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Upper atmosphere during geomagnetic disturbances—III
Planet. Space Sci. 1969, Vol.
17, pp. 181 to 187.
FWgamon Picas. Printed in Northern Iceland
UPPER ATMOSPHERE DURING GEOMAGNETIC DISTURBANCES-III SOME REGULARITIES
IN DENSITY
VARIATIONS
YU. L. TRUTHE Institute of the Physics of the Atmosphere, USSR Academy of Sciences, Moscow (Received 22 July 1968)
At&met-Upper atmospheric density and the sum of AE indices for the previous 10 hr have a linear relationship, while the relationship between the former and solar radio flux F,,., is nonlinear. The increase in density slows down at great solar activity levels. Some considerations are presented on the nature of the relationship between density and AE and F,,.,.
It has been shown earlier (Truttse, 1968a, b, c) that during intense geomagnetic storms the decimal logarithm of the intensity ofthe atomic oxygen emission at 6300 A is proportional to oat and the maximum intensity of this emission is localized in the region of middle latitudes. Since energy release in oxygen red emission has turned out to be very great and since it seems natural that this metastable emission appears at high altitudes, it was expected that the appropriate heating source would be in these regions of the atmosphere. It was shown that the density and temperature of the upper atmosphere, if one judges from an in-phase character and dispersion of values, are better described by D,, than by a, indices of geomagnetic activity. However, density and temperature variations are nearly identical at all latitudes and their relationships with a, and D,, do not differ considerably from a linear relationship. Any abrupt change in the pattern of density and temperature variations, in cases of variations of these indices, was maximum at the commencement of geomagnetic storms. This discrepancy can be explained by the fact that the D,, index reflects both the value of the ring current and other types of geomagnetic perturbations which do not affect the atmosphere, especially at the commencement of a geomagnetic storm. Since the most exact coincidence of D,, variations with the change in the logarithm of the intensity of emission at 6300 A, as well as upper atmospheric density and temperature, took place with large Dst, it can be expected that the magnitude of the ring current plays a leading role. A paper by Davis and Parthasarathy (1967) is of great interest here for it shows that a lO-hr sum of AE indices for the preceding time reflects the magnitude of the ring current. These indices are a measure of electrojets in the aurora1 zone, as geomagnetic activity and aurorae sums of these indices for different time intervals show, on average, a linear dependency on solar radio flux i-&.,, 27-day and seasonal variations. This circumstance has compelled us to explore the relationship between the upper atmospheric density and lo-hr summary indices X AE. Figure 1 shows upper atmospheric density at a height of 270 km as a function of solar radio flux Flo., when I; AE do not exceed 1000 gammas. The effect of such I: AE does not exceed actual errors in the determination of density, and, therefore, one can expect that this relationship reflects only the role of solar radio flux Fl,,.,. Figure 2 shows a relationship between Ap and X AE exceeding 2000 gammas. The value Ap-the difference between the magnitude of the measured density and the density 181
YU. L. TRUTTSE
182
I
I
/
/
’
I /
6-
4-
a_
O0
Fro. 1.
H = 270km AS A FUNCTION OF SOLAR INJUNIII (JACCHUet al., 1963a) (CIRCLES) ANDEXPLOREX VI (MOE, 1966) (DOB). The values of density are cmrected for seasonal (JACCHUet al., 1968) and diurnal variations. For all cases 8 AE < 1000 gammas. The dashed line shows density vs. &., according to CIRA 1965.
RADIO
UPPER
FLUX
ATMOSPHERIC
F,,.,
DENSITY
Cl’Il FROM
DATA
FOR
A HEIGEIT
OF SA-
I
.
2
“E Q
h $
4.
I
3
.
.
. .
. .*
I
I
FIG. 2. UPPER ATMOSPHERIC DENSITY VARIATION FOR THE HEIOHT u = 270 km As A FUNGI-ION AE ACCDRDINO TO DATA OF ~ATELLI~ INJUNIII (JACCIUAet al., 1963a) (CIRCLES) AND EXF%OlWR VI (MOE, 1966) (DO-IS). The values of density are corrected for seasonal (Jaechia et al., 1968) and diurnal variation.
