Synoptic meteorological study of high latitude field of polar disturbance

Maysuradze, P. A.

English

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National Aeronautics and Space Administration 
Godeard Space Flight Center 
Contract No. -5-12487. 
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aFT-GM-AI- 10617 \J 
5 H I G H  LATITUDE FIELD OF POLAR DISTURBANCES 5 
by 
b P. A. Maysuradze 9 
(USSR) 
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ST-GM -AI -10617 
HIGH LATITUDE FIELD OF POLAR DISTURBANCES 
(*I 
GEOFIAGNETIZM I AERONOMIYA 
Tom 7, No.2, 369 - 372 
Izd-vo '"AUKA", 1967. 
by P. A. MAYSURADZE 
The high-latitude field of DP-disturbances is studied by construction of 
charts of successive disturbed field moments. Since DP-disturbances have their 
source in the high-latitude ionospheric currents, their dynamics were object 
of study as a function of Dst-variations by means of synoptic charts. 
patterns obtained .are discussed at length. 
The 
* 
* * 
Ray-like disturbances lasting usually about two hours are observed on 
high-latitude stations' magnetograms even in quiet days. It is customary 
to call them elementary polar storms, or polar sub-stonns and denote them 
by the symbol DP. Numerous investigations of DP show that their source is 
in high-latitude ionospheric currents excited by short-lived action of the 
corpuscular stream. 
occur 
For a prolonged action of the stream the polar sub-storms 
The space-time distribution of the field of polar disturbances is us'bally 
investigated by way of construction of ionospheric current systems, equivalent 
to the distribution of DP field vectors on the surface of the Earth. 
latitudes the distribution of the DP field is characterized by a substantial 
complexity, and the net of the registering stations is limited. In order to 
bypass this difficulty we utilized during the construction of current systems 
the distribution in the course of the day of averaged polar disturbances in 
separate stations. Hcwever, such a construction is linked with a series of 
assumptions, disclosing only the average characteristics of the DP field. 
The first constructions of the mean current systems in the form of two vortices 
(morning and evening) in the region bounded by the Fritz zone (Q x 60")were 
performed by Chapman [l]. 
the current systems were refined by numerous authors [2-71. Attempts were 
made to construct also the current systems related to a specific moment of time 
[2, 5, 8, 9 et all. Because of insufficiency of stations such current systems 
could contain significant errors. 
of the number of stations during the IGY, we undertook the investigation of 
d>.nmics of current systems as a function of the phase of Dst-variation in low 
latitude stations. 
optic charts of successive moments of the disturbed field. 
(*qWLE P O L Y A R "  VOZWSHCHENIY VYSOKIKH SHIROT. 
in a nearly continuous sequence. 
At high 
Subsequently, as the number of stations increased, 
- This is why, taking advantage of the increase 
The method o f  analysis consists in the construction of syn- 
2. 
Ihringfhe construction of synoptic charts hourly values of vectors 
CX, &)Y and dZ were utilized as departures from the quiet undisturbed level 
in the days preceding the considered storm. 
part of the values obtained was eliminated, which was caused by induced cur- 
rents in the Earth: the values of horizontal components were multiplied by 0.7, 
and those of vertical components were divided by 0.7. Then arrows were placed 
on the map (limited to @ = 50') at places of location of stations for a chosen 
h B r  U.T.,representing the perturbation vectors of the horizontal component 
(AThor - A X  + A?), and the values of the perturbation vectors of the vertical 
component A? were marked by numerals. Then a line was drawn through the region 
between positive and negative values of A? (A? = 0). In the presence of a large 
number of successive synoptical charts (we had 480 of them), the line A 2  = 0 
is drawn sufficiently reliably. At the same time, as a rule, the vector ? 
is perpendicular to the line ~2 = 0; it is maximum on that line (within the 
region bpunded by the Fritz zone) and directed from the region A2 > 0 to the 
region A Z  < 0 [lo]. 
morning vortex is characterized by the values A? > 0, while the region of the 
evening vortex is marked by the values A? < 0. 
the line A? = 0, the center of gravity of the basic current, responsible for 
the polar disturbances, is located. 
In the first approximation the 
It should be noted that the region of the current systems' 
At the boundary, that is, along 
:ea 
\ 
\a 
I 
I1 
\ 
\ 
-100. 
io  1u- 
