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Published byJoshua Whitehead Modified over 9 years ago
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Study of the aurora emissions during substorms connected with different solar wind streams I.V. Despirak 1, Zh. V. Dashkevich 1, V. Guineva 2 1. Polar Geophysical Institute, Apatity, Russia 2. Solar-Terrestrial Influences Institute, Stara Zagora Department, Bulgaria
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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 I 6300 /I 5577 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.
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Wind: 05-08 January 2008 2 Cases: a Reccurent stream and a magnetic cloud 1) 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. RS CIR Green vertical lines mark the photometer measurements times
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Substorm onset 22:50 05 January 2008
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Recurrent stream
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06 January 2008 Recurrent stream 0.2 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.
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06 January 2008 Recurrent stream Intensity ratio inside the auroral bulge ~0.2; Intensity ratio at the polar edge of the substorm ~0.4;
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24-25 December 2005Magnetic cloud WIND: Sheath Substorm onset 20:25 MC Substorm onset 20:25 Sheath
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Substorm onset at 20:25 UT on 24 Dec. 2005
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Magnetic cloud24 December 2005 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
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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 E o ~ 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: Hviuzova and Leontyev, ”Geomagnetism and Aeronomy” (1997, 2001) - at the polar edge of the auroral bulge - inside the auroral bulge 3) for substorms during magnetic clouds:
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