OF Z
UPPER ATMOSPHERE
DURING
GEOMAGNETIC
DISTURBANCES-III
183
determined after Fig. 1 for corresponding &,.,. The solid line in Fig. 1 is an average curve obtained by the exclusion of mean Ap values according to Fig. 2 from a large number of measured density values with different F,,.,. Figure 3 shows the ratio of Ap and X AE vs. the value F&,.,. It is evident that this relationship does not depend on F,., within the limits of actual errors in determining the density. The relationship between the density and Fl,,., is clearly of a non-linear nature while the relationship between Ap and X AE is linear within the errors of determining the density. For the sake of comparison, Fig. 1 shows by a dashed line the relationship between p and Fl,,., for the same altitude according to CIRA 1965. 4r
I
x “E
l
I
0
e E 0 m g w
I
-
. .
0
.
. .
2-
‘s
.
zi B _
000 0
.
l
:. .
l.
.
. ..*
l
..
l.
J3
0 0 m OO
0. I
I
100
200
xx,
FIO.7
FIc3.3. RELATMZ VARIATIONSOF DENSRYAP/~ AEAS A FIJNClTONOF Flo., DURING GEQMAGNEITC WHEN z AE > 2000 GAMMAS, FOR A HEIGHT H = 270 km ACCORDING TO DATA
DBTDRRANCl?S,
OFSATEL~~TESINXTNUI(JACCHIA~~~~.,~~~~~)(~IRC~)ANDEXPLORERVI(MOE,~~~~)(D~T~).
The relationship indicated in Figs. 4,5 and 6 for a height of 730 km have been obtained by a method similar to the relationship in Figs. 1, 2 and 3, respectively. In the main, the picture at this altitude too is similar to that which is observed at a height of 270 km. For a height of 730 km a wider section of linear relationship between p and Fl,,, is typical. It is worth noting that in the case of large values of Flw, there is a trend towards a density decrease (Fig. 4). However, there is nothing unexpected in this, if one takes into account that cases of low densities with large Flo., refer to summer time. At this level (H = 730 km) the atmosphere contains a large amount of light elements which can be transferred to the winter hemisphere. Thus, there is an abundance in the winter hemisphere and a deficiency in the summer hemisphere (Shefov, 1968). A similar relationship is obtained for other altitudes too, but attention is not drawn to these since the main data on density derived from satellite drag was obtained at a low level of solar activity, when non-linearity could not be detected. Figure 7 shows upper atmospheric density variation from 8 August to 7 September, 1959 according to Moe’s (1966) data (the thin line) and according to CIRA 1965 (the dashed line), taking into consideration Flo., and a, indices corresponding to this time. The same figure shows (the thick line) upper atmospheric density calculated for the same time instants from its relationship with F,,., and B AE presented in Figs. 1 and 2. A similar picture is observed for other altitudes too. Thus, combined use of a non-linear relationship between density and F,., and a linear relationship between density and E AE leads to the so far optimal description of upper atmospheric density, which does not deviate from density measured within the limits of errors ofinitial data. To describe the upper atmospheric
YU. L. TRUTTSE
184
-,. ”
FIG.4.
UPPER ATMOSPHERIC DENSITY FOR A HEIGHT H= 730klll VS. .WLAR RADIO FLUX F,,., ACCORDING TO DATA OF SATELLITES EXPLORER IX (JACCHU et al., 1963b) (CIRCLES) AND
VANGUARD I (1958 82) (JACCHIAet al., 1963c) (DOTS). The values of density are corrected for seasonal (Jacchia et al., 1968) and diurnal variation. For all cases B AE > 1000 gammas. The dashed line shows density vs. Fio., according to the CIRA 1965.
I
I .
.
a’ .
.
e .
30
FIG. 5. UPPERATMOSPHERIC DENSITY VARIATION FORTHEHEIGHTH = 730 km ASA FUNCTION (JA~wIA~~ al., 1963b) (CIRCLES) al., 1963c) (DOTS). The values of density are corrected for seasonal (Jacchia et al., 1968) and diurnal variations.
