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May 1998

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      April 29, 1998

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From Scott Paswaters (SOHO/LASCO)

1998/05/06 00:02 A bright partial halo CME appears in the C2 FOV. Most of the material is directed to the SW, but there is a faint front to the N and E. A plane of the sky velocity was measured of ~750 km/sec.

1998/05/06 02:28 A small slower CME appears in C2 to the E apparently originating from behind the limb. (this is not a halo)

1998/05/06 08:29 A very wide and fast (~1070 km/sec) CME appears in C2. It appears to be mostly confined to the West limb. This CME was associated with the X-Flare and enegertic particle event.


From Shane Stezelberger (SOHO/LASCO)

LASCO detected two halo events associated with recent on-disk solar activity: 1. A partial-halo CME, concentrated in the NE, was in progress at 23:56 UT on 01 May. The plane-of-sky speed was approx. 500 km/s. EIT detected several candidate on-disk events, e.g. at 18:02 UT, 20:41 UT, 22:06 UT, and 23:15 UT. Further ejections continued for several hours subsequently.

2. A bright partial-halo CME began at 14:06 UT, May 2, concentrated in the NW. The measured speed was approx. 750 km/s (west limb front).

From Don Michels (SOHO/LASCO)

X-class flare 980502 at 1340 UT, from region 8210 which is magnetically well connected to Earth. LASCO CCD detectors were flooded with proton hits, and the telemetry buffer was slowing down owing to the large number of image features to be handled by the compression algorithms.

From Patrick S. McIntosh (NOAA/SEC)



Region 8210 (S17 W17) produced a Class-X1 flare at approx. 1340 UT 980502 and high energy protons arrived in less than 40 minutes. The event occurred near the rapidly developing delta configuration. The sunspots are now very complex and showing clockwise rotation, including the delta-configuration. These are classic properties of proton-flare sunspots.

From Mike Kaiser (WIND/WAVES)

Following the X1.1 flare was a relatively intense interval of what we think is a moving type IV event -- from the ejecta itself. This emission is seen from the top of the band (14 MHz) down to ~8 Mhz and from about 14:05 - 15:50 UT. At lower frequencies, there are two different episodes of type II-like emissions. The first is in the 4-3 MHz range at about 14:15 to 14:45 UT. The second episode is a bewildering complex of many narrow-band emissions drifting downward from ~3 to 1 MHz in the 16:50 to 18:30 UT interval.

Starting mid-day on May 4, there is a weak fundamental-harmonic pair drifting from ~55 kHz to ~35 kHz (fundamental). Although these are very low frequencies, the in situ solar wind density is extremely low right now (~1 cm^-3) so the shock is probably not too close to 1 AU.


From Scott Paswaters (SOHO/LASCO)

LASCO/EIT observed a halo CME on 1998/04/29 from the same AR that produced the halo CME on 1998/04/27. In LASCO data this event has a very similar shape to that event 2 days ago, although it appears to be slightly more centered on the Sun as to be expected. The event began in EIT around 16:00 UT showing a coronal wave in subsequent frames. The event appears in LASCO/C2 at 16:58 and is still in the C3 FOV. Measurements on the frames we have received so far give a plane of the sky velocity to the NE of ~900 km/sec.

From Dave Speich (SEC/NOAA)

Active to minor storm conditions are predicted to occur 01-02 May in response to the 980429 halo event. Isolated periods of major storm are considered possible during the 30 Apr-02 May period.

From Murray Dryer

There was a strong Type IV (Type II hiding behind its skirts?), starting at 1707 UT on April 29 (continuing to the 30th) from a S18E20 flare at 1606-1638-1639..start, max, end of X-rays....M6.8/3B with a well-defined halo CME, having plane-of-sky speed of 900 km/sec.

From Fred Ipavich (SOHO/Celias)

SOHO/PM detected a clean shock at 2115 UT on 1 May. The shock travel time (~53 hours) is, I believe, the shortest we've seen on SoHO. The shock/CME produced a very impressive Forbush Decrease.

From Patrick S. McIntosh

The magnetic storm expected from the X1 event of 29 April arrived late on 01 May and is now of major proportions.

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Last Updated: 03/26/99