THEMIS Burst-Mode Observations of Kinetic Signatures of Reconnection at the Magnetopause Tai Phan (UC Berkeley) Contributors: Chris Pasma, Vassilis Angelopoulos, Jim McFadden, Davin Larson, Chuck Carlson, Jonathan Eastwood, Marit Oieroset, and K-H Glassmeier

Outline: - Burst-mode trigger performance at the bow shock, magnetopause and in the magnetotail - Multiple ion populations in reconnection layers

THEMIS Burst-Mode Triggers: -  Capture and transmit ~1-hour/orbit of super high-time resolution plasma and field data in regions of interest. -  Use extremely simple automated onboard trigger algorithms based on a single parameter such as N, B, V, P, or wave power. - All instruments burst at the same time.

Burst Mode Data at the Magnetopause (MP), Bow Shock, Foreshock (FS) Wave bursts (2s interval): - 4 KHz E and B

BGSE (nT)

BS SW

FS

Ions (eV) VGSE (km/s)

MP

magnetosheath

M’sphere Vx

Par$cle
Bursts
(5‐min
intervals):
 ‐ 
3s
full
3D
ion
and
electron
distribu$ons
 ‐ 
128
DC
magne$c
field
vectors/s
 ‐ 
256
DC
electric
field
vectors/s



a 5-min burst contains 100 full 3D particle distributions

Density and Bz Particle Burst Triggers (based on N and Bz gradients) BGSE (nT) Ions (eV) VGSE (km/s)

Vx

N (cm-3) N trigger quality index Bz trigger quality index

Wave bursts are based on amplitude of E and B wave power

Burst (Density) Trigger Capture of FTEs

Ions (eV)

BGSE

VGSE

Flux Transfer Events

On the dayside: - Density burst trigger on THEMIS-C (18 Re apogee) also captured Hot Flow Anomalies and Foreshock Cavities. - Bz trigger on THEMIS-B (30 Re apogee) captured solar wind reconnection events.

On the nightside: -  Bz trigger on inner 3 spacecraft captured dipolarization and bursty bulk flows. -  Bz trigger on the two outer spacecraft captured BBF and X-line crossings. A (11 Re) D,E (12 Re) 30 Re B

C (18 Re) 18 Re C B (30Re)

Example of Tail Reconnection X-line Crossing 2008-02-26 BGSE (nT)

2 consecutive Bursts = 10 min

Ions (eV) VGSE (km/s)

Vx

earthward

tailward Angelopoulos et al. [2008]

THEMIS B

Burst-mode observations at the magnetopause Multiple reconnecting magnetopauses

BGSE

Ions (eV) Electrons (eV) VGSE N

mixing of accelerated magnetosheath and cold and hot magnetospheric ions Ions (eV)

Bz = 26 nT, Vz= -12 km/s, N= 30

1

1

magnetosphere

VGSE

magnetosheath

BGSE

1

velocity moment does not give any indication of the accelerated magnetosheath ions

X-line crossing: Ion distributions on opposite sides of an X-line Bz = +38nT, Vz = +200 km/s BGSE

1

THEMIS E

Bz = +34nT, Vz = -210 km/s

VGSE

2

N

1

2

120 full 3D particle distributions in reconnection layer!

magnetosphere

Elec (eV)

magnetosheath

Ions (eV)

Another example of X-line crossing

VGSE N

Vz

THEMIS D

30 full 3D ion and electron distributions in the vicinity of an X-line

magnetosphere

Ions (eV) Electrons (eV)

magnetosheath

BGSE

Summary

-  THEMIS burst triggers are highly successful in capturing bow shock, foreshock, HFA, magnetopause, BBF, dipolarization, and X-line crossings. -  Cold magnetospheric ions present in reconnecting magnetopause in more than 50% of the crossings. This cold population needs to be taken account in studies of ion heating and ion acceleration.

Electrons distributions in the magnetopause reconnection layer

Never balanced? Cold in, hot out, always? Electron heating: very little, 20-30 percent increase at the most? Hand sketched cartoon to show field lines

Example 3: accelerated cold magnetospheric ions detected on the outer edge of the magnetopause current layer BGSE

Hand sketched cartoon to show field lines Accelerated cold ions can be seen if the sheath flow is low, correct?

Electron heating in the magnetopause reconnection layer ?

Electron heating: very little, 20-30 percent increase at the most? What does this mean for the all assumptions we have made before?

Summary •  THEMIS burst triggers successfully captured the magnetopause, FTE, bow shock, foreshock, HFA, solar wind reconnection, tail dipolarization and reconnection •  Ion distributions often display mixing of multiple populations. •  Field-aligned and anti-field aligned electrons are unbalanced throughout reconnection layer. •  Ion heating: the only T//>Tp is double beam? •  Electron heating, very little. •  Electric field?

Burst Mode (High Resolution) Data at the Magnetopause and Bow Shock Wave bursts: - 4 KHz E and B

Select another example that does not have Double bursts inside the sphere for no reason FTE would be nice THEMIS
C


BGSM
 (nT) Ions
 (eV)


Trigger on N gradients

M’sphere

Density
 
(cm‐3)


Fast Survey: - 3s reduced 3D ions and electrons -  Ions: 24 energies x 50 angles -  electrons: 24 energies x 6 angles -  ? B and E vectors /s

magnetosheath Remove N If space needed

Par$cle
Bursts:
 ‐ 
3s
full
3D
ion
and
electron
distribu$ons
 ‐ 
128
DC
magne$c
field
vectors/s
 ‐ 
256
DC
electric
field
vectors/s