OF 22 AE ACOORDINGTODATAOF SATELLITZSERPLORERIX AND VANGUARD I (1958 82) (JACCHUet
UPPER ATMOSPHERE DURING GEOMAGNETIC DISTLJRBANfXS-III
x3
I
“E
O
I
P
El-
8 8
E*-
b’
P
Q90
.*
*
l
l .
,a0 0
I
0
.
.
0
0 : 0 0 O08
P
185
l
*
.. .*
t
200
loo
Jo0
F107 FIG. 6. REtmn% VARIATIONS OF DENSITY ApiE AE As A FUNCXION OF F,,., DURING GEGMAGNKiW DIED, WHEN z: AE > 2000 OMBrlAs,FGR A iiEiGBTH = 730 km ACCORDING To
DATA OF SATELLW
EXPLORER IX (JACCX-Uet al., 1963b) (cmcus) AND VANCWARDI (1958 @2) (JACWJA et al., 1963c) (WTS).
A%rYCT
RO.7. bU?4RISONOF WITH VALUESiXLCULA_
1959
CeHT5SPb
MEASURED VALUESOF DENSITY(EXPLORERVI, MOE, 1966) (THIN I.& BY US (THICK LINE) AND ACCORDING TO ch?A 1965 (DASHEDLINS).
structure more precisely, one needs more exact measurements of the upper atmospheric density with high resolution in time, as well as more perfect AE indices, which at present are determined only from data of eight stations in the northern auroral zone. However, the auroral zone changes its position during the day (Feldstein, 1960; Khorosheva, 1962) and therefore, it is desirable to obtain AE indices from the data of a more widely dispersed network of stations both in the Northern and Southern Hemispheres. However, results obtained when use is made of existing indices and data about upper atmospheric density required an explanation. In the first place, one should understand a non-linear relationship between density and F1,,., with the discontinuation of the growth
186
YU. L. TRUTTSE
of density in case of high F,,.,. The nature of this relationship differs essentially from a corresponding relationship represented in CZZU 1965. The limitation of density growth may be for two reasons. In the first place, this can be the consequence of the expansion of the heated region and of its penetration into a given height region. Secondly, it is highly probable that it is caused by a non-linear relationship between the ultraviolet radiation absorption in the upper atmosphere and Fle,, and by the increase in the outflow of heat from the upper atmosphere with the increase of the temperature. The latter is very likely since, with the increase in the temperature, enhanced concentrations of NO may come into being which cool the atmosphere at the expense of infrared radiation. The increase in the molecular NO content during geomagnetic disturbances is confirmed by the increase in the intensity of the night sky emission continuum (Truttse, 1968). However, if during geomagnetic disturbances an additional heating of the upper atmosphere occurs, its contribution must be lower in the case of great values of Fle,, and the relationship between hp and Z AE be as non-linear as the relationship between p and Flo.,. However, so far this has not been observed within the accuracy of initial data. At present, we are unable to explain the above features. However, when this problem was discussed with Professor Krassovsky, he expressed the idea that the effect of geomagnetic disturbances is not necessarily associated with global heating of the upper atmosphere. This effect can also reflect the process of the oscillation in the height of the levels of similar density. This may be the consequence of the generation of infrasonic or gravitational waves in the regions of pulsed electrojets in the aurora1 zone and their rapid propagation throughout the atmosphere. It is noteworthy that the most intense elcctrojets appear during break-ups, when aurorae are broken into separate short-lived rays. During even very intense aurorae no increase in the temperature of the upper atmosphere below 200 km has so far been observed (Hilliard et al., 1966), i.e., at a height where the main heating and expansion of the atmosphere should have taken place. This has already been explained (Krassovsky, 1968) by the appearance of a great number of molecules NO cooling the upper atmosphere. All these indicate that there are no reasons for the heating of the upper atmosphere at levels below 200 km outside the aurora1 zone. On the other hand, magnetohydrodynamic, gravitational and infrasonic waves can be absorbed at higher regions of the atmosphere and create localized heating there in the regions of middle latitudes, where intense emission of atomic oxygen at 6300 A originates. However, to explain all above-mentioned circumstances reliably, it would be necessary to carry out direct temperature measurements in the upper atmosphere and use groundbased determination of Doppler contours of its emissions, and to make a thorough check of the known spectroscopic determinations of temperatures (Hilliard et al., 1966) at different latitudes during geomagnetic perturbations. Acknowledgement-The author would like to express his gratitude to Professor Krassovsky for continued interest and for active discussion of the results of this paper.
