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R. A. D. Fiori 1,2 , D. Boteler 1 , A. V.  Koustov 2

Magnetometer and radar study of the ionospheric convection response to sudden changes in the interplanetary magnetic field. R. A. D. Fiori 1,2 , D. Boteler 1 , A. V.  Koustov 2.

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R. A. D. Fiori 1,2 , D. Boteler 1 , A. V.  Koustov 2

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  1. Magnetometer and radar study of the ionospheric convectionresponse to sudden changes in the interplanetary magnetic field R. A. D. Fiori1,2, D. Boteler1, A. V.  Koustov2 1Natural Resources Canada, Geomagnetic Observatory, Ottawa, ON, Canada2University of Saskatchewan, Institute for Space and Atmospheric Studies, Saskatoon, SK, Canada

  2. Effect to be Investigated Following a southward turning of the IMF the convection pattern must transition from a Bz<0 multi-celled to a Bz<0 two-celled convection pattern ? Bz > 0 Bz < 0

  3. Two reconfiguration scenarios • Scenario 1: Ionospheric convection response begins at the dayside cusp region and propagates toward the nightside. • Scenario 2: The entire high-latitude ionosphere responds simultaneously in all MLT sectors.

  4. Objective • In this work, simultaneous observations and mapping of measurements from both the SuperDARN and ground-based magnetometer instruments are examined to attempt a more comprehensive picture of the phenomenon. • Resolve peculiarities!

  5. Event Study • Criteria • ACE data available • Sudden (<5 min) transition from at least +5nT to -5nT preceded by at least 1 hour of relatively stable IMF Bz • SuperDARN data available on a large scale (>500 points) • SuperMAG data available (2000 or 2001) • Transition in the early to mid afternoon to ensure good radar location • Events selected • January 20, 2001 • November 02, 2001

  6. IMF • A sharp southward transition in the IMF Bz at 10:25 UT is expected to arrive at the ionosphere at 11:58 UT

  7. Magnetometer-observed response delay=0 10.3 MLT (dayside) delay=12 1.5 MLT (nightside) • Magnetometer response time was identified as the start of any noticeable change to the perturbation magnetic field • In general, responses were delayed on the nightside compared to the dayside

  8. Magnetometer-observed response • The perturbation in the H component of the magnetic field was generated for all stations available from the SuperMAG data repository • Station locations are mapped in MLAT/MLT coordinates at 12:00 UT 14 MLT 10 MLT 05 MLT 03 MLT

  9. Magnetometer-observed response delay=6-8 min delay=0-8 min delay=5-12 min delay=0-1 min • The perturbation magnetic field enhanced to more positive or more negative values in response to a sharp transition in the IMF Bz • The shortest delays of 0-1 minutes were observed in the 10 MLT sectors, and the longest delays of 9-12 minutes were observed in the 14 MLT sector

  10. MLT/MLAT dependence observed by magnetometers 37 km/s January Event 1.5 km/s 21 km/s November Event • For the January and November events, 142 and 157 magnetometer traces were examined and 38 and 26 events were identified as having clear transition onsets. • Red and blue dots indicate enhancements and depressions in the magnetic field • Ionospheric response was first observed 1-2 MLT before noon, and then progressed toward midnight over 10-15 minutes • MLAT dependence is suggested by the November event

  11. MLT/MLAT dependence observed by magnetometers 37 km/s January Event #1 1.5 km/s 21 km/s November Event • For the January and November events, 142 and 157 magnetometer traces were examined and 38 and 26 events were identified as having clear transition onsets. • Red and blue dots indicate positive and negative gradients in the magnetic field • Ionospheric response was first observed 1-2 MLT before noon, and then progressed toward midnight over 10-15 minutes • MLAT dependence is suggested by the November event

  12. SuperDARN-observed response • The gridded l-o-s velocity was plotted for all grid cells of the 8 SuperDARN radars available for this event. • Radar fields-of-view and sample grid cells are mapped in MLAT/MLT coordinates at 12:00 UT.

