha , Lybeta , and Hα lines and find that
  the profiles of these lines are quite different from the ones caused by
  bombardment by a proton beam moving vertically. The intensity and the
  asymmetry of the non-thermal emission profiles strongly depend on the
  beam pitch angle alpha and on the angle theta between the direction
  of magnetic field and the line of sight. By computing the thermal
  emission under the semi-empirical flare atmospheric models F1, F2, and
  the quiet-Sun atmospheric model C, we compare the relative importance
  of thermal and non-thermal emission. For the Hα line, the non-thermal
  emission, with the proton flux used, is too small to be detectable; for
  the Lyalpha line, the contribution of non-thermal emission to the line
  wings is smaller than the one of a vertical beam; while for the Lybeta
  line, line wing enhancement and broadening are significant. Thus, Lybeta
  line is a good diagnostic tool for non-thermal proton beam bombardment.

---------------------------------------------------------
Title: A study of activity in interacting sunspot groups
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Hénoux, J. -C.
1998PAICz..88...13S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Application to Astrophysics of Collisional Polarization
    Spectroscopy
Authors: Hénoux, J. -C.; Vogt, E.
1998PhST...78...60H    Altcode:
  Collisional polarization specroscopy brings unique information on
  the anisotropies of the velocity distribution function of energetic
  particles, allowing the identification of these particles and
  the evaluation of the energy flux they carry. The application of
  collisional polarization spectro-scopy is still limited to Solar
  Physics. Chromospheric hydrogen Balmer lines Hα and Hβ have been found
  to be linearly polarized in solar flares. The polarization seems to
  be associated with enhanced soft X-ray emission and is found to be in
  the flare to disk center direction. In the hypothesis where particles
  are accelerated higher in the solar corona, protons of energy lower
  than 1MeV are found to be the best candidates to explain the observed
  polarization. The significant degree of polarization of a few per cent
  observed may also indicate a low local acceleration site but still
  requires the acceleration of protons in the 10 to 100keV energy range.

---------------------------------------------------------
Title: Particle Beam Diagnostics Based on UV and Optical Spectra of
    Solar Flares (invited)
Authors: Fang, C.; Ding, M. D.; Hénoux, J. C.
1998asct.conf..497F    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: FIP Fractionation: Theory
Authors: Hénoux, J. -C.
1998sce..conf..215H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Quasi-separatrix layers in solar flares. II. Observed magnetic
    configurations.
Authors: Demoulin, P.; Bagala, L. G.; Mandrini, C. H.; Henoux, J. C.;
   Rovira, M. G.
1997A&A...325..305D    Altcode:
  We show that the location of Hα or OV flare brightenings is related
  to the properties of the field-line linkage of the underlying magnetic
  region. The coronal magnetic field is extrapolated from the observed
  photospheric field assuming a linear force-free field configuration
  in order to determine the regions of rapid change in field-line
  linkage, called "quasi-separatrix layers" or QSLs. They are open
  layers that behave physically like separatrices: breakdown of ideal
  magnetohydrodynamics and release of free magnetic-energy may occur
  at these locations when their thickness is small enough. A feature
  common to all the flaring regions studied is found to be the presence
  of QSLs where Hα flare kernels are observed. The brightenings are
  along restricted regions of very thin QSLs; an upper bound of their
  thickness is 1Mm but it is several order of magnitude smaller in most
  of the cases. These places coincide in general with zones where the
  longitudinal field component is greater than 100G. These results allow
  us to constrain present models of solar flares and localise where a
  break-down of ideal MHD can occur. The studied flares are found to be
  fed in general by only one electric current loop, but they imply the
  interaction of two magnetic bipoles. The extrapolated coronal field
  lines involved in the process have their photospheric footpoints
  located at both sides of QSLs, as expected in recent 3D magnetic
  reconnection models.

---------------------------------------------------------
Title: Evidence of Magnetic Reconnection from Hα, Soft X-Ray and
    Photospheric Magnetic Field Observations
Authors: Mandrini, C. H.; DÉmoulin, P.; BagalÁ, L. G.; Van
   Driel-Gesztelyi, L.; HÉnoux, J. C.; Schmieder, B.; Rovira, M. G.
1997SoPh..174..229M    Altcode:
  A conventional view of magnetic reconnection is mainly based on
  the 2-D picture of an X-type neutral point, or on the extension of
  it to 3-D, and it is thought to be accompanied by flux transport
  across separatrices (places where the field-line mapping is
  discontinuous). This view is too restrictive when we realize the variety
  of configurations that are seen flaring. We designed an algorithm,
  called Source Method (SM), to determine the magnetic topology of
  active regions (ARs). The observed photospheric field was extrapolated
  to the corona using subphotospheric sources and the topology was
  defined by the link between these sources. Hα flare brightenings
  were found to be located at the intersection with the chromosphere
  of the separatrices so defined. These results and the knowledge we
  gained on the properties of magnetic field-line linkage, led us to
  generalize the concept of separatrices to `quasi-separatrix layers'
  (QSLs) and to design a new method (`quasi-separatrix layers method',
  QSLM) to determine the magnetic topology of ARs. QSLs are regions where
  the magnetic field-line linkage changes drastically (discontinuously
  when they behave like separatrices) and the QSLM can be applied to ARs
  where the photospheric field has been extrapolated using any kind of
  technique. In this paper we apply the QSLM to observed flaring regions
  presenting very different configurations and also to a decaying AR where
  a minor phenomenon, like an X-ray bright point (XBP), is observed. We
  find that the locations of flare and XBP brightenings are related to the
  properties of the field-line linkage of the underlying magnetic region,
  as expected from recent developments of 3-D magnetic reconnection. The
  extrapolated coronal field lines representing the structures involved
  in the analyzed events have their photospheric footpoints located
  at both sides of QSLs. Our results strongly support the hypothesis
  that magnetic reconnection is at work in various coronal phenomena,
  ranging from the less energetic ones to large-scale eruptions.

---------------------------------------------------------
Title: Polarization of the hydrogen H<SUB>alpha</SUB>_ line in solar
flares: contribution of the different radiative and collisional
    processes.
Authors: Vogt, E.; Sahal-Brechot, S.; Henoux, J. C.
1997A&A...324.1211V    Altcode:
  Linear polarization of the H<SUB>alpha</SUB>_ line of hydrogen has
  been observed in solar flares. The observed polarization degree
  can be as high as 10% for a flare located near the limb and a one
  minute integration time. This polarization is currently explained
  as anisotropic collisional excitation of the n=3 level by vertical
  beams of protons with an energy greater than a few keV. Transfer of
  population between the Zeeman excited states by the local protons with
  an isotropic velocity distribution may reduce the polarization expected
  from the beam bombardment only. The amplitude of this effect has been
  computed by solving the statistical equilibrium equations for a 9-level
  hydrogen atom (all the levels of n=1, 2,3 including fine structure)
  for three different atmospheric models. The different collisional and
  radiative processes for populating and depopulating the Zeeman sublevels
  have been taken into account: excitation and deexcitation by collisions
  with the protons of the beam and with the local electrons and protons,
  excitation by the local Ly<SUB>alpha</SUB>_, Ly<SUB>beta</SUB>_
  and H<SUB>alpha</SUB>_ radiation, and deexcitation by spontaneous
  emission. It has been found that the polarization is not destroyed but
  reduced by a factor two to ten. Beams of non-thermal particles can be,
  as assumed previously, at the origin of the observed polarization,
  however, to get a significant degree of polarization, the flux of these
  particles must be significantly higher than that originally expected.

---------------------------------------------------------
Title: Can we Extrapolate a Magnetic Field when its Topology is
    Complex?
Authors: DÉmoulin, P.; HÉnoux, J. C.; Mandrini, C. H.; Priest, E. R.
1997SoPh..174...73D    Altcode:
  In order to understand various solar phenomena controlled by the
  magnetic field, such as X-ray bright points, flares and prominence
  eruptions, the structure of the coronal magnetic field must be
  known. This requires a precise extrapolation of the photospheric
  magnetic field. Presently, only potential or linear force-free
  field approximations can be used easily. A more realistic modelling
  of the field is still an active research area because of well-known
  difficulties related to the nonlinear mixed elliptic-hyperbolic nature
  of the equations. An additional difficulty arises due to the complexity
  of the magnetic field structure which is caused by a discrete partition
  of the photospheric magnetic field. This complexity is not limited
  to magnetic regions having magnetic nulls (and so separatrices)
  but also occurs in those containing thin elongated volumes (called
  Quasi-Separatrix Layers) where the photospheric field-line linkage
  changes rapidly. There is a wide range for the thickness of such layers,
  which is determined by the character (bipolar or quadrupolar) of the
  magnetic region, by the sizes of the photospheric field concentrations
  and by the intensity of the electric currents. The aim of this paper
  is to analyse the recent nonlinear force-free field extrapolation
  techniques for complex coronal magnetic fields.

---------------------------------------------------------
Title: Determination of proton beam energy from data of
    spectropolarimetric studies of H<SUB>α</SUB>-emission of th esolar
    chromosphere, as carried out at the Paris Observatory
Authors: Kazantsev, S. A.; Petrashen', A. G.; Henoux, J. -C.
1997OptSp..82..627K    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Spectroscopolarimetric Sensing of Energy Deposition Into the
    Chromosphere during Solar Flares - I. Observations
Authors: Firstova, N. M.; Hénoux, J. -C.; Kazantsev, S. A.; Bulatov,
   A. V.
1997SoPh..171..123F    Altcode:
  Measurements of linear polarization in hydrogen Hα and Hβ lines,
  made with the Large Solar Vacuum Telescope of Baikal Astrophysical
  Observatory and Automated Solar Telescope of Sayan Solar Observatory,
  affiliated with the Russian Institute of Solar and Terrestrial Physics,
  are reported in this paper. Short-term polarization associated with
  solar flares is found to be present in active regions. There is
  a significant tendency for the Hα polarization vector to be radial,
  i.e., in the flare-to-disk-center direction. This polarization may be
  due to atmospheric bombardment by hecta keV protons. On the other hand,
  the polarization vector is found to be perpendicular to the radial
  direction at some locations where the line profile has a typical
  mustache shape suggesting a bombardment by energetic electrons. The
  Hβ line is also linearly polarized. However, no preferential direction
  of polarization is found in this line, which is formed more deeply in
  the solar atmosphere.

---------------------------------------------------------
Title: The photospheric dynamo. I. Physics of thin magnetic flux
    tubes.
Authors: Henoux, J. C.; Somov, B. V.
1997A&A...318..947H    Altcode:
  In a previous paper (Henoux and Somov, 1991A&amp;A...241..613H) it
  has been shown that, in an initially weak magnetic field, a radial
  inflow of neutrals can generate azimuthal DC currents, and that an
  azimuthal velocity field can create radial DC currents leading to
  the circulation of vertical currents. The effects of such azimuthal
  velocity field on the intensity and topology of electric currents
  flowing in thin magnetic flux tubes is now investigated in detail in
  this paper. Two systems of currents flowing in opposite direction are
  created connected at photospheric level by transverse currents. The
  electromagnetic forces produced by these currents play a significant
  role in the structure and dynamics of flux tubes. Even for moderate
  values of the azimuthal photospheric velocities, the currents created
  are strong enough to prevent by the pinch effect an opening of the flux
  tube with height; despite the decrease of the ambient gas pressure with
  height, the thin flux tube extends into the solar atmosphere above the
  temperature minimum region. In the internal current shell, the rise from
  the photosphere of a partially ionized gas is found to have two main
  effects: (a) the upflow of this gas associated to a leak of neutrals
  across magnetic field lines leads to an increase of the ionization
  degree with altitude typical for the chromosphere, and brings above
  the temperature minimum region an energy flux comparable to the flux
  required for chromospheric heating, (b) the outflow of neutrals that
  takes place at the chromospheric level across magnetic field lines,
  and leads to ion-neutral separation, may explain the observed abundance
  anomalies in the corona by enhancing in the upper part of the tube
  the abundances of elements of low ionization potential. Upward motions
  are also present between the two current systems outside the internal
  cylindrical current. Their velocity is high enough to lift the matter
  to an altitude characteristic of spicules.

---------------------------------------------------------
Title: Spectral Diagnostics of the Energetic Particles in Solar Flares
Authors: Fang, C.; Ding, M. D.; Henoux, J. C.; Gan, W. Q.
1996JKASS..29..295F    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Quasi-Separatrix Layers and Their Relationship with Solar
    Flares
Authors: Bagala, L. G.; Mandrini, C. H.; Rovira, M. G.; Demoulin,
   P.; Henoux, J. C.
1996RMxAC...4Q..90B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Quasi-Separatrix Layers in Simple Magnetic Configurations
Authors: Mandrini, C. H.; Demoulin, P.; Henoux, J. C.; Priest, E.
1996RMxAC...4Q.104M    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The Viability of Energetic Protons as an Agent for Atmospheric
    Heating during the Impulsive Phase of Solar Flares
Authors: Emslie, A. Gordon; Henoux, Jean-Claude; Mariska, John T.;
   Newton, Elizabeth K.
1996ApJ...470L.131E    Altcode:
  Recent observations of gamma -ray line intensities in solar flares
  results have led to the suggestion that the energy content in
  accelerated protons may rival that of accelerated electrons. However,
  simply having a large energy content in accelerated protons is not
  sufficient to ensure an important role for protons in driving the
  response of the atmosphere to flare energy input: a viable model
  must also deposit a large fraction of the particle energy at the top
  of the chromosphere to account for the large increase in soft X-ray
  emission measure that characterizes the main phase of a flare. While
  hard X-ray producing electrons indeed deposit a sufficient amount of
  energy at the appropriate depths in the atmosphere, only protons with
  a characteristic energy of order 1 MeV do likewise. It is intriguing
  that a characteristic energy of just this value has been obtained
  through independent analysis of gamma -ray line intensities. However,
  it must be noted that protons of this energy do not have a signature
  in hard X-rays, leading us to conclude that a substantial fraction of
  the flare energy budget must still reside in deka-keV electrons. In
  order to complete the global energetic picture, further corroborating
  observational diagnostics for MeV protons are desirable. In this Letter,
  we discuss such suitable observations.

