Joint Discussion JD16 IHY Global Campaign Whole Heliosphere Interval

1

Perturbations in helio- and magnetosphere ruled
by solar magnetic field
Elena Gavryuseva
INR RAN



Joint Discussion JD16 - IHY Global Campaign -
Whole Heliosphere Interval August 12 - 14, 2009,
Rio de Janeiro, Brazil
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Perturbations in helio- and magnetosphere ruled
by solar magnetic field Abstract

• Relationships between the photospheric magnetic
  field, interplanetary field, solar wind
  characteristics near the Earth orbit and
  geomagnetic perturbations was studied using WSO
  observations of large scale magnetic field of the
  Sun (SMF) and OMNI data taken since 1976 to 2008
  taken duduring 21, 22 and 23 solar activity
  cycles to perform long - term predictions of
  space weather events.
• Connection between SMF and interplanetary
  magnetic field (IMF) was analyzed on a short time
  scale (day-to-day comparison) for several years
  during minimum and maximum of solar activity and
  after the polarity change at high latitudes) to
  reveal the efficient delay between the processes
  on the Sun and on the Earth orbit.
• The correlation between the temporal beh?vior of
  SMF and IMF, solar wind characteristics and
  geomagnetic perturbations was calculated for data
  sets of 29-year long and for the short subsets to
  reveal the heliolatitudes where the solar wind is
  originated from and how they depend on the phase
  of the activity.
• Such complex approach to the problem of
  SOLAR-TERRESTRIAL relations helps to find
  physical connections between the processes on the
  way from the Sun to the Earth.
• These results are useful for the understanding of
  the heliospheric structure and for the prediction
  of the magnetospheric perturbations.

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Introduction

• The long-term rise of the geomagnetic
  activity observed in XX century has provoked
  numerous investigations on solar drivers of
  geomagnetic disturbances.
• It was shown that this rise in geomagnetic
  activity is due to the rise in the interplanetary
  magnetic field (IMF) strength, solar wind
  concentration and speed, and attributed the rise
  of the IMF magnitude, the largest single
  contributor to the rise in the solar coronal
  field. The contribution of polar zones to the IMF
  near the ecliptic is significant around solar
  minimum, while around solar maximum low-latitudes
  and mid-latitudes are dominant.
• This finding contradicts the paradigm of a
  solar wind source consisting of two polar
  outflows flanking a planar current sheet, where
  the flow velocity has a minimum, but is in
  agreement with the results that, around solar
  minimum, the sources of the Suns open magnetic
  field, whose extension is the IMF, are the big
  polar coronal holes, while at the maximum these
  sources are the small low-latitude coronal holes.

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Wilcox Solar Observatory data
Fig.1.

• The observations of the large scale magnetic
  field in the photosphere taken at the Wilcox
  Solar Observatory (WSO) since May 27, 1976
  up to 2008 have been analyzed (http//wso.stanfor
  d.edu/synoptic.html).
• This interval of time covers the solar activity
  cycles No 21, 22 and 23 and corresponds to the
  Carrington Rotations (CR) since 1642 to 2027.
• The line-of-sight component of the photospheric
  magnetic field (SMF) is measured by the WSO's
  Babcock solar magnetograph using the Zeeman
  splitting of the 525.02 nm Fe I spectral line.
• The grid of the available data is made of 30
  equal steps in latitude sine from 75.2 North to
  75.2 South degrees and of 5 degrees steps in
  heliographic longitude.
• Each longitudinal value is a weighted average of
  the observations made
• in the longitudinal zone within 55 degrees
  around central meridian.

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The solar wind and geomagnetic data

• The solar wind and geomagnetic data were taken
  from the OMNI data base (http//nssdc.gsfc.nasa.go
  v/omniweb). In this paper we use the Bartels mean
  values of the interplanetary magnetic field
  (IMF) Bx, By and Bz components and
  average field vector
• B sqrt(Bx2By2Bz2), in nT and solar wind
  plasma parameters measured by various space
  crafts near the Earth's orbit such as proton
  density,
• Np, in N/cm3 plasma speed,
• Vp, in km/s
• and geomagnetic activity characteristics Kp
  and DST indices.
• First the comparison between the daily SMF and
  OMNI data were performed and an optimal delay of
  4 days was determined 11 which was always used
  later in the cross-correlation between the
  Bartels means of the SMF and OMNI data sets
  (Fig. 1) .

