SWO PRF 1263 16 November l999
Space Weather Highlights
08-14 November 1999
Solar activity was moderate during most of the period, but increased to high levels on 14 November. Activity rose to high levels on 14 November due to a pair of major flares. The first was an M8/2B at 14/1801UT from Region 8763 (S14, L=249, class/area Dao/170 on 11 November). The second was an M5/2N at 14/1607UT from Region 8766 (N18, L=210, class/area Dao/190 on 14 November). Both flares were impulsive and were associated with relatively minor discrete radio emission. There were several regions on the disk (including those mentioned above) that produced isolated M-class subflares during the period (see the Energetic Event Summary for event times). All of these regions exhibited mixed-polarity magnetic structures of varying complexity. Regions 8759 (N10, L=287, class/area Fkc/920 on 09 November), 8765 (S12, L=235, class/area Ekc/640 on 14 November, and 8766 (N18, L=210, class/area Dao/190 on 14 November) also contained magnetic delta configurations.

SWO PRF 1264 23 November l999
Space Weather Highlights
15 - 21 November 1999
Solar activity was moderate during most of the period, but increased to high levels during 16 - 17
November. Activity increased to high levels on 16 November with five low-level M-class flares fromfour different regions (see the Energetic Event list for event times/sources). Activity remained high on
17 November by virtue of an M7/2B flare at 17/0957UT with associated Type II and IV radio sweeps
and a 390 SFU Tenflare from Region 8766 (N18, L=213, class/area Eac/360 on 17 November). This
region had been in a period of gradual decay when the M7/2B flare occurred, then stabilized on 18
November as a medium-sized, magnetically complex E-type spot group. Region 8765 (S12, L=234,
class/area Ekc/1280 on 18 November) was the largest, most structurally complex region on the visible
disk with multiple magnetic delta configurations observed within the group. It produced isolated M-class flares early in the period during a gradual growth phase. It also produced a couple M-class flares
on 21 November as it entered a period of gradual decay, though it remained large and magnetically
complex. Region 8771 (S15, L=174, class/area Eai/220 on 21 November) developed at a moderate
pace during 18 - 20 November and produced isolated M-class flares. This medium-sized, mixed-polarity region was still developing as the period ended, but at a slower pace.

SWO PRF 1265 30 November l999
Space Weather Highlights
22 - 28 November 1999
Solar activity was low for the first three days of the period and then increased to moderate to high
levels for the remainder. Region 8771 (S14, L=173, class/area Eki/720 on 28 November) produced
multiple M-class events during the period 25-28 November (see the Energetic Event list for event
times/locations) including an X1/2B with a 260 SFU Tenflare on 27/1212UT. This region was starting
to show some decay by the end of the period and was due to rotate off of the disk by 29 November.
Region 8778 (S15, L=113, class/area Cao/80 on 24 November) produced an isolated M2/1B flare on
24/2156UT. The rest of the regions were mostly quiet and stable during the period.

SWO PRF 1266 07 December l999
Space Weather Highlights
29 Nov – 05 Dec 1999
Solar activity was moderate on 29 November, but decreased to low levels during the rest of the week.
Region 8773 (S15, L = 164, class/area Dro/030 on 26 November) produced an impulsive M1/SF flare
at 29/1414UT as it rounded the west limb. There were a few small- to moderate-sized sunspot groups
that produced occasional C-class flares during the rest of the period. Two events of interest were a C3
x-ray flare at 05/2221UT with an associated Type II radio sweep and an optically uncorrelated Type II
radio sweep at 05/2332UT.

SWO PRF 1267 14 December l999
06-12 Dec 1999
Solar activity was low through much of the period with isolated C-class flares observed during most
days. However, activity briefly rose to moderate levels on 07 December by virtue of an M1/SN flare at
07/2120UT from Region 8791 (S14, L = 262, class/area Bxo/010 on 09 December). Most visible
regions were small and simple, which accounted for the relatively low activity levels. The anticipated
strong return of old active Regions 8765 (S12, L = 234) and 8766 (N18, L = 213) did not materialize
and appeared to interrupt the recurrent pattern of moderate to high activity witnessed during the last
few solar rotations.
 

SWO PRF 1268 21 December l999
SWO PRF 1268
21 Dec 1999
Space Weather Highlights
13 – 19 Dec 1999
Solar activity ranged from low to moderate levels. Activity was low through 16 December due to
isolated C-class subflares, most of which came from Region 8798 (S13, L = 171, class/area Dkc/550
on 17 December). This region began a gradual growth phase on 15 December and by the end of the
period had become large and magnetically complex. An optically unassociated Type II radio sweep at
16/0744UT may have been associated with flare activity in Region 8798. Region 8806 (N19, L = 115,
class/area Fkc/890 on 19 December) rotated into view on 17 December as a large, magnetically
complex sunspot group. It produced an M1 X-ray flare at 17/2141UT with an associated loop
prominence system and an M1/1N flare at 18/1912UT. Activity decreased to low levels on 19
December due to occasional C-class flares from Region 8806.