---------------------------------------------------------
Title: Proton transport in a magnetic loop and Hα impact line
    linear polarization.
Authors: Karlicky, M.; Henoux, J. -C.; Smith, D.
1996A&A...310..629K    Altcode:
  Using a 1-D test particle model with 350000 numerical protons,
  we study the evolution of the proton distribution function in a
  magnetic loop. A continuous injection of low-energy 200-1500keV
  protons with a distribution function proportional to a E^-3^
  power-law is considered. The acceleration region is assumed to be
  at the top of a flare loop where the protons are injected into a
  cone of pitch angles centered along the loop axis. The computations
  are made for a static loop of length 20880km with the parameters
  in the chromosphere corresponding to the VAL-C model of the solar
  atmosphere. Coulomb collisions, mirroring, and Alfven wave scattering
  in an intermediate regime (W_a_^tot^=10^-1^erg/cm^3^) relative to
  prior analyses corresponding to saturated scattering are taken into
  consideration. The proton distribution function in the chromosphere
  at the Hα formation layer is computed. The resulting anisotropy of
  the proton distribution function in a quasi-stationary state of proton
  bombardment is analyzed from the point of view of its expected effects
  on the impact linear polarization of chromospheric lines.

---------------------------------------------------------
Title: Energetic Protons as a Form of Energy Transport During The
    Impulsive Phase of Solar Flares?
Authors: Emslie, A. G.; Henoux, J. -C.; Mariska, J. T.; Newton, E. K.
1996AAS...188.2601E    Altcode: 1996BAAS...28..857E
  Recent results based on hard X-ray and gamma-ray observations of solar
  flares have suggested that the energy content in accelerated protons
  may rival that of accelerated electrons. However, simply having a large
  energy content in accelerated protons is not sufficient to ensure an
  important role for protons in driving the response of the atmosphere to
  flare energy input: a viable model must also deposit a large fraction
  of the particle energy at the top of the chromosphere, to account for
  the large increase in soft X-ray emission measure that characterizes
  the main phase of a flare. While hard X-ray-producing electrons indeed
  deposit a sufficient amount of energy at the appropriate depths in the
  atmosphere, we show that only protons with a characteristic energy of
  order 1 MeV do likewise. Since protons of this energy do not have a
  signature in hard X-rays, we conclude that a substantial fraction of the
  flare energy budget must indeed reside in deka-keV electrons. In order
  to complete the global energetic picture, observational diagnostics
  for MeV protons are required; suitable observations are discussed. This
  work was supported by the NASA Office of Space Science and by the NSF
  International Programs Division.

---------------------------------------------------------
Title: Spectropolarimetry of solar flare based on measurements of
    the H<SUB> beta </SUB> hydrogen line
Authors: Kazantsev, S. A.; Petrashen', A. G.; Firstova, N. M.; Henoux,
   J. -C.
1996OptSp..80..635K    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Quasi-Separatrix layers in solar flares. I. Method.
Authors: Demoulin, P.; Henoux, J. C.; Priest, E. R.; Mandrini, C. H.
1996A&A...308..643D    Altcode:
  Magnetic reconnection is usually thought to be linked to the presence
  of magnetic null points and to be accompanied by the transport of
  magnetic field lines across separatrices, the set of field lines where
  the mapping of field lines is discontinuous. In view of the variety
  of observed flaring configurations, we show that this view is too
  restrictive. Instead, Priest and Demoulin (1995) have explored a way
  of generalising the concept of separatrices to magnetic configurations
  without field-line linkage discontinuities. They propose that magnetic
  reconnection may also occur in 3D in the absence of null points at
  "quasi-separatrix layers" (QSLs), which are regions where there is
  drastic change in field-line linkage. In previous studies we have shown
  that solar flare kernels are linked to the topology of the active-region
  magnetic field. The observed photospheric field was extrapolated to
  the corona using subphotospheric magnetic sources and the topology was
  defined by the magnetic linkage between these sources, the method being
  called SM (for Source Method). In this paper we define a new method,
  called QSLM (for Quasi-Separatrix Layers Method), which finds the
  location of QSLs above the photosphere. It is designed to be applied to
  any kind of magnetic field representation, while, in the present paper,
  we apply it only to simple theoretical magnetic configurations in order
  to compare it with the SM. It generalises the concept of separatrices to
  magnetic configurations without field-line linkage discontinuities. The
  QSLM determines elongated regions that are in general located along
  small portions of the separatrices defined by the SM, and in the limit
  of very concentrated photospheric fields both methods give the same
  result. In bipolar magnetic configurations two QSLs are found at both
  sides of the inversion line, while in quadrupolar configurations four
  appear. We find that there is a wide range for the thickness of the
  QSLs, which is determined by the character (bipolar or quadrupolar)
  of the magnetic region and by the sizes of the photospheric field
  concentrations. We then show that smooth photospheric motions induce
  concentrated currents at the locations defined by the QSLM. We prove
  this only for initially potential configurations but, due to the form
  of the equations, we conjecture that it is also valid for any kind
  of initial magnetic equilibrium. We conclude that, even in bipolar
  configurations, there are localized places where current build-up can
  be induced by photospheric motions, leading to ideal MHD breakdown
  with strong flows and magnetic energy release.

---------------------------------------------------------
Title: Polarimetric Study of Solar Flares
Authors: Vogt, E.; Hénoux, J. C.
1996SoPh..164..345V    Altcode:
  The theory of impact polarization is briefly
  reviewed. Spectropolarimetry provides a tool to derive the nature,
  the number flux, and the main characteristics of the angular velocity
  distribution function of energetic particles accelerated in solar
  flares. As an exemple of application of polarimetry the spatial and
  temporal characteristics of the linear polarization of the hydrogen
  Hα line observed in a solar flare is presented.

---------------------------------------------------------
Title: 3D Magnetic Reconnection: Example of an X-Ray Bright Point
Authors: Demoulin, P.; Mandrini, C. H.; van Driel-Gesztelyi, L.;
   Priest, E. R.; Henoux, J. C.; Schmieder, B.
1996ASPC..111...49D    Altcode: 1997ASPC..111...49D
  In the classical view magnetic reconnection occurs at neutral points
  and implies transport of magnetic field-lines across separatrices. The
  authors show that reconnection may also occur in the absence of neutral
  points at so-called "quasi-separatrix layers" (QSLs), where there is a
  steep gradient in field-line linkage at the boundaries. Reconnection
  occurs in QSLs where the field-line velocity becomes larger than the
  allowed maximal plasma velocity or where the electric-current density
  becomes too great. The authors describe both a theoretical and an
  observed configuration. In the case of a simple sheared X-field they
  show that even a smooth continuous shear flow, imposed at the boundary,
  gives strong plasma jetting inside and parallel to the QSLs. Applying
  the QSL method to an X-ray bright point observed by Yohkoh, they find
  field lines in the extrapolated field which are on both sides of QSLs
  and which are in good agreement with loops observed in Hα and X-rays
  related to emerging flux. The evolution of the QSL width may explain
  the brightness evolution of the XBP.

---------------------------------------------------------
Title: Impact spectropolarimetry of solar flares.
Authors: Henoux, J. -C.; Vogt, E.
1996joso.proc...60H    Altcode:
  Hydrogen Hα spectropolarimetry provides a tool to derive the nature,
  the number flux, and the main characteristics of the angular velocity
  distribution function of energetic particles accelerated in solar
  flares. As an example of application, the main characteristics of the
  linear polarization of the hydrogen Hα line observed in a solar flare
  are briefly presented.

---------------------------------------------------------
Title: Effects on Non-Thermal Particles on the UV and Optical Spectra
    of Solar Flares
Authors: Henoux, J. -C.; Fang, C.
1996mpsa.conf..561H    Altcode: 1996IAUCo.153..561H
  No abstract at ADS

---------------------------------------------------------
Title: Constraints on flare models set by the active region magnetic
    topology Magnetic topology of AR 6233.
Authors: Mandrini, C. H.; Demoulin, P.; Rovira, M. G.; de La
   Beaujardiere, J. -F.; Henoux, J. C.
1995A&A...303..927M    Altcode:
  We present a detailed analysis of the magnetic topology of AR 6233
  on two consecutive days (August 28 and 29, 1990) and compare the
  location of the magnetic separatrices and separators with off-band
  Hα observations and other flare manifestations, such as intense
  nonthermal electron precipitation and high coronal pressure sites,
  for two flares that occured on these days. Since for one of the days
  of our analysis we have two magnetograms covering fields of view with
  different scale lengths, we analyzed the dependence of the topology
  of the region of interest on the presence of external magnetic field
  concentrations. We have found that considering these concentrations
  does not modify the location of separatrices in the region. Because
  transverse magnetograms indicate that strong magnetic shear is present
  along the longitudinal inversion line where flare brightenings are
  located, the observed photospheric magnetic field is modeled in an
  approach in which a combination of sources with current-free and non
  current-free magnetic field is used. This model allows us to obtain a
  better fit between the observed and modeled transverse field, then we
  find a closer relationship between separatrices and flare features. The
  results of a current-free and of a linear force-free approach are also
  shown for comparison. As in other flaring regions studied previously,
  chromospheric flare brightenings are found on separatrices. The
  topological structure obtained for these flares is rather complex. We
  find that the connectivity of field lines may change drastically
  from one edge of a ribbon to the other. Electron precipitation and
  high coronal pressure sites, and some photospheric intense currents
  are also found in the immediate vicinity of separatrices. The early
  kernels of August 28 flare are found closer to the separatrices of
  the nonpotential field, while the later are closer to those of the
  potential field. All these results agree with the hypothesis that
  magnetic energy is stored in field-aligned currents and released due
  to magnetic field reconnection, with a noticeable relaxation of the
  field, either at the separator region or on separatrices.

---------------------------------------------------------
Title: A Topological Approach to Understand a Multiple-Loop Solar
    Flare
Authors: Bagalá, L. G.; Mandrini, C. H.; Rovira, M. G.; Démoulin,
   P.; Hénoux, J. C.
1995SoPh..161..103B    Altcode:
  We analyze the UV and X-ray data obtained by the SMM satellite for
  the flare starting at 02:36 UT on November 12, 1980 in AR 2779. From
  a detailed revision of the OV emission, we find that the observations
  are compatible with energy being released in a zone above the magnetic
  inversion line of the AR intermediate bipole. This energy is then
  transported mainly by conduction towards the two distant kernels located
  in the AR main bipole. One of these kernels is first identified in
  this paper. Accelerated particles contribute to the energy transport
  only during the impulsive phase.

---------------------------------------------------------
Title: Models for explaining the observed spatial variation of
    element abundances - a review
Authors: Henoux, J. -C.
1995AdSpR..15g..23H    Altcode: 1995AdSpR..15...23H
  Recent results on the spatial dependence of low and high-FIP (First
  Ionization Potential) element abundances in the sun, and on the fine
  structure of this FIP dependence, are briefly discussed. Existing
  models of FIP fractionation are reviewed. The main models are based on
  ion-neutral separation in a magnetic field and they differ fundamentally
  by the nature of the forces - gravity pressure or electric forces -
  acting on the particles - neutrals or ions - that cross the lines of
  force. These models predict an enhancement of low-FIP elements at the
  coronal level. However, a quantitative prediction of the resulting
  coronal abundances is still not possible. Abundance enhancements
  of ^3He and of heavy elements observed in solar energetic particles
  accelerated in impulsive flares are also quoted, and the most recent
  particle acceleration theories are briefly presented. In conclusion
  we emphasize the need to understand the origin of coronal abundances
  in order to obtain clues on mechanisms for chromospheric formation.

---------------------------------------------------------
Title: The Electrical Current Structure Associated with Solar Flare
    Electrons Accelerated by Large-Scale Electric Fields
Authors: Emslie, A. Gordon; Henoux, Jean-Claude
1995ApJ...446..371E    Altcode:
  We consider the scenario in which the high-energy electrons responsible
  for hard X-ray production in the impulsive phase of solar flares are
  accelerated by a large-scale direct electric field. We point out that
  both Ampere's and Faraday's laws require that the current pattern
  associated with the accelerated electrons be highly filamented,
  with the degree of filamentation dependent on the assumed structure
  of the preflare current pattern. Recognizing that cospatial return
  currents are not permitted in such models, we consider the closure
  of the current pattern using a cross-field drift of protons at the
  chromospheric footpoints of the elementary magnetic flux tubes. We
  demonstrate that there is a sufficient rate of ionization (both
  collisional and radiative) and recombination to create and absorb,
  respectively, the necessary electron fluxes, and we also demonstrate
  that pressure gradients in the chromosphere are adequate to drive the
  opposite flows of protons and hydrogen atoms against the frictional
  forces there. We further argue that the current closes within a
  vertical layer of order the thickness of the current channel, i.e.,
  a few meters, and that this layer is most likely situated at the
  base of the transition region, where the conductivity tensor first
  becomes roughly isotropic. A possible diagnostic of this model is the
  polarization of the Hα line produced by an unequal population of the
  n = 3 hydrogen atom sublevels in the presence of the anisotropic proton
  distribution function commensurate with the above current structure.

---------------------------------------------------------
Title: Hydrogen line spectra of a nonthermal proton beam. due to
    charge exchange in solar flares
Authors: Fang, C.; Feautrier, N.; Henoux, J. -C.
1995A&A...297..854F    Altcode:
  Using more recent values of the atomic parameters and a more refined
  atmospheric model, the nonthermal line emission resulting from
  proton-hydrogen charge exchange has been recomputed. Confirming the
  results of Canfield &amp; Chang (1985), the hydrogen Hα nonthermal
  line emission was found too small to be detectable. On the other hand,
  the nonthermal emission in the red wings of the Lyα and Lyβ lines
  is significantly high and can be used as a diagnostic of low energy
  protons. However, this emission is at least one order of magnitude
  lower than the value derived by Canfield and Chang.

