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HELIOS no. 55        01.February 1999


This Helios Newsletter continues a series newsletters under the same name as above and that were issued as the newsletter of the Solar Section of the Norwegian Astronomical Society.  Helios no. 1 was issued on 2nd May 1979 and ended almost simultaneously as I resigned as the leader of that section, i.e. in August 1989.   Now I bring it to life again, started where I left it. 
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Extracts from Preliminary Report and Forecast, SEL, Boulder, CO. USA:
SWO PRF 1209
03 November 1998
Space Weather Highlights
26 October - 01 November 1998
Solar activity ranged from very low to low. Isolated B- and C-class subflares were detected, none of
which were associated with significant radio emission.
Real-time solar wind data were available from the Advanced Composition Explorer (ACE) spacecraft
during most of the period. Solar sector orientation shifted from away (phi angle near 135 degrees) to toward (phi angle near 315 degrees) on 27 October. The shift was accompanied by increased velocitiesduring 27 - 30 October (460 - 660 km/sec) and a brief particle density enhancement (peak 17 p/cc on 27 October). Bz became slightly more variable as well and ranged from minus 08 nT to plus 10 nT (GSM) during 27 - 29 October. 

*** 

SWO PRF 1210
10 November 1998
Space Weather Highlights
02-08 November 1998

Solar activity ranged from low to high. Region 8375 (N18, L = 182, class/area Ekc/410 on 05November) grew gradually in size and magnetic complexity during the period and produced numerous flares, the largest of which reached the major category - an M8/2B at 05/1955UT with a significant Type II radio sweep, moderate discrete radio emission, and a full-halo CME (detected by the now fully-functional SOHO/LASCO instrument). Region 8375 also produced numerous C-class subflares and several low-level M-class flares during the period (see the Energetic Events list, p. 5), a few of which were followed by halo or partial-halo CMEs. Region 8375 remained moderately large and complex as it approached the west limb late in the period.

***

SWO PRF 1211
17 November 1998
Space Weather Highlights
09-15 November 1998

Solar activity ranged from low to moderate. Region 8375 (N18, L = 183, class/area Eki/720 on 08 November), producer of last week's major flare, remained moderately large in size and magnetic complexity until it crossed the west limb on 11 November. It produced a few M-class flares as it crossed, including an M1/SF at 10/1544UT with an associated loop prominence system. Region 8375 was also responsible for a C-class flare observed about two days beyond the west limb at 14/0508UT with an associated major Type IV radio sweep and a solar proton event. Region 8385 (N20, L = 114, class/area Eso/110 on 13 November) showed minor growth during the period and produced an isolated M1/1N at 12/0528UT and occasional C-class flares, all with weak radio emission. A prominence erupted from the northwest limb late on 09 November and was associated with a partial-halo CME. Active to major storm levels occurred during this disturbance with brief severe storm periods detected at high latitudes. The storm ended on 15 November as field activity declined to quiet to unsettled levels.

***

SWO PRF 1212
24 November 1998
Space Weather Highlights
16-22 November 1998

Solar activity ranged from very low to high. Very low to low levels occurred through 21 November with isolated B- and C-class flares reported. One event of note during this period was a C4/SF from Region 8383 (S15, L = 042, class/area Eso/110 on 14 November) with an associated Type II radio sweep. Activity increased to high levels on 22 November when Region 8384 (S27, L = 029, class/area Dkc/610 on 11 November) produced two X-class flares as it crossed the southwest limb. The first was an X3/1N at 22/0642UT with associated Types II and IV radio sweeps, a 340 SFU Tenflare, and moderate discrete radio emission. The second was an X2/2N at 22/1623UT, also with moderate discrete radio emission and a loop prominence system. The sudden increase to high levels was surprising, given the stability exhibited by Region 8384 during the days preceding the X-flares.
A solar proton enhancement at geosynchronous altitude followed the X3/1N flare.

