Diagnostics of solar wind streams

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Diagnostics of solar wind streams

• N.A.Lotova, K.V.Vladimirsky, and V.N.Obridko
• IZMIRAN

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Main stages in the solar-wind studies
Object of investigation Authors Years
1 First evidence of the solar-wind streams obtained from the orientation of cometary tails L.Bierman, S.K.Vsekhsvyatsky et al. early 1950s
2 Discovery of the solar supercorona near-solar and interplanetary plasma up to 15Rs. Radioastronomic occultation method V.V.Vitkevich 1955
3 Radial extension of magnetic irregularities in interplanetary medium. V.V.Vitkevich, B.N.Panovkin 1957
4 Model of the solar wind flux from the source in the solar corona to the Earth E.N.Parker 1958
5 The first measurements of proton fluxes on board the Luna space mission K.I.Gringauz 1959
6 In-situ measurements of particle velocities on board the Mariner-2 and Mariner-4 space missions K.U.Snayder, M.Neugebauer 1962
7 Measurements of the solar-wind velocity vector by the radioastronomic scintillation method V.V.Vitkevich, V.I.Vlasov 1968
8 Origin of the irregularities responsible for radio scattering associated with the wave processes in interplanetary plasma N.F.Lotova, A.A.Rukhadze, I.S.Baikov 1968 1969
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Main stages in the solar-wind studies
Object of investigation Authors Years
9 Discovery of fast solar-wind streams at the magnetic field sector boundaries. Helios space mission R.Schwenn H.Rosenbauer E.M.Neubauer 1970s
10 Coronal holes identified as the source of the high-speed solar wind Krieger et al. 1973
11 The fast and slow solar-wind streams were measured from scintillation observations. The fast solar wind was shown to originate at the poles and the slow wind, in equatorial regions. W.A.Coles, B.J.Rickett 1976 1980
12 Discovery of the solar-wind transonic transition region by radio occultation method on board the Venera-10 space mission and by scintillation of mazer sources of the water vapour line. Formation of the transition region. Regime of mixed flow solar-wind A.I.Efimov, O.I.Yakovlev, N.A.Lotova R.L.Sorochenko, D.F.Blums N.A.Lotova, K.V.Vladimirsky 1977 1981 1983
13 Mass probing of interplanetary plasma at large distances from the Sun V.I.Vlasov
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Main stages in the solar-wind studies
Object of investigation Authors Years
14 Large-scale jet structure of the solar wind ?) radio maps of the solar-wind velocity at large distances from the Sun (by scintillations) ?) radio maps of the solar-wind transonic transition region in the vicinity of the Sun. Annual radio maps of the heliolatitude structure of the solar-wind streams T.???inuma, M.Kojima M.Kojima N.A.Lotova, K.V.Vladimirsky, O.A.Korelov, Ya.V.Pisarenko 1973- 1985 Since 1985 Since 1988
15 Correlation study of the solar-wind stream structure and sources in the solar corona. Method of correlation analysis Rin F(BR). The main types of the streams. N.A.Lotova, K.V.Vladimirsky V.N.Obridko 1995
16 Formation mechanisms of the stable solar-wind stream N.A.Lotova, K.V.Vladimirsky 1986 2003 2005
17 Evolution of the stream sources and components over an activity cycle N.A.Lotova, V.N.Obridko 1997- 2004
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Formation of the solar-wind streams,
irregularities, and jet structure

• The analysis was based on three sets of
  independent experimental data.
• ? data on radio scattering on circumsolar
  plasma obtained with the large radio telescopes
  of the Lebedev Physical Institute (Pushchino)
• ? coronal magnetic field strength and
  configuration calculated from the
  J.Wilcox/Stanford Zeeman observations in the
  photosphere
• ? LASCO/SOHO white-light images of the solar
  corona

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Examples of the radial dependence of radio
scattering ??(R)

• Routine radio occultation experiments in
  circumsolar plasma have provided the radial
  dependences of radio scattering the scattering
  angle 2?(R) and scintillation index m(R), which
  allow us to locate the solar-wind transition
  region on the scale of radial distances from the
  Sun.

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Correlation between the supersonic stream
velocity and the location of the transition
region inner boundary V(Rin)

• The large distance Rin from the Sun
  corresponds to the low speed and slow
  acceleration of the solar wind streams the small
  distance, on the contrary, corresponds to the
  high speed and fast acceleration

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Radio maps of the solar-wind transition region
for the epoch of maximum of cycle 23 2000-2002

• The use of a few occultation sources
  approaching the Sun simultaneously at different
  heliolatitudes made it possible to construct
  radio maps of the transition region. Here, the
  higher are the stream velocities the closer to
  the Sun are Rin and Rout. The radio maps display
  the jet structure of the flow. They show that the
  solar wind stream is essentially inhomogeneous
  and has a significant N-S asymmetry.