Fig. 1 
k t  us examine several typical examples of synoptic charts of perturbed 
iield distributions at high latitudes. Fig.la represents a synoptic chart 
constructed for 0400 hours UT of the storm of 11 February 1958. 
circles indicate the geomagnetic latitudes; the denotations of geomagnetic 
longitudes and latitudes are given in degrees and the position of the Sun is 
marked by a circle with a dot. This moment of time refers to the period of 
the initial phase of a very powerful magnetic storm. 
time to develop as yet, and its field near the equator constituteQD,t(H)= 9y 
(refer to [ll]). At the same time ap = 236. In Fig.la the region A Z  > 0 is shaded. 
Concentric 
The ring current had no 
I -  
3 .  
Such 3 case, when near this zone all the three branches of A I  = 0 are prescnt 
(morning, night and evening), corresponds to the distribution of the field of 
polar disturbances or polar sub-stom. The well known fact+that in night and 
carly morning hours vectors AGor.are maximum on the line AZ = 0 is not very 
well shown in Fig.la. 
ing the current system. 
were especially so chosen that the existing station network allow the consider- 
ation of the pecularity of the evening vortex. 
This was taken subsequently into account, when construct- 
The moments of U.T. shown in Figures la as well as 2a 
i I 
Fig. 2 
The idealized system of currents, equivalent to the perturbation field 
represented in Fig.la for substantial ap and DSf = O  
For its construction we used the approximate Chapman methqd and we involved 
additional data, namely, the latitude cross sections of AThor for the meridians 
of local geomagnetic time 1200, 1500, 1800 and 2100 h urs. When constructing 
the line A;? = 0 for analogous cases when D # ,  = o 
system includes two vortices with foci on evening and morning meridians. 
intensities of both vortices are of same order. 
current of the evening vortex is slightly smaller than that of the morning 
vortex (2.2 * lC5 and 3.5 lo5 respectively). 
agrees well with the distribution of the field of polar sub-storms, brought 
out in references [2, 3, 5 et all, 
of vortices is concentrated on their boundaries. 
is plotted in Fig.1 . 
the latter we took into account the distribution of A f hor vectors relative to 
and ap is significant. The 
At the same time, the full 
The 
In its general traits Fig.1 
differing by the fact that the basic current 
4 .  
An entircly different pattern is obtained when considering the perturbed 
field during the main phase of Dst-variation. 
Fig.2 a. llere the synoptic chart refers to 1000 hours U.T. of the same storm 
of 11 February 1958. This moment of time corresponds to the period of a well 
developed and intense ring current in the region of radiation belts. 
equator the value of the outer part of Dst(H)=-270 [ll]; ap= 236, thus the, 
same as in Fig.1. Inside the Fritz zone the "evening" branch of the line AZ = 0 
to which in Fig.1 a corresponded the horizontal vectors directed toward the 
pole (positive bays in the H-component), is no longer visible. This branch 
moves away to lower latitudes, where the current intensity decreases abruptly, 
nearly by one order by comparison with the values in the Fritz zone. Besides, 
the horizontal vectors of the "evening" branch in Fig.2 a are decreased by com- 
parison with the case of Fig.1 a because Dst(H) and DP(H) are here directed 
oppositely. By comparison with Fig.1, the night and morning branches of the 
line AT = 0 in Fig.2 shifted substantially toward lower latitudes and formed 
near the midday meridian an open oval. The latter is displaced relative to 
the geomagnetic pole toward lower latitudes on the night side. 
rent amplification in these branches of the line A? = 0 may be explained by 
the geometrical addition of horizontal vectors of the polar perturbation with 
a field of Dst@) of identical sign. A particularly large amplification of 
polar storm's AThor will take place on the night side of these branches, since 
they are disposed in lower latitudes. 
Such a case is illustrated in 
Near the 
A certain cur- 
However, m e  influence of the field of Dst on the distribution of the 
perturbed field at high latitudes can not be reduced to a simple geometrical 
addition of fields DP and Dst. 
fields are spatially dispersed: the source of DP is in ionospheric currents 
induced by the penetration of corpuscular particles; the source of Ds is in 
currents at a range of several Earth's radii. 
tion there apparently takes place a particle intrusion. 
substantial redistribution of current lines' position in high latitudes. It is 
obvious that the displacement of the evening branch of the line A? = 0 toward 
lower latitudes in Fig.2 a is precisely due to this redistribution. Had there 
been only a simple geometrical addition of fields DP and D s t ,  the evening 
branch should have shifted in the opposite direction, that is, toward higher 
latitudes. Indeed, during the main phase of the storm Dst(?) 
tudes of the northern hemisphere, and the addition with the field DP should be 
leading to the shift of the evening branch to higher latitudes. 
it may be seen in Fig.2 that the evening branch moved away to lower latitudes. 
This is corroborated by the presence of negative values of G on the day-eve- 
ning side near the night branch of the line A? = 0. 
station Irhutsk were especially plotted in Fig.2 a, though this station+is lo- 
cated beyond the circle o€ latituds @ = 50'. 
points to the fact that the line AZ = 0 passes somewhere between Irkutsk and 
Ynhatsk, where A? = - 1 0 2 ~ .  
storm (on the equator the outer part Dst(H) = -270v), having caused a substan- 
tial shift toicard lower latitudes of the branches forming the oval. 
average mgnetic storms, when Dst(H)=lOOy on the equator, the branches of the 
line A? = 0 are less displaced toward lower latitudes, and the oval on the 
night side coincides with the Fritz zone. 
It is well known that the sources of both 
Besides the geometrica! addi- 
This will lead to a 
0 at high lati- 
However, 
Moreover, data of the 
Here the positive value A Z  = 254y 
'Ihe case considered in Fig.2 a corresponds to a very powerful magnetic 
During 
If we convert the distribution of 
5 .  
perturbed field illustrated in Fig.2 a into an equivalent current system, we 
shall obtain in high latitudes a single vortex of oval shape (Fig.2 ) .  
may be seen that nearly the entire near-polar region is occupied by the morning 
vortex, whereupon the main current is concentrated at its boundary. 
morning vortex the total current rose to 7 . lo5 a. The evening vortex has been 
shifted to lower latitudes and attenuated (0.4 * lo5 a). 
acquires such a form under the action in the region of radiation belts of the 
extra-ionospheric current system D,t. 
In ref.[6, 71 the winter distribution of the perturbed field in high la- 
titudes was constructed by the international perturbed days of the period 
November-December 1957 and January-February 1958. 
mean value of the Ds (H)-variation according to [ll] gives for that period 
near the equator DstfH) =-57y. At the same time the mean value of intensity 
of corpuscular stream's action is estimated by the value a = 44. From the 
above it is clear that for such a relation between D s t  and a one should not 
neglect the value of Dst and in this case it is essential to-distort the real 
field of LIP. 
It 
In the 
The polar disturbance 
A simple calculation of the 
It should be noted that the intensity of polar sub-stons is essentially 
dependent on ionosphere conduction. 
sity of DP is significantly less than that of summer DP, induced by a corpus- 
cular stream of identical intensity. This stems from the fact that in the 
sumner season such a substantial shift toward lower latitudes and the conqxn- 
sation of the evening branch of the line A;? = 0 do not usually take place. 
This may also be well seen from summer synoptical charts of ref. [lo]. 
In winter period (polar night) the inten- 
- -  
In conclusion I wish to express my gratitude to S. M. Mansurov and V. M. 
Yishin for their interest in the work and useful discussions. 
I Z M I R A N  
CONTRACT No.NAS-5-12487 
I VOLT 'IECINNICAL CORPORATIOJ 
1 L4.5 . I%h-StTtdW-- - 
GWASIIINGTON D. C . 20036.3 
Tel: 223-6700; 223-4930. 
Manuscript received on 18 February 
1966 
Translated by ANDRE L. BRICHANT 
on 30 - 31 May 1967 
References follow ../.. 
!TI'- 0 1 -  AI- 10617 
R E F E R E N C E S  
I 
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2. 
3. N. P. BEN'KOVA. Tr. NIISM, vyp.10(20), 1953. 
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5. T. NAGATA, S. KOKUBAN, N. FUKUSHIMA. J.Phys.Soc.Japan, !%p.Al, K, 35, 1962. 
6. YA. I. FEL DS", A. N .  ZAYTSN. Ceom. i Aeronam. 5, 3, 477, 1965. 
7. YA. I. FEL DS", A. N. ZAYTSEV. Ib. 5, 6, 1123, 1965. 
8. S. I. AKASOFU, S. C", C. I. MENG. J.Atm. a. Terr.Phys. 27, 11/12, 1275, 
9. D. H. FAIRFIELD. J.Geophys. Res., 68, 3589, 1963. 
E .  H. VESTINE, L. LAFORTE, I. LANGE, W. E. s(xrTr. The geomagnetic field, 
1 its description and analysis. Washington, 1947. 
1965. 
10. P. A. MAYSURADZE. Gem. i Aeronomiya, 5, 6, 1071, 1965. 
11. M. SUCIURA. h . I G Y ,  35, 7, 1964. 
same as for ST-AI -GM-10612 


High latitude field of polar disturbances

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