saps intensification during substorm recovery: a multi-instrument case study roman a. makarevich
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SAPS intensification during substorm recovery: A multi-instrument case study Roman A. Makarevich University of Alaska Fairbanks , USA A. C. Kellerman, J. C. Devlin, H. Ye La Trobe University, Australia L. R. Lyons and Y. Nishimura University of California Los Angeles, USA. - PowerPoint PPT PresentationTRANSCRIPT
SAPS intensification during substorm recovery:
A multi-instrument case study
Roman A. MakarevichUniversity of Alaska Fairbanks, USA
A. C. Kellerman, J. C. Devlin, H. YeLa Trobe University, Australia
L. R. Lyons and Y. NishimuraUniversity of California Los Angeles, USA
Subauroral Polarization Stream
Den
sity
Latitude
Magnetospheric Current Generator
Anderson et al. (1991):
Electric Field Recombination Density Conductivity
(Current = const) Electric Field …
Trough
R2 FAC
R1 FAC
++++
++------------
Magnetospheric Voltage Generator
-------------
++++++
++++
Magnetospheric Voltage Generator
Southwood and Wolf (1978):
V = Ed
Charge separation d
(Voltage = Ed = const)
Electric Field E
Evidence for Generator Scenarios
Voltage Generator Current Generator
SAID as a substorm recovery phenomenon
(Anderson et al., 1993)
Density profiles mimicking E-field profiles (Anderson et al., 1991)
SAID narrowing and strengthening in successive satellite passes (Anderson et al., 2001)
Statistically similar to trough in MLT and Kp dependence (Karlsson et al., 1998)
E-region density decreasing with SAPS intensification (Lyons et al., 2010)
Voltage Generator Current Generator
Radial separation occurs within 10 min of substorm onset, i.e. during the expansion phase
MI feedback becomes effective 10-20 min after the substorm onset
Separation decreases as substorm progresses, i.e. during late expansion and recovery
FAC and SAPS diminish during recovery
Timing of Generator Scenarios
Objective: investigate timing and causes of major SAPS intensifications
SAPS Event
Fig01.ps
TIG beam 4
UNWbeam 0
SAID
SAPS and Substorm Phases
IMAGE
Ground
UNW
Recovery
SAPS intensification during recovery phase
arb
un
its
UNW All Beams
UNW all beams
UNW keogram
TEC Observations
SD FIT
GPS TEC
SD FIT
Vorticity
(~FAC)
SAPS and Auroral Precipitation
SAPS narrows and separation from precipitation increases
SAPS and TEC Trough
Strong 2D association between SAPS and TEC trough
Voltage Generator Current Generator
SAPS Characteristics and Evolution:
Narrowing and strengthening with time
SAPS and TEC trough association
No density decrease in line with SAPS strength
SAPS Intensification Timing:
Should start within 10 min of substorm onset
Should start 10-20 min after substorm onset
FAC should diminish during recovery
Magnetospheric and Topside Signatures
Magnetosphere (LANL, GOES):
No parameter was found to exhibit similar time dependence to the SAPS strength during recovery apart from energetic electron fluxes at 01 and 15 MLT (but not at 00 MLT)
Topside ionosphere (DMSP IDM):
Significant ion upflows
Some topside density enhancement
1. Strong, 2-D association between SAPS and TEC trough was found, but no density decrease during recovery and SAPS intensification
2. Both voltage and current generator scenarios had difficulties explaining observations
3. No parameter was found that exhibited similar time dependence to the SAPS intensity, suggesting that it may be triggered, e.g. by convection and auroral bursts
Conclusions
PBI and Convection Burst
Fig01.ps
Some evidence of equatorward motion
SAPS and PBI
PBI appears and propagates equatorward