CIRA (1965). COSPAR International Reference Atmosphere, 1965 North-Holland, Amsterdam. DAVIS,T. N. and PARTIMM~Y R. (1967). J. geophys. Res. 72,582s. FELD~~FXN, Y. I. (1960). Invest. of aurorae, USSR Acud. Sci. 4,61. HILLIARD,R. L. and SHBPHERD, G. G. (1966). Planet. Space Sci. 14,383. JACCHIA,L. G. and SLOW, J. (1963a). Smithson. Astrophys. Obs. Spec. Rep. No. 136. JACCHU,L. G. and SLOWEY,J. (1963b). Smithson. Astrophys. 06s. Spec. Rep. No. 125.
UPPER ATMOSPHERE
DURING
GEOMAGNETIC
DISTURBANCES-III
187
JACCHIA, L. G. and SLOWBY,J. (1963c). Smithson. Contr. Astrop&. 8,l. JACCHIA, L. G., SLOWEY,J. W. and CAMPBELL, I. G. (1968). Smithson. Astrophys. Obs. Spec. Rep, No. 265. KRA.WNSKY, V. I. (1968). Nature, Lad 217, 1136. KHOROSHEVA, 0. V. (1962). Geomag. & Aeronomy, U.S.S.R. 2, 696. (English Transl.) MOE, K. (1966). Planet. Space Sci. 14, 1065.
Smov, N. N. (1968). Planet. Space Sci. 16, 1103. Tkmrsts, Yu. L. (1968). Planet. Spuce Sci. 16, 140. TRUTTSE,Yu. L. (1968). Planet. Space Sci. 16,981. TRUTTSE,Yu. L. (1968). Planet. Space Sci. 16, 1201.
17, pp. 181 to 187.
FWgamon Picas. Printed in Northern Iceland
UPPER ATMOSPHERE DURING GEOMAGNETIC DISTURBANCES-III SOME REGULARITIES
IN DENSITY
VARIATIONS
YU. L. TRUTHE Institute of the Physics of the Atmosphere, USSR Academy of Sciences, Moscow (Received 22 July 1968)
At&met-Upper atmospheric density and the sum of AE indices for the previous 10 hr have a linear relationship, while the relationship between the former and solar radio flux F,,., is nonlinear. The increase in density slows down at great solar activity levels. Some considerations are presented on the nature of the relationship between density and AE and F,,.,.
It has been shown earlier (Truttse, 1968a, b, c) that during intense geomagnetic storms the decimal logarithm of the intensity ofthe atomic oxygen emission at 6300 A is proportional to oat and the maximum intensity of this emission is localized in the region of middle latitudes. Since energy release in oxygen red emission has turned out to be very great and since it seems natural that this metastable emission appears at high altitudes, it was expected that the appropriate heating source would be in these regions of the atmosphere. It was shown that the density and temperature of the upper atmosphere, if one judges from an in-phase character and dispersion of values, are better described by D,, than by a, indices of geomagnetic activity. However, density and temperature variations are nearly identical at all latitudes and their relationships with a, and D,, do not differ considerably from a linear relationship. Any abrupt change in the pattern of density and temperature variations, in cases of variations of these indices, was maximum at the commencement of geomagnetic storms. This discrepancy can be explained by the fact that the D,, index reflects both the value of the ring current and other types of geomagnetic perturbations which do not affect the atmosphere, especially at the commencement of a geomagnetic storm. Since the most exact coincidence of D,, variations with the change in the logarithm of the intensity of emission at 6300 A, as well as upper atmospheric density and temperature, took place with large Dst, it can be expected that the magnitude of the ring current plays a leading role. A paper by Davis and Parthasarathy (1967) is of great interest here for it shows that a lO-hr sum of AE indices for the preceding time reflects the magnitude of the ring current. These indices are a measure of electrojets in the aurora1 zone, as geomagnetic activity and aurorae sums of these indices for different time intervals show, on average, a linear dependency on solar radio flux i-&.,, 27-day and seasonal variations. This circumstance has compelled us to explore the relationship between the upper atmospheric density and lo-hr summary indices X AE. Figure 1 shows upper atmospheric density at a height of 270 km as a function of solar radio flux Flo., when I; AE do not exceed 1000 gammas. The effect of such I: AE does not exceed actual errors in the determination of density, and, therefore, one can expect that this relationship reflects only the role of solar radio flux Fl,,.,. Figure 2 shows a relationship between Ap and X AE exceeding 2000 gammas. The value Ap-the difference between the magnitude of the measured density and the density 181
YU. L. TRUTTSE
182
I
I
/
/
’
I /
6-
4-
a_
O0
Fro. 1.
