PLASMA SHEET FLOWS AND
RELATIONSHIP TO SUBSTORMS
Vassilis Angelopoulos
Space Sciences Lab., UC Berkeley
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
OUTLINE:
Historical perspective
Organization based on downtail distance
Examples at various substorm phases
Open questions
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
Historical perspective.
Pre-ISEE era (~<1977) [Pytte and Hones series]:
Vela at 18RE (and Ogo, Esro, ISIS) establish:
Substorm flows agree with Rx@15RE geometry.
Growth phase thinning and PS recovery.
Poleward leap of auroras at PS recovery.
Arc maps to very near Earth; seed for CD model
established. No flow observations.
IMP6, 7, 8 at ~20-35RE establish:
50% of onset conditions are associated with PS
activity.
80% of onset flows tailward but field topology
complex [Hones et al.; Caan et al. JGR’79]
Boundary layer quite distinct [Lui et al., JGR’77]
Plasma sheet flows ubiquitous, Rx unsteady,
activity high latitude [Coroniti, JGR’78]
Source location bracketed and size (∆X~500 km)
identified [Sarris et al., GRL’76]
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
ISEE and IRM era (1977-1990):
ISEE:
PSBL dynamically important [Eastman et al.,’84]
PSBL represents non-local activity; ion DF’s
dispersed; retreating NL? [Forbes et al.’81]
Retreating plasmoids discovered and linked to
substorms [Hones et al.,’82]
IRM [BJ et al.’88; ’89; ’90]:
Near NS flows just as important statistically as
PSBL flows.
Average PS flow small (~30 km/s) both near NS
and at PSBL.
PS flow interrupted by short-lived, fast flows.
Positive relationship with geomagnetic activity.
CCE@9RE [Lui; Lopez; Ohtani: late 80’s-’90s]
“Whatever causes onset is close and is moving
tailward.”
Supported by imagers and mapping arguments.
[Elphinstone, et al. JGR’95; Samson, et al., GRL’92]
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
pre-ISTP era (1990-1994):
ISEE-IRM [Angelopoulos et al.’92;’94]:
Fast flow samples of BJ revisited:
Flow bursts (1min) within BBFs (10 min).
Transport properties of BBFs dominant in PS.
Relationship to substorm phase unclear.
Relationship to substorm activity is positive.
Bimodal nature of flows established.
Geotail era (1994+):
Most frequent observation of Rx=28RE [Nagai et
al.’98]
Fast flows and substorms: Ongoing research.
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
Log(
)
Log(
)
Probability distribution of the flows suggests
intermittent turbulence operative.
Log-Normal
Gauss
Angelopoulos et al., Phys. of Plasmas, submitted, 1999.
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
PS flows are bimodal; flow bursts are likely drivers:
Vxmedian
,nonBBF = GEOTAIL
2km/s
PERCENT
1
10
100
-8 RE < XAGSE < -20 RE ; |YAGSE | < 15 RE
2 km/s
WIND
4 km/s
500
-500
IRM
non-BBF samples
0.01
0.1
All samples
0
Vx , km/s
500
-500
0
Vx , km/s
0
Vx , km/s
500
|Yagse |< 5RE
occurrence rate
flux transport
energy
particle
WIND IRM/3D GT/LEP
% in X-bin
-500
Xagse ( R E )
C
t
T M k i S K k b
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
Remnant flow is primarily cross-tail drifts at midnight
with small Earthward flow near flanks.
IPS Avrg Vxy (with BBFs; GEOTAIL)
(a)
50 km/s
XAGSM(R E)
-10
-20
-30
20
10
0
-10
-20
-10
50 km/s
XAGSM(R E)
nonBBF IPS Avrg Vxy (ISEE 1978, 1979)
-16
(b)
-22
12
6
0
-6
-12
-10
50 km/s
XAGSM(R E)
T87; V=VE B+ VCorotation + VDiamagnetic; (ISEE 1978, 1979)
-16
(c)
-22
12
6
0
-6
-12
YAGSM(R E)
Reproduced from Walker et al., ISSI volume on Sources and Losses of Plasmas,
[1999]. (a) From Maezawa and Hori, JGG, 1999. (b) and (c) from Angelopoulos,
ICS3, 1996.
