Author name code: aiouaz
ADS astronomy entries on 2022-09-14
author:"Aiouaz, Tayeb" 
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Title: Relentless Reconnections at Boundaries of Supergranular
    Network Lanes
Authors: Aiouaz, T.
Bibcode: 2008ESPM...12.2.80A
Altcode:
  Doppler-shift properties of the solar transition region (TR) and low
  corona are investigated in relation to the underlying chromospheric
  supergranular network, with particular regard to the role of the
  magnetic field. EUV line properties were obtained from a large raster
  scan of the solar transition region and corona acquired by the UV/EUV
  spectrometer SUMER on board SOHO. The observed regions include an
  equatorial coronal hole, as well as surrounding quiet Sun areas. I
  present correlations between the chromospheric network, and the N IV
  (765.15 Å), O IV (790.19 Å), S V (786.50 Å), O V (760.45 Å) Doppler
  shifts in quiet Sun and coronal hole. <P />It is established that the
  maximum inflow (redshift) at transition region temperatures appears
  statistically toward the center of the network lanes in the quiet
  Sun areas and toward the boundary of the network lanes in the coronal
  hole part. Furthermore, while the strong red-shifts in the TR lines
  complement spatially blue-shifts from the low corona (Ne VIII, 770.41
  Å) in a puzzle-like pattern, bi-directional flows (i.e. cospatial
  strong red/blue-shits in the TR/Corona) appear predominantly in the
  coronal hole. The bi-directional flows happen almost systematically
  at boundaries of magnetic field concentrations when compared to the
  reconstructed magnetogram from a MDI/SOHO series. <P />These results
  allow to propose for the first time a coherent interpretation involving
  a single driver for almost thirty years of unexplained statistical
  Doppler shift variations in the transition region and corona for quiet
  Sun and coronal hole. The proposed scenario involves reconnections
  between the strong network magnetic field and continuously advected
  weak field from the supergranular cell interior.

Title: Evidence of Relentless Reconnections at Boundaries of
    Supergranular Network Lanes in Quiet Sun and Coronal Hole
Authors: Aiouaz, T.
Bibcode: 2008ApJ...674.1144A
Altcode:
  Doppler-shift properties of the solar transition region (TR) and low
  corona are investigated in relation to the underlying chromospheric
  supergranular network, with particular regard to the role of the
  magnetic field. EUV line properties were obtained from a large
  raster scan of the solar chromosphere, transition region, and corona
  acquired by the SUMER spectrometer on board SOHO. The observed region
  includes an equatorial coronal hole, as well as surrounding quiet-Sun
  areas. The chromospheric supergranular network pattern is enhanced
  using a filter defined previously by Aiouaz and coworkers applied to
  a Lyman continuum image. The filtered continuum image and Dopplergrams
  are used to produce dispersion plots. We find correlations between the
  chromospheric network, and the N IV (765.15 Å), O IV (790.19 Å),
  S V (786.50 Å), O V (760.45 Å) Doppler shifts in quiet Sun and
  coronal hole. It is established that the maximum inflow (redshift)
  at transition region temperatures appears statistically toward the
  center of the network lanes in the quiet-Sun areas and toward the
  boundary of the network lanes in the coronal hole. Furthermore, while
  the strong redshifts in the TR lines complement spatially blueshifts
  from the low corona (Ne VIII 770.41 Å) in a puzzle-like pattern,
  bidirectional flows (i.e., cospatial strong red- and blueshifts in the
  TR/Corona) appear predominantly in the coronal hole. The bidirectional
  flows congregate almost systematically at boundaries of magnetic field
  concentrations seen in SOHO MDI magnetograms. These results support a
  coherent interpretation of almost 30 years of unexplained statistical
  Doppler-shift variations in the transition region and corona for quiet
  Sun and coronal hole. The proposed scenario involves reconnections
  between the strong network magnetic field and continuously advected
  weak field from the supergranular cell interior.

Title: Role of Magneto-Convection in Plasma Dynamic and Energy
    Balance Above the Supergranular Network
Authors: Aiouaz, T.
Bibcode: 2008ASPC..383..173A
Altcode:
  The current project aims to model the upper solar atmosphere taking
  in account the magnetic complexity of the supergranulation pattern. <P
  />The result of a potential field extrapolation is used as the initial
  condition for the magnetic field <P />in the framework of a forward 3D
  MHD model including the calculation of EUV emission lines. <P />The MHD
  model describes the solar atmosphere from the high chromosphere to the
  lower solar corona above a synthetic supergranular cell. <P />I present
  preliminary results on the relation between the magnetic topology,
  the thermodynamic properties of the plasma (e.g., flow, temperature,
  density) and the EUV intensity as calculated from the synthetic
  emission lines. <P />Signatures of the magnetic field concentration
  is to be found in the corona in the density and temperature structure,
  and thus in emissivity and intensity, while the magnetic field is almost
  homogeneous. <P />This model succeeds in reproducing for the first time
  the supergranular pattern as observed with a spectrometer in the EUV.

Title: The correlation between coronal Doppler shifts and the
    supergranular network
Authors: Aiouaz, T.; Peter, H.; Lemaire, P.
Bibcode: 2007A&A...466..689A
Altcode:
  No abstract at ADS

Title: Expansion of the Supergranular Magnetic Network through the
    Solar Atmosphere
Authors: Aiouaz, T.; Rast, M. P.
Bibcode: 2006ApJ...647L.183A
Altcode:
  The solar magnetic field has its footpoints in the photosphere,
  extends through the chromosphere, and is thought to expand through
  the transition region and into the corona. It is organized by fluid
  motions to form strong flux concentrations within the boundaries of
  the supergranular convection cells. These boundaries are the network
  lanes observed in line emission, and they display increasing width with
  height through the solar atmosphere. The network field concentrations
  are surrounded by a mixed-polarity internetwork magnetic field on the
  scale of granulation. We use a potential magnetic field extrapolation
  of synthetic photospheric magnetograms to study the magnetic network
  topology and the effects of a mixed-polarity background field on
  the network expansion with height through the solar atmosphere. We
  find that the expansion of the network boundary with height deviates
  significantly from the funnel expansion model. Moreover, we find that
  the background magnetic field has a considerable effect on the filling
  factor of the network area with height, even though the background
  flux is strictly equal to zero.

Title: Expansion of the supergranular magnetic network through the
    solar atmosphere
Authors: Aiouaz, T.; Rast, M. P.
Bibcode: 2006IAUS..233..161A
Altcode:
  The solar magnetic field that extends through the chromosphere is
  thought to expand through the transition region into the corona. The
  strong flux concentrations are located within the boundaries
  of supergranular convection cells. These boundaries form network
  lanes, observed in emission lines as bright lanes with varying width
  throughout the solar atmosphere. These network field concentrations
  are surrounded by mixed-polarity magnetic field with a scale of the
  granule diameter, as suggested by observations. We use potential
  magnetic field extrapolations on synthetic magnetograms to study
  the magnetic network topology and the effects of background magnetic
  field on the network expansion through the solar atmosphere. We find
  that the background magnetic field has a considerable effect on the
  ratio of network area over field of view. Furthermore we find that the
  expansion of the network boundaries with height deviate significantly
  from well-assumed funnel model expansion.

Title: Forward modeling of coronal funnels
Authors: Aiouaz, T.; Peter, H.; Keppens, R.
Bibcode: 2005A&A...442L..35A
Altcode:
  We propose a forward modeling approach of coronal funnels to investigate
  the outer layers of the solar atmosphere with respect to their
  thermodynamical properties and resulting emission line spectra. We
  investigate the plasma flow out of funnels with a new 2D MHD time
  dependent model including the solar atmosphere all the way from
  the chromosphere to the corona. The plasma in the funnel is treated
  in the single-fluid MHD approximation including radiative losses,
  anisotropic thermal conduction, and two different parameterized heating
  functions. We obtain plasma properties (e.g. density, temperature
  and flow speed) within the funnel for each heating function. From
  the results of the MHD calculation we derive spectral profiles of a
  low corona emission line (Ne VIII, 770 Å). This allows us e.g. to
  study the Doppler shifts across the funnel. These results indicate a
  systematic variation of the Doppler shifts in lines formed in the low
  corona depending on the heating function used. The line shift above
  the magnetic field concentration in the network is stronger than in the
  inter-network in both cases. However, for one of the heating functions,
  the maximum blue-shift (outflow) is not to be found in the very center
  of the funnel but in the vicinity of the center. This is not the case
  of the second heating function where the maximum is well aligned with
  the centre of the funnel. This model directly relates for the first
  time the form of the heating function to the thermodynamic and spectral
  properties of the plasma in a funnel.

