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The energy hysteresis of the galactic cosmic ray intensity
0273- 1177(95)00340-2
Adv. Space Res. Vol. 16, No. 9, pp. (9)227-(9)231. 1995 Copyright 0 1995 COSPAR Printed in Great Britain. All ti hts reserved. 0273-I 177/9 f $9.50 + 0.00
THE ENERGY HYSTERESIS OF THE GALACTIC COSMIC RAY INTENSITY G. A. Bazilevskaya, M. B. Krainev, V. S. Makhmutov, Yu. I. Stozhkov, A. K. Svirzhevskaya and N. S. Svirzhevsky P. IV.Lebedev Physical Institute, Russian Academy of Sciences, Leninsky Prospect 53, 117924 Moscow, Russia
ABSTRACT
The time series on the galactic cosmic ray (GCR) intensity in the rigidity range -i-l0 GV for 1957-93 are correlated so as to isolate the periods of the energetic hysteresis. A significant excess of the low energy GCR intensity was found for 1988-90. During all four periods of high solar activity and the inversion of the solar magnetic field the phenomena similar to the well-known hysteresis of 1969-71 occur though of different magnitudes. INTRODUCTION When considering the history of the GCR intensity one can isolate the periods when the low and high energy particle intensities change in phase in accordance with the energy dependence of the long-term variation (the “normal” behavior) separated by the shorter periods when this correlation breaks down. The outstanding phenomena of this kind occurred in 1969-71 (see /l/j, 1981-84 /2/ and, as we shall show, in 1988-90. It is widely believed that they are due exclusively to the different time of response of the high and low energy particles to the sudden changes in the heliospheric characteristics (the phase-lag effect) /3/. We worked on the different hypothesis and associated the energy hysteresis during the periods of high solar activity with the inversion of the global magnetic field on the Sun and in the heliosphere /4-6,‘. In this paper we consider the long time series, mainly our stratospheric data, to separate the periods of the normal behavior of the GCR intensity in the -1-10 GV rigidity range during the 1i-year variation from the anomalous ones. THE EXPERIMENTAL DATA AND METHOD OF THEIR ANALYSIS From the monthly averaged stratospheric data we obtain two time series: the low rigidity (Ri=i-2 GV) intensity, Ii, (the count rate at 8-16 g/cm2 atmospheric depth due to the primary particles in the 0.6-2.4 GV rigidity range) and the intermediate rigidity (R2=3-6 GV) intensity, 12, (the count rate in the transition maximum, Murmansk). As a higher rigidity (R3=6-12 GV) intensity, 13, we use the Climax neutron monitor count rate. The above limits approximately correspond to the changes in the effective rigidity for each time series during the solar cycle. To analyse the rigidity dependence of the GCR intensity variations in, e.g., RI-R2 range we, as usual,
keep track of the point (12, Ii) in plane 12-11. If in the course (9)227
G. A. Bdevskaya
(9)228
et al.
of I l-year cycles this point tracks the same path II with one-to-one correspondence between 11 and 12 we refer to this path as the “normal” one for the quasistationary 1l-year variation. Of course, there are the short-term variations superposed on the long-term one so the normal path is substituted by the normal band. The excursion of the point (12, II) beyond this band for an extended time period (r 1 year long) forms a loop or at least breaks the above one-to-one correspondence and this phenomenon is called the energy hysteresis. As for the cosmic rays of reasonably high rigidity R the intensity is often represented by by ICR, t) = Io(R)exp(-BCR. t )) and the energy dependence of its variation d1/1 =AR-Y, it makes sense to track the trajectory of the above point in the (lnI2lnIl)-plane.
5.61-4.69 -.+-+*-+7. 57- 5. 61
/ / ---
I /
-
--__-
.+,-++-*
~-.--__-.-
7. 81- ‘l 1 . 88 --.-a-c+-* 11.88-72.93
1.71-5.8
7.84-l 1 5. 8@_ 7.
-_-.-------__._..~-_._
L_N C II
3- 6
CA/>
,‘*
’ )\ J
-_. _. _____..-_-
>
Fig. 1. The regression curves in log-log scale between the intensity in 3-6 GV rigidity range (the higher energy, X-axis) and the intensity in O-6-2.4 GV rigidity range (the lower energy, Y-axis) for the periods indicated in each quadrant.