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
FLOWS BY DISTANCE:
Very Near-Earth (|X|~<15 RE)
Tailward Flows
(all short lived prior to small onset):
Angelopoulos et al., ICS2, 1994 (ISEE 1&2)
Sergeev et al., JGR, 1995 (same as above)
Nagai et al., JGR, 1998 (GT@15 RE)
Petrukovich et al., JGR’98 (IB@12RE-GT@28RE)
Earthward Flows
(at onset):
Fairfield et al., JGR, 1998 (GT@12 RE)
Shiokawa et al., JGR 1997 (IRM@13 RE)
Angelopoulos et al., JGR, 1999 (GT@10 RE)
Near-Earth (15<|X|<25 RE)
[onset, recovery, all latitudes]
Angelopoulos et al., JGR, 1996 (GT@18 RE)
Lyons et al., JGR, 1999 (GT@16-30RE)
Fairfield et al., JGR, 1999 (GT@16-20 RE)
Mid-tail (|X|>25 RE)
Plasmoids seen at onset (Ieda et al., JGR 1998;
Machida et al., GRL, 1999)
Nagai et al., JGR, 1998: (28RE is most likely site
of X-line at or prior to substorm onset.)
Angelopoulos et al., JGR 1995; 1996 (IMP8-GT:
even for flows at 28RE, classical substorm signatures)
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
EXAMPLE #1: GROWTH PHASE / PSEUDOBREAKUPS
GROUND@13:00 UT
FCC
FSP
KTN
FYU
KOT
TIX
CHD
MCQ
MLT=0
Angelopoulos et al.,
GRL, 1997
00
09
IMP8
15
00
1200
0900
1200
1500
D
0900
WIN
GEOTA
0
0900
1200
150
IL
1500
12GOE
00
S9
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
...Input-Output
POLAR/UVI Energy Flux (ergs/s cm )2
0-10
0-10
0-12
0-10
0-15
0-10
1256
1306
1315
1340
1404
1409
1414
1102
12
0943
4
13 2
13 01
15
0-8
03 425
1
14
FCC
200 nT
MIN-MAX=
FSP
FYU
KTN
1st substorm
2nd substorm
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
EXAMPLE #2: ONSET FLOWS
UT=1996-Aug-14, 04:00
Projection: T89
Grid=CGM
RAN
CHU
GIL
SPA
A81
A80
GT
PBQ
STJ
OTT
CGMLAT=66.1o
A80_Z
-
o
64.5
-
PBQ_Z
o
67.1
o
69.5
+
-
GIL_Z
CHU_Z
0404 UT
Angelopoulos et al., submitted, GRL, 1999.
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
At 10 RE...CD and BBFs seen (flows ahead of dipolarization)
SUNWARD
DIST. FUNCTIONS
SUNWARD
COUNTS
DUSKWARD
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
While further downtail, flow onset and dipolarization are increasingly
displaced.
EXAMPLE 3: Shiokawa et al., JGR 1997
90
7
0
6
-90
5
-180
4
BBF
CD
Onset
Log (Eflux) [cm^2 sec str]
8
Therman Ion Azimuth
180
-1
TYPICAL BURSTY FLOW SIGNATURES AT Xgsm=-12.5 RE
Adapted from Shiokawa et al, 1997
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
EXAMPLE #4. LATE EXPANSION PHASE
Association with high latitude (71 deg) activation.
1
2
Pi2 pulsations (arbitrary scale); HER_H
1
-10
-20
-30
5.
0
0
10.0
40
053
.0
20
.0
2.5
.0
80
320
2
0
5.
10.0
40
053
037 G6
.0
20
.0
ISEE 2
IRM
G5
SC
-10
019
2.5
.0
20
.0
80
2.5
IRM
019
G5
ISEE 2
320
SC
5.
0
10.0
40
053
ISEE 2
.0
320
Ygsm
0
.
80
019
0
037 G6
IRM
10
G5
SC
037 G6
0
-10
-20
-30
Xgsm
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
EXAMPLE #5. RECOVERY
Near-Earth field is dipolar but occasionally punctuated by localized
“super-dipolar” fast flows, [Sergeev et al., 1996 JGR] reminiscent of
the bubbles of Chen and Wolf [1993].
More recently Kauristie et al. find evidence that ionospheric signature
of such flows is twin current vortex (ICS3 and JGR-submitted, 1999)
ONSET AT ~17:50 UT
bubble
(Adapted from Kauristie et al., ICS3, 1996)
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
EXAMPLE #6. LATE EXPANSION/ RECOVERY
Sergeev et al.,
GRL 1999 and
Henderson et al.,
GRL 1998 both
showed that late
substorm
expansion or
recovery
activations (at the
poleward
boundary) may
protrude from last
close field line all
the way to
geosynchronous
region.