***

SWO PRF 1213
01 December 1998
Space Weather Highlights
23 - 29 November 1998

Solar activity ranged from low to high. High activity occurred during 23 - 24 November as Region 8384 (S27, L = 029, class/area Dkc/610 on 11 November) produced an X-class flare each day. The first flare was an X2 at 23/0642UT with a Type IV radio sweep and a loop prominence system. The second was an X1 at 24/0220UT accompanied by a Type II radio sweep and a 380 SFU Tenflare. These flares occurred as this region was crossing the southwest limb. Activity dropped to low levels during 25 - 26 November, once Region 8384 rotated beyond the limb. Activity increased to moderate levels on 27 November by virtue of an M1/2N parallel ribbon flare at 27/0743UT from Region 8392 (S23, L = 239, class/area Cao/040 on 23 November) with an associated Type II radio sweep and a 390 SFU Tenflare. Activity increased to high levels on 28 November when Region 8395 (N18, L = 186, class/area Fao/480 on 28 November) produced an X3/3N flare at 28/0552UT with associated Types II/IV radio sweeps, a 3600 SFU Tenflare, and a partial-halo CME. Region 8395 was the return of old Region 8375, which produced a major flare and a solar proton event during its previous rotation. Activity dropped to low levels on 29 November with occasional small flares from Region 8395.

***

SWO PRF 1214
08 December 1998
Space Weather Highlights
30 November - 06 December 1998

Solar activity was low throughout the period. Region 8395 (N19, L = 182, class/area Fao/480 on 28 November), producer of last week's major flare, slowly decayed and  produced isolated C-class subflares. Region 8402 (N17, L = 117, class/area Eao/390 on 01 December) showed minor growth on 04 December and produced a few C-class subflares, then gradually simplified during the rest of the period. Spots were visible near the southeast limb on 06 December and signaled the return of old Region 8384, which produced two X-class flares during its previous rotation. By issue time the spots had been numbered as Region 8406 (S27, L = 031, class/area Cso/100 on 07 December), but did not appear impressive.

***

SWO PRF 1215
15 December 1998
Space Weather Highlights
07-13 December 1998

Solar activity was low throughout the period. C-class flares occurred  each day, none of which had significant radio emission. Regions 8408 (S18, L = 034, class/area Dao/190 on 13 December) and 8409 (S29, L = 021, class/area Eao/210 on 11 December) showed gradual growth beginning 11 December. Both regions produced C-class flares and had become moderate in size and magnetic complexity by the end of the period.

***

SWO PRF 1216
22 December 1998
Space Weather Highlights
14-20 December 1998

Solar activity ranged from low to high. Activity rose to high levels on 18 December as Region 8415 (N20, L = 253, class/area Eai/270 on 19 December) produced an M8/2N flare at 18/1722UT following a period of moderate growth. Spotless plage Region 8414 (N26, L = 287) produced a long-duration M2 X-ray flare that was time-coincident with the M8 flare above. A weak Type II radio sweep, 880 SFU Tenflare and halo-CME were associated with the M8/M2 event. Region 8415 slowly decayed during the remainder of the period but produced an M1/1N flare at 20/0900UT associated with minor radio emission. Region 8409 (S28, L = 021, class/area Esi/270 on 15 December) produced an M3/1N at 17/0745UT accompanied by a Type II radio sweep and a 200 SFU Tenflare. It also produced a C7/SN flare at 17/1418UT with a Type II radio sweep.

***

SWO PRF 1217
29 December 1998
Space Weather Highlights
21-27 December 1998

Solar activity ranged from low to moderate. The week began with activity at low levels due to isolated subflares from a couple of decaying regions. Activity increased to moderate on 23 December with an M2 X-ray flare from the northeast limb at 23/0816UT with associated Types II and IV radio sweeps and a loop prominence system. This active area appeared to be the return of old active Region 8395 (which had a history of major flare production) and was numbered as 8421 (N27, L = 171, class/area Eac/360 on 28 December). Activity remained at moderate levels through 25 December as Region 8421 produced isolated low-level M-class flares. Region 8421 was moderate in size and magnetic complexity at the end of the period. Activity dropped to low levels during 26 - 27 December with Regions 8421 and 8419 (N27, L = 224, class/area Eai/540 on 28 December) producing C-class subflares. Region 8419 entered a rapid growth phase on 27 December and had developed into a large, magnetically complex spot group by the end of the day.

