LIST OF SELECTED EVENTS AND DESCRIPTIONS

A. October 22-23, 1996

(prepared by E.Budnik) 
Intense storm. Peak Dst value -110 nT. 
Main phase 22:00 22/10 - 05:00 23/10.
Caused by passage of the region (IR) of interaction of high-speed stream 
with preceeding low-speed SW (?)

Data.

 WIND: Ram Pressure > 4 nPa.
       Vsw increases from 450 km/s to 550 km (in IR, 20:00 - 06:00) and
       then to 650 km/s
       Nsw decreases from 12 cm-3 to 8 cm-3 (in IR, 20:00 - 06:00) and
       then to 4 cm-3       
       IMF Bz turns southward  (up to - 12 nT) at about 22:00 and remains
       negative till 04:00
 
 IMAGE magnetometer network:
  
       Breakup in magnetic field at 21:24.
       Set of substorms.
       The 2 largest substorms have onsets at 21:54 an 01:50.
       
 GEOTAIL: (data available from 22:30)
  
  Location (at 00:00 23/10) Xgsm=-16 Ygsm=0.4 Zgsm=-1.3 
  LEP: 22:30 - 23:00 PS electrons - Eav = 2-3 keV, dense
                      ions - Eav = 8-9 keV, Sunward and Duskward flow
                       
       23:00 - 01:50 PS electrons - Eav 7-8 keV
                     ions - Eav about 30 keV, directed fluxes
       01:50 - 02:30 lobs
       02:30 .... PS
   MF: 23:00 - sharp increase of Bz (dipolarization)
       23:00 - 02:00 practically permanent decreasing of Bz up to
                     negative values 
                      
        02:00 - new large increase of Bz (dipolarization) 
  
  INTERBALL-TAIL:
   
   Location (at 00:00 23/10) Xgsm=-20. Ygsm=-14. Zgsm=1.4
   Distance to model MP about 4-5 Re.
   
   21:00 - 22:14 Highly structured PS - strong convection.
   21:19 - MS-like plasma (FTE?)
   22:14 - 23:20 Complicated picture - MS, FTE, BL
   23:30 - 02:05 very hot PS
   02:05 - 02:20 lobes, ionosperic ions tailward flow.
   
  INTERBALL-AURORAL:(data available from 20:00 to 23:00)
   
    S/c moves from midnight to the morning (MLT=08:00) sector.
    Very hot PS Ei > 20 keV  
    21:15 (MLT=4.5) up- and downgoing ionosperic ions appear.
    After 22:00 - (MLT 06:00 - 07:00, Linv 69 - 65) - very strong 
    injections showing practically no dispersion features, Accelerated
    up to 20 keV O+ ions, total disappearence of plasma at some L-shells.
    Strong wave activity.

B. November 13-14, 1996.

(prepared by N.Borodkova)

Substorm I on November 13, 1996.

Interplanetary conditions.

WIND in the solar wind at R=44 Re observed strongly negative Bz (up to -13 nT) from 17.40 to 20.10 UT with sharp decreasing at ~ 17.55 UT from -13 to -2 nT and returning to previous value at ~ 18.10 UT as a possible substorm triggering. RAM pressure ~4-5 nPa.

Ground based data.

IMAGE magnetometer network recorded substorm between ~ 18.40 and 21.00 UT with onset at ~18.40 UT.

Available satellites data: INTERBALL/Tail and Auroral, GEOTAIL.