Energy Hysteresis of the Galactic Cosmic Ray Intensity
(9)229
THE DATA ANALYSIS AND DISCUSSION rw In each quadrant, a-d, of Figure 1 the regression is shown between 12 and 11 ‘intensities for the period of high solar activity (the dashed line with asterisks) and the adjacent periods of reasonably low activity (the solid lines). The intervals were chosen in such a way that the solid lines fit into the about linear regression band (shown by the dashed right-hand band in all four quadrants). The only exception is that in Figure 1, d, we show by the dashed line with asterisks all the 11.1988-12.1993 period (as the low activity period for the 1990s has only recently begun). One can see that the later part of this line (since the end of 1992) also lies for the most part within the right-hand band. In spite of the diversity of the dashed regression lines one can notice that on the average they lie in some band (the left-hand band in Figure 1, a-d). Sometimes there are small-scale excursions of the regression line beyond the left-hand “normal” band, for periods about the same when the energy hysteresis occurs in the high rigidity part of the range (see below). However the only systematic large-scale energy hysteresis is the loop in Figure 1, d, formed by the significant excess of the low rigidity particles in 1988-90. To consider this phenomenon further we show in Figure 2, a-c, the regression curves between 12 and II (in the normal scale) for all three complete 1l-year cosmic ray cycles. One can see the similar, though smaller in magnitude, effect in the 1970s and the small but discernible hysteresis in the 1960s. Of course, this effect should be carefully correlated with the GCR behavior at the same and lower rigidities in the interplanetary space. For the time being it looks as if this low energy GCR excess during the fall in the GCR intensity coupled with the strong deficit during the recovery of the intensity in 1981-84 / 2/ can be considered as a manifestation of a strong phase-lag effect due to the fast change of the modulating factor (whatever it is) in the 1980s. The smaller magnitude of this effect in the
195%1970 %/
B,
69
l-T-r-r-l-7-r-Tr-T-
24ti
~
c
in.
* I ..T I
.
ill
I... *.
Fig. 2. The regression between the intensity in the 3-6 GV range (X-axis) and that in l-2 GV range (Y-axis) for the periods indicated in each part of the figure. Both series are smoothed with 3 month period.
(9)230
G. A. Bazilevskaya et al.
1960s and the intermediate magnitude in the 1970s fit at least qualitatively into the above scheme, as in the 1986s the intensity changed much faster than in 1960s
while the time scale of the intensity decrease in 1978-80 was intermediate between those for 1967-69 and 198890. At the same time the periods when the excess of the low energy GCR occurs are about the same when the global merged interaction regions become the main factor of the Ii-year modulation /7/. They may cause the relative growth of the low energy cosmic ray intensity because of local acceleration.
The (R2-R3) riaiditv range. In Figure 3, a-d, the regression is shown between 13 and 12 intensities in the same format as in Figure I. One can see that for almost all the time the curves fit well into one linear rectangular band. The systematic excursions beyond this band occur during the periods of high solar activity and the inversion of the solar magnetic field. The sense of the effect is always the same (the -
I
3.58-6.69 \ / 2.72-8.79 *J-*-L-* 6.69-2.72
3.58-6.69 *-*-a+-.-* 7. 57-3. 58
I
-
-2.72-8.79 9.81-5.90 t-+-.-t-* 8.79-9.81
9.81-5.90 ' **-**-*5.90-12.93
LN
(
1(6--12
GVI
>
Fig. 3, The same as in Figure 1, but with the intensities in 6-12 GV and in 3-6 GV rigidity ranges serving as the higher (X-axis) and lower (Y-axis) energy intensities, respectively.