---------------------------------------------------------
Title: Determination of the energy of the proton beam formed in a
    solar flare on the basis of spectropolarimetric data
Authors: Kazantsev, S. A.; Firstova, N. M.; Petrashen', A. G.; Henoux,
   J. -C.; Bulatov, A. V.
1995OptSp..78..655K    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Diagnostics of non-thermal processes in chromospheric
    flares. III. Lyα and Lyβ spectra for an atmosphere bombarded by
    electron or proton beams.
Authors: Henoux, J. C.; Fang, C.; Gan, W. Q.
1995A&A...297..574H    Altcode:
  The Lyα and Lyβ line profiles, including the nonthermal excitation
  and ionization of hydrogen by electron or proton bombardment, have
  been computed for atmospheres with the temperature distributions of the
  semi-empirical models F_1_ and F_2_. These computations indicate that
  the intensities at the line wings are greatly enhanced by nonthermal
  effects, especially for an electron beam bombardment. These effects are
  the most obvious when the coronal column mass is relatively small. Thus,
  nonthermal effects should be the most pronounced just at the beginning
  of the impulsive phase. After the maximum of the impulsive phase,
  due to a fast increase of the coronal column mass, these effects will
  rapidly decrease.

---------------------------------------------------------
Title: Semi-Empirical Models of the White-Light Flare on October
    24, 1991
Authors: Fang, C.; Henoux, J. C.; Ju, Hu; Yin-Zhang, Xue; Xiu-Fa,
   Gao; Qi-Jun, Fu
1995SoPh..157..271F    Altcode:
  On October 24, 1991, a white-light flare was observed both from space
  and from the ground. A multi-waveband spectral analysis shows that
  the peak time of the continuum emission coincides well with that of
  a radio burst at 2840 MHz and with the hard X-ray emission. Three
  semi-empirical models, corresponding to the pre-flare condition and to
  the peak time of continuum emission both with and without non-thermal
  excitation and ionization of hydrogen by an electron beam, have been
  obtained. The results indicate that there is fast heating both in the
  chromosphere and the photosphere. Some evidence is given that this WLF
  is very likely a result of bombardment by an electron beam. By taking
  into account non-thermal effects, the chromospheric temperature of
  the semi-empirical model is significantly reduced.

---------------------------------------------------------
Title: Current Closure in the Impulsive Phase of Solar Flares
Authors: Emslie, A. G.; Hénoux, J. -C.
1995SPD....26.1313E    Altcode: 1995BAAS...27..989E
  No abstract at ADS

---------------------------------------------------------
Title: Polarization spectroscopy of ionized gases
Authors: Kazantsev, Sergei A.; Henoux, Jean-Claude
1995ASSL..200.....K    Altcode: 1995psig.book.....K
  No abstract at ADS

---------------------------------------------------------
Title: Impact spectropolarimetry in the hydrogen Hα line: present
    atomic data and astrophysical applications
Authors: Kazantev, S. A.; Feautrier, N.; Henoux, J. C.; Liaptsev,
   A. V.; Luchinkina, V. V.
1994A&ARv...6....1K    Altcode:
  The physics of impact polarization is briefly reviewed in this
  paper. Methods for derivating the impact spectropolarimetric
  parameters relevant for the formation of Hα linear polarization are
  summarized. Spectropolarimetric techniques can provide information
  on the velocity distribution function of energetic particles. Since
  the most advanced application of this technique to astrophysics is
  in solar flare physics, recent results achieved by its application to
  particles accelerated in solar flares are presented.

---------------------------------------------------------
Title: Energy Release in Solar Flares
Authors: Brown, John C.; Correia, Emilia; Farnik, Frantisek; Garcia,
   Howard; Henoux, Jean-Claude; Larosa, Ted N.; Machado, Marcos E.;
   Nakajima, Hiroshi; Priest, Eric R.
1994SoPh..153...19B    Altcode:
  Team 2 of the Ottawa FLARES 22 Workshop dealt with observational and
  theoretical aspects of the characteristics and processes of energy
  release in flares. Main results summarized in this article stress
  the global character of the flaring phenomenon in active regions, the
  importance of discontinuities in magnetic connectivity, the role of
  field-aligned currents in free energy storage, and the fragmentation
  of energy release in time and space.

---------------------------------------------------------
Title: Energy Transport and Dynamics
Authors: Schmieder, B.; Peres, G.; Enome, S.; Falciani, R.; Heinzel,
   P.; Hénoux, J. C.; Mariska, J.; Reale, F.; Rilee, M. L.; Rompolt, B.;
   Shibasaki, K.; Stepanov, A. V.; Wülser, J. P.; Zarro, D.; Zharkova, V.
1994SoPh..153...55S    Altcode:
  We report findings concerning energy transport and dynamics in flares
  during the impulsive and gradual phases based on new ground-based and
  space observations (notably fromYohkoh). A preheating sometimes occurs
  during the impulsive phase. CaXIX line shifts are confirmed to be
  good tracers of bulk plasma motions, although strong blue shifts are
  not as frequent as previously claimed. They often appear correlated
  with hard X-rays but, forsome events, the concept that electron beams
  provide the whole energy input to the thermal component seems not
  to apply. Theory now yields: new diagnostics of low-energy proton
  and electron beams; accurate hydrodynamical modeling of pulse beam
  heating of the atmosphere; possible diagnostics of microflares (based
  on X-ray line ratio or on loop variability); and simulated images of
  chromospheric evaporation fronts. For the gradual phase, the continual
  reorganization of magnetic field lines over active regions determines
  where and when magnetic reconnection, the mechanism favoured for energy
  release, will occur. Spatial and temporal fragmentation of the energy
  release, observed at different wavelengths, is considered to be a
  factor as well in energy transport and plasma dynamics.

---------------------------------------------------------
Title: Evolution of Active Regions Leading to Flares
Authors: Schmieder, B.; Demoulin, P.; Henoux, J. -C.; Driel-Gesztelyi,
   L. V.; Mandrini, C.; Rovira, M.
1994kofu.symp..297S    Altcode:
  We model observed longitudinal magnetic fields obtained in Potsdam,
  Meudon, MSFC Hunstville by a series of magnetic sources located
  below the photosphere. H_alpha flare kernels are found situated on
  intersecting separatrices (surfaces delimiting regions of different
  magnetic connectivities). We deduce that energy release occurs
  mainly at the separator by magnetic reconnection. Evidence for both
  neutralized and un-neutralized currents are observed in different
  flaring regions. Moreover we have found two photospheric currents of
  opposite sign, linked in the corona by field lines, at the border of
  flare kernels.

---------------------------------------------------------
Title: Are magnetic null points important in solar flares ?
Authors: Demoulin, P.; Henoux, J. C.; Mandrini, C. H.
1994A&A...285.1023D    Altcode:
  When they are present, null points (points where the 3 components of
  the magnetic field vanish) determine the topology of the magnetic
  field configuration. It has been suggested that the presence of
  nulls is related to flares, and that they settle the region where
  the energy is released by magnetic reconnection. Since solar flares
  are initially coronal events, nulls should be located above the
  photosphere. Therefore, we investigate the location of nulls in
  configurations formed by a parasitic and a main bipole (4 magnetic
  sources). For both potential and linear-force free field approaches,
  we have found that a null was present in the corona only when the two
  bipoles were nearly antiparallel. The flaring regions analysed here
  are those where the magnetic topology has been related to flare kernels
  in previous papers. These observations show that flares occur for any
  horizontal orientation of the parasitic bipole to the main one, having
  only in particular cases a null in the extrapolated field. When a null
  is present, it can be at any place along the separator and it is not
  necessarily related to the region where the energy is released. These
  results are found both in the subflares and the intense X-ray flares
  studied. Examples of observed configurations that can be analysed
  with 2D or 3D models are presented. We conclude that nulls above the
  photosphere are not needed for flaring but that the spatial properties
  of the coronal field still determines the location where reconnection
  takes place. Results are discuss in the context of present understanding
  of 3D reconnection.

---------------------------------------------------------
Title: Observational support of reconnection in solar flares
Authors: Démoulin, P.; Hénoux, J. C.; Schmieder, B.; Mandrini,
   C. H.; Rovira, M. G.; Somov, B.
1994SSRv...68..129D    Altcode:
  We present a detailed analysis of the magnetic topology of flaring
  active region. TheH <SUB>α</SUB> kernels are found to be located at the
  intersection of the separatrices with the chromosphere when the shear,
  deduced from the fibrils or/and transverse magnetic field direction,
  is taken into account. We show that the kernels are magnetically
  connected by field lines passing close to the separator. We confirm,
  for other flares, previous studies which show that photospheric current
  concentrations are located at the borders of flare ribbons. Moreover
  we found two photospheric current concentrations of opposite sign,
  linked in the corona by field lines which follow separatrices. These
  give evidence that magnetic energy is released by reconnection processes
  in solar flares.

---------------------------------------------------------
Title: Interpretation of multiwavelength observations of November 5,
    1980 solar flares by the magnetic topology of AR 2766
Authors: Demoulin, P.; Mandrini, C. H.; Rovira, M. G.; Henoux, J. C.;
   Machado, M. E.
1994SoPh..150..221D    Altcode:
  We present a detailed analysis of the magnetic topology of AR 2776
  together with Hα UV, X-rays, and radio observations of the November
  5, 1980 flares in order to understand the role of the active region
  large-scale topology on the flare process. As at present the coronal
  magnetic field is modeled by an ensemble of sub-photospheric sources
  whose positions and intensities are deduced from a least-square fit
  between the computed and observed longitudinal magnetic fields. Charges
  and dipole representations are shown to lead to similar modeling of
  the magnetic topology provided that the number of sources is great
  enough. However, for AR 2776, departure from a potential field has to
  be taken into account, therefore a linear force-free field extrapolation
  is used.

---------------------------------------------------------
Title: Space and time distribution of hard X-ray emission in a loop
    at the beginning of a flare
Authors: Karlicky, Marian; Henoux, Jean-Claude
1994A&A...283..202K    Altcode:
  Using a 1-D hybrid model of the electron bombardment in flare
  loops, we study not only the evolution of densities, plasma
  velocities and temperatures in the loop, but also the temporal and
  spatial evolution of hard X-ray emission. In the present paper
  a continuous bombardment by electrons isotropically accelerated
  at the top of flare loop with a power-law injection distribution
  function is considered. The computations included the effects of the
  return-current that reduces signifcantly the depth of the chromospheric
  layer which is evaporated. These computations were made to study
  the contribution of various processes - chromospheric evaporation,
  mirroring and high pitch angle of superthermal electrons - to the
  hard X-ray emission at the top of a loop at the very beginning of
  flares. Therefore the present modelling was made with superthermal
  electron parameters coresponding to the classical resistivity regime
  for an input energy flux of superthermal electrons of 10<SUP>9</SUP> erg
  cm<SUP>-2</SUP>/sec. Chromospheric evaporation density waves generated
  at both feet of the loop propagate up to the top, where they collide
  and cause a temporary electron density enhancement. Electron mirroring
  at magnetic mirrors increases the population of superthermal electrons
  at the top loop. These two processes lead to hard X-ray emission at
  the top of the loop and dominate over the effect of high pitch-angle
  superthermal electrons.

---------------------------------------------------------
Title: Observational characteristics of explosive events
Authors: Hénoux, J. -C.; Dere, K. P.
1994LNP...432..203H    Altcode:
  The characteristics of dynamic phenomena observed in the EUV with
  the HRTS instruments, chromospheric jets and explosive events, are
  reviewed here. Most of the review is devoted to explosive events that
  are short duration explosions involving a plasma at 105 K. These
  events are characterised by strong Doppler shifts rather than by
  brightness enhancements, contrary to EUV impulsive brightenings
  observed by SMM. They are presumably due to magnetic reconnection
  involving unresolved fine structures of the magnetic field near the
  network. The role of the density of concentrated magnetic fluxtubes
  in a reconnection scenario has still to be understood.

---------------------------------------------------------
Title: On the Role of Separatrices and Separators of Coronal Magnetic
    Fields in Solar Flares
Authors: Henoux, J. C.; Somov, B. V.
1994ASPC...68..258H    Altcode: 1994sare.conf..258H
  No abstract at ADS

---------------------------------------------------------
Title: Role of Electric Currents in Magnetic Flux Tube Physics
Authors: Henoux, J. C.; Somov, B. V.
1994ASPC...68..158H    Altcode: 1994sare.conf..158H
  No abstract at ADS

---------------------------------------------------------
Title: Magnetic topology of a complex active region
Authors: Mandrini, C. H.; Rovira, M. G.; Démoulin, P.; de La
   Beaujarière, J. -F.; Hénoux, J. C.
1994BAAA...39...52M    Altcode:
  We present a detailed analysis of the magnetic topology of AR 6233
  on two consecutive days (August 28 and 29, 1990). We compare the
  location of the magnetic separatrices and separators with off-band Hα
  observations and other flare manifestations, such as intense non-thermal
  electron precipitation and high coronal pressure sites, for two flares
  that occurred on these days. Because transverse magnetograms indicate
  that strong magnetic shear is present along the longitudinal inversion
  line, where flare brightening are located, the observed photospheric
  magnetic field is modeled in an approach in which a combination
  of sources with current-free and non current-free magnetic held is
  used. This model allows us to obtain a better ht between the observed
  and modeled transverse held. Then, we find a closer relationship between
  separatrices and hare features. The results of a current-free and of
  a linear force-free approach are also discussed. As in other haring
  regions studied previously, chromospheric flare brightening are found
  on separatrices. The topological structure obtained for these flares is
  rather complex and cannot be explained by classical flare models. We
  find that the connectivity of field lines may change drastically from
  one edge of an Ha; ribbon to the other. Electron precipitation and
  high coronal pressure sites, and some photospheric intense currents
  are also found in the immediate vicinity of separatrices. The early
  kernels of August 28 flare are found closer to the separatrices of the
  non-potential held, while the later are closer to those of the potential
  held. All these results agree with the hypothesis that magnetic energy
  is stored in field-aligned currents and released due to magnetic held
  reconnection, with a noticeable relaxation of the held, either at the
  separator region or on separatrices.

