May 10-12, 1999
Time Interval of a Stretched Out Magnetosphere:

Long duration event of an unusually tenuous solar wind

      Data Sources

      Studies, Publications, Presntations

      Interplanetary Conditions

      Geomagnetic Response

      Distant Bow Shock Observation

May 10-12, 1999 EVENT SUMMARY

Chronology of the Event (by D. Berdichevsky and M. Desch)

May 10, 1999
Beginning before noon the proton density in the solar wind (SW) starts its almost monotonic decrease.

1645 UT on May 10
GEOTAIL in its INBOUND trajectory encounters the bow-shock at 26.6 Re from Earth.

18 UT, May 10 to approximately 5 UT, May 12
The Earth's magnetosphere does not show usual signatures of day-side compression nor night-side stretching either in the
Hp component nor the more than 0.6 (and 2) MeV electrons monitored with the geostationary environmental GOES

21 UT, May 10 to approximately 2 UT on May 12
The density of the solar wind is below the mark of 1 particle per cubic cm.

1115 UT on May 11
IMP-8 crosses the bow-shock at 42.7 Re from Earth.

12 UT to 24 UT on May 11
The global geomagnetic Kp index makes an excursion from 0 to 3 (15 to 18 UT) and back to the quiet value of 1.

1730 UT on May 11,
Wind appears to cross the bow-shock, as well as Lunar Prospector, at 52.3 and 60 Re from Earth respectively.

"These likely bow-shock crossings occur at the time when the preliminary readings of the WIND/SWE plasma
instruments indicate that the solar wind ram-pressure was the lowest of the interval"
"This coincides in time with the Kp index reaching its maximum value 3 for the day"

1830 UT on May 11 to 2 UT on May 12
The solar wind density starts to rise after an initial jump by a factor of two or three, this near monotonic rise
extends until approximately 18 UT on May 11

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