Cluster 911 Plasmoid Substorm Sept 11, 2002 DOY 254 Onset at 1600 UT Shock at Cluster 16:23 Plasmoid 16: :40 UT

RAPID data by Zong These remarkable data show that Cluster was in a plasmoid (PD) for over 1 hour! Trapped fluxes within the plasmoid (a bubble) A hurricane or tornado in space ! What is the source of energy? For tailward flow, and particles? Here is our chance to look, study

Photo by Tom Eklund View looking NNW near Tampere, FI Just after sunset Lake reflections Timing not determined Beginning of WTS: note bright aurora on the left

IMAGE data Onset occurred at 16:00 UT in Finland near KEV or KIL An isolated substorm One auroral arc

Cluster position At 16:00 Cluster at X = -19, Y = +3, Z =-1 in the southern lobe Low plasma density Density rises quickly n ~ 1 cm -3 (CIS) until 17:40 then falls to n = 0.02

FGM data From 16:00 Cluster was in distant plasma sheet tailward of the disturbance Sharp onset at 16:23 UT (see By) may be a shock preceeding the plasmoid Average tailward velocity of PD after onset 50 km/s

CIS data C4 showing high density in the plasmoid

EFW data Electric field Fluctuations on C4

WHISPER data Data by Canu Most dramatic emission is at Shock Or at the entrance to the plasmoid Within PD the noise is fairly unform

Taylor et al. JGR Nov 2006 (Different event)) Burst of electrons to high energies Such bursts are likely involved in WTS and Omega band auroras It may, or may not, be related to particle energization in plasmoid (to be determined)

Electric potential contours (plasma flow lines), the westward traveling surge, electric currents, auroral bulge [Weimer et a., JGR 1994]. This figure puts the WTS in context of the total activation.

Proposed model Upper part shows the assumed perturbations Lower part shows δJ This involved with the induction electric field E IND = -  A/  t This has, in general, components both transverse and parallel to B in a realistic magnetic field

3-D view of plasma sheet Dusk side has WTS electron precipitation at high latitudes Morning side has ion precipitation at high latitudes Reverse at lower latitudes in cyclical order Reaction: Newton’s third law (e.g. Bursty Bulk Flow)

We can learn from this, for the Earth's magnetosphere is a cosmic laboratory Emslie and Miller [2003] in “Dynamic Sun” noted that “Despite decades of observations in X-rays and gamma-rays, the mechanism for particle acceleration remains an enigma”. Our suggestion, that this field-aligned electric field may be true in general, on a transient basis, points out a new approach to energization of charged particles in space. This is at odds with the current fashions. Parker [2003, Forward to the same book] stated that “The essential point is that the gas is ionized and, therefore, on the large scale of the Sun, the gas cannot support any significant electric field in its own moving frame of reference”. Here on Earth, the westward traveling surge at the onset of a magnetospheric substorm, is similar to solar flares; precipitating electrons are abruptly energized to about 100 keV It all follows from a direct application of Maxwell’s equations, not resorting immediately to MHD