Diffusion processes in the transition layer of the Earth's magnetosphere
Turbulence has a different nature in the interplanetary magnetic field and in the transition region, thus it requires a different type of analysis. The "Cluster 2" satellite mission provides magnetic measurements with a temporal resolution of 22.5 Hz. We analysed the evolution of the proba...
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irk-123456789-1199322017-06-11T03:02:51Z Diffusion processes in the transition layer of the Earth's magnetosphere Prokhorenkov, A.S. Kozak, L.V. Lui, A.T.Y. Gala, I.V. Turbulence has a different nature in the interplanetary magnetic field and in the transition region, thus it requires a different type of analysis. The "Cluster 2" satellite mission provides magnetic measurements with a temporal resolution of 22.5 Hz. We analysed the evolution of the probability density function over time, as well as that of the structural function. From the analysis we can conclude that for small time scales, the fluctuation distribution differs significantly from the Gaussian. Furthermore, we see that in the foresho k region, the fluctuation be comes almost Gaussian. Using the extended self-similarity structure function we compare the experimental data with the Kolmogorov K41 model. Calculated diffusion coeficients have a good agreement with the analysis of the probability density function and this can prove the existence of superdiffusion processes in the transition region of the Earth's magnetosphere. 2015 Article Diffusion processes in the transition layer of the Earth's magnetosphere / A.S. Prokhorenkov, L.V. Kozak, A.T.Y. Lui, I.V. Gala // Advances in Astronomy and Space Physics. — 2015. — Т. 5., вип. 2. — С. 99-103. — Бібліогр.: 23 назв. — англ. 2227-1481 DOI:10.17721/2227-1481.5.99-103 http://dspace.nbuv.gov.ua/handle/123456789/119932 en Advances in Astronomy and Space Physics Головна астрономічна обсерваторія НАН України |
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Turbulence has a different nature in the interplanetary magnetic field and in the transition region, thus it requires a different type of analysis. The "Cluster 2" satellite mission provides magnetic measurements with a temporal resolution of 22.5 Hz. We analysed the evolution of the probability density function over time, as well as that of the structural function. From the analysis we can conclude that for small time scales, the fluctuation distribution differs significantly from the Gaussian. Furthermore, we see that in the foresho
k region, the fluctuation be comes almost Gaussian. Using the extended self-similarity structure function we compare the experimental data with the Kolmogorov K41 model. Calculated diffusion coeficients have a good agreement with the analysis of the probability
density function and this can prove the existence of superdiffusion processes in the transition region of the Earth's magnetosphere. |
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Prokhorenkov, A.S. Kozak, L.V. Lui, A.T.Y. Gala, I.V. |
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Prokhorenkov, A.S. Kozak, L.V. Lui, A.T.Y. Gala, I.V. Diffusion processes in the transition layer of the Earth's magnetosphere Advances in Astronomy and Space Physics |
author_facet |
Prokhorenkov, A.S. Kozak, L.V. Lui, A.T.Y. Gala, I.V. |
author_sort |
Prokhorenkov, A.S. |
title |
Diffusion processes in the transition layer of the Earth's magnetosphere |
title_short |
Diffusion processes in the transition layer of the Earth's magnetosphere |
title_full |
Diffusion processes in the transition layer of the Earth's magnetosphere |
title_fullStr |
Diffusion processes in the transition layer of the Earth's magnetosphere |
title_full_unstemmed |
Diffusion processes in the transition layer of the Earth's magnetosphere |