INTERBALL/Tail.
INTERBALL/Tail was located in the tail lobes in the dawn flank at R=-27 Re and measurements performed by ELECTRON, MIF-M, CORALL, PROMICS, CKA-2 are available. Before 17.50 UT tail lobe magnetic field increased to ~ 34 nT. 18.38-18.45 UT appearance of 87-633 eV electrons accompanied by sharp and transient decreasing of magnetic field value and increasing of Bz component. 19.30-22.00 UT recovery phase of the substorm.
INTERBALL/Auroral.
INTERBALL/Auroral moved from evening to the morning sector with MLT changing from 22 to 5.30. Dok-2 observations are available for all of the time of this event. ION data are available from 20.40 to 21.45 UT. At 20.40 UT ION experiment observed magnetosphere filled by ions of 80-18000 eV and electrons of 50-20000 eV and unusially big amount of O+ ions.
GEOTAIL.
GEOTAIL also was located in the plasma sheet/tail lobes in the dawn flank at R=-20 Re. At 18.35 UT satellite passed off from the plasma sheet to the tail lobes. The behaviour of the magnetic field is similar to that at the INTERBALL/Tail

Substorm II on November, 14 at 19 - 22 UT.

Interplanetary conditions.

WIND was in the solar wind at R=30 Re and observed negative Bz from 17.10 to 18.30 UT and from 19.05 to 20.15 UT.

Ground based data.

IMAGE magnetometer network recorded substorm between ~ 19.15 and 21.40 UT with onset at ~19.15 UT.

Available satellites data: INTERBALL/Tail and Auroral.

INTERBALL/Tail.
INTERBALL/Tail was located in the plasma sheet at X=-27 Re and measurements performed by ELECTRON, MIF-M, FM-3, PROMICS, VDP, CKA-1 are available. >From 19.20 UT energy of the plasma sheet began monotonically decrease. 20.30 - 21.02 - tail lobes. There are several features in the plasma sheet: structured magnetic field, thinning, plasmoids formation. After 21.08 UT - neutral sheet observations.
INTERBALL/Auroral.
INTERBALL/Auroral moved from the evening to the morning sector with MLT change from 22.30 to 5.37. PROMICS and ION observations are available from 17.55 to 21 UT. Both experiments observed very dense polar cap, injections in the polar cap and aurora (elevated konics?) .

C. November 24 - 25, 1996.

(prepared by V.Stepanov & Yu.Yermolaev)

WIND data.

This time interval was characterized by solar wind pressure decresing from ~4 to ~2 nPa; IMF $B_z$ component changed sign many times including southward return at ~20.30 and northward return at ~22.15 UT on November 24.

Ground based data.

At ~22.30 UT on November 24 the ground stations observed beginning of the strong magnetic disturbance.

INTERBALL Tail Probe.

It had GSM coordinates X=-25, Y=+2 and Z=-10 Re at 22.00 UT on Nov.24. Tail Probe was initially in the north lobe, but during geomagnetic disturbance the plasma bursts appeared.

INTERBALL Auroral Probe.

Orbits passed the north auroral region and polar cap, and MLT changed from evening to morning sectors. Ion and electron data are available for time intervals: 15.00- 18.00, 21.00-23.30 on Nov.24. During geomagnetic disturbances at ~16.40 and at ~22.45 the ion injections (with O+ fluxes) were observed.

GEOTAIL data.

The satellite had GSM coordinates about X=-25, Y=-8 and Z=-3 Re during interval discussed (i.e. on another flank of magnetosphere that the Tail Probe but closer to the geomagnetic equator). Plasma and magnetic field data are available almost for complete interval and the satellite was initially in the plasma sheet but at ~22.30 a disruption of plasma sheet is observed.

Geosynchronous satellites.

LANL electron data show increasing fluxes near midnight in disturbed interval.

Possible interpretation:

The event observed on the 24th of November, 96 was very interesting in various aspects. The substorm has happened, during which the pressure in the plasma sheet has been changed by a factor of more than two according to GEOTAIL data. The substorm onset is related to 22:27 UT, when the pressure in the PS experienced the first sharp increase (GEOTAIL data), and ground-based observations revealed the first burst of pulsations at that moment. The preliminary AL index, as it was showed by ground-based magnetometers, dropped off to very low level at approximately 22:27 UT.

