Flux Transfer Event on the dayside observed by the THEMIS satellites and the at P1 of the US Antarctic

Observatory chain. (2007_08_12/ 17:29 UT)

S. B. Mende, Harald Frey,

UC Berkeley and the AGO and THEMIS teams.

During the observing period (May-August, 2007) THEMIS apogee swung through the midday region and there were several opportunities when the magnetic field conjugate of the satellites foot point was in the FOV of the cameras in the Antarctica.

South Pole Kepogram. The activity shifted to P1 off on the pole-ward horizon.

Top Keogram is 427.8 nm representing harder precipitation

1 hour off 17:29 is marked as 18:29

Activity is much shown much better in AGO-1 data.

AGO-1 is located at 80 degrees magnetic

Aug 12, 2007

17:20

2007_08_12/17:30 coming in

The THEMIS 5 satellite cluster was in a close spaced formation crossing the magnetopause on the field line near South Pole and the AGO 1 on the 12th of August 2007.

The positions of the satellites is illustrated graphically and in a tabular form at the time when the satellites were crossing the dayside magnetospheric boundary.

The magnetogram of 4 TEHMIS satellite with P1 Keog.

P1 images taken at the same time.

Left images are 427.8 nm, an emission primarily produced by energetic electrons. Right images are 630 nm characterizing soft electrons. Event 2007_08_12/ 17:29 (Field line tracing is 414 km from South Pole Station)

The magnetogram of 4 TEHMIS satellite with P1 Keog.

A Keogram was produced from the images. The y coordinate is the meridional zenith angle signifiyin latitude with Poleward direction up.

The magnetic data of TEHMIS a,b,c,d satellites with P1 Keogram. Magnetogram shows the bipolar FTE signature while the aurora shows poleward motion at P1.

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July 23, 2007 00 UT Moon Azimuth = 273

01 UT Moon Azimuth = 259

GOES 10 -59.7 deg 3 GOES 11 -135.6 deg 1 GOES 12 -74.6 deg 2 GOES 13 -105.6 deg

G12G13

G11

P1Aug 12,2007 17:20 UT

Propagation away from afternoon side at a speed of 485 km/s

The GOES satellites picked up the same signature showing distinct propagation direction.

Summary.

During the Austral winter of 2007 the apogee of the THEMIS satellite were placed in a parking orbit and this orbit swung through the midday region and there were several opportunities when the magnetic field conjugate of the satellites foot point was in the FOV of the cameras in the Antarctica. Thus the THEMIS satellites were in favorable positions to study intermittent dayside reconnection in the form of Flux Transfer Events while the ground based AGO chain and the South Pole observatories were simultaneously recording the aurora during the polar winter night.

An event was detected by the satellites that had the magnetic characteristics of a flux transfer event.

The magnetic signature was global because it was seen by 3 Goes satellites at synch altitude and on the ground.

The simultaneous auroral Keograms showed a slight poleward motion of the poleward auroral boundary which had been previously identified as a possible auyroral signature of flux transfer events.

The ground based magnetic signature was accompanied by the intensification of aurora at lower latitude boudary seen at South Pole station.