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 1 Natural Resources Canada, Geomagnetic Observatory, Ottawa, ON, Canada 2 University of Saskatchewan, Institute for Space and Atmospheric Studies, Saskatoon, SK, Canada

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

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

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. 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! Resolve peculiarities!

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

IMF A sharp southward transition in the IMF B z at 10:25 UT is expected to arrive at the ionosphere at 11:58 UT A sharp southward transition in the IMF B z at 10:25 UT is expected to arrive at the ionosphere at 11:58 UT

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

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

Magnetometer-observed response The perturbation magnetic field enhanced to more positive or more negative values in response to a sharp transition in the IMF Bz 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 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 delay=6-8 mindelay=0-8 min delay=0-1 min delay=5-12 min

MLT/MLAT dependence observed by magnetometers 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. 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 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 minutes Ionospheric response was first observed 1-2 MLT before noon, and then progressed toward midnight over minutes MLAT dependence is suggested by the November event MLAT dependence is suggested by the November event January Event November Event 37 km/s 21 km/s 1.5 km/s

MLT/MLAT dependence observed by magnetometers 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. 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 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 minutes Ionospheric response was first observed 1-2 MLT before noon, and then progressed toward midnight over minutes MLAT dependence is suggested by the November event MLAT dependence is suggested by the November event January Event November Event 37 km/s 21 km/s 1.5 km/s #1

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

SuperDARN-observed response 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 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 The average response time was 5 and 9 minutes for the SAS and STO radars located in the late morning sector delay=~10-15 min delay=~5 min delay=~10 min delay=~5 min delay=~10 min

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

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

MLT/MLAT dependence observed by SuperDARN For the January and November events, 171 and 116 grip points were identified as having clear transition onsets 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 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) Ionospheric response was observed first at higher latitudes and then increasingly lower latitudes for the November event (opposite to magnetic data) January Event November Event 23 km/s 17 km/s 1.5 km/s

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

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

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

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

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 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 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

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 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 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

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 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 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 MLT region and longer delays closer to 02 MLT. Line plots of the gridded l-o-s velocity were generated throughout the 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 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. 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.

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 minutes. 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 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 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. The southward transition of the IMF was immediately marked by an increase in the CPCP determined by SuperDARN.

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

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

The End