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Correlation coefficient between Photospheric and
Interplanetary Magnetic Fields as a function of
heliolatitude and time delay.

• Fig.2. Correlation coefficients between the
  photospheric magnetic field and interplanetary
  magnetic field intensity B and components Bx, By,
  Bz as a function of delay in days and of
  latitude. Yellow and red (blue and green)
  colors correspond to the positive
  (negative) values of the correlation
  coefficients.

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• We use the latitudinal distribution of the large
  scale solar magnetic field (SMF) as a more
  detailed solar index for the study of the
  relations between solar drivers at different
  solar latitudes and solar wind and geomagnetic
  disturbances.
• The solar magnetic field has a 4-zonal structure
  with the 22-year periodicity and additionally
  running waves through latitudes (RWL) with 2-year
  periodicity 9 12. The 4-zonal structure with
  the boundaries at 25, 0 and -25 degrees is
  asymmetric. The RWL field is in phase in both
  hemispheres each 10-11 years about.
• Bartels rotational averages for each latitudinal
  step have been deeply analyzed.

Fig.3.
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Correlation between SMF and OMNI data
Fig.4. Correlation coefficients between the
photospheric magnetic field and interplanetary
magnetic field, solar wind and geomagnetic
characteristics as a function of delay in years
and of latitude. Yellow and orange (blue and
violet) colors correspond to the
positive (negative) values of the correlation
coefficients.
9

• Fig.5 Correlation coefficients between the
  photospheric magnetic field and
• the interplanetary magnetic field, solar wind and
  geomagnetic characteristics as a function of
  latitude.

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Correlation between ABS(SMF) and ABD(OMNI)

• Fig.6. Correlation coefficients between the
  absolute value of the photospheric magnetic field
  and absolute values od the interplanetary
  magnetic field, solar wind and geomagnetic
  characteristics as a function of delay in years
  and of latitude.

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• Fig.7. Correlation coefficients between the
  absolute value of the photospheric magnetic field
  and absolute values od the interplanetary
  magnetic field, solar wind and geomagnetic
  characteristics as a function of latitude.

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Discussions

• The Kcor between the SMF and
  solar wind and geomagnetic perturbations should
  be compared with the Kcor between the SMF and
  IMF intensity B and all the IMF components since
  the physical connection between the solar
  magnetic field and interplanetary space and
  geomagnetic activity is due to the interplanetary
  magnetic field leading the solar wind.
• The correlation coefficient between the SMF
  latitudinal means and Np behaves similarly to the
  Kcor between the SMF and B (and AE).
• The Kcor between the SMF means and Vp is similar
  to the Kcor between the SMF and Bx, By, Bz, Kp
  and -DST.
• The correlation between the latitudinal
  means of the absolute values of the photospheric
  field and the absolute values of the solar and
  geomagnetic characteristics Np, Vp, Kp and DST
  are plotted in Fig. 5 to verify the dependence on
  the SMF intensity.
• Kcor between the SMF absolute values and Np is
  similar to the one between the SMF absolute
  values and B. The Kcor between the absolute
  values of the SMF and the Vp is analogous to the
  Kcor between the absolute values of the SMF and
  By,
• while the Kcor between the SMF intensity and the
  Kp and DST is similar to the relationship
  between the SMF intensity and absolute value of
  the Bz component. This is in agreement with the
  chain deduced for the connection between the real
  values of solar, interplanetary and geomagnetic
  characteristics 11.
• We could conclude that
• the photospheric field influences the magnitude
  of the interplanetary field and, in the same way,
  the proton density and flow pressure.
• The AE-index behaves in a similar way to
  these solar wind characteristics.
• On the contrary for the planetary geomagnetic
  activity index Kp the following chain was
  deduced
• solar activity events (CME, magnetic field
  intensity, sunspots, etc.) through perturbations
  of Bz component (Bx, By components) of the IMF
  and through the plasma speed Vp influence the Kp
  index
• variations of the -Bz (By) component produce the
  perturbations of the DST index, which are of
  opposite sign to the Kp and Bx time
  dependence.
• These results help to understand the
  origin of solar wind and geomagnetic
  perturbations and to predict them on a long term
  scale.