---------------------------------------------------------
Title: Understanding Solar Active Phenomena: A Phenomenological
    Approach
Authors: Machado, M. E.; Demoulin, P.; Gary, G. A.; Henoux, J. C.;
   Mandrini, C. H.; Rovira, M. G.
1994step.conf..125M    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Space and Time Distribution of Hard X-Ray Emission in a Loop
    at the Beginning of a Flare
Authors: Karlicky, M.; Henoux, J. -C.
1994scs..conf..275K    Altcode: 1994IAUCo.144..275K
  Using a new 1D hybrid model of the electron bombardment in flare
  loops, the authors study not only the evolution of densities, plasma
  velocities and temperatures in the loop, but also the temporal and
  spatial evolution of hard X-ray emission. In this paper a continuous
  bombardment by electrons isotropically accelerated at the top of flare
  loop with a power-law injection distribution function is considered.

---------------------------------------------------------
Title: Observational characteristics of explosive events.
Authors: Hénoux, J. C.; Dere, K. P.
1994LNP...432..205H    Altcode: 1994LNPM...11..205H
  The characteristics of dynamic phenomena observed in the EUV with
  the HRTS instruments, chromospheric jets and explosive events, are
  reviewed. Most of the review is devoted to explosive events that are
  short duration explosions involving a plasma at 10<SUP>5</SUP>K. These
  events are characterised by strong Doppler shifts rather than by
  brightness enhancements, contrary to EUV impulsive brightenings
  observed by SMM. They are presumably due to magnetic reconnection
  involving unresolved fine structures of the magnetic field near the
  network. The role of the density of concentrated magnetic fluxtubes
  in a reconnection scenario has still to be understood.

---------------------------------------------------------
Title: Magnetic reconnection as a mechanism for solar flares
Authors: Bagala, L. G.; Rovira, M. G.; Mandrini, C. H.; Demoulin,
   P.; Henoux, J. C.
1994iaf..conf.....B    Altcode:
  In this paper we summarize the results of our quantitative analysis of
  the 3D magnetic topology of several active regions (ARs). We show that
  the flare brightenings in different wavelengths (H-alpha, UV, X-rays)
  are located at the intersection of separatrices with the chromospheric
  plane. Flare kernels are magnetically connected by field lines passing
  close to the separator in different types of configurations. We also
  find that photospheric current concentrations are associated with flare
  brightenings and can be linked in the corona by field lines following
  separatrices, supporting the hypothesis that magnetic energy is stored
  in field-aligned currents. Since magnetic reconnection is expected to
  take place at the separator region or on separatrices, these results
  strongly suggest that this is the process driving energy release in
  solar flares.

---------------------------------------------------------
Title: Electron acceleration due to beam flux increase in a converging
    magnetic field
Authors: Karlicky, M.; Henoux, J. -C.
1993A&A...278..627K    Altcode:
  The effects of the magnetic field mirroring and backscattering of beam
  electrons in a time varying return-current electric field are studied
  with a 1-D hybrid test particle model of the electron bombardment in
  flare loops. These effects are analyzed for monoenergetic electron
  beams with an energy flux increasing with time, for different widths
  of their pitch-angle distribution. The consequence of a weak linear
  increase of the magnetic field from the apex to the feet of the
  loop is considered. The number and therefore the role of mirroring
  electrons are increasing with the broadening of the pitch-angle
  distribution. While in the case of bombardment by an unidirectional
  beam only few particles are reflected by back-scattering in the dense
  layers of the loop and then accelerated in the return-current electric
  field, in the case of a broader pitch-angle distribution of beams
  much more electrons are mirrored and accelerated. Part of them are
  accelerated to energies higher than the initial ones. Consequently,
  a collisionless return-current is formed, which decreases the beam
  return-current losses. The possible role of these effects in the solar
  flare scenario is shortly discussed.

---------------------------------------------------------
Title: Multiwavelength Observations and Magnetic Field Modelling of
    a Solar Flare
Authors: Bagala, L. G.; Rovira, M. G.; Mandrini, C. H.; Demoulin,
   P.; Henoux, J. C.
1993RMxAA..26..135B    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Spectropolarimetric determination of the energy contribution
    to the optically active region of the chromosphere
Authors: Kazantsev, S. A.; Petrashen, A. G.; Firstova, N. M.; Hénoux,
   J. C.
1993OptSp..75..382K    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Return current losses in pulse beam heating of the solar
    atmosphere
Authors: Karlický, Marian; Hénoux, Jean-Claude
1993AdSpR..13i.195K    Altcode: 1993AdSpR..13..195K
  The influence of return current losses on pulse beam heating of the
  solar atmosphere is studied using a 1 D-hybrid code. While heating
  of the coronal plasma by the penetrating electron beam is obtained,
  as expected, strong return current losses of beam electrons at the
  resistivity jump in the transition region are also found. The electron
  beam energy is deposited at greater heights in the solar atmosphere
  than in the case of pure collisional losses. At the starting time
  of the flare, due to a strong return current heating, a very steep
  transition region is formed where upwards and downwards plasma flows
  are generated. However, this state has a transitory character. The
  atmosphere is heated and a channel of hot, low resistivity plasma
  is formed, by which the following electron beams can penetrate more
  easily to deep chromospheric levels, where they are then thermalized.

---------------------------------------------------------
Title: Sites of flares and filaments in solar active regions
Authors: Schmieder, B.; van-Driel, L.; Hofmann, A.; Démoulin, P.;
   Hénoux, J. C.; Hagyard, M.
1993AdSpR..13i.119S    Altcode: 1993AdSpR..13..119S
  We applied a method developed to derive from magnetic field data the
  location of energy release in solar active regions. This method has
  been applied to two sets of data (June 13-15 1980 and June 23-25 1989)
  using magnetograms (Meudon, MSFC, Potsdam) and Hα data (Debrecen,
  MSDP Meudon). The Hα flares are located at intersections of the
  separatrices with the chromosphere in places where high density currents
  are observed. This supports the idea that the energy released in flares
  is due to magnetic reconnection at the location of a separator and
  subsequently transported to the chromosphere along field lines. It is
  found that strong magnetic shear is a necessary condition for filament
  formation. Magnetic shear merely determines the importance of the
  flare and is certainly not a necessary condition for flare activity.

---------------------------------------------------------
Title: Electric currents in magnetic flux-tubes
Authors: Hénoux, J. C.; Somov, B. V.
1993AdSpR..13i..23H    Altcode: 1993AdSpR..13...23H
  The effect on magnetic flux-tubes formation and equllibrium of the DC
  currents generated in the tubes by radial and azimuthal motions are
  investigated. These currents are found to be high enough to modify
  significantly the horizontal and vertical pressure distribution
  distribution at photospheric level. Consequently a radial variation
  of pressure can also be created and maintained at chromospheric levels
  leading to diffusion of neutral particles across the lines of force. The
  leakage of neutrals procedures a rise of the degree of ionization in
  the flux-tube and an enrichment in elements of high first ionization
  potential.

---------------------------------------------------------
Title: Diagnostics of non-thermal processes in chromospheric
    flares. I. H alpha and CaII K line profiles of an atmosphere bombarded
    by hecta keV electrons.
Authors: Fang, C.; Henoux, J. C.; Gan, W. Q.
1993A&A...274..917F    Altcode:
  The significance of non-thermal excitation and ionization of hydrogen
  and CaII, by an electron beam, on the line profiles of Hα and CaII K
  line has been investigated. Non-LTE Hot and CaII K line profiles have
  been calculated for the temperature distributions of semi-empirical
  flares models F<SUB>1</SUB> and F<SUB>2</SUB> (Machado et al. t980). For
  reasonable values of the beam energy flux and power index, the hydrogen
  lines are greatly strengthened and broadened, and an obvious central
  reversal appears. The effects are weaker for the CaII K line. These
  effects can be used to diagnose electron beam bombardment during a
  solar flare, especially at its early phase. Any semi-empirical flare
  model that does not take into account non-thermal effects overestimates
  the heating of the solar atmosphere.

---------------------------------------------------------
Title: Diagnostics of non-thermal processes in chromospheric
    flares. II. H alpha and CaII K line profiles of an atmosphere
    bombarded by 100 KeV-1 MeV protons.
Authors: Henoux, J. C.; Fang, C.; Gan, W. Q.
1993A&A...274..923H    Altcode:
  The effects on the Hα line profile of non-thermal excitation
  and ionization of hydrogen by a 100 KeV- 1 MeV proton beam have
  been investigated. Non-LTE Hα line profiles have been calculated
  for the temperature distributions of semi- empirical flares models
  F<SUB>1</SUB> and F<SUB>2</SUB> (Machado et al. 1980). For reasonable
  values of the beam energy flux and power index, the hydrogen lines are
  greatly strengthened. However, contrary to the case of an electron
  bombarded atmosphere, the line is not broadened, and no central
  reversal appears. These effects, alone or in conjunction with linear
  polarization measurements or Lyα red wing observations, can be used
  to diagnose proton beam bombardment.

---------------------------------------------------------
Title: Evidence for magnetic reconnection in large-scale magnetic
    structures in solar flares
Authors: Mandrini, C. H.; Rovira, M. G.; Demoulin, P.; Henoux, J. C.;
   Machado, M. E.; Wilkinson, L. K.
1993A&A...272..609M    Altcode:
  Modelling the observed vertical magnetic field of an active region (NOAA
  2372) for two consecutive days, April 7 and 8, 1980, by the potential
  field of an ensemble of magnetic dipoles, we derived the location of
  the separatrices, surfaces that separate cells of different field line
  connectivities, and of the separator which is the intersection of the
  separatrices. The overall temporal evolution of the magnetic fields
  and the location of the off-band Hα kernels of flares, that occurred
  before the obtention of the magnetograms, support the hypothesis that
  the flares were due to magnetic reconnection taking place in the main
  separator of the active region. The triggering of reconnection in
  a second separator appearing on April 8 by reconnection in the main
  separator is strongly suggested by the observed magnetic connectivities
  and the kernels locations. The location of the emerging currents on
  the separatrices support the idea that flares are fed by the release
  of magnetic free energy.

---------------------------------------------------------
Title: Electron acceleration and heating in solar flares:
    Interpretation of Hα signatures
Authors: Smith, D. F.; Henoux, J. C.
1993SoPh..143..247S    Altcode:
  Vector magnetogram, Hα, and hard X-ray observations of flares
  are reviewed which show that nonthermal electron signatures in
  Hα are never cospatial with regions of maximum current density
  for the small number of flares analyzed, but lie to the sides of
  these regions. By considering electron acceleration and transport
  requirements, four conditions are found that must be fulfilled to
  observe nonthermal electron signatures in Hα: (1) The plasma betaβ
  ≤ 0.3 in the acceleration region. (2) The energy flux of electrons
  above 20 keV is greater than 10<SUP>10</SUP> erg cm<SUP>−2</SUP>
  s<SUP>−1</SUP>. (3) The column densityN ≤ 10<SUP>20</SUP>
  cm<SUP>−2</SUP> between the electron source and the chromosphere. (4)
  The coronal pressure in the flux tube connecting to the Hα layerp
  ≤ 100 dyne cm<SUP>−2</SUP>. Condition 2 can be most easily met
  in the initial stages of flares. In contrast, the only condition for
  a high-pressure Hα signature isp ≥ 1000 dyne cm<SUP>−2</SUP>,
  which is most easily met in a region of maximum current density or
  heating and far enough into the flare for significant heating to have
  occurred. Thus, high-pressure signatures should be expected to occur
  more frequently than nonthermal electron signatures and to occur
  generally later in time.

---------------------------------------------------------
Title: Observational Evidence for Magnetic Reconnection in Solar
    Flares (Invited)
Authors: Henoux, J. C.; Demoulin, P.; Mandrini, C. H.; Rovira, M. G.
1993ASPC...46..333H    Altcode: 1993IAUCo.141..333H; 1993mvfs.conf..333H
  No abstract at ADS

---------------------------------------------------------
Title: Interpretación de las observaciones de fulguraciones solares
    en función de la topología de la región activa
Authors: Rovira, M. G.; Mandrini, C. H.; Demoulin, P.; Henoux, J. C.;
   Machado, M. E.
1993BAAA...38..114R    Altcode:
  Con el objeto de comprender el rol que juega la topología a gran escala
  durante las fulguraciones solares, realizamos un estudio detallado de la
  estructura topológica de la región activa (AR) 2776 y la comparamos
  con observaciones en Hα , UV, rayos X y radio de dos fulguraciones
  que tuvieron lugar el 5 de Noviembre de 1980. Como en casos anteriores
  el campo magnético coronal se modeló usando un conjunto de fuentes
  subfotosféricas, cuyas posiciones e intensidades se dedujeron a partir
  de un ajuste por cuadrados mínimos al campo longitudinal observado. En
  este caso, dado que el campo de AR 2776 no es potencial, se uso en
  el modelo una extrapolación libre de fuerzas lineal. La relación
  entre la posición de los cuatro abrillantamientos en Hα de distintas
  fulguraciones y la topología de regiones activas cuadrupolares ha
  sido estudiada anteriormente. En este caso la región es bipolar y
  las fulguraciones muestran una estructura de dos bandas. Estas se
  ubican sobre las separatrices cuando se tiene en cuenta el shear del
  campo, deducido de la dirección de las fibrillas observadas a nivel
  cromosférico. Este estudio esta de acuerdo con la hipótesis de que
  la energía magnética está almacenada en corrientes alineadas con
  el campo y que se libera por reconección del mismo, en la región
  del separador, antes de ser transportada a la cromosfera. También es
  posible que parte de la energía magnética se almacene y se libere
  sobre las separatrices. La ubicación de las corrientes fotosféricas,
  deducidas de los magnetogramas vectoriales, en la intersección de
  las separatrices con la fotosfera concuerda con este último punto.

