Succession of Flares, CMEs Upsets Spacecraft,
Presages Solar Maximum
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From April 27 through May 6, ISTP spacecraft and observatories got
a sample
of what is to come during the maximum of the solar cycle. In the
span of
10 days, the Sun produced seven coronal mass ejections, two X-class
flares
(the most energetic type), and at least two energetic particle
events. At
Earth, several major magnetic storms upset several spacecraft,
brought
auroras to lower-than-normal latitudes, and forced power companies
to
reconfigure the grid in New England.
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On April 29, a "halo" CME left the Sun and its shock arrived at the
SOHO
spacecraft within 53 hours. The shock arrived faster than any
other
detected so far by SOHO. A magnetic storm followed on May 2.
Contrary to
rumors and anecdotal reports, the failure of the Equator-S
satellite was
not necessarily a result of CME or magnetic storm.
ISTP observers have noted that sunspots are becoming more
complex and
moving with a clockwise rotation--telltale properties of proton
flare
sunspots. |


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On May 1-2, ISTP observed two halo CMEs, as well as an X-class
flare.
High-energy protons from the flare arrived at SOHO within 30
minutes, and
a major magnetic storm developed on May 4.
During the storm, the disturbance storm-time index (Dst) reached
-218 on
the scale of 0 to -220. It is the largest storm of the current
solar cycle.
An ISTP ground station (CANOPUS) measured electric currents in the
ionosphere well above 2000 nanotesla, about 3-4 times the norm for
solar
minimum. The January 1997 event that knocked out Telstar 401 had
currents
of 1800 nT.
In response to the magnetic storm, power companies in New England
reduced
their power sharing capacity with Canadian utilities. Auroras were
reported as far south as Boston and Chicago. |