H = 270km AS A FUNCTION OF SOLAR INJUNIII (JACCHUet al., 1963a) (CIRCLES) ANDEXPLOREX VI (MOE, 1966) (DOB). The values of density are cmrected for seasonal (JACCHUet al., 1968) and diurnal variations. For all cases 8 AE < 1000 gammas. The dashed line shows density vs. &., according to CIRA 1965.
RADIO
UPPER
FLUX
ATMOSPHERIC
F,,.,
DENSITY
Cl’Il FROM
DATA
FOR
A HEIGEIT
OF SA-
I
.
2
“E Q
h $
4.
I
3
.
.
. .
. .*
I
I
FIG. 2. UPPER ATMOSPHERIC DENSITY VARIATION FOR THE HEIOHT u = 270 km As A FUNGI-ION AE ACCDRDINO TO DATA OF ~ATELLI~ INJUNIII (JACCIUAet al., 1963a) (CIRCLES) AND EXF%OlWR VI (MOE, 1966) (DO-IS). The values of density are corrected for seasonal (Jaechia et al., 1968) and diurnal variation.
OF Z
UPPER ATMOSPHERE
DURING
GEOMAGNETIC
DISTURBANCES-III
183
determined after Fig. 1 for corresponding &,.,. The solid line in Fig. 1 is an average curve obtained by the exclusion of mean Ap values according to Fig. 2 from a large number of measured density values with different F,,.,. Figure 3 shows the ratio of Ap and X AE vs. the value F&,.,. It is evident that this relationship does not depend on F,., within the limits of actual errors in determining the density. The relationship between the density and Fl,,., is clearly of a non-linear nature while the relationship between Ap and X AE is linear within the errors of determining the density. For the sake of comparison, Fig. 1 shows by a dashed line the relationship between p and Fl,,., for the same altitude according to CIRA 1965. 4r
I
x “E
l
I
0
e E 0 m g w
I
-
. .
0
.
. .
2-
‘s
.
zi B _
000 0
.
l
:. .
l.
.
. ..*
l
..
l.
J3
0 0 m OO
0. I
I
100
200
xx,
FIO.7
FIc3.3. RELATMZ VARIATIONSOF DENSRYAP/~ AEAS A FIJNClTONOF Flo., DURING GEQMAGNEITC WHEN z AE > 2000 GAMMAS, FOR A HEIGHT H = 270 km ACCORDING TO DATA
DBTDRRANCl?S,
OFSATEL~~TESINXTNUI(JACCHIA~~~~.,~~~~~)(~IRC~)ANDEXPLORERVI(MOE,~~~~)(D~T~).
