Ionospheric Convection Response to High-Latitude Reconnection and Electrodynamics of a...
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Ionospheric Convection Response to High-Latitude Reconnection and Electrodynamics of a Split-Transpolar Aurora S. Eriksson 1, G. Provan 2, F. J. Rich 3,
Ionospheric Convection Response to High-Latitude Reconnection
and Electrodynamics of a Split-Transpolar Aurora S. Eriksson 1, G.
Provan 2, F. J. Rich 3, C. Mouikis 4, M. W. Dunlop 5, M. Kuznetsova
6, S. Massetti 7, B. Anderson 8, M. Lester 2, J. T. Gosling 1, H.
Reme 9, and A. Balogh 10 1 LASP, University of Colorado, Boulder,
CO, USA 2 University of Leicester, Leicester, UK 3 AFRL, Hanscom
AFB, MA, USA 4 SSC, University of New Hampshire, Durham, NH, USA 5
Rutherford Appleton Laboratory, Chilton, UK 6 NASA/GSFC, Greenbelt,
MD, USA 7 Istituto di Fisica dello Spazio Interplanetario, Roma,
Italy 8 JHU/APL, Laurel, MD, USA 9 Centre dEtude Spatiale des
Rayonnements, Toulouse, France 10 The Blackett Laboratory, Imperial
College, London, UK Contact:
[email protected]@lasp.colorado.edu
Slide 2
Outline Part I Global Observations Cluster lobe reconnection
observations: 14 February 2003 1840-2000 UT BATSRUS MHD simulation
1830-2030 UT http://ccmc.gsfc.nasa.gov [c.f.
Stefan]http://ccmc.gsfc.nasa.gov SuperDARN noon response to IMF
1940-2200 UT: Schematic NBZ field-aligned current (FAC) and ExB
flow driven by lobe reconnection Iridium Birkeland Currents Summary
Part I
Slide 3
Outline Part II Electrodynamics Polar UVI & All-sky Camera
observations DMSP F13 observations: 2107-2114 UT -- ExB drift
velocity -- FAC system -- Electron precipitation Summary Part
II
Slide 4
Part I Global Observations
Slide 5
Lobe Reconnection Schematic Dungey [1963] (courtesy of J. C.
Dorelli, UNH)