  13. SuperDARN-observed response delay=~10 min delay=~10-15 min delay=~5 min delay=~5 min delay=~10 min • The average response time was 11 minutes for the PGR, KOD, and KAP radars located in the early morning sector • The average response time was 5 and 9 minutes for the SAS and STO radars located in the late morning sector

  14. SuperDARN-observed response delay=~5 min delay=~2-4 min • The average response time was 2 minutes for the GBR radar located in the 9 MLT sector • The average response time was 3 and 7 minutes for the PYK and HAN radars located in the ~16 MLT sector

  15. SuperDARN-observed response delay=~5 min #2 delay=~2-4 min • The average response time was 2 minutes for the GBR radar located in the 9 MLT sector • The average response time was 3 and 7 minutes for the PYK and HAN radars located in the ~16 MLT sector

  16. MLT/MLAT dependence observed by SuperDARN 23 km/s January Event 17 km/s 1.5 km/s November Event • For the January and November events, 171 and 116 grip points were identified as having clear transition onsets • Ionospheric response was first observed in the pre-noon sector and then progressed toward midnight in 5-20 minutes • Ionospheric response was observed first at higher latitudes and then increasingly lower latitudes for the November event (opposite to magnetic data)

  17. MLT/MLAT dependence observed by SuperDARN 23 km/s January Event #1 17 km/s #3 1.5 km/s November Event • For the January and November events, 171 and 116 grip points were identified as having clear transition onsets • Ionospheric response was first observed in the pre-noon sector and then progressed toward midnight in 5-20 minutes • Ionospheric response was observed first at higher latitudes and then increasingly lower latitudes for the November event (opposite to magnetic data)

  18. CPCP • Dawnside vortex begins close to midnight and then shifts eastward at onset, reaching a steady position near 4 MLT after 16 minutes • Location of the duskside vortex was highly variable until after the transition onset where it settled at 16 MLT • During periods of Bz>0 the CPCP was small, compared to periods of Bz<0 • Transition was marked by an immediate increase in the CPCP, reaching a maximum value ~40 minutes later.

  19. Residual convection-1 • At 12:04 a positive cell starts to form near midnight and then shifts eastward over the next four intervals.

  20. Residual convection-2 • At 12:14 UT the vortex of the dawnside convection cell settles at 07 MLT • After 12:14 UT convection evolves becoming stronger, but the vortices are stationary

  21. Summary of convection response based on the residual convection pattern • Convection vortices do not simply ‘snap’ to their final location, but develop over a period of time • Dawnside convection vortex takes 4-6 minutes to form and 8-10 minutes to move to a final location and then continues to enhance until a steady state is reached ~40 minutes after the initial onset

  22. Summary of convection response based on the residual convection pattern • Convection vortices do not simply ‘snap’ to their final location, but develop over a period of time • Dawnside convection vortex takes 4-6 minutes to form and 8-10 minutes to move to a final location and then continues to enhance until a steady state is reached ~40 minutes after the initial onset #4

  23. Summary and Conclusions – 1 • Line-plots of the perturbation magnetic field were generated in the 03, 05, 10, and 14 MLT sectors. The delay between the expected arrival time of the ionospheric onset and the magnetometer-observed response was shorter for stations in the 10 and 14 MLT sectors, and longer in the 03 and 05 MLT sectors. • Line plots of the gridded l-o-s velocity were generated throughout the 02-17 MLT sector. The delay between the expected arrival time of the ionospheric onset and the SuperDARN-observed response varied from 0-20 minutes, with shorter delays observed in the 09-17 MLT region and longer delays closer to 02 MLT. • Ionospheric onset times were determined for all available magnetometer stations and all available SuperDARN grid-cells. For both data sets, the initial onset was observed near noon and propagated toward the nightside.

  24. Summary and Conclusions - 2 • Prior to the southward transition, the vortex of the dawnside convection cell was located close to midnight. After the southward transition, the vortex of the dawnside cell propagated eastward and settled at ~05 MLT within 12-16 minutes. • The location of the duskside convection cell was erratic during periods of northward IMF, but settled at 16 MLT within ~16 minutes of the southward transition. • The southward transition of the IMF was immediately marked by an increase in the CPCP determined by SuperDARN.

  25. Two-stage process • Stage 1 (~15 min): • Noon-to-midnight progression of the ionospheric onset of the observed magnetic and electric field response (5-6 min) • Foci of the Dungey convection cells moves from the nightside to the dayside (8-10 min) • Stage 2 (~25 min): • Overall convection pattern intensifies

  26. Curiosities • (1) Noon to midnight progression not really seen on the dusk side • (2) Conflicting results for the PYK/HAN radars and magnetometer data • (3) MLAT dependency for magnetometers and SuperDARN data • (4) CPCP shows immediate response but residual convection shows a delay of 5-6 minutes

  27. The End

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