---------------------------------------------------------
Title: Estabilidad de la estructura topológica de una región activa
    en presencia de fuentes de campo externas
Authors: Mandrini, C. H.; Rovira, M. G.; Demoulin, P.; Henoux, J. C.;
   de La Beaujardiere, J.
1993BAAA...38..115M    Altcode:
  A partir de las observaciones del campo magnético longitudinal
  de la región activa (AR) 6233, obtenidas en el Observatorio Mees
  (Universidad de Hawaii), derivamos su estructura topológica y
  estudiamos la evolución de la misma a lo largo de dos días. En
  el bipolo principal de esta región se desarrollaron numerosas
  fulguraciones y microfulguraciones en el período de estudio. Dado que
  en este caso contamos con magnetogramas que cubren distintas escalas
  espaciales, analizamos la influencia que las fuentes de campo externas
  a dicho bipolo tienen sobre la estructura topológica de la zona en
  donde se produjeron las fulguraciones. Esta se obtiene a partir de
  un modelo del campo de AR 6233 tanto en la aproximación potencial,
  como en la libre de fuerzas lineal. Nuestros resultados muestran
  que la estructura topológica básica de la región de interés
  permanece invariante en ambos casos. Esto justificaría el uso, debido
  a limitaciones instrumentales, de magnetogramas que cubren una porción
  limitada de la región activa al modelar el campo como se ha hecho en
  estudios anteriores.

---------------------------------------------------------
Title: First ionization potential fractionation.
Authors: Henoux, J. C.; Somov, B. V.
1992ESASP.348..325H    Altcode: 1992cscl.work..325H
  The authors briefly review the existing models for FIP
  fractionation. First they recall the main characteristics of the
  observed abundance anomalies that must be taken into account by
  FIP fractionation models. Two main models are presented. They are
  all based on ion-neutral separation in a magnetic field and differ
  fundamentally by the nature of the particles - neutrals or ions -
  that cross the lines of force under the constraint of pressure or
  electric forces. A qualitative model of FIP fractionation is described
  based on a quantitative estimate of the characteristics of DC currents
  generated into magnetic flux tubes and of their mechanical effects. FIP
  fractionation appears as a natural consequence of the circulation
  of currents in magnetic flux-tubes and it can be associated with the
  formation of the solar chromosphere.

---------------------------------------------------------
Title: Return current losses in pulse beam heating of the solar
    atmosphere
Authors: Karlicky, M.; Henoux, J. -C.
1992A&A...264..679K    Altcode:
  A 1D-hybrid code is employed to examine the influence of return
  current losses on pulse beam heating of the solar atmosphere. While
  heating of the coronal plasma by the penetrating electron beam is
  obtained as expected, strong return current losses of beam electrons
  at the resistivity jump in the transition region are also found. The
  electron beam energy is deposited at greater heights in the solar
  atmosphere than in the case of pure collisional losses. At the
  starting time of the flare, due to a strong return current heating,
  a very steep transition region is formed where upward and downward
  plasma flows are generated. The atmosphere is heated and a channel of
  hot low-resistivity plasma is formed by which the following electron
  beams can penetrate more easily to deep chromospheric levels where
  they are then thermalized.

---------------------------------------------------------
Title: Line polarization observed in chromospheric flares -
    Calculations for electron impact excitation of H-alpha
Authors: Aboudarham, J.; Berrington, K.; Callaway, J.; Feautrier,
   N.; Henoux, J. C.; Peach, G.; Saraph, H. E.
1992A&A...262..302A    Altcode:
  The observation of chromospheric flares accompanying coronal
  flares in the sun indicates fast energy transfer between the two
  layers. Polarization observed in the H-alpha and S I lines can help
  to explain the nature of this energy transfer if accurate atomic data
  for the line polarization is available. Calculations for H-alpha line
  polarization by low-energy electron impact are presented, using the most
  sophisticated collision data available to date. The theoretical results
  compare well with polarization measurements dating from 1968. Low-energy
  electrons with anisotropic velocity distributions could be present in
  solar flares. They could be associated either with proton bombardment
  or with the existence of large temperature gradients. Assuming that
  the polarization of H-alpha observed in chromospheric flares is due
  only to electron impact, the ratio of the two even moments J2 and J0
  of the electron velocity distribution is inferred. Further, under the
  hypothesis that the anisotropy is due to a high temperature gradient,
  a velocity distribution function for electrons carrying a conductive
  heat flux is linked to the observed polarization.

---------------------------------------------------------
Title: Development of a Topological Model for Solar Flares
Authors: Demoulin, P.; Henoux, J. C.; Mandrini, C. H.
1992SoPh..139..105D    Altcode:
  The main theoretical studies of the process involved in solar flares
  have been made in the two-dimensional approximation. However, the
  preliminary studies made with three field components suggest that
  reconnection could take place in the separatrices, the separator
  (intersection of separatrices) being a privileged location for this
  process. As a consequence the sites of flare kernels must be located on
  the intersections of the separatrices with the photosphere. Therefore,
  in order to understand the role of interacting large-scale structures
  in solar flares, we have analysed the topology of three-dimensional
  potential and linear force-free fields. The magnetic field has been
  modelled by a distribution of charges or dipoles located below the
  photosphere. This modelling permits us to define the field connectivity
  by the charges or the dipoles at both ends of every field line.

---------------------------------------------------------
Title: Reconección magnética entre estructuras a gran escala
    durante fulguraciones solares
Authors: Mandrini, C. H.; Rovira, M. G.; Demoulin, P.; Henoux, J. C.;
   Machado, M. E.
1992BAAA...37..112M    Altcode:
  A partir del modelado del campo magnético de la región activa
  NOAA 2372 se determina la ubicación de sus distintas estructuras
  topológicas: separatrices y separador. Este análisis se hace
  en base a observaciones del campo magnético a lo largo de tres
  días. La evolución temporal del campo global y la ubicación de los
  abrillantamientos en H a de varias fulguraciones, en relación con
  la topología determinada, están de acuerdo con el hecho de que las
  fulguraciones son el resultado del proceso de reconección que tiene
  lugar en el separador principal de la región activa.

---------------------------------------------------------
Title: The solar X-ray/cosmic gamma-ray burst experiment aboard
    ULYSSES
Authors: Hurley, K.; Sommer, M.; Atteia, J. -L.; Boer, M.; Cline,
   T.; Cotin, F.; Henoux, J. -C.; Kane, S.; Lowes, P.; Niel, M.
1992A&AS...92..401H    Altcode:
  The scientific objectives of the Ulysses solar X-ray/cosmic gamma-ray
  burst experiment, and the unique features of the Ulysses mission which
  will help to achieve them are described. After a discussion of the
  special design constraints imposed by the mission, the sensor systems,
  consisting of two CsI scintillators and two Si surface barrier detectors
  covering the energy range 5-150 keV are described. Their operating
  modes and inflight performance are also given.

---------------------------------------------------------
Title: White-Light Flares
Authors: Henoux, J. C.; Aboudarham, J.
1992LNP...399..118H    Altcode: 1992esf..coll..118H; 1992IAUCo.133..118H
  The observed good temporal correlation between white-light flares
  and hard X-ray bursts suggests that energetic electrons could be the
  cause of white-light flare emission. However, even if sufficient energy
  can be deposited in the chromosphere by electron bombardment, direct
  collisional heating of the photosphere requires too high a flux of
  electrons of a few hundred keV and does not appear plausible. We show
  that nonthermal effects increase the opacity of the upper photosphere
  and temperature minimum region. Then these regions are consequently
  radiatively heated both by the beam-produced flare chromospheric
  emission and by the quiet photospheric emission. As a consequence,
  a temporary decrease of the continuum intensity ( negative flare ) is
  expected. After less than 20 seconds, the radiative heating of the upper
  photosphere and temperature minimum region produces a white-light flare.

---------------------------------------------------------
Title: Interaction of Largescale Magnetic Structures in Solar Flares
Authors: Mandrini, C. H.; Demoulin, P.; Henoux, J. C.
1992LNP...399...54M    Altcode: 1992IAUCo.133...54M; 1992esf..coll...54M
  Modelling the observed vertical magnetic field of active region (AR)
  NOAA 2372 by the potential field of an ensemble of magnetic dipoles,
  we have derived the likely location of the separatrices, surfaces
  that separate cells of different field line connectivities, and of
  the separator which is the intersection of the separatrices. The
  connectivity of every magnetic field line, which is defined by the
  dipoles located at its ends, is computed by a code that, starting
  from any pixel in the photospheric plane, integrates numerically the
  differential equation defining a line of force towards both ends of
  this line until one dipole is reached. This code allows us to obtain the
  topology of the field in three dimensions. We have compared our results
  with observations of a 1B/M1 flare that developed in AR 2372 on April
  6, 1980 at 20:53 UT (Lin and Gaizauskas, 1987), twenty minutes before
  obtaining the magnetogram. We found that four of the five off-band Ha
  kernels were located near or at the separatrices. These Ha kernels
  are connected by field lines that pass close to the separator. This
  indicates that the flare may have resulted from the interaction of
  large scale magnetic structures in the separator region. Moreover, Lin
  and Gaizauskas (1987) showed that the Ha flare kernels coincided with
  the peak values of the longitudinal electric current density. This
  finding and the fact that no strong current and no Ha kernel are
  observed at the intersection of the separator with the photosphere,
  lead to the conclusion that the magnetic energy released during the
  flare is mostly stored in an ensemble of currents flowing along lines of
  force. Some instability, presumably due to reconnection taking place
  in the separator, is likely to be the origin of the energy release
  and of the observed flare.

---------------------------------------------------------
Title: Evidence for the interaction of large scale magnetic structures
    in solar flares.
Authors: Mandrini, C. H.; Demoulin, P.; Henoux, J. C.; Machado, M. E.
1991A&A...250..541M    Altcode:
  By modeling the observed vertical magnetic field of an active region
  AR 2372 by the potential field of an ensemble of magnetic dipoles, the
  likely location of the separatrices, surfaces that separates cells of
  different field line connectivities, and of the separator which is the
  intersection of the separatrices, is derived. Four of the five off-band
  H-alpha kernels of a flare that occurred less than 20 minutes before
  obtaining the magnetogram are shown to have taken place near or at
  the separatrices. These H-alpha kernels are connected by field lines
  that pass near the separator. This indicates that the flare may have
  resulted from the interaction in the separator region of large scale
  magnetic structures.

---------------------------------------------------------
Title: Conditions for flare and filament formation in interacting
    solar active regions
Authors: Schmieder, B.; Henoux, J. -C.; van Driel-Gesztelyi, L.;
   Simnett, G. M.
1991A&A...244..533S    Altcode:
  The evolution of two interacting sunspot groups of different ages is
  traced over a period of three days. The photospheric velocity field is
  obtained and compared with the general evolution of the region in an
  attempt to better understand the conditions that lead to flare activity
  and filament formation. It is shown that the observed photospheric
  motions can generate dc electric currents, which, in effect, could
  lead to energy storage.

---------------------------------------------------------
Title: Solar Flare X-Ray Observations with Ulysses
Authors: Kane, S. R.; Hurley, K.; Cotin, F.; Niel, M.; Vedrenne, G.;
   Henoux, J. C.; Sommer, M.
1991BAAS...23.1042K    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Flares and filament formation due to the interaction between
    two active regions
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Hénoux, J. C.;
   Simnett, G.
1991AdSpR..11e..95S    Altcode: 1991AdSpR..11...95S
  We follow the evolution (flare activity, filament formation) of two
  interacting active regions of different ages over three days, through
  observations at white-light, Hα, UV, and X-ray wavelengths. We show
  that the observed photospheric motions could generate DC electric
  currents and that they could lead to free energy storage. Flares
  were observed more-or-less simultaneously in remote locations of the
  sunspot group. This suggests that the same perturbation affected an
  ensemble of lines of force. Filament formation took place due to DC
  current generation by photospheric shearing motions with a velocity
  up to 350 m s<SUP>-1</SUP>.

---------------------------------------------------------
Title: Observation and interpretation of Hα polarization in solar
    flares.
Authors: Hénoux, J. C.
1991sopo.work..285H    Altcode:
  Impact linear polarization of the Hα chromospheric line has been
  observed in some flares and reported (Hénoux et al., 1990). A new
  observation made on July 17th 1982 is presented. The characteristics
  of the 10 minutes time integrated polarization are similar to the
  characteristics of the polarization observed in other flares, i.e. the
  main direction of the polarization is close to the radial direction
  and the polarization degree reaches 5%. However, in a few locations,
  an higher polarization fraction as high as 15% is observed in the one
  minute time integrated data. The observational method is described
  and the origin of the observed polarization is discussed.

---------------------------------------------------------
Title: Chromosphere Generation in Magnetic Flux-Tubes (With 1 Figure)
Authors: Hénoux, J. C.; Somov, B. V.
1991mcch.conf..567H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The energy budget in active regions and flares
Authors: Henoux, J. C.
1991AdSpR..11e...7H    Altcode: 1991AdSpR..11....7H
  Information on the energetic balance in active regions derived from
  space observations is reviewed. It suggests both a global balance
  with some lag between sunspot darkening and plage brightening and
  the existence of a solar-cycle modulation. Some recent models are
  quoted. Recent works on the role of the global magnetic field topology
  and on flare energy storage are briefly discussed. The role of large
  scale structures is emphasized. Progress on the understanding of the
  energy transport mechanisms in solar flares is reviewed. It includes
  new observational indications of the existence of low energy protons
  and confirmation of the significance of the coupling between modes
  to the transport of energy. The role of the radiative transport
  mechanism is underlined. Observations support for the model of
  chromospheric evaporation derived from multiwavelength observations
  is presented. Other possible interpretations are briefly discussed.