Slide 6
Cluster C1 Cluster C2 Cluster C3 Cluster C4 Solar Direction
View from aboveSide view 18 19 20 UT
Slide 7
Cusp Schematic - Cluster FGM Cluster C3 Cluster C1 Direction of
magnetic field Lobe field Dayside closed field x z
Slide 8
Bx By Bz Vx Vy Vz
Slide 9
Bx By Bz Vx Vy Vz x-comp y-comp z-comp Walen Test: Quantitative
agreement with high-latitude magnetic reconnection
Slide 10
Walen Test: Quantitative agreement with high-latitude magnetic
reconnection Bn z x magnetotail lobe magnetosheath
Slide 11
Slide 12
YZ GSM Plane B Jpar Vx Vy
Slide 13
YZ GSM Plane Cluster C1 position ~1800-1900 UT BVx VyJpar
Slide 14
XZ GSM Plane VxVy P
Slide 15
XZ GSM Plane
Slide 16
Cluster C1 18, 19, 20 UT Cluster C3 18, 19, 20 UT XZ GSM
Plane
Slide 17
SuperDARN noon-sector flow in agreement with Cluster C3
observations at 1940 UT and 1950 UT. one clockwise lobe cell is
present in the dayside sector with sunward and dawnward flow across
12 MLT.
Slide 18
How does the sunward flow in the noon sector respond as the IMF
clock angle changes? 11 MLT 80 o 1213 82 o 78 o
Slide 19
11 MLT 80 o 1213 82 o 78 o
Slide 20
IMF during SuperDARN high- latitude noon convection changes TPA
TPA: Transpolar Aurora (Polar UVI) Red Vertical Line: Time of DMSP
F13 TPA Observation
Slide 21
IMF during SuperDARN high- latitude noon convection changes A:
Two-cell pattern B: Strong predominantly dawnward flow C: One
clockwise global lobe cell D: One counterclockwise postnoon dayside
lobe cell E: Two dayside lobe cells (reverse dayside flow) AB
CDE
Slide 22
A: Two-cell pattern B: Strong predominantly dawnward flow C:
One clockwise global lobe cell D: One counterclockwise postnoon
dayside lobe cell E: Two dayside lobe cells (reverse dayside
flow)
Slide 23
A: Two-cell pattern B: Strong predominantly dawnward flow C:
One clockwise global lobe cell D: One counterclockwise postnoon
dayside lobe cell E: Two dayside lobe cells (reverse dayside
flow)
Slide 24
A: Two-cell pattern B: Strong predominantly dawnward flow C:
One clockwise global lobe cell D: One counterclockwise postnoon
dayside lobe cell E: Two dayside lobe cells (reverse dayside
flow)
Slide 25
A: Two-cell pattern B: Strong predominantly dawnward flow C:
One clockwise global lobe cell D: One counter- clockwise postnoon
dayside lobe cell E: Two dayside lobe cells (reverse dayside
flow)
Slide 26
A: Two-cell pattern B: Strong predominantly dawnward flow C:
One clockwise global lobe cell D: One counterclockwise postnoon
dayside lobe cell E: Two dayside lobe cells (reverse dayside
flow)
Slide 27
A: Two-cell pattern B: Strong predominantly dawnward flow C:
One clockwise global lobe cell D: One counterclockwise postnoon
dayside lobe cell E: Two dayside lobe cells (reverse dayside
flow)
Slide 28
A: Two-cell pattern B: Strong predominantly dawnward flow C:
One clockwise global lobe cell D: One counterclockwise postnoon
dayside lobe cell E: Two dayside lobe cells (reverse dayside flow)
upward NBZdownward NBZ
B: Strong predominantly dawnward flow IMF clock angle +90 C:
One clockwise global lobe cell IMF clock angle +45 E: Two dayside
lobe cells (reverse dayside flow) IMF clock angle 0 F: One
anti-clockwise global lobe cell ??? IMF clock angle -45 Proposed
model: The sunward flow and the bounding NBZ FAC system are
directly driven by lobe reconnection. As the IMF By changes during
positive Bz, so does the lobe reconnection site and thus the
location and deflection of the joint sunward flow channel and NBZ
system. A TPA is expected within the upward NBZ system. See also:
Southwood, 1987; Vennerstrom et al., 2005
Slide 33
Summary Part I The IMF from ACE and Cluster is strongly
northward and duskward. The IMF Bx is negative in the solar wind
(ACE) and in the magnetosheath (Cluster C1). Lobe reconnection is
favored tailward of the northern cusp. Following a southward IMF Bz
excursion, the IMF By decreases gradually toward By~0. The Cluster
s/c moved through the northern cusp at the beginning of the event.
Two s/c (C1 and C3) observed enhanced sunward and dawnward velocity
in agreement with high-latitude lobe reconnection tailward of the
cusp. MHD simulations confirm the general magnetic field and flow
topology consistent with these Cluster observations. NBZ-type FACs
are suggested on either side of the MHD lobe reconnection region
and in the duskside ionosphere. SuperDARN ExB drift is sunward and
dawnward across the 12 MLT meridian at the time of the Cluster C3
flow enhancements. The subsequent direction of SuperDARN noon
sector flows (after a southward excursion) tracks the IMF clock
angle changes well with different time delays. A faster response
time is suggested to the southward (100 to 156 deg) turning (3-6
min) than either the duskward (135 to 34 deg) or due northward (45
to 8 deg) turnings that take 8-9 min and 12-14 min,
respectively.
Slide 34
Part II Electrodynamics
Slide 35
Slide 36
Polar UVI
Slide 37
Slide 38
All-sky Camera, Daneborg (DNB)
Slide 39
Slide 40
Slide 41
Slide 42
Slide 43
Slide 44
Clockwise Lobe Cell
Slide 45
NBZR1 R2 Clockwise Lobe Cell
Slide 46
Slide 47
DMSP Electron Precipitation
Slide 48
Slide 49
Slide 50
Summary Part I-II SuperDARN verified a sunward flow channel
over the TPA as part of a clockwise global lobe cell that covered
much of the polar cap. This is consistent with the positive IMF By
and northward IMF Bz (~30-50 deg clock angle). A DMSP F13
dusk-to-dawn pass verified a structured sunward lobe cell flow
channel over the split-TPA and an NBZ current system on either side
of it [Iijima and Shibaji, JGR, 1987; Southwood, 1987]. The TPA was
found within the upward NBZ region. Two inverted Vs were detected
in agreement with sunward flow shear and local upward FAC filaments
at each of the two Sun-aligned arcs of the split- TPA. The
high-latitude current system poleward of the duskside R2 system was
locally balanced assuming a Pedersen closure. The increased
Pedersen conductance at both arcs self-consistently explains the
structured sunward drift velocity.
Slide 51
Summary Part I-II The dual arc separation is consistent with a
prior Akebono study [Obara et al., 1996]. The structure &
dual-arc system is in general agreement with the Zhu et al. [1994,
1996] MI-coupling model. The second (poleward) arc is due to the
ionospheric response to an initial magnetospheric flow shear. We do
not fully understand the cause and effect of the energy-dependence
of the dual-arc separation. It may be related to stronger Hall
current system relative to the Pedersen currents. We propose the
following response of high-latitude dayside electrodynamics during
northward IMF. The sunward flow & the bounding NBZ FAC system
are directly driven by lobe reconnection. As the IMF By changes, so
does the lobe reconnection site and thus the location and
deflection of the joint sunward flow channel & NBZ system. The
(dayside) TPA is expected within the upward NBZ system [see also
Vennerstrom et al., 2005].
Slide 52
Slide 53
Mach number Plasma Beta Dynamic pressure Northward IMF
epsilon: