spatial distribution of the auroral precipitation zones during storms connected with magnetic clouds...
TRANSCRIPT
Spatial distribution of the auroral
precipitation zones during storms
connected with magnetic clouds
O.I. Yagodkina1, I.V. Despirak1, V. Guineva2
1. Polar Geophysical Institute, Apatity, Russia
2. Solar-Terrestrial Influences Institute,
Stara Zagora, Bulgaria
Introduction
Solar wind flow may be different depending on the state of solar activity. During solar minimum, the recurrent streams (RS) originating from coronal magnetic holes, characterized by 27-day recurrence, are predominant. During solar maximum, most common are sporadic flows associated with coronal mass ejections (CME). Near the Earth they are observed as magnetic clouds (MC).
It should be noted that three of these structures, namely, Sheath, CIR, and MC, are the sources of geomagnetic storms.
Ahead of both MC and RS, the regions of interaction with undisturbed solar wind (Sheath and CIR) are known to form, which are characterized by high density, increased pressure and strong IMF variability.
The dynamics of the spatial distribution of the different auroral precipitations zones was studied by DMSP satellites data. The examination was implemented depending on the geomagnetic disturbance level, expressed by the AL- and Dst indices.
Three zones of auroral electron precipitation were determined:
1) DAZ - diffuse auroral zone, coinciding with the diffuse aurora;
2) AOP - auroral oval precipitation, coinciding with the statical discrete auroral oval;
3) SDP - soft diffuse precipitation
In this work, the mean position of the different precipitation zones boundaries were determined, depending on the level of the magnetic activity in 06-09 MLT and 18-21 MLT sectors for three cases of observed solar wind magnetic clouds: on January 10, 1997, on October 21-22, 2001 and on July 15, 2000.
Aim of this study: To investigate how different structures in the solar wind affect the different auroral presipitations zones (namely, the magnetic clouds)
Solar wind magnetic clouds (MC) were determined from interplanetary medium parameters registered by the Wind satellite.
-8 00
-4 00
0
-80
-40
0
40
80
-10
-5
0
5
10
-20
-10
0
10
20
-20
-10
0
10
20
3 00
4 00
5 00
6 00
0
20
40
60
80
0E + 0 001E + 0 052E + 0 053E + 0 054E + 0 055E + 0 05
0
5
10
15
20
AL, nT
Bx, nT
By, nT
Bz, nT
V, km /s
N, cm -3
T
P, nPa
08 16 24 08 16 2400January 10, 1997 January 11, 1997
D st nT ,
U T
Magnetic cloud 10 January 1997
Solar wind, IMF parameters and geomagnetic activity on January 10-11, 1997. From top to bottom the AL- and Dst-indices, the magnetic field components (Bx, By, Bz), the solar wind velocity, density, temperature and dynamic pressure from WIND spacecraft are shown.
The magnetic cloud has begun at 05:40 UT, 10 Jan. and has ended at 01 UT, 11 Jan. Inside the magnetic cloud the Bz component of IMF slowly rotated. The storm has been initiated when the sheath region of the interplanetary magnetic cloud reached the magnetosphere. During this storm the AL- and Dst indices reached values of 600 nT and 80 nT, accordingly.
0 5 10 15 20 25
-800
-600
-400
-200
0
AL
, nT
0 5 10 15 20 25
-80
-40
0
40
Dst
, nT
10/01/97
10 January 1997
1) 02 UT
2) 09 UT
3) 11 UT
4) 21 UT
02 UT 09 UT
11 UT 21 UT
60
70
80
90
60
70
80
90
50
60
70
80
0 8 16 24 32 40 48
50
60
70
80
D AZ eq(b1e)
AO Peq(b2e)
06-09
06-09
AO Pp(b5e)
SD Pp(b6)
18-21
18-21
U T
-100
0
100
-800
-400
0
D st, nT
January 10, 1997 January 11, 1997
18-21
06-09
06-09
AL, nT
de
gre
es
de
gre
es
de
gre
es
de
gre
es
18-21
Position of the DAZ, AOP and SDP zone boundaries and AL- and Dst indices of magnetic activity during January 10-11, 1997
06-09 MLT (blue lines) 18-21 MLT (black lines)
Crosses and circles show the boundaries location registered by DMSP F10 and F12.
variations of the magnetic activity in AL and Dst indices.
variations of the poleward boundary of soft diffuse precipitation zone (SDP), the poleward boundary of auroral oval precipitation zone (AOP p), the equatorward boundary of auroral oval precipitation zone (AOP eq) and the equatorward boundary of the diffuse auroral precipitation zone(DAZ).
The model calculations are generally in very good agreement with the experiment.
55 60 65 70 75
55
60
65
70
75
r=0 .67
January 10 -11 , 1997. 06-09 M LT. F10, F12 N - and S - hem ispheres.
