The method of spectrographic global survey was used to study the time variations in parameters of cosmic ray (CR) pitch angle anisotropy and their relationship with the variations of some solar wind characteristics under different electromagnetic conditions in interplanetary space. A classification is made of the conditions that are accompanied by the increase in CR anisotropy

Dvornikov, V. M.

Sdobnov, V. E.

Sergeev, A. V.

English

NASA Technical Reports Server

SH 4.5-19
151
DIAGNOSTIC OF ELECTROMAGNETIC CONDITIONS IN SPACE
USING COSMIC RAYS
V.M.Dvornikov, V.E.Sdobnov, A.V.Sergeev
Siberian Institute of Terrestrial Magnetism, Ionosphere
and Radio Wave Propagation, USSR Academy of Sciences,
Irkutsk 33, P.O.Box 4, USSR
Abstract. The method of spectrographic global survey
was used to study the time variations in parameters of cos-
mic ray (CR) pltch-angle anisotropy and their relationship
with the variations of some solar wind characteristics under
different electromagnetic conditions in interplanetary spa-
ce. A classification is made of the conditions that are accom-
panied by the increase in CR anisotropy.
According to the new ideas, under development now, of
the physics of modulational effects of cosmic rays (CR) in
the heliosphere /I, 2/, the crucial influence upon the CR
distribution function in interplanetary space is exerted by
effects that are accumulated during a multiple rotation of
particles in s Larmor circumference: drift motions, varia-
tions in pitch-angle due to an approximate conservation of
the transverse adiabatic invariant end particle energy varia-
tions in regular fields of solar wind (SW).
The development of these ideas has been stimulated by
the obtained phenomena of strong pitch-angle anisotropy of
CR during Porbush-effects /3/ whose explanation in terms of
a convection-diffusion model /4/ renders itself impossible.
In the context of the model under development, strong
pitch-angle CR anisotropy is a reflection of structural fea-
tures of large-scale fields in interplanetary spece due to
d_namical processes in the heliosphere, i.e. it is some
klnd of an indicator of these processes.
The aim of the present work is to study the time varia-
tions in parameters of CR pitch-angle anisotropy end their
relationships with the variations in some SW characteris-
tics under different electromagnetic conditions in interpla-
netary space. The analysis has been carried out using the
method of spectrographic global survey (SGS) that has been
devised using the physics, under development now, of CR mo-
dulational effects in the heliosphere, according to which
the variations in particle flux density in interplanetary
space can be described by a function of the form
= .+
Here _ = _ _ , _ is the pitch-angle of a particle in
https://ntrs.nasa.gov/search.jsp?R=19850026723 2020-03-20T16:52:14+00:00Z
SH 4.5-19
1@2
the i_, R is the magnetic rigidity
_oo_ _ _-__ ----_ of the particles,_(M) and_(sinA)
12_ are polynomials and associated Legen-d , _/ and _ ar
,IW ___ asymptotic angles that determine the
.__Or --4cv-_ocv...zocv 1 direction of the particles outside
.......v,._,.,.._,_,_....,_.... ......- ...........:, ,.......the magnetosphere in some selected
__,o['__v'- . . I system of coordinates, V/_ and Aoa
co 201JL_._.____,_ are the angles that characterize thedirection of the IN_ vector in this
same system, and _-n._ are the pars-
_L__ meters characterizing the amplitudesq00
.2o0____AP_ and rigidity dependences of the iso-
0__y_,_ ___LJ tropic component, and of the first andgo . L
°o o[m_f,........_k,_._.,._,_,:_,._,__,,_.,.jsecond harmonics of OR pitch-angle
, _ ,o anisotropy. The SGS method makes it
_a_,1_ possible to determine using ground-
based CR observations from the world-
Pig. I wide network of stations, theparame-
ters _ , _o , and
I I ] , I
_600_[ : iii i '' (accurate to within IP ) as well
as the variations of the planetary
' I I ! I I I
_ _! II !_I system of geomagnetic cut-off rigidl-
_I i_ii [ ties for each hour of the observa-
_ILI i.JJ i_ The SGS method was used to ana-
,_ , ,. _r__.._cv__0cv.._ocvlyze the variations of the CR dlstri-
_=:.;._>___.__! Ibution function for the periods I _ay
_-_. '_'-""_' , '- "'_'_,_..through 30 June and 1 through 15 Au
_Igust 1972. The analysis results as wellas direct measurements of SW charac-
teristics are presented in Pigs 1-5
_in the following order (from top to
_00 . .
w_o_.__.l_q4t ..__ bottom); V__ SW velocity, B - I_ mo-dulus; _e(_}-amplitudes of the iso-90
•_ o_._-,',_,,,.,,.._- ._ :_':_-'_. . ._w_"-'_"_-._"_,J.tropic,__. component of OR iutensity vari-
,_ _o z_ _o ations for particles of different
_.,s_2 .rigidity; _(8GV) and _(8GV) are
Pig. 2 respectively the amplitudes of the
first and second harmonics of CR
pitch-angle distribution (for R = 8 GV); and _,A,-angles
characterising the I_ direction (heavy lines - direct mea-
surements /5/, thin lines - CR data); in addition, Pig. _4
shows the variations in geomagnetic cut-off rigidity A _c
at Irkutsk, determined from CR variations, and Dst - index).
The comparison between the variations in CR pitch-angle
anisotropy and SW characteristics has led to the following