Energy Hysteresis of the Galactic Cosmic Ray Intensity
(9)23 I
excess of the higher rigidity intensity) although its magnitude in 1957-58, in 198990 and especially in 197981 is much smaller than in 1969-71. CONCLUSION The large-scale energy hysteresis between the intermediate (R=3-6 GV) and low (effective rigidity R=l-2 GV) rigidity GCR intensities is revealed for 198190 that means the considerable excess of the low energy particles in 198890. The loops of the same sense though of progressively smaller magnitudes are observed for the 1970s and 1960s. This effect may be a manifestation of the nonstationasity of the modulation. During all four periods of high solas activity and the inversion of the solas magnetic field the effects of the energy hysteresis occus between the high (R=6-12 GV) and intermediate (R=3-6 GV) rigidity intensities. In all cases the sense of the effect is the same, i.e., the relative excess of the higher rigidity particles, the magnitude being different for the different periods. ACKNOWLEDGEMENTS We would like to thank Dr. K.R. Pyle for providing us with the Climax neutron monitor data (University of Chicago, NSF Grant ATM-9215122). This research was supported, in past, by RFFI under Grant 93-02-3006 and by a Sosos Foundation Grant awarded by the American Physical Society. REFERENCES 1. H. Mosaal, Modulation observations, Prvc. Wh ICRC, Muochen, 1I, 3896-3906 (1975). 2. F.B. McDonald, T.T. van Rosenvinge, N. Lal, J.H. Tsainor, and R. Schuster, The recovery phase of galactic cosmic say modulation in the outer heliosphere, Pr-oc. 20th ICRC, Moscow, 3, 397-400 (1987). 3. J.J. O’Gallagh er, A time-dependent diffusion-convection model for the long-term modulation of cosmic says, Astmphysicul Journal, 197, 495 (1975). 4. A.K. Svirzhevskaya, Yu.1. Stozhkov, and T.N. Charakhchyan, Anomalous effect in the spectrum of cosmic say variations in 1971-1973, P~Yx. 14th ICRC, Munchen, 3, 985989 (1975). 5 M.B. Ksainev, Yu.1. Stozhkov, and T.N. Charakhchyan, On the energetic “hysteresis” in the galactic cosmic say intensity, PYCX. t8th ICRC, Bangalore, 3, 23-26 ( 1983). 6. M.B. Krainev, The intensity of the galactic cosmic rays in the periods of the beginning of the inversion of general magnetic field of the Sun, Imestiya AN S.!W?, ser. fiz., 55, 1942-1945 (in Russian) (1991) . 7. M.S. Potgieter, J.A. LeRoux, F.B. McDonald, and L.F. Burlaga, The causes of the ll-year and 22-year cycles in cosmic-ray modulation, Proc. 23-d ICRC, Calgary, 3, 525-528 (1993).
Adv. Space Res. Vol. 16, No. 9, pp. (9)227-(9)231. 1995 Copyright 0 1995 COSPAR Printed in Great Britain. All ti hts reserved. 0273-I 177/9 f $9.50 + 0.00
THE ENERGY HYSTERESIS OF THE GALACTIC COSMIC RAY INTENSITY G. A. Bazilevskaya, M. B. Krainev, V. S. Makhmutov, Yu. I. Stozhkov, A. K. Svirzhevskaya and N. S. Svirzhevsky P. IV.Lebedev Physical Institute, Russian Academy of Sciences, Leninsky Prospect 53, 117924 Moscow, Russia
ABSTRACT
The time series on the galactic cosmic ray (GCR) intensity in the rigidity range -i-l0 GV for 1957-93 are correlated so as to isolate the periods of the energetic hysteresis. A significant excess of the low energy GCR intensity was found for 1988-90. During all four periods of high solar activity and the inversion of the solar magnetic field the phenomena similar to the well-known hysteresis of 1969-71 occur though of different magnitudes. INTRODUCTION When considering the history of the GCR intensity one can isolate the periods when the low and high energy particle intensities change in phase in accordance with the energy dependence of the long-term variation (the “normal” behavior) separated by the shorter periods when this correlation breaks down. The outstanding phenomena of this kind occurred in 1969-71 (see /l/j, 1981-84 /2/ and, as we shall show, in 1988-90. It is widely believed that they are due exclusively to the different time of response of the high and low energy particles to the sudden changes in the heliospheric characteristics (the phase-lag effect) /3/. We worked on the different hypothesis and associated the energy hysteresis during the periods of high solar activity with the inversion of the global magnetic field on the Sun and in the heliosphere /4-6,‘. In this paper we consider the long time series, mainly our stratospheric data, to separate the periods of the normal behavior of the GCR intensity in the -1-10 GV rigidity range during the 1i-year variation from the anomalous ones. THE EXPERIMENTAL DATA AND METHOD OF THEIR ANALYSIS From the monthly averaged stratospheric data we obtain two time series: the low rigidity (Ri=i-2 GV) intensity, Ii, (the count rate at 8-16 g/cm2 atmospheric depth due to the primary particles in the 0.6-2.4 GV rigidity range) and the intermediate rigidity (R2=3-6 GV) intensity, 12, (the count rate in the transition maximum, Murmansk). As a higher rigidity (R3=6-12 GV) intensity, 13, we use the Climax neutron monitor count rate. The above limits approximately correspond to the changes in the effective rigidity for each time series during the solar cycle. To analyse the rigidity dependence of the GCR intensity variations in, e.g., RI-R2 range we, as usual,
keep track of the point (12, Ii) in plane 12-11. If in the course (9)227
G. A. Bdevskaya
(9)228
et al.
of I l-year cycles this point tracks the same path II with one-to-one correspondence between 11 and 12 we refer to this path as the “normal” one for the quasistationary 1l-year variation. Of course, there are the short-term variations superposed on the long-term one so the normal path is substituted by the normal band. The excursion of the point (12, II) beyond this band for an extended time period (r 1 year long) forms a loop or at least breaks the above one-to-one correspondence and this phenomenon is called the energy hysteresis. As for the cosmic rays of reasonably high rigidity R the intensity is often represented by by ICR, t) = Io(R)exp(-BCR. t )) and the energy dependence of its variation d1/1 =AR-Y, it makes sense to track the trajectory of the above point in the (lnI2lnIl)-plane.
5.61-4.69 -.+-+*-+7. 57- 5. 61
/ / ---
I /
-
--__-
.+,-++-*
~-.--__-.-
7. 81- ‘l 1 . 88 --.-a-c+-* 11.88-72.93
1.71-5.8
7.84-l 1 5. 8@_ 7.
-_-.-------__._..~-_._
L_N C II
3- 6
CA/>
,‘*
’ )\ J
-_. _. _____..-_-
>
Fig. 1. The regression curves in log-log scale between the intensity in 3-6 GV rigidity range (the higher energy, X-axis) and the intensity in O-6-2.4 GV rigidity range (the lower energy, Y-axis) for the periods indicated in each quadrant.
Energy Hysteresis of the Galactic Cosmic Ray Intensity
(9)229
THE DATA ANALYSIS AND DISCUSSION rw In each quadrant, a-d, of Figure 1 the regression is shown between 12 and 11 ‘intensities for the period of high solar activity (the dashed line with asterisks) and the adjacent periods of reasonably low activity (the solid lines). The intervals were chosen in such a way that the solid lines fit into the about linear regression band (shown by the dashed right-hand band in all four quadrants). The only exception is that in Figure 1, d, we show by the dashed line with asterisks all the 11.1988-12.1993 period (as the low activity period for the 1990s has only recently begun). One can see that the later part of this line (since the end of 1992) also lies for the most part within the right-hand band. In spite of the diversity of the dashed regression lines one can notice that on the average they lie in some band (the left-hand band in Figure 1, a-d). Sometimes there are small-scale excursions of the regression line beyond the left-hand “normal” band, for periods about the same when the energy hysteresis occurs in the high rigidity part of the range (see below). However the only systematic large-scale energy hysteresis is the loop in Figure 1, d, formed by the significant excess of the low rigidity particles in 1988-90. To consider this phenomenon further we show in Figure 2, a-c, the regression curves between 12 and II (in the normal scale) for all three complete 1l-year cosmic ray cycles. One can see the similar, though smaller in magnitude, effect in the 1970s and the small but discernible hysteresis in the 1960s. Of course, this effect should be carefully correlated with the GCR behavior at the same and lower rigidities in the interplanetary space. For the time being it looks as if this low energy GCR excess during the fall in the GCR intensity coupled with the strong deficit during the recovery of the intensity in 1981-84 / 2/ can be considered as a manifestation of a strong phase-lag effect due to the fast change of the modulating factor (whatever it is) in the 1980s. The smaller magnitude of this effect in the
195%1970 %/
B,
69
l-T-r-r-l-7-r-Tr-T-
24ti
~
c
in.
* I ..T I
.
ill
I... *.
Fig. 2. The regression between the intensity in the 3-6 GV range (X-axis) and that in l-2 GV range (Y-axis) for the periods indicated in each part of the figure. Both series are smoothed with 3 month period.
