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Introduction

Spatial distribution of the auroral precipitation zones during storms connected with magnetic clouds O.I. Yagodkina 1 , I.V. Despirak 1 , V. Guineva 2 1. Polar Geophysical Institute, Apatity, Russia 2. Solar-Terrestrial Influences Institute, Stara Zagora, Bulgaria. Introduction.

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Introduction

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  1. 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

  2. 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). Ahead of both MC and RS, the regions of interaction with undisturbed solar wind (Sheathand CIR) are known to form, which are characterized by high density, increased pressure and strong IMF variability. It should be noted that three of these structures, namely, Sheath, CIR, and MC, are the sources of geomagnetic storms.

  3. Aim of this study: To investigate howdifferent structures in the solar windaffect the different auroral presipitations zones (namely, the magnetic clouds) 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. 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. 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

  4. Magnetic cloud 10 January 1997 Solar wind magnetic clouds (MC)were determined from interplanetary medium parameters registeredby theWindsatellite. 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.

  5. 10 January 1997 02 UT 09 UT 21 UT 11 UT 2) 09 UT 4) 21 UT 1) 02 UT 3) 11 UT

  6. Position of the DAZ, AOP and SDP zone boundaries and AL- and Dst indices of magnetic activity during January 10-11, 1997 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). 06-09 MLT (blue lines) 18-21 MLT (black lines) Crosses and circles show the boundaries location registered by DMSP F10 and F12. The model calculations are generally in very good agreement with the experiment.

  7. 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.

  8. Magnetic cloud 21 October 2001 19 UT 22 UT 01 UT 04 UT 19 UT 04 UT 22 UT 01 UT

  9. 15-16.07.2000 Magnetic cloud 16, 22 UT 08 ,12, 18, 22 UT

  10. The global distribution of auroral precipitations zones Magnetic cloud 15 – 16 July 2000 22 UT 08 UT 16.07 16 UT 12 UT 22 UT 18 UT

  11. 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

  12. 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

  13. Conclusions An empirical model has been used to study the auroral precipitation during MC. The following conclusions were made: • 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.

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