The relationship indicated in Figs. 4,5 and 6 for a height of 730 km have been obtained by a method similar to the relationship in Figs. 1, 2 and 3, respectively. In the main, the picture at this altitude too is similar to that which is observed at a height of 270 km. For a height of 730 km a wider section of linear relationship between p and Fl,,, is typical. It is worth noting that in the case of large values of Flw, there is a trend towards a density decrease (Fig. 4). However, there is nothing unexpected in this, if one takes into account that cases of low densities with large Flo., refer to summer time. At this level (H = 730 km) the atmosphere contains a large amount of light elements which can be transferred to the winter hemisphere. Thus, there is an abundance in the winter hemisphere and a deficiency in the summer hemisphere (Shefov, 1968). A similar relationship is obtained for other altitudes too, but attention is not drawn to these since the main data on density derived from satellite drag was obtained at a low level of solar activity, when non-linearity could not be detected. Figure 7 shows upper atmospheric density variation from 8 August to 7 September, 1959 according to Moe’s (1966) data (the thin line) and according to CIRA 1965 (the dashed line), taking into consideration Flo., and a, indices corresponding to this time. The same figure shows (the thick line) upper atmospheric density calculated for the same time instants from its relationship with F,,., and B AE presented in Figs. 1 and 2. A similar picture is observed for other altitudes too. Thus, combined use of a non-linear relationship between density and F,., and a linear relationship between density and E AE leads to the so far optimal description of upper atmospheric density, which does not deviate from density measured within the limits of errors ofinitial data. To describe the upper atmospheric
YU. L. TRUTTSE
184
-,. ”
FIG.4.
UPPER ATMOSPHERIC DENSITY FOR A HEIGHT H= 730klll VS. .WLAR RADIO FLUX F,,., ACCORDING TO DATA OF SATELLITES EXPLORER IX (JACCHU et al., 1963b) (CIRCLES) AND
VANGUARD I (1958 82) (JACCHIAet al., 1963c) (DOTS). The values of density are corrected for seasonal (Jacchia et al., 1968) and diurnal variation. For all cases B AE > 1000 gammas. The dashed line shows density vs. Fio., according to the CIRA 1965.
I
I .
.
a’ .
.
e .
30
FIG. 5. UPPERATMOSPHERIC DENSITY VARIATION FORTHEHEIGHTH = 730 km ASA FUNCTION (JA~wIA~~ al., 1963b) (CIRCLES) al., 1963c) (DOTS). The values of density are corrected for seasonal (Jacchia et al., 1968) and diurnal variations.
OF 22 AE ACOORDINGTODATAOF SATELLITZSERPLORERIX AND VANGUARD I (1958 82) (JACCHUet
UPPER ATMOSPHERE DURING GEOMAGNETIC DISTLJRBANfXS-III
x3
I
“E
O
I
P
El-
8 8
E*-
b’
P
Q90
.*
*
l
l .
,a0 0
I
0
.
.
0
0 : 0 0 O08
P
185
l
*
.. .*
t
200
loo
Jo0
F107 FIG. 6. REtmn% VARIATIONS OF DENSITY ApiE AE As A FUNCXION OF F,,., DURING GEGMAGNKiW DIED, WHEN z: AE > 2000 OMBrlAs,FGR A iiEiGBTH = 730 km ACCORDING To
DATA OF SATELLW
EXPLORER IX (JACCX-Uet al., 1963b) (cmcus) AND VANCWARDI (1958 @2) (JACWJA et al., 1963c) (WTS).
A%rYCT
RO.7. bU?4RISONOF WITH VALUESiXLCULA_
1959
CeHT5SPb
MEASURED VALUESOF DENSITY(EXPLORERVI, MOE, 1966) (THIN I.& BY US (THICK LINE) AND ACCORDING TO ch?A 1965 (DASHEDLINS).