(9)230
G. A. Bazilevskaya et al.
1960s and the intermediate magnitude in the 1970s fit at least qualitatively into the above scheme, as in the 1986s the intensity changed much faster than in 1960s
while the time scale of the intensity decrease in 1978-80 was intermediate between those for 1967-69 and 198890. At the same time the periods when the excess of the low energy GCR occurs are about the same when the global merged interaction regions become the main factor of the Ii-year modulation /7/. They may cause the relative growth of the low energy cosmic ray intensity because of local acceleration.
The (R2-R3) riaiditv range. In Figure 3, a-d, the regression is shown between 13 and 12 intensities in the same format as in Figure I. One can see that for almost all the time the curves fit well into one linear rectangular band. The systematic excursions beyond this band occur during the periods of high solar activity and the inversion of the solar magnetic field. The sense of the effect is always the same (the -
I
3.58-6.69 \ / 2.72-8.79 *J-*-L-* 6.69-2.72
3.58-6.69 *-*-a+-.-* 7. 57-3. 58
I
-
-2.72-8.79 9.81-5.90 t-+-.-t-* 8.79-9.81
9.81-5.90 ' **-**-*5.90-12.93
LN
(
1(6--12
GVI
>
Fig. 3, The same as in Figure 1, but with the intensities in 6-12 GV and in 3-6 GV rigidity ranges serving as the higher (X-axis) and lower (Y-axis) energy intensities, respectively.
Energy Hysteresis of the Galactic Cosmic Ray Intensity
(9)23 I
excess of the higher rigidity intensity) although its magnitude in 1957-58, in 198990 and especially in 197981 is much smaller than in 1969-71. CONCLUSION The large-scale energy hysteresis between the intermediate (R=3-6 GV) and low (effective rigidity R=l-2 GV) rigidity GCR intensities is revealed for 198190 that means the considerable excess of the low energy particles in 198890. The loops of the same sense though of progressively smaller magnitudes are observed for the 1970s and 1960s. This effect may be a manifestation of the nonstationasity of the modulation. During all four periods of high solas activity and the inversion of the solas magnetic field the effects of the energy hysteresis occus between the high (R=6-12 GV) and intermediate (R=3-6 GV) rigidity intensities. In all cases the sense of the effect is the same, i.e., the relative excess of the higher rigidity particles, the magnitude being different for the different periods. ACKNOWLEDGEMENTS We would like to thank Dr. K.R. Pyle for providing us with the Climax neutron monitor data (University of Chicago, NSF Grant ATM-9215122). This research was supported, in past, by RFFI under Grant 93-02-3006 and by a Sosos Foundation Grant awarded by the American Physical Society. REFERENCES 1. H. Mosaal, Modulation observations, Prvc. Wh ICRC, Muochen, 1I, 3896-3906 (1975). 2. F.B. McDonald, T.T. van Rosenvinge, N. Lal, J.H. Tsainor, and R. Schuster, The recovery phase of galactic cosmic say modulation in the outer heliosphere, Pr-oc. 20th ICRC, Moscow, 3, 397-400 (1987). 3. J.J. O’Gallagh er, A time-dependent diffusion-convection model for the long-term modulation of cosmic says, Astmphysicul Journal, 197, 495 (1975). 4. A.K. Svirzhevskaya, Yu.1. Stozhkov, and T.N. Charakhchyan, Anomalous effect in the spectrum of cosmic say variations in 1971-1973, P~Yx. 14th ICRC, Munchen, 3, 985989 (1975). 5 M.B. Ksainev, Yu.1. Stozhkov, and T.N. Charakhchyan, On the energetic “hysteresis” in the galactic cosmic say intensity, PYCX. t8th ICRC, Bangalore, 3, 23-26 ( 1983). 6. M.B. Krainev, The intensity of the galactic cosmic rays in the periods of the beginning of the inversion of general magnetic field of the Sun, Imestiya AN S.!W?, ser. fiz., 55, 1942-1945 (in Russian) (1991) . 7. M.S. Potgieter, J.A. LeRoux, F.B. McDonald, and L.F. Burlaga, The causes of the ll-year and 22-year cycles in cosmic-ray modulation, Proc. 23-d ICRC, Calgary, 3, 525-528 (1993).