title_sort |
diffusion processes in the transition layer of the earth's magnetosphere |
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Головна астрономічна обсерваторія НАН України |
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2015 |
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http://dspace.nbuv.gov.ua/handle/123456789/119932 |
citation_txt |
Diffusion processes in the transition layer of the Earth's magnetosphere / A.S. Prokhorenkov, L.V. Kozak, A.T.Y. Lui, I.V. Gala // Advances in Astronomy and Space Physics. — 2015. — Т. 5., вип. 2. — С. 99-103. — Бібліогр.: 23 назв. — англ. |
series |
Advances in Astronomy and Space Physics |
work_keys_str_mv |
AT prokhorenkovas diffusionprocessesinthetransitionlayeroftheearthsmagnetosphere AT kozaklv diffusionprocessesinthetransitionlayeroftheearthsmagnetosphere AT luiaty diffusionprocessesinthetransitionlayeroftheearthsmagnetosphere AT galaiv diffusionprocessesinthetransitionlayeroftheearthsmagnetosphere |
first_indexed |
2025-07-08T16:55:56Z |
last_indexed |
2025-07-08T16:55:56Z |
_version_ |
1837098606641807360 |
fulltext |
Di�usion pro
esses in the transition layer
of the Earth's magnetosphere
A. S. Prokhorenkov
1∗
, L.V.Kozak
1
, A.T.Y. Lui
2
, I. V.Gala
1
Advan
es in Astronomy and Spa
e Physi
s, 5, 99-103 (2015)
A.S. Prokhorenkov, L.V.Kozak, A.T.Y.Lui, I. V.Gala, 2015
1
Taras Shev
henko National University of Kyiv, Glushkova ave. 4, 03127, Kyiv, Ukraine
2
Johns Hopkins University Applied Physi
s Laboratory, Laurel MD, USA
Turbulen
e has a di�erent nature in the interplanetary magneti
�eld and in the transition region, thus it
requires a di�erent type of analysis. The �Cluster 2� satellite mission provides magneti
measurements with a tem-
poral resolution of 22.5 Hz. We analysed the evolution of the probability density fun
tion over time, as well as that
of the stru
tural fun
tion. From the analysis we
an
on
lude that for small time s
ales, the �u
tuation distribution
di�ers signi�
antly from the Gaussian. Furthermore, we see that in the foresho
k region, the �u
tuation be
omes
almost Gaussian. Using the extended self-similarity stru
ture fun
tion we
ompare the experimental data with the
Kolmogorov K41 model. Cal
ulated di�usion
oe�
ients have a good agreement with the analysis of the probability
density fun
tion and this
an prove the existen
e of superdi�usion pro
esses in the transition region of the Earth's
magnetosphere.
Key words: solar wind-magnetosphere intera
tions nonlinear phenomena; transport pro
esses
introdu
tion
A new type of instability arises in inhomogeneous
plasma, as
ompared with a
lassi
al des
ription. In
the
ase of evolution of these instabilities, the plasma
an be
ome a turbulent medium. In addition, the
transverse di�usion of plasma in the magneti
layer
an play a signi�
ant role in areas where magneti
re
onne
tions are ine�e
tive. Thus, di�usion in the
absen
e of a
tual parti
le
ollisions
an be ensured
as a wave-parti
le intera
tion (anomalous resistive
di�usion). Sin
e gradients of density, temperature,
magneti
�eld and �ow are observed in the transi-
tion region of the magnetosphere, a large number
of instabilities for anomalous di�usion evolves. A
number of ma
ro-instabilities may also
ontribute to
the di�usion. The Kelvin-Helmholtz instability and
eddy turbulen
e are the most important instabilities
to evolve the inhomogeneous plasma
hara
teristi
s.
Both me
hanisms
an promote mixing of the plasma
on a large s
ale, and
an
reate the ne
essary
on-
ditions for mi
ro-instabilities. Chaoti
ele
tri
and
magneti
�elds that o
ur, lead to anomalous trans-
port pro
esses that are orders of magnitude higher
than that of
lassi
al pro
esses. Ma
ros
opi
�ows
of parti
les, momentum, and energy are de�ned not
only by the mean �eld and pro�les, but also by the
�u
tuation spe
trum [17℄.