Title: Relation of the Chromospheric Network to Coronal Funnels and
    the Solar Wind
Authors: Aiouaz, T.; Peter, H.; Keppens, R.
Bibcode: 2005ESASP.592..135A
Altcode: 2005ESASP.592E..20A; 2005soho...16E..20A
  No abstract at ADS

Title: The correlation between coronal Doppler shifts and the
    supergranular network
Authors: Aiouaz, T.; Peter, H.; Lemaire, P.
Bibcode: 2005A&A...435..713A
Altcode:
  We examine properties of line profiles as found with large raster
  scans of the solar corona acquired by the UV spectrometer SUMER on
  board SOHO. The observed regions include an equatorial coronal hole,
  a polar coronal hole, as well as surrounding quiet Sun areas. In
  order to reveal the network and remove strong local brightenings,
  a filter is applied to a continuum image. The filtered continuum
  image, the intensity image and the dopplergram are used to produce
  “scatter diagrams” (dispersion plots). We find correlations
  between the chromospheric network, the Ne VIII (770 Å) intensity
  and the Ne VIII (770 Å) Doppler shift in quiet Sun areas and in
  coronal holes. We establish that the maximum outflow (blue-shift) at
  low corona temperatures does not appear in the centre of the network
  but rather near network boundaries. Furthermore the maximum blue-shift
  seems to appear in the dark regions in Ne VIII line intensity, which
  is in agreement with Wilhelm (2000). The opposite correlation appears
  for very low intensities (less than half of the average intensity),
  revealing in these regions a lack of energy to either accelerate the
  solar wind or produce any detectable radiation. The absence of magnetic
  field concentration in these regions in a reconstructed magnetogram
  from a MDI/SOHO series seems to confirm the lack of energy.

Title: On the Outflow at Solar Corona Heights
Authors: Aiouaz, T.; Peter, H.; Lemaire, P.
Bibcode: 2004ESASP.575..331A
Altcode: 2004soho...15..331A
  No abstract at ADS

Title: Forward Modelling of Coronal Funnels
Authors: Aiouaz, T.; Peter, H.; Keppens, R.
Bibcode: 2004ESASP.575..337A
Altcode: 2004soho...15..337A
  No abstract at ADS

Title: Dynamics and Properties of Coronal Funnels
Authors: Aiouaz, T.; Peter, H.; Lemaire, P.; Keppens, R.
Bibcode: 2004ESASP.547..375A
Altcode: 2004soho...13..375A
  Coronal funnels are open magnetic structures connecting the chromosphere
  with the solar corona [5, 3]. We investigate the stationary plasma
  flow out of funnels with a 2D- MHD model. The funnel area function is
  derived from a magnetic field model and the funnel is approximately 10
  Mm high and 20 Mm wide. The energy balance includes radiative losses,
  thermal conduction, and a parametrized heating function. We adjust the
  parameters to the quantities measured in the lower solar corona. We
  obtained 2D plasma properties (e.g. density, temperature, flow speed,
  etc.) within the funnel. From the results of the MHD calculation we
  synthesize emision profiles of various lines formed in the transition
  region from the chromosphere to the corona. This allows us to study
  e.g. the Doppler shifts at various temperatures across the funnel
  and thus enables a detailed comparison of the model results with
  observations. For this we investigate SUMER data and study Doppler
  shifts perpendicular to the chromospheric network for different emission
  lines, where a tessalation technique is used to derive the outlines of
  the chromospheric network. In this paper typical results are presented
  for the Ne VIII(770.4 Å) line. Preliminary results show that these
  model caclulations compare well to the observations.

Title: Dynamics and Properties of Coronal Funnels
Authors: Aiouaz, T.; Peter, H.; Lemaire, Philippe; Keppens, Rony
Bibcode: 2003ANS...324....7A
Altcode: 2003ANS...324..B01A
  No abstract at ADS