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Differential Rotation of the Solar Magnetic
FieldSideral Periods Deviations from P mean,
in days

• The differential rotation appears also for
  the large scale solar magnetic field.Additionally
  in the sub-polar zones there is a clearly
  visible decrease of the rotational rate in 1985
  and 1994 during solar activity minima and an
  increase of the rotation rate approximately in
  1990 and in 1991 after the polarity inversion.
  This happens with the 11-year periodicity.
  

q
q
Fig. 8
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Period of Differential Rotation of the SMF

• In Fig. 9 the SMF mean synodic rotational
  period deduced from the full sets of 29 years
  long (composed of 27721 points) are plotted as a
  function of latitude for the first (continuous
  line) and second (dashed line) maximum of
  auto-correlation as well as for the mean between
  them (dotted line).There is a 0.5--0.7-day
  decrease of the period at latitudes higher than
  56-60 degrees in both the hemispheres,correspon
  ding to the 1.7--2.3 level.
• The accuracy of the autocorrelation method
  for the full data sets is limited by the
  longitudinal resolution of 5 degrees, and equals
  1.3 at most. This result coincides with the
  latitudinal dependence of the rotation rate
  calculated by the FFT method for the full data
  sets, and with the rotation rate calculated by
  both methods as a mean of the rotation rates
  corresponding to the shorter sub-sets.The
  accuracy of the mean rotation rate is at least 10
  times better.

Psideral days
q
Latitude in degrees
Fig. 9
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Rotation of the WSO Magnetic Field

• The sideral SMF
  rotation period agrees with the results of the
• spectroscopic measurements of the solar
  rotation in the interval of
• latitudes q from -40 to 40 degrees ( Howard
  Harvey, 1970, 1991
• Stenflo, 1974 LaBonte Howard, 1981, 1982
  Snodgrass, 1983
• Howard et al., 1984 Bumba and Heina,
  1987 Ulrich et al., 1988
• Snodgrass and Ulrich, 1990 Beck, 1999
  Ivanov et al., 2001 and
• Ossendrijver, 2003.
  On the contrary at the latitudes between 40 and
  55 degrees the
• SMF rotates faster than other tracers and the
  photospheric plasma
• this results agrees with the finding of Obridko
  and Schelting, 2001
• that the solar magnetic field rotates more
  rigid at high latitudes.
  The decrease of the SMF rotation period at
  latitudes above 55-60
• degrees (deduced from the full 29 years long
  data sets) was never
• found for other tracers or in spectroscopic
  measurements (see Beck,
• 1999) while during some intervals of time the
  SMF rotation at high
• latitudes is rigid. This could be
  attributed to the presence of slow
• rotating coronal holes.

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Longitudinal structureof Real SMF in Carrington
System
?
?
of Random SMF in Carrington System
?
?
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Longitudinal structurein Carrington System
MF
Longitudinal structures for Real and 10 Random
Distributions
Longitudinal structures for SMF Intensity and 10
Random SMFI Distributions
IMF
?
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Auto-correlation of SMF (q, f)
q
f
Eq 1/5, 4/5 , ½ Act. lat 2/5, 3/5 of
Rotation ? MAX -7 TOPOLOGY
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Longitude structure of Solar Magnetic Field
T synodic 30.31 d
?
?
Kcor
Tcor40 deg
?
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Longitude structure of Solar Magnetic Field
T synodic 30.31 d
?
?
Kcor
Tcor40 deg
?
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Longitude structure of Solar Magnetic Field
T synodic 30.31 d
?
?
Kcor
Tcor40 deg
?
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Period of Differential Rotation of the SMF

• Continuos line is a
• sideral period of
• the SMF by auto-
• correlation method.
• Dashed line is a
• period of plasma
• rotation by different
• methods.
• Red line

Psideral days
?
Latitude, in degrees
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Inferred solar internal rotation
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The main results

• Differential rotational rate of the magnetic
  field
• and its temporal dependence has been
  evidenced
• at different latitudes through activity
  cycles.
• Extremely interesting quasi-stable over 30
  years
• longitudinal structure has been found.
• COROTATING STREAMS have to be expected in the
  HELIOSPHERIC FIELD.
• These results are fundamental for the
  understanding
• where the magnetic field is originated,
• how does it connected with internal
  structure and
• variability of the Sun, its activity and
  dynamics.

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"Eppur si muove!"
"Eppur si muove!"
26
??????
The latitudinal distributions of sunspot areas
and magnetic fields and their correlation with
the background solar magnetic field in the cycle
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