IDENTIFICATION OF THE ONSET
TIME AND LOCATION OF AN
ISOLATED SUBSTORM
USING SATELLITE AND
MULTIPLE
GROUND
BASED
OBSERVATIONS.
W.K. PETERSON
PETERSON,,D.N.
D.N.Baker,
Baker,X.X.Li,
Li,M.W
M.W..
Dunlop
Dunlop,,
A. Korth, E. Donovan, R. Friedel, S.B. Mende,
and H.J. Singer
On August 27, 2001, the
ground (current
signature
disruption)of an isolated
signature
substorm
was observed at 04:08. ~Eight
minutes earlier at ~04:00
aplasmoid was observed on
the
Cluster spacecraft at
19Re.
Do Substorms begin
with disruption followed
current
by
reconnection
?OR
Do they begin with
reconnection
followed by current
disruption?
Red dots: Cluster observations of energetic electron bursts in 2001.
* Location of Cluster, Polar, and GOES-8 at 04:00 August 27,
2001
The August 27 event is a small, isolated
substorm
•Bz was < 0 for ~ 2 hours
before
the
event
•Psuedobreakup starting
at
~03:45
does not develop into
a
substorm
•Optical signature of
substorm
onset
~04:08
•Confirmed by
Canopies
magnetometer
s
CANOPUS
Magnetometer
Vertical lines
are
at
~04:08
The Pesudobreakup before the substorm clearly
shows up in both the magnetometer and
optical
Data
.
GOES-8
Dipolarization event
and
assoicated PI-2 burst
~04:08
Goes-8 was near the CANOPUS
chain at this
time.
Cluster
•H+ and O+
sheet energy
plasma
and
angular
distributions
until
~04:08
BUT CIS
data
displayed
on the
nextslides show
few
aplasmoid
passing
from ~04:00
to
~04:08 …the
signature
of
reconnectio
noccurring
Earthward
of
Cluster
04:08
Cluster
CIS shows a
plasmoid
passing
from ~04:00
to
~04:08
IN ALL
Satellites
•Tailward
flow to
~04:01
04:06
•Bz
Southward
~03:59
to
04:08
•Ey
Duskward
~04:01
to
04:08
Plasmoid Passage Observed by Cluster 1/2/3/4 at ~19 RE
~8 minutes before dipolarization, optical onset, and magnetic
bay
04:1
8
04:2
0
04:2
2
Cluster/04:20 60N 60W
Approximate Foot
Points
Polar/04:20 65N 50W
45 degrees
West
90 degrees
West
2 minute
resolution
WIC
images show
a
feature
near the Polar
magnetic footpoint
at
~04:20
Consistent
with
Plasma Observations on
Polar
August 27, 2001, Time line
• ~02:00 Southward Turning of IMF
• ~03:45 Pseudobreakup observed by UV camera and
CANOPUS
magnetometers
• ~04:00
Plasmoid passage at 19 Re observed by the
cluster spacecraft. Robust signature included
Bz
Southward, Ey Duskward, and Tailward
flow
• ~04:08Auroral
breakup observed by
• CANOPUS magnetometers
• UV Camera on IMAGE
• GOES -8 dipolarization signature
• ~04:20 Plasma sheet expansion reaches the Polar satellite
locatio
n
~ 0401
UT
~ 0230
UT
~ 0408:30
UT
0300 ~ 0400
UT
~ 0422
UT
Conclusions:
• Many data sources identify over central Canada on August
27,
- A Psuedobreakup at ~03:45
2001.
- A small substorm at 04:08
in this
• Cluster satellites show the clear signature of a
plasmoid passing over them at 19 RE starting at 03:59,
significantly before the substorm onset signatures on
the ground
• These observations are most consistent with the
reconnection scenario for substorm
onset observations do not rule out the occurrence of the
• These
current disruption scenario----except
case.
Dawnward flow EARTHWARD flow
04:1
0
CIS moments 03:50 to 04:20
Red vectors at 5 minute
intervals04:00
~4:01 to
flow
~4:06
TAILWARD
Green X-Z GSE
Black X-Y
GSE