60 65 70 75 80
60
65
70
75
80
r=0 .61
D A Z eq A O P eq
60 65 70 75 80
60
65
70
75
80 r=0.56
60 65 70 75 80 85
60
65
70
75
80
85
r=0 .75
A O P po lS D P
calcu late
experim ent
55 60 65 70 75
55
60
65
70
75
r=0.64
January 10-11 , 1997. 18 -21 M LT. F10, F12, F13 N - and S - hem ispheres .
55 60 65 70 75
55
60
65
70
75
r=0.61
D A Z eq D A Z po l
65 70 75 80
65
70
75
80 r=0.34
65 70 75 80
65
70
75
80
r=0.55
A O P po l SD P
experim ent
ca lcu late
The correlation between the experimental and the calculated boundaries on January 10-11, 1997
The vertical axis represents the registered by the satellite (Φ´exp) boundary latitudes, and the horizontal axis - the obtained by the use of analytical formulas ones (Φ´calc). The correlation coefficients are shown for each case.
0 1 2 24 3 6 4 8
-2 00-1 60-1 20
-80-40
0
0 12 24 3 6 48
-1 50 0
-1 00 0
-5 00
0
D st, nT
A L, nT
O ctober 21, 2001 O ctober 22 , 2001
Magnetic cloud 21 October 2001
19 UT 22 UT
01 UT 04 UT
19 UT22 UT
01 UT
04 UT
15-16.07.2000 Magnetic cloud
0
1 0 0 0 0 0 0
2 0 0 0 00 0
3 00 0 0 0 0
T, K
0
10
2 0
30
N, c
m-3
0
2 0
40
P, n
Pa
-1 2 0 0
-10 00
-8 0 0
-6 0 0
Vx, k
m/s
0
2 0
4 0
BT
, Bz ,
nT
1 2 :0 0 2 4 :0 0 3 6 :0 01 5 .0 7 .2 0 0 0 1 6 .0 7 .2 0 0 0
S h ea th M C
0 12 24 36 48
-300
-200
-100
0
Dst
, nT
l
-400
-300
-200
-100
0
AL
, n T
l
16, 22 UT
08 ,12, 18, 22 UT
The global distribution of auroral precipitations zones Magnetic cloud 15 – 16 July 2000
16 UT 22 UT 08 UT 16.07
- SD P
- AO P
- D AZ
12 UT 18 UT 22 UT
0 -400 -800 -1200
1.5
2
2.5
3
3.5
4
4.512-15 M LT
AL, nT
0 -400 -800 -1200
1
2
3
4
5
6
09-12 M LT
AL, nT
degrees
0 -400 -800 -1200
3
4
5
6
7
15- 18 M LT
AL, nT
0 -400 -800 -1200
4
4.4
4.8
5.2
5 .6
6
06- 09 M LT
AL, nT
0 -400 -800 -1200
0
4
8
12
16 18-21 M LT
AL, nT
0 -400 -800 -1200
4
4.4
4.8
5.2
5 .6
6
06- 09 M LT
AL, nT
0 -400 -800 -1200
0
4
8
12
16
20
2421- 24 M LT
AL, nT
0 -400 -800 -1200
4
8
12
16
20
00-03 M LT
AL, nT
The AOP region width depending on AL variations for different type of storms.Red – 15.07.2000. Blue – 21-22.10.2001. Black – 10-11.01.1997
100 0 -100 -200 -300 -400
1
2
3
4
512-15 M LT
D st, nT
degrees
100 0 -100 -200 -300 -400
1
2
3
4
5
6
09-12 M LT
Dst, nT
degrees
100 0 -100 -200 -300 -400
3
4
5
6
7
15-18 M LT
Dst, nT
100 0 -100 -200 -300 -400
4
4.4
4.8
5.2
5.6
6
06-09 M LT
Dst, nT
100 0 -100 -200 -300 -400
0
4
8
12
16
18-21 M LT
Dst, nT
100 0 -100 -200 -300 -400
4
8
12
16
2003-06 M LT
Dst, nT
100 0 -100 -200 -300 -400
0
4
8
12
16
20
24
21-24 M LT
Dst, nT
100 0 -100 -200 -300 -400
4
8
12
16
20
00-03 M LT
D st, nT
The AOP region width depending on Dst variations for different type of storms.Red – 15.07.2000. Blue – 21-22.10.2001. Black – 10-11.01.1997
Conclusions
• Comparisons between the precipitation boundary position observed by DMSP and the calculated precipitation characteristics show a very good correlation.
• An equatorward displacement of precipitation up to 40° CGL is observed.
• DAZ and AOP appear to be the widest auroral precipitation zones in the evening – morning MLT sectors. The AOP size does not change on the dayside.
• The latitudinal size of AOP is controlled by the Dst and AL indices.
An empirical model has been used to study the auroral precipitation during MC. The following conclusions were made: