THEMIS SWT, SSL Berkeley, Dec 20, 2008 1 THEMIS First Tail Season: What Did We Learn? In-situ data...

THEMIS SWT, SSL Berkeley, Dec 20, 2008 1

THEMIS First Tail Season:What Did We Learn?

In-situ data analyst view


THEMIS presentations on AGU 2008 FM:

New Perspectives on Substorms: 10 of 14 oral presentations 27 of 43 posters

Modes of Solar Wind Magnetosphere Energy Transfer: 2 of 7 oral presentations 7 of 31posters

Publications:http://themis.ssl.berkeley.edu/publications.shtml


Substorm event studies:Results and open questions

Topics highlighted:

Timing and event sequence Problem of t0; Inside-out or inside-in? Neither? CD or MRX? Are they necessarily competetitve?

MI communication during substorms Do we understand it?

Dipolarizations: Is there break of the frozen-in?

When and where is “frozen-in” violated?


1st tail season (Jan-Mar 2008)

Feb-14Feb-10

Feb-6Feb-2

Feb-18 Feb-22 Feb-26

Midnight Pre-midnight

Jan-29

Mar-01


Magnetic FieldB (nT)d Z

FlowV (km/s)Z

AuroralIntensity

(Relative Units)

P1

P2

P3


FlowV (km/s)Z


FlowV (km/s)X

TRx

TAI

TCD3r

d

1st

2n

d

P2 P1P3P4

P5 T =0Rx

x

X [R ]GSM E

Z [R

]G

SM

E

T =182sCD

T =96sAI

Magnetotail

Earth

ToSun

3rd

1st

2nd

Substorm Timing: Problem of t0

Similar approach: C. Gabrielse et al., JGR, in press J. Liu et al., Ann Geophys., in press


Alternative view:“Traditional” RX signatures-Bz, -Vx +Bz, +Vx




Although we have five spacecraft and the dense GBO network, timing is still sort of an art.

What are in-situ observable signatures of substrom/intensification onset in the plasma sheet?

The definition should be based on detectable signatures of a clear physical mechanism (M. Sitnov, AGUFM 08 presentation).


Substorm Timing: MI Communication

Angelopoulos et al., Feb. 26, 2008: 96 sC. Gabrielse et al., Feb. 16, 2008: 89 sJ. Liu et al., Feb. 22, 2008: 70 - 100 s.Runov et al., March 1, 2008: 20 s ?!! (marginal)


Substorm Timing: MI Communication

Communication time inferred from in-situ and ground-based measurements seems to be inconsistent with the Alfvenic interaction (~2 min).

What did we learn from AGU FM presentations:

MHD RX modeling shows that RX starts from slow Sweet-Parker regime and gradually evolves to fast regime (e.g., G. Lapenta, AGUFM 2008);

The magnetotail plasma sheet becomes unstable BEFORE the reconnection starts (G. Siscoe, AGUFM 2008 poster, J. Raeder, AGUFM 2008, P. Zhu, AGUFM 2008 poster).

What are ionospheric signatures (if any) of this pre-reconnection plasma/current sheet activity? Can this causes initial auroral intensification?

MI communication via KAW (J. Drake’s comment, Bob Lysak’s presentation). What are observable signatures?


Inside out model

1st2nd 3rd

AuroraCurrent Disruption

Reconnection

3rd 1st

Outside-In model

2nd

P2 P1P3P4

P5 T =0Rx

x

X [R ]GSM E

Z [R

]G

SM

E

T =182sCD

T =96sAI

Magnetotail

Earth

ToSun

3r

d

1st2n

d

THEMIS

Outside-in vs inside-out: Neither?


CD vs RX: Are they necessarily competitive?


March 1, 2008 Summary of observations

01:54:30 UT

0148:25

0154:40

P2X=-17 RE

ASI

MAG (Pi2)

0148:42

0148:45

SST Twd fluxIVD


Processes of rapid plasma energization in the near-Earth plasma sheet (R~-8 RE) and in the mid-tail plasma sheet (R~-20) may act simultaneously and, likely, independently.

Similar conclusion: X Cao et al. (presented by J. Wang) AGUFM 08.

Global modeling of the 2008/03/01 event: M. El-Alaoui et al, AGUFM 08 poster, M. Ashour-Abdalla et al., AGUFM 2008.

Similar model results: R. Winglee et al., AGUFM 2008.


Dipolarization – Is it MHD process?


Dipolarization – Is it MHD process?

The answer is “YES” (J. McFadden, AGUFM 2008)

Always? Let’s see what the current tail season will show…

Dipolarizations: Patchy (“turbulent”, “granulated”) highly fluctuating field (V. Sergeev, AGUFM 08, Retino et al., AGUFM 08).

What about plasma and total pressures?

How do plasma and total pressures behave during dipolarizations?

increase of Pp and Pt at R~-11 RE (V. Sergeev, AGUFM 2008, Y. Miyashita (Geotail statistics), AGUFM 2008 poster

Pp increases at R<11 RE downtail and strongly decreases beyond -16 RE after onset (X. Xing, AGUFM 2008 poster)


Do we see violations of the “frozen-in”

Yes, we do!During current sheet thinning.(J. McFadden et al.)


Ion Distribution Function During CS Thinning

Ion distribution functions observed by the THEMIS P1 probe at the end of the growth phase of the Feb. 26 substorm ( Angelopoulos et al., Science, 2008) and one calculated using the Sitnov et al. (2006) model. The dashed white line in indicates the boundary between gyrating and meandering particles (X.-Z. Zhou et al. AGUFM 08 poster)

The THEMIS P3, P4, and P5 configuration during current tail season will allow us to estimate gradients directly (A. Albert et al., Analysis of Three-spacecraft data Using Planar Reciprocal Vectors, AGUFM 08 poster)


Non-substorm studies

Magnetotail plasma/current sheet flapping L. Kepko et al., AGUFM 2008 Poster A. Runov et al., AGUFM 2008 Poster


4/5 THEMIS probes observed periodic kink structures. SMC interval.

No correlation of kinks with substorm activity/phase (above).

Activations temporarily disrupt kink (right figure) but kink continues to propagate (see esp. 0900)

Aurora show large loop structure, bright spots circle around loop. Probes map to Harang discontinuity (generally).

L. Kepko et al.,AGUFM 2008poster


Back–up slides


Space twister, A. Keiling et al.

THEMIS SWT, SSL Berkeley, Dec 20, 2008 1 THEMIS First Tail Season: What Did We Learn? In-situ data...

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