---------------------------------------------------------
Title: The photospheric dynamo. I - Magnetic flux-tube generation
Authors: Henoux, J. C.; Somov, B. V.
1991A&A...241..613H    Altcode:
  Velocities of electrons, ions and neutrals are computed, in the
  three-fluid approximation, for an axisymmetrical magnetic field. By
  prescribing a radial dependence of the velocity of neutrals, in
  agreement with a downflow, the radial dependence of the magnetic field
  energy density is derived. This gives the radial flux of neutrals
  that is required to increase the magnetic field from 0.01 G to 1000 G
  inside thin magnetic flux tubes in the photosphere. The hypothesis of
  local cooling by advection of ionization energy of Schatten and Mayr
  (1985) is tested, and it is seen that this flux of neutrals is high
  enough to affect significantly the energy balance in the tube and
  to maintain the pressure gradient necessary to produce the radial
  inflow of neutrals. In agreement with recent infrared observations,
  the inside of the flux-tube is predicted to be cooler than the outside.

---------------------------------------------------------
Title: Effect of Electron Beams during Solar Flares
Authors: Aboudarham, J.; Henoux, J. C.; Brown, J. C.; van den Oord,
   G. H. J.; van Driel-Gesztelyi, L.; Gerlei, O.
1990SoPh..130..243A    Altcode:
  Electron bombardment of the solar atmosphere has two effects: one is
  to enhance hydrogen recombination emission, the other is to increase
  the opacity via an increase of H<SUP>−</SUP> population. The first
  effect is the most important in the upper part of the atmosphere and
  the second in the lower part. We predict that, when enhanced absorption
  dominates in the part of the atmosphere where radiation originates,
  there will be a decrease in the white-light emission, leading to a
  `negative flare', or what we call a `Black-Light Flare'. This phenomenon
  occurs only for a short duration, not more than ∼ 20 s. `Black-Light
  Flares' have already been observed in the case of flare stars and we
  suggest here that they could also be present on the Sun, just prior
  to a White-Light Flare.

---------------------------------------------------------
Title: Coronal Proton Transport in the Presence of Alfven Waves and
    Implications for Impact Line Linear Polarization
Authors: Smith, Dean F.; Chambe, G.; Henoux, J. C.; Tamres, D.
1990ApJ...358..674S    Altcode:
  The transport of fast (about 1 MeV) protons in the corona is considered
  when their density and ansiotropy are sufficiently large to excite
  Alfven waves. The Alfven waves scatter the protons and make them
  almost isotropic. The Alfven wave instability remains in a marginally
  stable state in which the proton anisotropy is just large enough
  to excite Alfven waves to a level which would eliminate any greater
  anisotropy. The protons propagate diffusively down a coronal loop and
  have a path length of order 100 times their length in the absence of
  Alfven waves. This increases their Coulomb losses, and much higher
  energy protons (2-20 MeV) are required initially to produce H-alpha
  impact line linear polarization in the chromosphere as compared to the
  case in the absence of Alfven waves (about 200 keV) for loop lengths
  about 10 to the 9th cm. The interpretation of the observed polarization
  becomes less direct because it depends on more poorly known parameters
  than in the case of the absence of Alfven waves.

---------------------------------------------------------
Title: Black and white flares?
Authors: Henoux, J. -C.; Aboudarham, J.; Brown, J. C.; van den Oord,
   G. H. J.; van Driel-Gesztelyi, L.
1990A&A...233..577H    Altcode:
  It is shown that the nonthermal ionization of a solar flare atmosphere
  by beam bombardment can result, in the initial stages of a flare, in
  dimunitions in the continuum solar flare brightness (termed 'black
  light flares'). The most favorable conditions for observing this
  diagnostic phenomenon are investigated in terms of flare location and
  wavelength. In terms of bombarding beam parameters, electron beams
  of large peak flux are shown to be the most favorable as are target
  atmospheres with minimal preheating.

---------------------------------------------------------
Title: Hα impact polarization observed in solar flares as a
    diagnostic of energy transport mechanisms.
Authors: Henoux, J. C.; Chambe, G.
1990JQSRT..44..193H    Altcode:
  Various mechanisms of energy transport and energy release in
  solar flares create a population of energetic particles with an
  anisotropic velocity distribution function. By collisional excitation,
  these particles may produce linearly polarized line emission. The
  characteristics of the impact polarization associated with diverse
  mechanisms of energy transport are reviewed. Observations of linear
  polarization at some locations of Hα filtergrams, taken at the
  time of three solar flares, are reported. The polarized electric
  vector is directed in the flare-to-disk-center direction. This
  polarization indicates that energetic particles with anisotropic
  velocity distributions are present in the high chromosphere during
  solar flares. They could be either deca-eV electrons coming from the
  transition zone or produced in local acceleration in weak double-layers
  or deca-keV protons accelerated in the corona.

---------------------------------------------------------
Title: Impact Line Linear Polarization as a Diagnostic of 100 keV
    Proton Acceleration in Solar Flares
Authors: Henoux, J. C.; Chambe, G.; Smith, D.; Tamres, D.; Feautrier,
   N.; Rovira, M.; Sahal-Brechot, S.
1990ApJS...73..303H    Altcode:
  The use of impact linear polarization of chromospheric lines as a
  diagnostic of 100 keV protons is proposed. Observations of hard X-ray
  emission are examined, noting the possibility that 100 keV proton
  beams bombarding the atmosphere could create a hot thermal plasma at
  the origin of X-ray emission. The application of impact linear line
  polarization as a diagnostic of the existence of energetic particles
  with anisotropic velocity distribution functions is described. The
  mechanisms leading to an anisotropic proton distribution in the solar
  chromosphere are discussed and the required initial energy and energy
  flux for accelerated protons in the corona are derived. It is suggested
  that it is possible to infer the original proton anisotropy in the
  corona and the effect of this anisotropy on the proton energy and
  proton energy flux required to reach the H-alpha-forming layers.

---------------------------------------------------------
Title: Generation of Magnetic Fields and Electric Currents in the
    Solar Photosphere
Authors: Henoux, J. C.; Somov, B. V.
1990IAUS..138..273H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Negative Flares on the Sun
Authors: van Driel-Gesztelyi, L.; Brown, J. C.; Hénoux, J. -C.;
   Aboudarham, J.; van den Oord, G. H. J.; Gerlei, O.; Fárnik, F.
1990PDHO....7..202V    Altcode: 1990dysu.conf..202V; 1990ESPM....6..202V
  The authors showed that under certain conditions at the beginning
  of a solar white-light flare (WLF) event an electron beam can cause
  a transient darkening before the WLF emission starts. They propose
  optimal conditions for possible observation of solar negative flares and
  present an observation, which may be the first identified observation
  of such events.

---------------------------------------------------------
Title: Electrodynamic conversion of energy: Magnetic field
    amplification in the solar photosphere
Authors: Henoux, J. C.; Somov, B. V.
1990AdSpR..10i.179H    Altcode: 1990AdSpR..10R.179H
  Velocities of electrons, ions and neutrals are computed, in the
  three-fluid approximation, for an axisymmetrical magnetic field. By
  prescribing a radial dependence of the velocity of neutrals, in
  agreement whith a downflow, the radial dependence of the magnetic
  field energy density is derived. This gives the radial flux of neutrals
  that is required to increase, in the photosphere, the magnetic field
  from 5 Gauss to 1000 Gauss. We test the hypothesis of local cooling
  by advection of ionization energy of Schatten and Mayr/1/, and find
  that this flux of neutrals is high enough to affect significantly
  the energy balance in the tube and to maintain the pressure gradient
  necessary to produce the radial inflow of neutrals. The product of
  the tube radius by the radial velocity V<SUB>r,n</SUB>r being, in the
  photosphere (τ<SUB>5000</SUB> = 1), lower than a few 10<SUP>5</SUP>
  m.<SUP>2</SUP> s.<SUP>-1</SUP>, the associated velocity would presumably
  not exceed a few meters per second. This supports the idea of creation
  of strong fields by enhancement of a preexisting magnetic field in
  the photosphere, i.e. superficial creation of magnetic fluxtubes.

---------------------------------------------------------
Title: The Solar X-Ray/Cosmic Gamma-Ray Burst Experiment Aboard the
    Ulysses Mission
Authors: Hurley, K.; Sommer, M.; Paschmann, G.; Boer, M.; de Jager,
   C.; Heise, J.; van Rooijen, J.; Niel, M.; Vedrenne, G.; Cline, T.;
   Henoux, J. -C.
1990ICRC....5...74H    Altcode: 1990ICRC...21e..74H; 1989ICRC....5...74H
  No abstract at ADS

---------------------------------------------------------
Title: Electron Beam as Origin of White-Light Solar Flares
Authors: Aboudarham, J.; Henoux, J. C.
1989SoPh..121...19A    Altcode: 1989IAUCo.104...19A
  We study the effect of chromospheric bombardment by an electron
  beam during solar flares. Using a semi-empirical flare model, we
  investigate energy balance at temperature minimum level and in the
  upper photosphere. We show that non-thermal hydrogen ionization (i.e.,
  due to the electrons of the beam) leads to an increase of chromospheric
  hydrogen continuum emission, H<SUP>−</SUP> population, and absorption
  of photospheric and chromospheric continuum radiation. So, the upper
  photosphere is radiatively heated by chromospheric continuum radiation
  produced by the beam. The effect of hydrogen ionization is an enhanced
  white-light emission both at chromospheric and photospheric level, due
  to Paschen and H<SUP>−</SUP> continua emission, respectively. We then
  obtain white-light contrasts compatible with observations, obviously
  showing the link between white-light flares and atmospheric bombardment
  by electron beams.

---------------------------------------------------------
Title: Flare Energy Release and Deposition
Authors: Holman, G.; Benka, S.; de La Beaujardiere, J.; Dulk, G.;
   Gabriel, A.; Henoux, J. C.; Hiei, E.; Kane, S.; Klein, L.; Kuin, P.;
   Larosa, T.; MacKinnon, A.; McClements, K.; Moses, D.; Ramaty, R.;
   Tromans, N.; Vilmer, N.
1989tnti.conf....3H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The Global Energy Balance in Flares
Authors: Simnett, G. M.; Linford, G. A.; Metcalf, T. R.; Henoux,
   J. C.; Spicer, D. S.
1989tnti.conf....4S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Spectroscopie des éruptions solaires: éruptions en noir
    et blanc.
Authors: Henoux, J. -C.; Aboudarham, J.
1989JAF....34Q...8H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Spectroscopy of solar flares: black and white flares.
Authors: Henoux, J. -C.; Aboudarham, J.
1989musi.work...89H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Generation and structure of the electric currents in a flaring
    activity complex
Authors: Henoux, J. C.; Somov, B. V.
1987A&A...185..306H    Altcode:
  Assuming the existence of organized photospheric velocity fields in an
  active region, the creation of photospheric and coronal dc currents
  by vortex and radial motions is studied. Vortex motions leading to
  opposite temporal evolutions of the magnetic flux in old and new
  centers of activity create two systems of coronal currents flowing
  along the lines of force that, in the active region complex, connect
  the old center of activity to the new. The magnetic energy stored in
  these currents is higher than the energy of the largest flares. The
  effect of radial photospheric motions is also discussed. Two systems
  of coronal currents can be distinguished. They are located inside
  two different magnetic cells, and interact along the separator which
  is the intersection of the magnetic line surfaces that separate the
  magnetic cells produced by the photospheric magnetic sources. Due
  to source motions and electric current evolution, the separator may
  be the location of reconnection of the magnetic field. The separator
  being perpendicular to the two current systems, this reconnection may
  affect the magnetic field lines of a significant fraction of the loop
  current systems, interrupting the currents and quickly releasing the
  stored magnetic energy.

---------------------------------------------------------
Title: Non-thermal excitation and ionization of hydrogen in solar
    flares. II - Effects on the temperature minimum region Energy balance
    and white light flares
Authors: Aboudarham, J.; Henoux, J. C.
1987A&A...174..270A    Altcode:
  This paper is the second of a series of two papers on the effects on the
  non-thermal excitation and ionization of hydrogen by electron beams on
  the solar atmosphere. Here the modification of the energy balance at the
  temperature minimum level and in the upper photosphere is studied. The
  authors show that enhanced hydrogen ionization at the base of the
  chromosphere and at the flare temperature minimum region leads to an
  increase of the H<SUP>-</SUP> population and to enhanced absorption
  of photospheric and chromospheric continuum radiation. Consequently
  the upper photosphere is radiatively heated at the expense of the
  chromospheric continuum radiation produced by the beam. A second
  consequence of the hydrogen ionization is the increase of the white
  light emission both at chromospheric and photospheric levels.

---------------------------------------------------------
Title: REVIEW ARTICLE: Galactic ultraviolet astronomy
Authors: Vidal-Madjar, A.; Encrenaz, T.; Ferlet, R.; Henoux, J. C.;
   Lallement, R.; Vauclair, G.
1987RPPh...50...65V    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Dynamo Theories of Solar Flares
Authors: Henoux, J. C.
1987sman.work..109H    Altcode:
  In flare models based on magnetic field reconnection, the energy is
  liberated in a very thin layer. This makes difficult an explanation
  of the high rate of energy release observed in solar flares. The
  limitation of these models is briefly discussed. Flare models
  based on the disruption of current flowing from the photosphere
  to the corona have been proposed. Direct currents can be generated
  by organized motions of the neutral photospheric plasma across the
  magnetic field. Observations of organized photospheric velocities are
  reviewed, and the main characteristics of the electric current system
  are presented.

---------------------------------------------------------
Title: Sunspots rotation and electric currents in a flaring activity
    complex.
Authors: Henoux, J. C.; Somov, B. V.
1987PAICz..66..153H    Altcode: 1987eram....1..153H
  Assuming the existence of organised photospheric velocity fields in
  an active region, the authors study the creation of photospheric and
  coronal D.C. currents by vortex motions.

---------------------------------------------------------
Title: Non-thermal excitation and ionization of hydrogen in solar
    flares. I. Effects on a flaring chromosphere.
Authors: Aboudarham, J.; Henoux, J. C.
1986A&A...168..301A    Altcode:
  By using a semiempirical flare model and assuming that the observed
  heating is produced by electron bombardment, a computation is made
  of the energy flux above 20 keV that is required in the beam to
  compensate for radiative losses. It is then shown that nonthermal
  processes strongly increase the radiative losses in the middle
  chromosphere. As a consequence, the temperature increase of existing
  semiempirical flare models is shown to be overestimated in the low
  chromosphere. The inclusion of nonthermal processes reduces but does
  not eliminate the difference between energy gains and losses in the
  middle chromosphere.Consequently, existing empirical models are not
  in a static energy balance.

---------------------------------------------------------
Title: Energy deposit at temperature minimum level and white light
    flares
Authors: Aboudarham, J.; Henoux, J. C.
1986A&A...156...73A    Altcode:
  Empirical atmospheric models are used to estimate the energy deposit
  required to heat the temperature minimum region of the quiet sun to
  flare temperature. The calculations show that the necessary energy
  deposit in the temperature minimum region can be accounted for by
  electron bombardment. Electron beam heating of the temperature minimum
  and chromospheric regions produces white light emission with an energy
  output of about 5×10<SUP>9</SUP>erg cm<SUP>-2</SUP>s<SUP>-1</SUP>. Also
  the upper photosphere is heated to about 30° above its quiet sun value
  by the downward radiation field. All layers from the chromosphere to
  the photosphere contribute to the white light emission process. The
  emission mechanisms are H<SUP>-</SUP> and hydrogen bound-free
  emission. The authors conclude, that no in-situ energy release is
  necessary to explain the heating of the temperature minimum region. An
  electron bombardment can increase the temperature of this region,
  and subsequently of the photosphere via radiative back heating, hence
  producing a white light flare.

---------------------------------------------------------
Title: White light flares and atmospheric modeling (Working Group
    report).
Authors: Machado, M. E.; Avrett, E. H.; Falciani, R.; Fang, C.;
   Gesztelyi, L.; Henoux, J. -C.; Hiei, E.; Neidig, D. F.; Rust, D. M.;
   Sotirovski, P.; Svestka, Z.; Zirin, H.
1986lasf.conf..483M    Altcode:
  The authors give a short summary of their discussions, and a set
  of recommendations which may help in the study of white light flare
  emission processes.

---------------------------------------------------------
Title: Non-thermal collisional excitation and ionization by electron
beams: Effect on the atmospheric energy balance and white-light
    emission in solar flares
Authors: Aboudarham, J.; Henoux, J. C.
1986AdSpR...6f.131A    Altcode: 1986AdSpR...6..131A
  In the middle chromosphere and below, at the time of atmospheric
  heating by electron bombardment, the electrons of a beam lose most of
  their energy in inelastic collisions with neutral hydrogen. Then the
  hydrogen non-thermal excitation and ionization can be more important
  that the thermal one and can lead to a significant increase of the
  electron number density. In the chromosphere the enhancement of the
  hydrogen ionization leads to an increase of the hydrogen continuum
  emission. In the temperature minimum region (TMR) the enhancement of
  the electron number density produces an increase of the H<SUP>-</SUP>
  population. Then the absorption by H<SUP>-</SUP> of both photospheric
  radiation and chromospheric emission produced by the beam increases
  the temperature of the TMR and upper photosphere. Both effects lead
  to a White-Light Flare with a minimum contrast of 5% at disk center
  at 600 nm.

---------------------------------------------------------
Title: White light flares: heating of the temperature minimum region
    by electron beams.
Authors: Aboudarham, Jean; Henoux, Jean-Claude
1986lasf.conf..205A    Altcode: 1986lasf.symp..205A
  Empirical atmospheric models are used to estimate the energy deposit
  required to heat the temperature minimum region of the quiet sun to
  flare temperature.

---------------------------------------------------------
Title: Energy Release and Energy Transport Below the Transition Zone
    in Solar Flares
Authors: Hénoux, J. C.; Chambe, G.; Heristchi, D.; Semel, M.;
   Woodgate, B.; Shine, R.; Beckers, J.
1985spit.conf..758H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Study of energy release in flares
Authors: Henoux, J. -C.
1984AdSpR...4g.227H    Altcode: 1984AdSpR...4..227H
  Recent advances in the study of energy release in Flares are
  reviewed. Progress has been made in modelling coronal X-ray emission
  and the chromospheric response to energy imput. These advances are
  based on theoretical studies and on the comparison of complementary data
  obtained from spacecraft and ground-based observatories. We first review
  the modelling of the coronal flare derived from radio, X-ray and XUV
  observations. Then we summarize results on the chromospheric response
  to various energy imput. Observations of X-ray continuum intensity
  and polarization, transition zone lines and chromospheric lines do not
  show evidence of particle trapping by a turbulent front. Although they
  might be in agreement with trapping and partial precipitation. White
  light flares appear to result from energy deposited above the
  photosphere. They are probably due to electron bombardment. The
  implication of these results on the primary energy release process
  are discussed and prospects for new research are presented.

---------------------------------------------------------
Title: Magnetic Energy Storage and Release in Solar Flares
Authors: Henoux, J. C.
1984apoa.conf..200H    Altcode:
  Accepting the concept of the magnetic origin of solar flares the
  mechanisms leading to the release of magnetic energy are reviewed.

---------------------------------------------------------
Title: Conductive Heat Flux in the Chromosphere Derived from Line
    Linear Polarization Observation
Authors: Henoux, J. -C.; Chambe, G.; Heristchi, D.; Semel, M.;
   Woodgate, B.; Shine, D.; Beckers, J.
1983SoPh...86..115H    Altcode:
  Linear polarization in two chromospheric lines (Hα and SI 1437 A) was
  observed in the gradual phase of solar flares. The polarized electric
  vector is directed towards disk center.

---------------------------------------------------------
Title: Conductive flux in flaring solar chromospheres deduced from
    the linear polarization observations
Authors: Henoux, J. C.; Heristchi, D.; Chambe, G.; Woodgate, B.;
   Shine, R.; Beckers, J.; Machado, M.
1983A&A...119..233H    Altcode:
  The linear polarization of Hα and S I 1437 Å lines produced in
  impact excitation by energetic electrons with an anisotropic velocity
  distribution function during solar flares is calculated. Selecting
  a function which represents the velocity distribution of electrons
  carrying heat flux, the relationship between conductive heat flux and
  linear line polarization has been computed. <P />The application of the
  relationship between linear polarization and heat flux to the observed
  degree of polarization leads to the determination of the conductive
  heat flux at the top of flaring chromospheric layers. This conductive
  flux is of the order of magnitude of the total radiation loss in the
  chromosphere and below, which is also of the order of magnitude of
  the conductive flux in the transition zone.

---------------------------------------------------------
Title: Self-consistent models of flare heated solar chromospheres
Authors: Fang, C.; Henoux, J. C.
1983A&A...118..139F    Altcode:
  For the first time self consistent models of an X-ray irradiated
  flaring chromosphere have been derived, together with a model of
  an electron heated chromosphere. The atmospheric radiation losses
  have been computed by including Lα, Lβ, LyC, Hα, Mg II and Ca
  II and H<SUP>-</SUP> emission. The hydrogen radiation losses were
  computed using complete linearization of the transfer, energy balance
  and hydrostatic equilibrium equations coupled with the statistical
  equilibrium equations. This method permits a substantial increase in
  the accuracy of the radiation loss estimate without requiring excessive
  computing time.

---------------------------------------------------------
Title: Impact linear polarization observed in a UV chromospheric
    line during a solar flare
Authors: Henoux, J. C.; Chambe, G.; Sahal, S.; Semel, M.; Woodgate,
   B.; Shine, D.; Beckers, J.; Machado, M.
1983ApJ...265.1066H    Altcode:
  Linear polarization was observed in the S 11437 A line in bright
  flaring points during the soft X-ray emission from a flare on 1980
  July 15. The degree of polarization is about 25% and is detected at a
  signal-to-noise ratio of 2.9. The polarized electric vector is directed
  toward disk center to within 3°. <P />This polarization could be due
  to collisional excitation of S I by energetic electrons beamed in the
  vertical direction. Direct excitation by a highly energetic beam of
  electrons of order 10-100 keV is doubtful. We suggest that the heat flux
  in the region connecting the transition zone to the high chromosphere
  during the gradual phase of a flare could lead to an anisotropic
  excitation. Then the observed polarization would be due to vertical
  motions of the transition zone sweeping the preexisting chromosphere.

---------------------------------------------------------
Title: The ISPM solar flare X-ray and cosmic gamma-ray burst
    experiment.
Authors: Cotin, F.; de Jager, C.; Henoux, J. -C.; Heise, J.; Hilhorst,
   M.; Hurley, K.; Niel, M.; Paschmann, G.; Sommer, M.; van Rooijen,
   J.; Vedrenne, G.
1983ESASP1050..209C    Altcode:
  The ISPM solar flare X-ray and cosmic gamma-ray burst instrument
  (designated the HUS experiment) consists of a pair of Cs I scintillators
  and a pair of Si surface barrier detectors for measuring X-rays in
  the ranges 15 - 150 and 5 - 15 keV, respectively. High-time-resolution
  X-ray measurements (up to 8 ms) will be used to study X- and gamma-ray
  bursts of solar and cosmic origin.

---------------------------------------------------------
Title: Chromospheric effects of XUV radiation emitted during solar
    flares
Authors: Machado, M. E.; Henoux, J. -C.
1982A&A...108...61M    Altcode:
  X and UV radiation emitted from the flare corona and transition zone
  are shown to affect both the energy balance and ionization balance
  of chromosphere layers. The effect of X-rays is most important in
  producing temperature increases through the chromosphere, while it
  does not affect in a substantial way the overall ionization balance of
  abundant elements, with the exception of He I and, possibly, O I. UV
  lines radiation, on the other hand, produces strong variations in the
  ionization balance of some elements, in particular C I and Si I, and
  induce non LTE effects which modify the emergent spectra. Variations
  in the Si I continuum intensities at wavelengths under 1682 A are shown
  to be strongly decoupled from local variations in the Planck function,
  and cannot be used to derive temperature changes at the temperature
  minimum level.

---------------------------------------------------------
Title: Impact linear polarization observed in a UV chromospheric
    line during a solar flare
Authors: Henoux, J. C.; Chambe, G.; Semel, M.; Woodgate, B.; Shine,
   R.; Beckers, J.
1982AdSpR...2k.155H    Altcode: 1982AdSpR...2..155H
  Linear polarization was observed in the S I 1437Å line in bright
  flaring points during the soft X-ray emission. The degree of
  polarization is about 25% and is detected at a signal to noise ratio
  of 2.9. The polarized electric vector is directed towards disk center
  to within 3°. <P />This polarization could be due to collisional
  excitationm of S I by energetic electrons beamed in the vertical
  direction. We suggest that the heat flux in the region interconnecting
  the transition zone to the high chromosphere during the gradual phase
  of a flare could lead to an anisotropic excitation. Then the observed
  polarization would be due to vertical motions of the transition zone
  sweeping the preexisting chromosphere.

---------------------------------------------------------
Title: Horizontal distribution of the X-ray energy deposit in the
    chromosphere and H alpha two ribbon flares
Authors: Henoux, J. C.; Rust, D.
1980A&A....91..322H    Altcode:
  The two-ribbon Hα brightening and the X-ray emitting coronal loop
  arcade during the very late phase of the 29 July 1973 flare are
  examined. By means of a simple geometrical model of the X-ray emitting
  structures, the horizontal distribution of X-radiation is computed
  for several different levels in the chromosphere. It is found that an
  arcade of X-ray emitting loops, commonly found over large two-ribbon
  flares, gives an energy deposit pattern in the chromosphere similar
  in shape to the Hα flare emission. Isophotes of the Hα brightening
  are compared to the X-ray energy deposit horizontal variation profiles
  from a single loop and from an arcade of loops. The brightest 29 July
  isophotes fit midway between the X-ray profiles associated respectively
  with a loop and an arcade. The maximum X-ray energy deposit rate of 1.5
  10<SUP>6</SUP> ergs cm<SUP>-2</SUP> s<SUP>-1</SUP> is slightly higher
  than the peak Hα emission rate. It is concluded that X-ray radiation
  is an important source of energy for Hz flares. There seems to be no
  need for in- situ energy release in the chromosphere.

---------------------------------------------------------
Title: The chromosphere and transition region
Authors: Canfield, R. C.; Brown, J. C.; Craig, I. J. D.; Brueckner,
   G. E.; Cook, J. W.; Doschek, G. A.; Emslie, A. G.; Machado, M. E.;
   Henoux, J. -C.; Lites, B. W.
1980sfsl.work..231C    Altcode: 1980sofl.symp..231C
  The physical processes occurring as a result of the transfer of
  energy and momentum from the primary solar flare energy release site
  in the corona to the underlying chromosphere and transition region
  during the course of the flare are investigated through a comparison
  of theoretical models and observational data. Static, dynamic and
  hydrodynamic models of the lower-temperature chromospheric flare are
  reviewed. The roles of thermal conduction, radiation, fast particles
  and mass motion in chromosphere-corona interactions are analyzed on
  the basis of Skylab UV, EUV and X-ray data, and empirical and synthetic
  models of the chromospheric and upper photospheric responses to flares
  are developed. The canonical model of chromospheric heating during
  flares as a result of primary energy release elsewhere is found to be
  justified in the chromosphere as a whole, although not entirely as the
  temperature minimum, and a simplified model of horizontal chromospheric
  flare structure based on results obtained is presented.

---------------------------------------------------------
Title: Energy Release and Energy Transfer in Flares
Authors: Henoux, J. C.
1980jfss.conf..210H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Japan-France Seminar on Solar Physics
Authors: Moriyama, F.; Henoux, J. C.
1980jfss.conf.....M    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Direct excitation of hydrogen by photoelectron and accelerated
    electron collisions in solar chromospheric flares - Effects on the
    profile and polarization of LY alpha
Authors: Chambe, G.; Henoux, J. -C.
1979A&A....80..123C    Altcode:
  Summary. The rate of direct collisional excitation of Ly by
  (superthermal) photoelectrons is compared to the thermal rates. These
  photoelectrons are produced via ionization of chromospheric material
  (mainly helium) by XUV radiation from the overlying flare source. We
  found that for intense XUV flares, with area not larger than 1018 cm2,
  there exists a layer in the atmosphere where direct excitation effects
  are significant, which leads to enhanced emerging intensity in the
  Ly wings (for A V &gt;3.5 A VD). These results were established by
  using a-priori given models for hydrogen and thermal electrons in
  flares, but the ionization of helium was independently calculated. We
  then calculated the velocity distribution of the photoelectrons, and
  found substantial anisotropy (the photoelectrons moving preferentially
  near the horizontal) increasing with the depth in the atmosphere and
  with the compactness of the XUV source. The Ly photons resulting from
  photoelectrons excitation alone are linearly polarized, with a degree
  increasing with the line of sight inclination, up to a value of 4.5
  %, but the polarization is lost during the travel outwards, unless
  practically 100% coherence in photon scattering is assumed. This
  does not preclude the possibility for other lines to be polarized,
  however. The other possible mechanism of direct excitation (collisions
  by electron beams) is shown to produce the same qualitative effects;
  in particular excitation is also due predominantly to electrons
  moving at small angle with the horizontal. Key words: solar flares :
  photoelectrons - accelerated electrons - Lya emission - Lyoc line :
  anisotropic excitation - polarization

---------------------------------------------------------
Title: Dynamics of an atmosphere irradiated by soft X-rays in flares.
Authors: Henoux, J.; Nakagawa, Y.
1978A&A....66..385H    Altcode:
  It was previously shown that the lower chromosphere can be heated
  substantially by soft X-ray radiation at wavelengths of 1-300 A arising
  from a high-temperature plasma in the corona during a flare. The
  analysis was, however, based on the steady-state approximation. In
  this paper, a more realistic dynamic response is examined utilizing
  numerical calculations. Specifically, the physical parameters,
  such as the temperature, emission measure, and physical size of the
  X-ray source, are taken similar to the previous study; i.e., typical
  values for one 1N flares. The initial atmosphere is represented by
  the HSRA model atmosphere. The results indicate that with continuous
  and constant irradiation by the soft X-ray flux: (1) the atmosphere
  undergoes an oscillating expansion characterized by an oscillation
  period of approximately 270 s before reaching a new steady state in
  about 30 min; (2) in the oscillatory motions, a temperature increase
  coincides with downward motions and with upward motions; and (3)
  the observed time variation of the H-alpha line profile in flares
  appears to be in agreement with the initial part of the oscillatory
  behavior. It is noted that the oscillatory motions may not arise for
  spatially as well as temporally inhomogeneous soft X-ray sources.

---------------------------------------------------------
Title: Effects of Soft X-Ray Flux on the Lower Solar Atmospherer in
    Flares (Proceedings of the Meeting `How Can Flares be Understood?',
    held during the 16th General Assembly of the IAU in Grenoble, France,
    on 27 August, 1976.)
Authors: Henoux, J. C.; Nakagawa, Y.
1977SoPh...53..279H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Anisotropy and Polarization of Solar X-Ray Bursts
Authors: Henoux, J. C.
1975SoPh...42..219H    Altcode:
  The effects of the Compton back-scattered X-ray flux from the
  photosphere on the directivity and polarization of flare X-rays between
  15 keV and 150 keV are computed. The calculations are made with a thin
  target model for flares of De Jager-Kundu type with electrons spiralling
  downward around a vertical magnetic field and for an Isotropie source.

---------------------------------------------------------
Title: Abstracts of papers from other journals
Authors: Namba, O.; Henoux, J. -C.
1975SoPh...41..771N    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Abstracts of papers from other journals
Authors: Henoux, J. C.
1973SoPh...33..259H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Abstracts of papers from other journals
Authors: Henoux, J. -C.
1973SoPh...31..532H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Abstracts of papers from other journals
Authors: Pasachoff, Jay M.; Uchida, Y.; Vassilyeva, G.; Henoux, J. C.
1973SoPh...30..273P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: X-rays spectroheliograms in lines of Mg  xi and Mg xii
Authors: Bonnelle, C.; Senemaud, C.; Senemaud, G.; Chambe, G.;
   Guionnet, M.; Henoux, J. C.; Michard, R.
1973SoPh...29..341B    Altcode:
  Spectroheliograms in the Lα Mg XII line and in the Mg XI resonance
  (R) 1s<SUP>21</SUP>S<SUB>0</SUB>-1s2p<SUP>1</SUP>P<SUB>1</SUB>
  line, intercombination (I)
  1s<SUP>21</SUP>S<SUB>0</SUB>-1s2p<SUP>3</SUP>P<SUB>1,2</SUB>,
  line, and the forbidden (F)
  1s<SUP>21</SUP>S<SUB>0</SUB>-1s2s<SUP>3</SUP>S<SUB>1</SUB> line,
  have been obtained.

---------------------------------------------------------
Title: Abstracts of papers from other journals
Authors: Uchida, Y.; Vassilieva, G.; Henoux, J. C.
1973SoPh...29..270U    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Abstracts of papers from other journals
Authors: Henoux, J. C.; Uchida, Y.; Vassilieva, G.
1973SoPh...28..546H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Abstracts of papers from other journals
Authors: Shaw, M. L.; Gussmann, E. A.; Stepayan, N.; Henoux, J. C.
1972SoPh...25..504S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Abstracts of papers from other journals
Authors: De Feiter, L. D.; Pasachoff, Jay M.; Vassilyeva, G.; Gussmann,
   E. A.; Vassilyeva, G. J.; Henoux, J. -C.; Uchida, Y.; Namba, O.
1972SoPh...23..501D    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Abstracts of papers from other journals
Authors: Henoux, J. -C.; De Feiter, L. D.; Ambroš, P.; Pasachoff,
   JAY M.
1972SoPh...22..252H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Abstracts of papers from other journals
Authors: Uchida, Y.; Namba, O.; Henoux, J. -C.
1971SoPh...21..255U    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Abstracts of papers from other journals
Authors: De Feiter, L. D.; Vassilyeva, G.; Henoux, J. -C.; Ambrož,
   Pavel
1971SoPh...20..517D    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Abstracts of papers from other journals
Authors: Pasachoff, Jay M.; Vassilyeva, G. J.; Henoux, J. -C.; De
   Fetter, L. D.
1971SoPh...19..494P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Isotopes of Magnesium in the Solar Atmosphere
Authors: Boyer, R.; Henoux, J. C.; Sotirovski, P.
1971SoPh...19..330B    Altcode:
  We have analysed MgH A<SUP>2</SUP>Π-X<SUP>2</SUP>Σ(0.0), (1.1),
  (2.2), (0.1) and (1.2) absorption bands in a sunspot spectrum. By two
  different methods, which are almost independent of the estimated value
  of the correction for stray light, we have determined the solar isotopic
  ratios of magnesium. These ratios are equal to the terrestrial ones -
  <SUP>24</SUP>Mg∶<SUP>25</SUP>Mg∶<SUP>26</SUP>Mg = 80∶10∶10.

---------------------------------------------------------
Title: Abstracts of papers from other journals
Authors: Henoux, J. C.
1971SoPh...17..512H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Abstracts of papers from other journals
Authors: Pasachoff, Jay M.; Henoux, J. -C.; de Feiter, L. D.
1971SoPh...17..277P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Abstracts of papers from other journals
Authors: Henoux, J. C.; Pasachoff, Jay M.; Vassilyeva, G. Y.
1970SoPh...11..343H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Abstracts of papers from other journals
Authors: Uchida, Y.; Gussmann, E. A.; De Feiter, L. D.; Henoux,
   J. -C.; Stepanyan, N. N.; Pasachoff, Jay. M.
1970SoPh...11..173U    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Abstracts of papers from other journals
Authors: Stepanyan, N.; Pasachoff, Jay M.; Ambrož, P.; Vassilyeva,
   G.; Henoux, J. -C.; Fokker, A. D.; De Feiter, L. D.; Gussmann, E. A.;
   Uchida, Y.; Namba, O.
1969SoPh....8..491S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: A Model of Sunspot Umbra
Authors: Henoux, J. C.
1969A&A.....2..288H    Altcode:
  In a preceding paper (He'noux, 1968) we have determined the temperature
  of a large umbra (A,e&gt; 100 X 10-6 Hem.), in the layers deeper than r
  = 0.3. The temperature structure has been deduced from measurements of
  infra-red umbral intensities, with an estimated accuracy of 60 K. In
  this paper another large umbra observed the 9/21/69 is studied. The
  study of proffles and equivalent widths of strong, medium or weak
  atomic lines, in the visible spectral region, permits a study of the
  temperature structure to higher layers and to show that umbra is in
  hydrostatic equilibrium. It is supposed that umbras of large areas (A
  &gt; 100 &gt;c 10-6 Hem.) have the same temperature, as that previously
  determined for r0 &gt; 0.3. This hypothesis is justffled in the first
  chapter: it is shown (Fig. 1) that two of the three mean relative umbral
  intensities deduced form the data of Makita and Morimoto (1960) must
  be corrected for the effect of lines. Some corrections must be applied
  also to the measurements of Kneer and Mattig (1968) (Fig. 3). These
  corrected values are nearly equal to the intensities we have measured
  (Tables 1 and 2). The true relative umbral intensities are computed
  with the thermal law previously determined, and compared with the
  observed one. In this way the stray light is determined (Table 2) as a
  function of the wavelength. Thus the proffles and equivalent widths are
  corrected for the stray light. In Chapter II the temperature structure
  is extended from r = 0.3 up to higher layers (r = 10- ). The wings
  of the strong Na 1) and Mg b lines are studied. The wings of the Na
  D lines are very sensitive to temperature (Figs. 46). The temperature
  structure at the optical depth r &lt;0.3 is determined by trial, and
  error until a good agreement between observed and computed Na D wings
  is obtained (Fig. 4). For this purpose the atmosphere is supposed to
  be in hydrostatic equilibrium. The model is then used to compute the
  wings of the b lines. The agreement obtained is good too (Fig. 8). It
  is shown that it is impossible to represent the observed wings with
  sub-hydrostatic pressures and the temperature structure O(r0&gt;
  0.3) which is reasonably well established. In the third chapter the
  equivalent widths of many ionic and atomic lines of Fe H, Cr H, Ti H, Fe
  I, Cr I, Ti I are measured and computed with the model. The selection of
  the unblended lines has been made by using a spectrum of the same umbra
  taken with a Babinet biprism. Many ionic lines studied by Makita (1963)
  and Fricke and (1965) are in fact blended with molecular lines. Their
  equivalent widths are probably as weak as the values predicted by the
  model. For example it is shown (half-tones 10a, b, c) that the atomic
  lines of large excitation potential observed in an umbra by Makita are
  in fact molecular lines. The measured equivalent widths are compared to
  the values computed with the model. The computations are made with a
  so called "turbulence" = 1.5 km/s; the influence of the Zeeman effect
  is neglected. The agreement obtained is good in the case of medium
  weak ionic lines (Tables 9) and of the ionic lines measured by Zwaan
  (1965). The representation of the equivalent width of the atomic lines
  is good too (Fig. 9). The model is given in Chapter IV (Tables 12,
  Figs. 11-12). The transparency of the umbra is computed; it equals
  the transparency of the photosphere at the same optical depth. We have
  not tried to relate the geometrical depth scales of the photospheric
  and umbral model, because it would have been necessary to make some
  unreliable assumption about the geometrical shape of the spot or about
  the curvature of the magnetic lines of force. The integrated radiative
  flux is computed in function of the optical depth (Fig. 13). Oniy the
  higher layers are in radiative equilibrium (Teff = 3650 K). There is
  no radiative equilibrium in the layers deeper than = 1.

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Title: Abstracts of papers from other journals
Authors: Pasachoff, Jay M.; Vassilyeva, G. Y.; Henoux, J. -C.;
   Stepanyan, N.
1968SoPh....5..588P    Altcode:
  No abstract at ADS

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Title: Sur une particularité de la composante π du triplet normal
    dans l'ombre d'une tache
Authors: Henoux, J. C.
1968SoPh....4..315H    Altcode:
  No abstract at ADS

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Title: Abstracts
Authors: Yassilyeva, G. Y.; Dupree, A. K.; Henoux, J. C.; Namba, O.
1968SoPh....4..127Y    Altcode:
  No abstract at ADS

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Title: Abstracts
Authors: Henoux, J. C.; Dupree, A. K.; Stepanyan, N. N.
1968SoPh....3..364H    Altcode:
  No abstract at ADS

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Title: Un modèle thermique de l'ombre d'une tache basé sur la
    spectrophotométrie du continuum infra rouge
Authors: Henoux, J. C.
1968AnAp...31..511H    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Abstracts
Authors: Dupree, A. K.; Henoux, J. -C.; Ambož, Pavel; Gussmann,
   E. A.; Vassilyeva, Galina. Y.
1967SoPh....2..502D    Altcode:
  No abstract at ADS

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Title: Étude du triplet b du magnésium sur le disque et sur la
    chromosphère
Authors: Henoux, J. C.
1966AnAp...29..271H    Altcode:
  No abstract at ADS

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Title: Essai de détermination des intensités et des orientations
    des champs magnétiques d'un groupe de taches solaires
Authors: Henoux, J. -C.
1963AnAp...26..159H    Altcode:
  No abstract at ADS