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Data Sources
• This Event

• This and Other Events

Studies, Publications, Presntations
• Papers for the GRL special section "The near disappearance of the solar wind at Earth"

• Announcement of Opportunity for Companion JGR papers

• ISTP Science Workshop, March 30, 2000

• AGU Fall 1999 Special Session

• Press coverage of The Day the Solar Wind Disappeared

Interplanetary Conditions

• ACE MAG Instrument Data: May 11, 1999
  
• ACE RTSW (Estimated) MAG & SWEPAM: May 10-13, 1999
  

Geomagnetic Response

Usual Quiet Times
• GOES 5-minute Electron Flux: May 8-11, 1999
  
• GOES Magnetometer (1 minute data): May 8-11, 1999
  

  This Event

• GOES 5-minute Electron Flux: May 10-13, 1999
  
• GOES Magnetometer (1 minute data): May 10-13, 1999
  

• Estimated Planetary KP Index (3 hour data): May 10-13, 1999
  

Distant Bow Shock Observation

• Extended Bow Shock: May 11, 1999

• WI/SWE-MFI: May 10-13, 1999

• Lunar Prospector Summary Plot: May 11, 1999 (M. Acuna PI magnetic field instrument)
  

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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

satellites

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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Other Links of Interest:

ISTP Program Homepage
SOHO Homepage
ISTP Public Outreach and Education Page
NOAA, Today's Space Weather

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