study of the aurora emissions during substorms connected with different solar wind streams i.v....
TRANSCRIPT
Study of the aurora emissions during
substorms connected with different
solar wind streams
I.V. Despirak1, Zh. V. Dashkevich1, V.
Guineva2
1. Polar Geophysical Institute, Apatity, Russia
2. Solar-Terrestrial Influences Institute,
Stara Zagora Department, Bulgaria
Aim of this study:
To investigate how the different streams in the solar wind: recurrent streams (RS) and magnetic clouds (MC) affect the variation of aurora emissions during substorms
Spistbergen PGI photometer data from the 2005/2008 winter seasons have been used to study the behaviour of auroral 6300 Å and 5577 Å emissions and I6300/I5577 intensity ratio.
Solar wind recurrent streams (RS) and magnetic clouds (MC) were determined from interplanetary medium parameters measured by the Wind satellite.
Substorm onset time and further development were verified by ground-based data of IMAGE magnetometers network and by data of all-sky camera at Spistbergen. Substorm westward electrojet development was defined by MIRACLE system.
The weather conditions have been checked using the all-sky camera images.
Wind: 05-08 January 20082 Cases: a Reccurent stream and a magnetic cloud1) CIR – 23:00 on 4 Jan.- 07:50 on 5 Jan.; RS - 07:50 on 5 Jan.– 18:00 on 8 Jan.,
3 substorms in the RS body:
• Substorm onset at 22:50 UT on 5 Jan. 2008, emissions from 22:50;
• Substorm - at 21:13 UT on 6 Jan. 2008, emissions from 21:15 UT;
• Substorm - at 21:55 UT on 6 Jan. 2008, emissions from 21:56 UT and from 22:32 UT.
RSCIR
Green vertical lines mark the photometer measurements times
Substorm onset 22:50
Substorm onset 22:50
05 January 2008
05 January 2008 Recurrent stream
23:00
0.2
0.24
0.28
0.32
0.36
0
1000
2000
3000
4000
5000
0
200
400
600
800
1000
05.01.2008
557.7nm
630.0 nm
I630/I557
22:50 23:00 23:10
0.2
0.21
0.22
0.23
0.24
0.25
0
1000
2000
3000
4000
5000
0
200
400
600
800
1000
05.01.2008
557.7nm
630.0 nm
I630/I557
21.05577/6300 II
06 January 2008 Recurrent stream
0.221:00 22:00 23:00
0
1
2
3
0
1000
2000
3000
0
400
800
1200
1600
2000
06.01.2008
557.7nm
630.0 nm
I630/I557
Intensity ratio inside the auroral bulge region ~0.2;
Intensity ratio at the polar edge of the substorm ~0.3÷0.5;
Ratio peaks correspond to softer energy of the electron precipitation flux.
06 January 2008Recurrent stream
21:40 21:50 22:00 22:10 22:20 22:30
0
0.4
0.8
1.2
1.6
2
0
1000
2000
3000
0
400
800
1200
1600
2000
06.01.2008
557.7nm
630.0 nm
I630/I557
Intensity ratio inside the auroral bulge ~0.2;
Intensity ratio at the polar edge of the substorm ~0.4;
24-25 December 2005 Magnetic cloudWIND:
Sheath
Substorm onset 20:25
MC
Substorm onset 20:25
Sheath
•Substorm onset at 20:25 UT on 24 Dec. 2005
Magnetic cloud24 December 2005
20:30 20:40 20:50
0
0.1
0.2
0.3
0.4
0.5
0
200
400
600
800
1000
R
0
40
80
120
160
200
240
24.12.2005557.7nm
630.0 nm
I630/I557
20:00 21:00 22:00
0
0.5
1
1.5
2
2.5
0
200
400
600
800
1000
R
0
200
400
600
24.12.2005557.7nm
630.0 nm
I630/I557
20:30 20:40 20:50
0
0.1
0.2
0.3
0.4
0.5
0
200
400
600
800
1000
R
0
40
80
120
160
200
240
24.12.2005557.7nm
630.0 nm
I630/I557
Substorm onset is on 20:25 UT by all-sky camera data and by IMAGE magnetometer network
Substorm reached Longyearbyen station in the interval 20:32 – 20:36 UT
Intensity ratio in this period is about 0.3
Discussion and conclusion
Annual average for Magnetic Clouds:6300/5577 = ~ 0.66 ±0.47
The auroral 5577 Å and 6300 Å intensity ratio characterizes the hardness of precipitation of the electron flux. This ratio is equal to ~(0.4-0.5) usually, that
corresponds to electron precipitation energy Eo ~ some keV.
Annual average for Recurrent streams: 6300/5577 = ~ 0.4
Our results: 1) the hardness of the precipitating electron flux increases during substorms;
2) for substorms during recurrent streams:
2.05577I/6300I
Hviuzova and Leontyev,
”Geomagnetism and Aeronomy” (1997, 2001)
5.03.05577/6300 II - at the polar edge of the auroral bulge
- inside the auroral bulge
3) for substorms during magnetic clouds:
3.05577I/6300I