The notions and
on
epts of anomalous dynami
properties, su
h as long-range spatial or temporal
orrelations manifested in power-laws, stret
hed ex-
ponentials, or non-Gaussian probability distribution
fun
tions (PDFs), have been predi
ted and observed
in numerous systems from various dis
iplines in
lud-
ing physi
s,
hemistry, engineering biology, meteo-
rology, astrophysi
s, and others. The standard tools
to des
ribe anomalous dynami
s are
ontinuous time
random walks [7, 8, 20℄ and fra
tional dynami
al
equations [15, 16, 21℄.
The anomalous features usually stret
h over the
entire data window, but there exist examples when
they develop after an initial period of sampling (�-
nite size/time e�e
ts), or they may be transient, i. e.,
eventually the nature of anomalous pro
ess turns
into normal transport or relaxation dynami
s. The
most fundamental de�nition of anomaly is the devi-
ation of the mean squared displa
ement 〈(∆r)2〉 =
〈(r − 〈r〉)2〉 ∼ Dt∝ from the `normal' linear depen-
den
e 〈(∆r)2〉 ∼ Dt over time. Here D is the gen-
eralized di�usion
onstant. The anomalous di�usion
exponent α 6= 1 determines whether the pro
ess will
be
ategorized as subdi�usive (dispersive, slow, et
.)
if 0 < α < 1, or superdi�usive (enhan
ed, fast) if
1 < α. Usually, the domain 1 < α ≤ 2 is
on-
sidered, α = 2 being the ballisti
limit des
ribed
by the wave equation, or its forward and ba
kward
modes [14℄. Pro
esses with α > 2 are known, su
h
as the Ri
hardson pair di�usion in fully developed
turbulen
e [18℄.
Generally, one
an not
reate a
losed system
of equations des
ribing the anomalous transport
pro
esses; the results are mostly limited to semi-
quantitative assessments. The weak turbulen
e,
∗
andrew.prokhorenkov�gmail.
om
99
Advan
es in Astronomy and Spa
e Physi
s A. S. Prokhorenkov, L.V.Kozak, A.T. Y. Lui, I. V.Gala
with quasi-linear approximation, is a
ase when the
anomalous transport pro
esses
an be analyti
ally
des
ribed.
Therefore, it is ne
essary to determine the statis-
ti
al properties of the environmental parameter �u
-
tuations from the experiment whi
h are related to
the s
ale invarian
e, and get estimates for the type
of di�usion pro
esses. This will qualitatively and
quantitatively des
ribe transport pro
esses in di�er-
ent regions of the magnetosheath.
methods to determine the
type of diffusion pro
esses
evolution of the flu
tuations PDF
Probability distribution of �u
tuation amplitudes
of a random pro
ess obeys the Gaussian law (the so-
alled normal law) [3, 10℄. The dependen
e of the
maximum probability density fun
tion in the analy-
sis of data series X(t) at di�erent time s
ales
an be
approximated by a power law: Pτ (0) ∼ τ−s
, where
τ is the s
ale shift over time, and s is a param-
eter that
hara
terizes the homogeneity or hetero-
geneity of the studied pro
ess (for Gaussian distri-
bution s ∼ 0.5 and the presen
e of heterogeneity
s > 0.5 [3, 6℄.
From the behaviour of the PDF the spatial or
temporal s
ales where the PDF losses the Gaussian
properties,
an be de�ned.
Evaluation of parti
le biases
an be
arried
out using the �Levy �ight� (Levy �ights) [2, 22℄:
〈X2(τ)〉 ∝ τ2s, where s is the maximum exponent
of magneti
�eld �u
tuations PDF Pτ (0).
Statisti
al averages properties.
For the turbulent �eld X(t), the stru
tural fun
-
tion (statisti
al average) of order q is de�ned as a
statisti
al average over the ensemble of relations [9℄:
δτX = X(t + τ) − X(t), Sq(t) = 〈|δtX|q〉 ∼ tζ(q),
where the exponent ζ(q) � des
ribes the type of
pro
ess and turbulent di�usion properties of the
medium. The linear dependen
e of ζ(q) indi
ates
homogeneity of turbulent pro
esses (parti
ularly,
for the Kolmogorov model � ζ(q) = q/3, and
Iroshnikov-Krai
hnan model ζ(q) = q/4) [9, 12, 13,
23℄. For turbulen
e intermitten
e of high order stru
-
ture fun
tions there is a nonlinear dependen
e of ζ(q)
on q. This re�e
ts the deviations from the Gaussian
law [5℄. In addition, the stru
ture fun
tions of high
orders allow one to
hara
terize the properties of het-
erogeneity on small s
ale pro
ess.
Analysis of experimental data has a great impor-
tan
e to the presen
e of extended properties of self-
similarity (ESS), for a power law of the stru
ture
fun
tions Sq ∼ S
ζ(q)/ζ(p)
p and allows one to
hara
-
terize �u
tuations in the turbulent �ow for a large
range of Reynolds numbers [1℄. Using the extended
self-similarity property, the good a
ura
y values of
ζ(q) and di�usion properties of the plasma
an be
evaluated. To interpret the nonlinear dependen
e
ζ(q) the log-Poisson model is used, for whi
h ζ(q) is
given by [4, 11, 19℄:
ζ(q) = (1−∆)
q
3
+
∆
1− β
[
1− β
q
3
]
,
where β and ∆ are parameters that
hara
terize the
intermediate and singularity pro
esses, respe
tively.
As a result of ESS-analysis for log-Poisson s
al-
ing parameters β and ∆ are used to determine the
hara
teristi
s of turbulent plasma transport. The
generalized di�usion
oe�
ient depends on the ζ(q)
as [22℄:
D ∝ tR,
where R = ∆(1/β − l).
This relation is used to evaluate transport prop-
erties in a heterogeneous environment. In general,
the parameter R is de�ned by the fra
tal properties
of the medium.
Thus, there is a relation between the exponent
that
hara
terizes the evolution of PDF, and the pa-
rameter R. Displa
ement law for the parti
les is
given by the relation: 〈δX2(τ)〉 ∝ Dτ ∝ τ2s ∝ τα,
with order of 2S = 1 + R [2, 22℄. Where, normal
di�usion
orresponds to α = 1, and the
onve
tive
(ballisti
) motion is
hara
terized by the α = 2.
satellites used for measurement
We used the data from �Cluster 2� spa
e mission.
We analysed 5 events of satellites C1 passing the
magnetosheath from 2004 to 2010, with a temporal
resolution of 22.5Hz. The examples of analysed mag-
neti
�eld �u
tuations are shown in Fig. 1. In two
events out of �ve (2009/05/11 and 2010/03/31), the
satellite
rossed the magnetosheath, moving from the
magnetopause region to the interplanetary medium.
In other
ases it was moving from the solar plasma
wind medium.
Fig. 1: Example of analysed magneti
�eld.
In di�erent regions of magnetosheath there are
di�erent levels of magneti
�eld �u
tuations ob-
served:
� in foresho
k region, the varian
e of variations
normalized with the
urrent mean value is
δB/B = 0.1− 0.25;
� after
rossing the sho
k wave in postsho
k re-
gion, �u
tuations in
rease several times,
om-
pared to the foresho
k δB/B = 0.5 − 0.6;
100
Advan
es in Astronomy and Spa
e Physi
s A. S. Prokhorenkov, L.V.Kozak, A.T. Y. Lui, I. V.Gala
� in deep magnetosheath region, �u
tuations de-
rease to a value of δB/B ∼ 0.15 − 0.2.
Even with almost
omplete absen
e of magneti
�eld �u
tuations in the solar wind, there are high
�u
tuations in the magnetosheath region.
results
To study the probability density fun
tion of �u
-
tuations of the magneti
�eld B(t) we
hose the o�set
time τ , whi
h is a multiple of dis
rete measurements
τ
min
= 0.0445s, and we analysed the statisti
al prop-
erties of the absolute value of the magneti
�eld vari-
ations dB = B(t+ τ)−B(t) in the foresho
k region,
postsho
k region, and magnetosheath, on di�erent
time s
ales.