structure more precisely, one needs more exact measurements of the upper atmospheric density with high resolution in time, as well as more perfect AE indices, which at present are determined only from data of eight stations in the northern auroral zone. However, the auroral zone changes its position during the day (Feldstein, 1960; Khorosheva, 1962) and therefore, it is desirable to obtain AE indices from the data of a more widely dispersed network of stations both in the Northern and Southern Hemispheres. However, results obtained when use is made of existing indices and data about upper atmospheric density required an explanation. In the first place, one should understand a non-linear relationship between density and F1,,., with the discontinuation of the growth
186
YU. L. TRUTTSE
of density in case of high F,,.,. The nature of this relationship differs essentially from a corresponding relationship represented in CZZU 1965. The limitation of density growth may be for two reasons. In the first place, this can be the consequence of the expansion of the heated region and of its penetration into a given height region. Secondly, it is highly probable that it is caused by a non-linear relationship between the ultraviolet radiation absorption in the upper atmosphere and Fle,, and by the increase in the outflow of heat from the upper atmosphere with the increase of the temperature. The latter is very likely since, with the increase in the temperature, enhanced concentrations of NO may come into being which cool the atmosphere at the expense of infrared radiation. The increase in the molecular NO content during geomagnetic disturbances is confirmed by the increase in the intensity of the night sky emission continuum (Truttse, 1968). However, if during geomagnetic disturbances an additional heating of the upper atmosphere occurs, its contribution must be lower in the case of great values of Fle,, and the relationship between hp and Z AE be as non-linear as the relationship between p and Flo.,. However, so far this has not been observed within the accuracy of initial data. At present, we are unable to explain the above features. However, when this problem was discussed with Professor Krassovsky, he expressed the idea that the effect of geomagnetic disturbances is not necessarily associated with global heating of the upper atmosphere. This effect can also reflect the process of the oscillation in the height of the levels of similar density. This may be the consequence of the generation of infrasonic or gravitational waves in the regions of pulsed electrojets in the aurora1 zone and their rapid propagation throughout the atmosphere. It is noteworthy that the most intense elcctrojets appear during break-ups, when aurorae are broken into separate short-lived rays. During even very intense aurorae no increase in the temperature of the upper atmosphere below 200 km has so far been observed (Hilliard et al., 1966), i.e., at a height where the main heating and expansion of the atmosphere should have taken place. This has already been explained (Krassovsky, 1968) by the appearance of a great number of molecules NO cooling the upper atmosphere. All these indicate that there are no reasons for the heating of the upper atmosphere at levels below 200 km outside the aurora1 zone. On the other hand, magnetohydrodynamic, gravitational and infrasonic waves can be absorbed at higher regions of the atmosphere and create localized heating there in the regions of middle latitudes, where intense emission of atomic oxygen at 6300 A originates. However, to explain all above-mentioned circumstances reliably, it would be necessary to carry out direct temperature measurements in the upper atmosphere and use groundbased determination of Doppler contours of its emissions, and to make a thorough check of the known spectroscopic determinations of temperatures (Hilliard et al., 1966) at different latitudes during geomagnetic perturbations. Acknowledgement-The author would like to express his gratitude to Professor Krassovsky for continued interest and for active discussion of the results of this paper.
CIRA (1965). COSPAR International Reference Atmosphere, 1965 North-Holland, Amsterdam. DAVIS,T. N. and PARTIMM~Y R. (1967). J. geophys. Res. 72,582s. FELD~~FXN, Y. I. (1960). Invest. of aurorae, USSR Acud. Sci. 4,61. HILLIARD,R. L. and SHBPHERD, G. G. (1966). Planet. Space Sci. 14,383. JACCHIA,L. G. and SLOW, J. (1963a). Smithson. Astrophys. Obs. Spec. Rep. No. 136. JACCHU,L. G. and SLOWEY,J. (1963b). Smithson. Astrophys. 06s. Spec. Rep. No. 125.
UPPER ATMOSPHERE
DURING
GEOMAGNETIC
DISTURBANCES-III
187
JACCHIA, L. G. and SLOWBY,J. (1963c). Smithson. Contr. Astrop&. 8,l. JACCHIA, L. G., SLOWEY,J. W. and CAMPBELL, I. G. (1968). Smithson. Astrophys. Obs. Spec. Rep, No. 265. KRA.WNSKY, V. I. (1968). Nature, Lad 217, 1136. KHOROSHEVA, 0. V. (1962). Geomag. & Aeronomy, U.S.S.R. 2, 696. (English Transl.) MOE, K. (1966). Planet. Space Sci. 14, 1065.
Smov, N. N. (1968). Planet. Space Sci. 16, 1103. Tkmrsts, Yu. L. (1968). Planet. Spuce Sci. 16, 140. TRUTTSE,Yu. L. (1968). Planet. Space Sci. 16,981. TRUTTSE,Yu. L. (1968). Planet. Space Sci. 16, 1201.