ISSI POLARIS Team:Octav Marghitu1, Joachim Vogt2, Andreas Keiling3, Rumi Nakamura4,

Tomas Karlsson5, Maria Hamrin6, Olaf Amm7, Harald Frey3, Costel Bunescu1, Eugen Sorbalo2, Vlad Constantinescu1, Hans Nilsson8, Joshua Semeter9

MPE Symposium on Auroral Physics and Plasma Boundary Analysis, Garching, 1–5 July, 2013

Multi-Scale M–I Coupling Effects of Magnetotail Flow Bursts:Event Study by Cluster, THEMIS, GOES, and Ground Stations

Magnetosphere–Ionosphere Coupling Associated with Magnetotail Flow Bursts:A Conjugate THEMIS/Cluster/Ground Event

1. Institute for Space Sciences, Bucharest, Romania2. School of Engineering and Science, Jacobs University Bremen, Bremen, Germany3. Space Sciences Laboratory, University of California at Berkeley, USA4. Space Research Institute, Austrian Academy of Sciences, Graz, Austria5. Space and Plasma Physics, Royal Institute of Technology, Stockholm, Sweden6. Department of Physics, Umeå University, Umeå, Sweden7. Arctic Research Unit, Finnish Meteorological Institute, Helsinki, Finland.8. Swedish Institute of Space Physics, Kiruna, Sweden.9. Department of Electrical and Computer Engineering, Boston University, Boston, USA

Introduction

While the large scale scene, in space and time, is set by the Sun, the terrestrial control may dominate at the M – I coupling end of the solar-terrestrial interaction.

An M – I coupling event, observed by several in-situ platforms and ground stations, during a relatively quiet interval, illustrates the internal dynamics of the M – I system.

In this case flow bursts in the tail, observed by THEMIS, appear to be related to: large-scale Pi2 pulsations over a wide range of latitudes and longitudes,

observed by the THEMIS GBO and by GOES in-situ. meso-scale vortical motion in the ionosphere, observed by equivalent

ionospheric current (EIC) maps; small-scale electron acceleration by dispersive Alfvén waves, observed by

Cluster-1 at about 2RE altitude.

Outline

Event context IMF, SuperDARN, Magnetic indices

Spacecraft location, mapping

Tail flow bursts association with: Large scale Pi2 pulsations, THEMIS / GOES / ground data

Meso-scale ionospheric vortical motion, THEMIS / ground data

Alfvénic electron acceleration, THEMIS / Cluster data

Summary

Open questions

Feb. 25, 2008 – IMF, SuperDARN

B_gsm_z

B_gsm_y

B_gsm_x

He++/H+

Tp

Np

106

2 0 -2

50

0-5

21

10:00 UT44 kV

4 nT

10:20 UT44 kV

5 nT

Magnetic indices, Ground magnetic field

Feb. 2008, Sol. rot. 2382

12 15 20 25

Kp=1+

Event Context – Spacecraft Location

TH-A TH-D TH-E

C1C2C3 C4

GOES-12

TH-A

TH-ETH-D

C1 C2 C3 C4

GOES-12

THEMIS GBO ASI / SuperDARN

2008-02-2510:03:00 UTP5/TH-A

P3/TH-DP4/TH-E

C2

C1

C3C4

GOES-12

P3P4

P5

THEMIS GBO ASI / SuperDARN

2008-02-2510:24:00 UTP5/TH-A

P3/TH-DP4/TH-E

C2

C1

C3C4

GOES-12

P3P4

P5

THEMIS GBO ASI / SuperDARN

THEMIS flow burstsTH-A

N

B

V_gsm

V_perp_gsm

V_para_gsm

TH-D TH-E

Flow bursts <-> Pulsations

Keiling et al., Chapman Conference, Iceland, 2013

Flow bursts <-> Pulsations

Keiling et al., Chapman Conference, Iceland, 2013

Flow bursts <-> Pulsations

Keiling et al., Chapman Conference, Iceland, 2013

During the first burst, 3 intensifications of the flow are observed, starting at about 10:03, 10:05, and 10:08 (TH-A is multiplied by 6 => actually quite small).

The flow speed decreases progressively, from the first to the last intensification.

During the first intensification, Vx on TH-D is largest, but Vy and Vz are also significant. On TH-E, all three components have comparable values.

During second and third intensifications, Vx on TH-D is small, but Vy and Vz are significant. On TH-E, Vx becomes negative.

Overall, the velocity components suggest 3D oscillatory motion, consistent with the

expectations in the flow braking region.

Flow bursts <-> Ionospheric vortical motion

P5/TH-A*6P3/TH-D P4/TH-E

Vx

V

Vz

Vy

THEMIS flow bursts

Nakamura et al., manuscript in preparation

Flow bursts <-> Ionospheric vortical motion

10:03EIC

10:24EIC

10:03FAC

10:24FAC

Flow bursts <-> Ionospheric vortical motion

10:01:40 – 10:09:50EIC

Flow bursts <-> Ionospheric vortical motion

10:21:40 – 10:30:50EIC

Paralel and anti-paralel low energy electron bursts are associated with the 3 intensifications of the flow.

The low energy counter-streaming electrons are suggestive for Alfvénic acceleration.

According to recent theoretical models and simulation studies, dispersive Alfvén waves launched by tail flow braking can indeed accelerate the electrons.

Flow bursts <-> Alfvénic acceleration

10:00 10:02 10:04 10:06 10:08 10:10

1000 800 600 400 200 0

V (k

m/s

)

TH-A*6TH-DTH-E

Flow bursts <-> Alfvénic acceleration

FYKN

KIAN

Summary Two flow bursts episodes in the tail are observed by THEMIS spacecraft during a

globally quiet magnetospheric interval. First episode is more prominent in TH-D and TH-E data, near midnight, while second episode is visible also in TH-A data, some 2.5 h in MLT to the dusk.

Both episodes are associated with large scale Pi2 pulsations, visible both in-situ, by THEMIS and GOES, as well as on ground, by THEMIS GBO.

The flow bursts are observed in the inner plasma sheet, presumably in the flow braking region. The flow features suggest oscillatory vortical motion – consistent with theoretical models, simulations, and recent observations by THEMIS.

The vortical motion in the tail is supported also by conjugate meso-scale EIC maps, showing as well vortical plasma convection.

On small scale, Cluster-1, conjugate to TH-D during the first flow burst, observes Alfvénically accelerated electrons, presumably related to dispersive Alfvén waves launched by the flow braking.

Overall, the event provides a remarkable illustration of the M–I system internal dynamics, which can be properly addressed only by multi-point in-situ observations and comprehensive networks of ground equipment.

With the launch of the ESA 3-satellite Swarm mission, now scheduled at the end of the year, future M–I coupling studies will benefit from multi-point in-situ observations also at ionospheric level.

Open Questions Oscillatory braking of one BBF or three separate BBFs? The progressive decrease

of the oscillations’ amplitude supports rather the first option. Also, the large scale pulsation episode suggests one driver, not three. On the other hand, C1 maps to 24 RE, 51 RE, and 58 RE in the equatorial plane, suggesting three different BBFs (Rumi).

Pulsations scenario?

Others?