archive: SETI [ASTRO] High Solar Activity Possible in June and July

SETI [ASTRO] High Solar Activity Possible in June and July

Larry Klaes ( )
Wed, 26 May 1999 09:41:26 -0400

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>Date: Wed, 26 May 1999 10:08:01 -0300 (ADT)
>From: Michael Boschat <andromed@ATM.DAL.CA>
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>To: ASTRO <>
>Subject: [ASTRO] High Solar Activity Possible in June and July
>Reply-To: Michael Boschat <andromed@ATM.DAL.CA>
> May 20, 1999 1900 UT
> REGION 8545 (N37 E03) has characteristics similar to the early stages
> of the large and long-lived active region which became the greatest
> flaring region of record in June 1991. If new spots develop within
> this region to increase its complexity it may begin to evolve toward a
> highly-active state for its return in June. Should this region
> verify this alert, the dates of the next two disk transits are:
> 11-25 June 1999 and 10-23 July 1999
> Strong flares at the solar limb could occur up to two days before and
> after these dates.
> The 1991 region formed at a similar high-northern latitude in April
> 1991, and it was not active on its first disk transit. It became
> mildly active in May, and peaked in June with the highest output of
> x-ray flares since satellite monitoring began. Activity in July 1991
> was much reduced, but included an impressive Class-4 optical flare (a
> rare. very large area of emissivity).
> One of the most remarkable attributes of the 1991 region was its
> eastward movement in solar longitude of nearly 80 degrees during its
> four disk transits. This motion exceeded the expected difference
> between Carrington rate and the normal, slower rate at this latitude.
> Furthermore, the spot-group motion decelerated relative to the
> Carrington rate during those four months (P. S. McIntosh, in
> Solar-Terrestrial Predictions - IV, Proceedings of a Workshop at
> Ottawa, Canada, J. Hruska, M. A. Shea, D. F. Smart and G. Heckman,
> eds., U. S. Dept. of Commerce, Boulder, Colorado USA, 1993, pp.
> 37-38.)
> The main spot in Region 8545 has moved eastward by two degrees of
> solar longitude during May 17-19, after no detectable eastward motion
> in the first three days of this disk transit. The dates for the next
> two disk transits of this region assume an eastward shift of 15
> heliographic degrees per solar rotation. The 1991 region motion was
> greater than this.
> This region is remarkable for just its high latitude to begin with.
> Spots are seldom this large at such high latitude, and the surrounding
> whorl of fibrils indicates the region is even more important than its
> spots would indicate. The fibril pattern shows the characteristic
> counter-clockwise twist common in the most-active of
> northern-hemisphere regions.
> This region developed on the suns backside in early May, emerging on
> the polar crown polarity boundary. The position on that boundary is at
> the longitude where the boundary leaves the polar latitudes and trends
> toward the solar equator. This is the eastern side of the polar crown
> gap that is the favored location for coronal holes extending
> equatorward from the polar cap. There is a narrow coronal hole north
> of this region, extending down from the polar cap. These circumstances
> are also similar to the great 1991 active region.
> Region 8545 became less stable during the time of its recent
> eastward movement. Yesterday two small bipolar sets of spots appeared
> near the east and north edges of the large Hhx spot, changing its
> classification to Cho. The main spot has elongated today and may begin
> to fragment during the remainder of its disk transit. While this may
> suggest decay, it may also signal the beginning of more rapid spot
> evolution that could include adding sunspot area and complexity in new
> locations.
> This alert is admittedly speculative, but any long-range solar
> prediction is speculative. There is time for modifying this prediction
> as the sunspot evolves toward either increased or decreased activity.
> It is possible for the region to decay on this disk passage and revive
> for its June transit.
>Patrick S. McIntosh ...a very great deal more truth
>HelioSynoptics can become known than can be
>3885 Paseo del Prado proven.
>Boulder, CO 80301-1527 Richard P. Feynman
>303-444-5880 FAX: 303-440-0102 1966 Nobel Prize in Physics