Fig. 2: Maximal value for magneti
�eld �u
tuations
PDF P (0) in logarithmi
s
ale for 3rd Mar
h 2004. Ex-
perimental data approximated with a line: P ∼ t−s
: 1
� foresho
k, 2 � magnetosheath, 3 � postsho
k. Val-
ues of s presented in Table 1.
Good temporal resolution of the measurement
allows us to observe the dependen
e of the maxi-
mum value of the PDF of magneti
�eld �u
tuations
Pτ (0) on a small s
ale (less than 1 se
ond), whi
h
is very important be
ause we
an analyse on a s
ale
smaller than the ion
y
lotron frequen
y. Logarith-
mi
s
ale plots for measurements on Mar
h 27, 2010
and Mar
h 20, 2006 are shown in Fig. 2, where the
experimental points were approximated by a straight
line Pτ ∼ τ−s
. The values for the exponents of the
events are presented in Table 1.
From the obtained values, we
an
on
lude that
for small s
ales in the transition region of the Earth's
magnetosphere, the distribution signi�
antly devi-
ates from the Gaussian distribution.
The largest deviations are observed for the post-
sho
k region. Furthermore, in foresho
k region we
have an almost Gaussian distribution for magneti
�eld �u
tuations. The generalized di�usion
oe�-
ient R is shown in Table 1. R > 0 indi
ates the
existen
e of superdi�usion.
The extended self-similarity stru
ture fun
tions
of high orders are spe
i�ed by the equation: Sq(t) =
〈|B(t+τ)−B(t)|q〉 ∼ τ ζ(q), where 〈. . .〉 � statisti
al
averaging of experimental data over time.
Fig. 3: Relation of stru
tural fun
tion on time s
ale for
a magnetosheath region (03/03/2004).
Stru
tural s
aling fun
tion normalized to s
aling
for the third moment, ζ(q)/ζ(3)
an be obtained
from the slope of a logarithmi
s
ale. This will allow
us to
ompare experimental data to the Kolmogorov
model of turbulen
e (K41) for whi
h ζ(3) = 3/3 = 1.
In Fig. 3 power law Sq(τ) ∼ τ ζ(q) (i. e. self-similarity)
is observed only in a limited range of time s
ales.
This interval
orresponds to the inertial range, whi
h
is
onsidered a
lassi
model of developed isotropi
turbulen
e (K41, et
.) [5℄. In the transition region of
the magnetosphere this interval is observed on s
ales
less than 1 se
ond (this will allow us to
ompare the
results obtained by di�erent approa
hes � from the
analysis of maximum height of magneti
�eld �u
-
tuation probability density fun
tion and statisti
al
average).
Cal
ulated results for ζ(q)/ζ(3) of di�erent orders
q in the analysis of small-s
ale turbulen
e and
om-
parison with Kolmogorov model for the events on 3rd
Mar
h 2004 and 3rd April 2006 are shown in Fig. 4
and 5. The most signi�
ant deviation from the Kol-
mogorov model is observed in the postsho
k region.
Determined by the ESS analysis parameters β and
∆ and
al
ulated values R = 0.3÷0.98 are presented
in Table 2.
The obtained values are in good agreement with
the data presented in Table 2.
101
Advan
es in Astronomy and Spa
e Physi
s A. S. Prokhorenkov, L.V.Kozak, A.T. Y. Lui, I. V.Gala
Thus, using two independent te
hniques, we
proved the existen
e of superdi�usion pro
esses in
the transition region of the Earth's magnetosphere.
Fig. 4: Relation of exponential value of stru
tural fun
-
tion of q-order to the 3-rd order stru
tural fun
tion for
3rd Mar
h 2004. K41 � values
al
ulated for Kol-
mogorovmodels; FSH� foresho
k region, MSH�mag-
netosheath, PSH � postsho
k.
