oler@HG.ULeth.CA (oler, CARY OLER) (06/19/91)
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GEOMAGNETIC STORM UPDATE
ALERT CANCELLATION
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17:00 UT, 18 June
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STORM UPDATE INFORMATION:
The minor geomagnetic storm ended early in the UT day of 18 June.
Conditions have now become generally active to unsettled. Conditions will
remain generally unsettled until 20 or 21 June, when recurrent effects should
begin to increase geomagnetic activity once again. The peak of the activity
may approach minor storm levels, but is not expected to be significant at
this time.
Region 6659 passed beyond the west limb on 16 June and is now out of
influential range. It continued to produce major M-class flares as it passed
beyond the west limb. Although this region has not been the only region so
far this solar cycle to produce very powerful X-class flares which have
saturated the GOES sensors, it is the only region observed so far this solar
cycle to have produced at least three of these events. It maintained a
complex configuration as it departed from view on 16 June. There is a chance
it may return in a configuration capable of supporting isolated major flares,
although there is a stronger chance that it will decay further behind the sun
and will return in a configuration capable of supporting only the lower-level
minor M-class flares. It will be interesting to observe the return of this
region near 01 July.
The barrage of major flares which occurred over the last two weeks has
ended. The regions presently visible are not capable of supporting major
flares. Isolated low-level M-class events may be observed, but major events
are not expected from the regions visible at the present time. Proton levels
are still above event thresholds at approximately 15 pfu at greater than 10
MeV. The satellite proton event should end later this UT day. The Polar Cap
Absorption (PCA) event ended fairly early in the UT day of 18 June. Sporadic
localized absorption has been observed since then over the polar regions,
although overall PCA has ended. Conditions are more favorable for polar path
signal propagation. Further improvements will occur over the next several
days.
Solar indices are dropping at the present time, and will continue to
drop towards a rotational minimum between 135 and 150 (for the 10.7 cm solar
radio flux).
The following alerts and/or warnings have been CANCELLED:
- LOW LATITUDE AURORAL ACTIVITY WATCH
- POTENTIAL GEOMAGNETIC STORM WARNING
- POLAR CAP ABSORPTION EVENT ALERT
- POTENTIAL MAJOR SOLAR FLARE WARNING
The following alert remains IN PROGRESS:
- SATELLITE PROTON EVENT ALERT (will end shortly)
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