The duration of that event was not very long: at 23:08 UT the PS pressure has started to recover, almost simultaneously with the AL index. During the storm there was no strong ring current formation, according to Dst index (-18 nT at the peak of the substorm).

Two points should be emphasized here:

1) Before the onset, at 21:45 UT, the small peak in the PS pressure was registered by GEOTAIL, probably related to change in the IMF Bz from -5 nT to -2 nT. At that moment, the particle detectors CORALL and ELECTRON aboard the Tail Probe (located in the North Lobe duskward, Xgsm = -26 Re, Ygsm = 2 Re, Zgsm = 9 Re) have detected the counterstreaming particle beams at energies about 1 keV. Onboard magnetometer has detected a dip in the magnetic field in that moment. Auroral Probe was within the Northern Polar Cap at 21:45 UT (ILAT = 73.9 deg, MLT = 23.9 hours). It's low-energy particle detectors SKA-3 and ION have detected some plasma signatures (E = 30eV - 15 keV) very close to that moment. The duration of the observed signatures was comparable to or less than the satellite spin period (120 s). The onboard magnetometer has not recognized any changes in the magnetic field that could accompany the observed plasmas.

2) During the substorm, within the interval from 22:30 to 23:07 UT there were some pulses in the PS pressure detected by GEOTAIL. The Auroral Probe was crossing the poleward auroral oval boundary near 22:47 UT, and just before that moment the low-energy particle detectors have registered a wide plasma region (from 22:37 to 22:44 UT) adjacent to the oval boundary but clearly distinguished from it. The plasma of that region is quite different from one of the observed auroral oval boundary.

Thus, we could make a conclusion that during and just before the substorm on the 24th of Nov. '96 in the time interval from 21:30 to 23:00 UT some particle activities were observed within the Northern Polar Cap, which well correspond in time development to the PS pressure behavior. The fact that substorm was not too strong, along with a good data available, makes possible to understand more precisely the time development and the consequences of that substorm.

D. December 22-23, 1996.

(prepared by Yu.Yermolaev & L.Zelenyi)

Observations of serie of substorms under small solar wind pressure and negative IMF Bz.

WIND data.

This time interval was characterized by almost constant solar wind pressure ~1.2 nPa; IMF $B_z$ component returned southward at ~11.20 UT on December 22 and was negative till ~12.00 UT next day.

Ground based data.

At ~12.00 UT on December 22 the ground stations observed beginning of the strong magnetic disturbance, and although IMF was relatively constant there were also two substorms at ~22.00 on December 22 and ~2.00 UT on December 23.

INTERBALL Tail Probe.

It had GSM coordinates X=-24, Y=+12 and Z=-2 Re at 12.00 UT on Dec.22 and -16, +8 and -6 at 04.00 UT on Dec.23. Tail Probe was initially in the plasma sheet, but during geomagnetic disturbances the PS plasma disappeared. At ~13.25 on Dec.22 energetic ion flux moving earthward was obsereved. At ~02.00 on Dec.23 a plasmoid moved tailward.

INTERBALL Auroral Probe.

Orbits passed the north auroral region and polar cap, and MLT changed from ~18 to ~02. Ion and electron data are available for time intervals: <11.45, 15.00- 18.00, 20.30-23.15 on Dec.22 and 02.30-06.00 on Dec.23. During geomagnetic disturbances the ion injections were observed.

The several interesting features of the events observed by Tail and Auroral Probes are:

GEOTAIL data.

The satellite had GSM coordinates about X=-25, Y=-15 and Z=-5 Re during interval discussed (i.e. on another flank of magnetosphere that the Tail Probe). Plasma and magnetic field data are available almost for complete interval and were similar to the Tail Probe ones.

Geosynchronous satellites.

LANL electron data show increasing fluxes near midnight in disturbed intervals.

Possible interpretation:

To our mind this event very well demonstrates the regime of bursty convection (BBF ?) occupying the wide range of local times in the magnetotail which might be very important for understanding of the importance of bursty-like transport in disturbed times.