SWO PRF 1269 28 December l999
Space Weather Highlights
20 – 26 Dec 1999
Solar activity ranged from low to high levels. Activity was low through 20 December with only C-class
subflares. Regions 8806 (N19, L=114, class/area Fhc on 23 Dec) and 8807 (N11, L = 111,
class/area Cao on 20 Dec) were the most active. Region 8798 (S13, L = 171, class/area Dkc on 17
Dec) was large and magnetically complex as was Region 8806. Both showed delta configurations. On
21 December activity increased from low to moderate due to an M1/1N at 21/1719UT. The activity
level increased to high on 22 December when Region 8806 produced an M5/1B event at 22/1904UT
with a 280sfu 10cm flare. Region 8807 produced an M1/2B with parallel ribbons at 22/0216UT and
with a Type II sweep event. The level of activity returned to low 23 through 26 December. Minor C-class flares
continued from regions 8798, 8806, and 8810. Region 8798 slowly decayed before it
rotated from view on December 26. Region 8806 has retained a beta gamma delta configuration.
Region 8810 (N35, L = 024, class/area Eko on 26 Dec) rotated into view on 24 December as a large
spot group.

SWO PRF 1270 04 January 2000
Space Weather Highlights
27 Dec 1999– 02 Jan 2000
Solar activity ranged from low to moderate levels. Activity was at moderate levels during 27 - 28
December as Region 8806 (N19, L = 114, class/area FHC/1100 on 23 December) produced three M-class
flares. The flares included a M1/1N at 27/0154UT with an associated Type II radio sweep, a
M2/SN at 27/1206UT, and a M4/2B parallel-ribbon flare at 28/0048UT accompanied by a Type II
radio sweep and a 1400 SFU Tenflare. Region 8806 was large and magnetically complex, but in a state
of gradual decay as the period began. It continued to decay until it crossed the west limb on 29
December. Activity decreased to low levels following the passage of Region 8806. As the period
ended, the visible disk was populated by four stable, simply-structured sunspot groups.
 

SWO PRF 1271 11 January 2000
Space Weather Highlights
03 - 09 Jan 2000
Solar activity was low throughout the period. Isolated C-class subflares occurred each day. The disk
was populated by a number of small, simply-structured regions. One event of note was a long-duration
C6 X-ray burst at 08/1645UT associated with a large eruptive prominence on the southeast limb.
 

SWO PRF 1272 18 January 2000
Space Weather Highlights
10 - 16 Jan 2000
Solar activity varied from low to moderate levels. Moderate levels occurred during 10 - 12 January by
virtue of isolated M-class flares from Regions 8824 (S13, L = 173, class/area Fki/430 on 13 January)
and 8829 (N16, L = 147, class/area Eso/170 on 13 January) (see the Energetic Events list for flare
times). Region 8824 increased in size and magnetic complexity during 10 - 14 January to include the
development of a magnetic delta formation in its leader portion. It gradually decayed during the final
two days of the period. Region 8829 produced a low-level M-class flare with an associated Type II
radio sweep while rotating into view on 12 January. It stabilized shortly thereafter. Activity declined to
low levels during 13 - 16 January. All visible regions were either stable or declining as the period
ended.

SWO PRF 1273 25 January 2000
Space Weather Highlights
17 - 23 Jan 2000
Solar activity fluctuated between low and moderate levels. Region 8831 (S18, L = 130, class/area
Eao/270 on 17 January) showed gradual growth during 17 - 18 January and produced a long-duration
M3/1N parallel-ribbon flare at 18/1727UT with associated Types II and IV radio sweeps and a halo-CME.
This region also produced an M1/SF flare at 22/1801UT during a period of gradual decay that
began on 19 January. Region 8824 (S13, L = 173, class/area Fki/430 on 13 January) produced an
M1/SF flare at 18/1008UT although it gradually decayed until it crossed the west limb on 21 January.
An optically uncorrelated M1 X-ray flare occurred at 21/0648UT. Activity dropped to low levels on
the last day of the period with the disk populated by ten mostly small regions, all of which were either
stable or decaying.
 

SWO PRF 1274 01 February 2000
Space Weather Highlights
24 – 30 Jan 2000
Solar activity varied between very low and low levels. Isolated B- and C-class subflares were the order
of the day. By and large, the visible regions were small and simply structured. 

SWO PRF 1275 08 February 2000
Space Weather Highlights
31 Jan – 06 Feb 2000
Solar activity ranged from very low to high levels. Occasional B- and C-class flares occurred during 31
January - 03 February. Activity increased to moderate levels on 04 February as Region 8858 (N26, L -
200, class/area Eai/170 on 05 February) produced an impulsive M3/SF at 04/0919UT during a period
of growth. Activity increased to high levels on 05 February by virtue of an impulsive X1/3B flare at
05/1928UT, also from Region 8858. A 350 SFU Tenflare and Type II radio sweep were associated
with this flare. Activity dropped to low levels on 06 February as Region 8858 stabilized as a moderate-sized,
mixed-polarity spot group.

SWO PRF 1276 15 February 2000
Space Weather Highlights
07-13 Feb 2000
Solar activity ranged from low to moderate levels. Region 8858 (N26, L = 200, class/area Eai/170 on
05 February), a small mixed-polarity group, gradually decayed throughout the period, but managed to
produce two M-class flares. The first was an M1/1B parallel-ribbon flare at 09/0900UT with an
associated Type II radio sweep and a full-halo coronal mass ejection (CME). The second was an
M1/1N at 12/0410UT associated with Types II and IV radio sweeps, and a 200 SFU Tenflare. Region
8858 also produced a long-duration C7/1N flare at 10/0208UT accompanied by a 240 SFU Tenflare,
Type II radio sweep, and a full-halo CME. Region 8853 (S13, L = 241, class/area Bxo/020 on 06
February) produced a long-duration C7/2F flare at 09/2006UT which was followed by a full-halo
CME. Region 8853 was a decaying plage area at the time of this flare. A partial-halo CME was
observed on 11 February following a C2 at 11/1234UT from Region 8856 (S14, L = 207, class/area
Eso/190 on 05 February).

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