classification of the events accompanied by the increase in
CR anisotropy of the type considered:
1. Anisotropy increases during powerful SW disturbances
(see Pigs 2, 4, and 5). During the growth phase of the I_
modulus, the amplitude of the first harmonic (&# _ 3%) in-
creases while during the declining phase, the amplitude of
the second harmonic does (_ 3%). A minimum flux density of
158
SH 4.5-19
oF11........................._;_",.?+++...... _++J
0_+_ _-_ .... . -. ,. _ j
, I
400 .
I 5 iO g°[ +i i_, lll_. _ AI_+A]. ll.l L I ,,I A+
• + 4_, i
_+: o ___
JUNE,IB?2 -+,+
• -gO .......... 0
Fig. 3 m.o6t _._l_-..i_,.,.,o...J-_-_+=
• l_, 13 16 IT lB ig £0 @l 2£ £3 24 '_3 20 X+ +o zs ++
JUNE 19 7 2
I  ig.4
m_ I_ _
_ j!! 7 r! i_flow is observed for particles with large
.! i!!: i Ifpitch-angles. A likely reason might be the
_:_ :I [i i_ ] I]influence upon the CR angle distribution of
,I+_,.+i+,..i_i' I_li; _Ilarge-scale magnetic traps that form in
°_+.t_v.._,._(_,..°.]+_interplanetary space at propagation of
+_ m++:+_+_+-t+Tqhigh-speed solar wind streams.
'li _-_'I:+_ II. Anisotropy increases at places of
..II (I'_++_I illllocal decreases in IM_ strength ( _4 and
+II ifI#[ !l!iIIll _a+2%). The character of pitch-angle dis-If!l+: I IIIIII ]Itribution is the same as for type I events.
.IfIIIii iJIIfllll;The likely reason might be trapping and
"L__ deceleration of particles with large pitch-
_'0 angles in the traps between the maxima of
III. Anisotropy increases at places
":_k_W__! _+_ of local increases in IMP strength accompa-
"tnied by an increase in flux dens_ y by 5-
:-,+i','_+?_"__'_ 15% from some selected direction. In the
Aucu_.n,,+.,+, opposite direction, throughout the entire
hemisphere the intensity remains unaltered
Fig. 5 and is almost independent of the OR direc-
tion. This type of anisotropy was observed during 25 to 30
May 1972 (see Fig. 2), with a maximum of the flux density
from directions 120-150 ° westward of the Earth-Sun line and
50-70 ° southward of the helioequatorial plane. A likely cause
of the observed anisotropy may be IMP structures arising as
the azimuthal and meridional components of the magnetic field
are carried away from the corona. In this case, arrival of CR
along the IMP flux tubes is possible from interplanetary space
regions (for example, from middle heliolatitudesJ where the
CR density exceeds s_gnificantly the observed density in
the helioequatorial region.
lS,# SH 4.5-19
IV. Recurrent double enhancements of pitch-angle aniso-
tropy were found assuming that geoeffective regions on the
Sun have their mappings in the IMF structure corresponding
to their structures. In this connection, an attempt was made
to trace, using CR, from rotation to rotation the d evelop-
ment of processes in the heliosphere prior to some geoeffec-
tive phenomenon with the aim to find distinctive features of
oaysmsoLorroTQno, the active region that is responsible
2_22ZSZq25 2q25 252728 _$tqt5t617
, for a given event. As the object of
8 N18_ 8 N18S8
_;_ . , study, we selected one of the events
203.S_,.,000.2,_ 0.6.,._ of most geoeffective interest, the
_ ""_' °[_ ._ solar proton flares.8 N_886 8 1_8_
°_,__._ 0_ _0...,0.,2,3,.,_._ The SGS method was used to analy-8 NI887 8 Ht900
_"_ ;_ o_ the fluctuations of CR pitch-angle
' 02'2829303_,12_,_013 _ 5 878.71
_"r'_,io,,,2,._2ze
_0 _o- , _o- - anisotropy in three solar rotations
_,0_.,0_ 00_ preceding four powerful solar CR en-
_:_01.=0A.s0,_0_,_0_.,_j_.._,_0_i'_8y_ hancements (outbursts) in 1971 and'72.
'}. I\_ % .]_ In order to simplify the an@ly-
_ and MS M . The SH -index defines the
Fig' 6 .... amplitude of pitch-angle anisotropy
at time ti of the observation; it is
calculated in the following way .2
, ,£/.,)]Rt:
We used as the indicator of t_e recurrent event the multi-
plicatlve index MS# _z) = _ S_ _ + k _),
where _ is the period of so_ar rotation.
The analysis (see Eig. 6) revealed that three or four
rotations before the onset of a solar proton event (SPE),two
comparatively narrow recurrent I_ structures spaced $y 15-
30° in heliolongitude and causing recurrent double outbursts
of CR pitch-angle anisotropy, form in interplanetary space.
The character of pitch-angle distribution of the particles at
these moments is the same as for type III events.
The four SCR outbursts were all observed on the ground
at moments of passage through one of the detected structures.
The fact that these structures are identifiable using CR
pitch-angle anisotropy in solar rotations preceding SPE can
be used for long-term prediction of regions of localization
of radiation-dangerous zones in interplanetary space and of
times when the Eart_ enters these zones.
REFERENCES
I. V.M.Dvornikov, Yu.G.Mstyukhin, 1976, Izv.AN SSSR,ser.fiz.
40, 624.
2. Vi_.Dvornikov, Yu.G.Matyukhln, Izv.AN SSSR, ser.fiz. 43,
2573.
3. V._.Dvornikov, V.P.Karpov, A.V.Sergeev, 1978, Izv.AN SSSR,
ser.fiz., 42, 1043.
4. E.N.Parker. "Dynamical Processes in the Interplanetary
Medium", _oscow, _ir, 1965, 216.
5. J.H.King, 1977, Interplanetary _edium Dats Book, NSSD C/H-
-C4.


Diagnostic of electromagnetic conditions in space using cosmic rays

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