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Comparison of radio maps for the epochs of
minimum and maximum solar activity

• A distinctive feature of the solar wind in
  the epoch of maximum is the prevalence of
  low-speed plasma streams. The slowest streams
  were recorded in 2000 during the first (highest)
  maximum.

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Radio maps of the solar wind transition region
juxtaposed with the heliolatitudinal velocity
patters at large distances from the Sun inferred
from the Japanese data (cycle maximum)
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Radio maps of the solar wind transition region
juxtaposed with the heliolatitudinal velocity
patters at large distances from the Sun inferred
from the Japanese data (cycle minimum)
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Radio maps for the epoch of maximum and beginning
of the declining phase of the solar cycle

• Radio maps visualize the stream structure. The
  map series corroborates the jet structure of the
  solar wind and the mixed flow regime in the
  transonic transition region.

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• Comparing the heliolatitudinal structure of the
  transition region near the Sun with the stream
  structure at a distance of about 1 a.u., we can
  see that, with allowance for non-stationary
  nature of the solar wind, they are quite similar.
  This suggests that the solar wind propagating
  from the transition region to 1 a.u. conserves
  its jet structure formed under the initial
  conditions at the source surface in the solar
  corona at R2.5Rs. Thus, the complicated
  acceleration processes in the solar wind do not
  change the initial inhomogenous structure of the
  stream.

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Comparison of the isophotes of the white-light
corona and the structure of the solar wind
transition region

• Taking into account the non-stationary
  character of the solar wind, the agreement
  between the shape of the averaged white-light
  corona and the structure of the transition region
  is quite satisfactory.

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• A complex analysis of radio astronomic, optical,
  and magnetic data on the solar wind structure and
  sources in the solar corona has revealed some
  typical features in the formation of the solar
  wind streams different from the previous epochs
• ? in 2000-2002, the transition region moved
  farther from the Sun to interplanetary space, and
  its boundaries were located at 15-60 Rs compared
  to 10-40Rs in the previous epoch
• ? this may be due to the predominance of the
  low-speed solar solar wind

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Rin as a function of the coronal magnetic field
intensity ?BR? data for 1997

• The existence of three different types of the
  flow manifests itself in several branches of the
  correlation dependence

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Rin as a function of the magnetic field intensity
?BR?for the epoch of solar maximum
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2003 2004
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TABLEStructure of the solar wind streams as
inferred from the correlation diagrams
RinF(?BR?)
N Type of the stream Magnetic field strength ?BR? Magnetic field structure Structure of the white-light corona Symbol
1 Fast stream Strong magnetic field Open field lines Large CH or polar CH ltgt
2 Fast stream Strong magnetic field Low loops in very strong magnetic field Weak diffusion emission ?
3 Fast stream Weak magnetic field Open field lines Local CH or CH neighborhood, between two streamer lobes ?
4 Slow stream Weak magnetic field High loops Streamers ?
5 Slow stream Weak and medium magnetic field Mixed Streamer neighborhood ?
6 Uncorrelated component the slowest streams Weak magnetic field Very low closed loops or a weak streamer Zone between the streamer and dark region or very weak streamer ?
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Correlation dependences RinF(?BR?) for the epoch
of solar maximum 2000-2002

• Evolution of the correlation between
  RinF(?BR?) and solar activity Rz in the epoch of
  solar maximum. The typical evolution features
  are the change of inclination of the correlation
  curves with solar activity variations appearance
  of the formerly unknown uncorrelated stream
  component

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• Example of the sources of the uncorrelated
  slowest component of the solar wind (E,
  ?42?) small, low-altitude magnetic loops
  interacting with the open field lines of the
  local coronal holes.

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Conclusion

• The main progress in the study of the solar-wind
  jet structure was achieved in the diagnostics of
  the stream components and their sources in the
  solar corona. The diagnostics is based on the
  analysis of correlation between the location of
  the transition region inner boundary Rin and the
  magnetic field intensity ?BR? on the source
  surface. The method was developed at IZMIRAN.
• Correlation analysis of the relationship
  RinF(?BR?) between the location of the inner
  boundary Rin and the source-surface magnetic
  field has shown that each of the stream
  components originating from different sources is
  the slower the higher the solar activity level.
• ? There appears a formerly unknown stream
  component, which displays no correlation
  dependence RinF(?BR?) at all these streams are
  usually the slowest in the general pattern of the
  solar wind.

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Conclusion

• Variations in the solar wind structure with the
  level of solar activity are associated with
• the change of the predominant type of the streams
  in the general pattern of the solar wind
• the change of inclination of the dependence
  RinF(?BR?) in two slow stream components
• the appearance of the formerly absent
  uncorrelated stream component on the correlation
  diagram RinF(?BR?) in the epoch of solar
  maximum
• significant variations in the contribution of the
  magnetic fields of different scales over the
  activity cycle. In particular, this manifests
  itself in intensity variations of the solar
  global magnetic field, which control the change
  of the cycle phases and evolution of the solar
  wind jet structure.