[Henderson et al.GRL’98]
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
PARTIAL SUMMARY
VERY CLOSE TO EARTH (10-13 RE):
BBFs nearly identical to CD,
except: remote sensing of hot plasma is Earthward.
Excellent correlation with SS onset when at SS meridian
AT PROGRESSIVELY TAILWARD DISTANCES:
Increased localization (and observation difficulty)
Delayed CD observation (if seen at all)
Activations likely to be poleward (be they onset,
intensification of recovery)
Reduced “Geoeffectiveness” (Pi2’s, injections,
aurora and EJ currents
FAST FLOWS SEEN AT ALL SUBSTORM PHASES:
NORMAL BECAUSE:
BBFs represent dominant means of
energy transport
Energy dissipation in ionosphere
continues at SS expansion and
recovery phases
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
PUZZLE
Ohtani et al., [1999 Spring AGU presentation]:
Revisited a classic CCE CD event (8.9 RE). Shown that
duskward anisotropy is consistent with pressure gradient,
not duskward flow.
Erickson et al., [1999 GEM meeting presentation]:
Ey
(mV/m)
Used CRESS data (6.2 RE). Shown that prior to onset,
waves grow out of “noise” with initial tailward flow
velocity and Poynting flux into the ionosphere.
0
-5
Bz
(nT)
55
45
Spara
(mW/m^2)
35
150
0
-150
Vx
(km/s)
50
0
Ground
Onset (Pi2, Bays)
-50
Space
Onset
t (min)
1st Auroral
Brightening
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
FOUR MAIN TYPES OF QUESTIONS:
GENERATION MECHANISM OF ELEMENTARY FBs
Reconnection versus current disruption:
DFs to test Rx model such as beam shape and speed: [Fujimoto et al.
JGR 1998; Hoshino et al., JGR, 1998]
deHoffman Teller frame [Oieroset et al., Spring AGU meeting, 1999]
PROPAGATION MECHANISM (Force Balance).
Pressure gradients? Interchange motion? Slingshot?
Particle distributions (e,i anisotropy as function of distance)
ENERGY DISSIPATION
Flow braking and connection to the ionosphere.
LOCAL TO GLOBAL
Self Organization? Role of turbulence in momentum and particle
diffusion away from BBFs / towards Rx site.
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99
Using the Whalen relation to test Rx hypothesis at 60RE on WIND
fast flows [Oieroset et al., Spring AGU meeting, 1999].
To Earth
-
+
+
-
Earthward Flows, South of NS
1000
slope = 0.54
cc = 0.88
200
V - VHT (km/s)
V - VHT (km/s)
400
Tailward Flows, South of NS
0
-200
slope = -0.70
cc = -0.69
500
0
-500
-400
-1000
-1000
-400 -200
0
200 400
VA (km/s)
1999-04-01/12:30:37 - 1999-04-01/12:41:12
3.45•10
1.06•10
V Perp (km/sec)
1000
3.26•10
3.07•10
9.43•10
2.90•10
-1000
8.90•10
2.73•10
-2000
8.39•10
-2000
-1000
0
1000
V Para (km/sec)
Pesa High 1999-04-01/09:33:17->09:34:06
1.80•10
2000
-10
5.27•10
-10
-11
10.00•10
0
Twd
-9
-12
-12
-13
-13
1.54•10
1000
4.52•10
1.33•10
0
3.88•10
1.14•10
3.34•10
-1000
-14
9.77•10
-14
-15
2.86•10
-2000
2000
8.39•10
-2000
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
-1000
0
1000
V Para (km/sec)
-9
-10
-10
-11
-11
-12
-12
-13
f (sec^3 / km^3 /cm^3)
1.12•10
V Perp (km/sec)
Pesa High 1999-04-01/06:35:36->06:37:14
2000
0
500
1000
VA (km/s)
1999-04-01/09:59:46 - 1999-04-01/10:10:22
f (sec^3 / km^3 /cm^3)
Ewd
-500
-14
-14
-15
2000
06/24/99
CONCLUSIONS:
Significant progress has been made in classification of fast flows and
recognition of their key role in global dynamics particularly fueled by
the Geotail dataset in conjunction with global POLAR imagery. The
potential riches of the above ISTP datasets are still to be fully
obtained.
Impulsive, localized acceleration events are key to understanding the
global energy transport processes in the tail during all substorm
phases. They represent a fundamental energy conversion and
transport unit that is ubiquitous across tail at all activity levels and
thus deserve our full attention.
V. Angelopoulos, SSL/UCB
1999 GEM Meeting
06/24/99