Fig. 5: Relation of exponential value of stru
tural fun
-
tion of q-order to the 3-rd order stru
tural fun
tion
for 3rd April 2006. K41 � values
al
ulated for Kol-
mogorovmodels; FSH� foresho
k region, MSH�mag-
netosheath, PSH � postsho
k.
on
lusions
The relative variations of the magneti
�eld in
magnetosheath ex
eed the values in the solar wind
by fa
tor of 2�5. However, the
onverse proposition
is in
orre
t � not all variations of parameters in the
magnetosheath are generated by �u
tuations of the
solar wind or the interplanetary magneti
�eld.
The largest deviation from a Gaussian pro
ess is
observed in the postsho
k region, and the distribu-
tion
losest to a Gaussian one is in the foresho
k
region.
The value of the generalized di�usion
oe�
ient
in
reases with time-s
aling. Thus, the analysis of
the evolution of the magneti
�u
tuations PDF �
the exponent �eld dependen
e on the generalized
di�usion
oe�
ient of the s
ale (R) in the transi-
tion regions of the Earth's magnetosphere: foresho
k
region, postsho
k and magnetosheath � is in the
range of 0.32�0.92. The highest value is observed for
the postsho
k region. The analysis of the statisti
al
properties of points determined the parameter R to
be in the range of 0.3�0.98. Likewise, the highest val-
ues are observed for the postsho
k region in this
ase
as well. It
an be noted that di�erent approa
hes to
the analysis of turbulent pro
esses give similar re-
sults and indi
ate the presen
e of superdi�usion pro-
esses in the transition region of the Earth's magne-
tosphere. This fa
t must be taken into a
ount when
onstru
ting quantitative models of transport.
a
knowledgement
The work is done in the frame of
omplex program
of NAS of Ukraine on spa
e resear
h for 2012-1016,
the grant Az. 90 312 from the Volkswagen Founda-
tion, and within the framework of the edu
ational
program No.2201250 �Edu
ation, Training of Stu-
dents, PhD Students, S
ienti�
and Sedagogi
al Sta�
Abroad� laun
hed by the Ministry of Edu
ation and
S
ien
e of Ukraine.
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Advan
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Table 1: Generalized di�usion
oe�
ient
al
ulated from the evolution of magneti
�eld �u
tuation PDF.
Date Region s R = 2s− 1
2009/03/23 Postsho
k 0.78 ±0.085 0.56
Magnetosheath 0.69 ±0.092 0.38
2006/04/03 Foresho
k 0.66 ±0.076 0.32
Postsho
k 0.96 ±0.098 0.92
Magnetosheath 0.89 ±0.088 0.78
2009/05/01 Magnetosheath 0.9 ±0.099 0.81
2004/03/03 Foresho
k 0.76 ±0.083 0.52
Postsho
k 0.96 ±0.087 0.92
Magnetosheath 0.66 ±0.054 0.32
2010/03/31 Magnetosheath 0.68 ±0.069 0.36
Table 2: Generalized di�usion
oe�
ient
al
ulated from ESS analysis.
Date Region β ∆ R = ∆( 1
β
− 1)
2004/03/03 Foresho
k 0.26 ±0.012 0.2 ±0.01 0.58
Postsho
k 0.45 ±0.017 0.8 ±0.011 0.98
Magnetosheath 0.66 ±0.009 0.6 ±0.009 0.3
2006/04/03 Foresho
k 0.67 ±0.008 0.69 ±0.007 0.35
Postsho
k 0.71 ±0.013 2.2 ±0.01 0.91
Magnetosheath 0.45 ±0.01 0.68 ±0.007 0.82
2009/03/23 Postsho
k 0.5 ±0.012 0.6 ±0.013 0.6
Magnetosheath 0.67 ±0.008 0.69 ±0.007 0.35
2009/05/01 Magnetosheath 0.5 ±0.011 0.4 ±0.012 0.81
2010/03/31 Magnetosheath 0.62 ±0.009 0.51 ±0.008 0.31
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