***

SWO PRF 1218
05 January 1999
Space Weather Highlights
28 Dec 1998 - Jan 03 1999

Solar activity ranged from low to moderate. Region 8419 (N27, L = 224, class/area Eai/540 on 28 December) was in a rapid growth phase at the beginning of the period and produced an M3/1B flare at 28/0548UT and an M2/1F flare at 28/2338UT. Region 8419 began a slow decay on 29 December which continued until it crossed the west limb on 01 January. Region 8421 (N27, L = 171, class/area Ekc/710 on 30 December) showed slow to moderate growth through 30 December, then stabilized as a large, magnetically complex sunspot group. It produced three M-class flares as it grew, including an M1/SF at 28/0531UT, an M1/1F at 28/2322UT and an M1/SF at 30/0536UT. None of these flares had significant radio emission. Region 8421 produced isolated B- and C-class subflares during the remainder of the period. Perhaps the most interesting event of the week was a long-duration C6/1N flare at 03/1501UT from Region 8422 (S23, L = 159, class/area Dao/190 on 27 December). This flare was associated with an 18-degree filament eruption and a Type II radio sweep. This eruption had characteristics indicative of a CME (see the geomagnetic field forecast below).

***

SWO PRF 1219
12 January 1999
Space Weather Highlights
04-10 January 1999

Solar activity was low. Isolated B- and C-class subflares occurred each day. A long-duration C8 X-ray flare occurred at 07/0006UT with an associated Type II radio sweep. Space-based images indicated the flare originated from beyond the west limb, perhaps from old Region 8421 (N27, L = 171, class/area Ekc/710 on 30 December), which crossed the limb on 05 January. Another optically uncorrelated C-class flare occurred at 08/0306UT, also associated with a Type II radio sweep. Once old Region 8421 departed the disk, 10.7 cm solar radio flux levels dropped to the lowest levels since last October.

***

SWO PRF 1220
19 January 1999
Space Weather Highlights
11-17 January 1999

Solar activity ranged from low to moderate. Activity was at low levels early in the period, but began to increase as new active regions 8439 and 8440 rotated into view. Both regions were moderate in size and magnetic complexity throughout the period. Region 8440 (N19, L = 265, class/area Eai/360 on 16 January) was the dominant flare producer during most of the period and provided four low-level M-class flares during 14 - 16 January along with numerous C-class subflares. However, none of these flares were impressive in radio aspects. Region 8439 (S24,L - 267, class/area Eai/270 on 14 January) showed increased activity on 17 January and produced C-class subflares, one of which was accompanied by a Type II radio sweep (C5/SF at   17/1955UT).  Space-based images indicated enhanced coronal emission near the northeast limb at the end of the period, perhaps indicating the return of old Region 8421 (N27, L - 171).

***

SWO PRF 1221
26 January 1999
Space Weather Highlights
18-24 January 1999

Solar activity ranged from low to high. Activity increased to high levels on 20 January due to a long-duration M5 X-ray flare at 20/2004UT with associated Types II and IV radio sweeps, a 230 SFU Tenflare, and a proton enhancement/event (see the discussion below). The flare source was behind the northeast limb near where old Region 8421 (N27, L = 171) was expected to return. However, the source region rotated into view as a large area of plage. Activity varied from low to moderate during the remaining days as Regions 8439 (S24, L = 268, class/area Ekc/480 on 22 January) and 8440 (N19,L = 265, class/area Fhi/360 on 22 January) each produced isolated, low-level M-class flares, none of which were impressive in radio emission. Both regions, which were moderate in size and magnetic complexity, appeared to be slowly decaying as they crossed the west limb on the last day of the period.

Space Weather Outlook
27 January 1999 - 22 February 1999
Solar activity is expected to be low to moderate. M-class flare probabilities may increase after 07 February, given the expected return of (old) Regions 8439 and 8440.

No significant proton enhancements are expected at geosynchronous altitude. The greater than 2 MeV electron flux at geosynchronous altitude is expected to be at normal to moderate levels during most of the period with high levels possible during 11 - 13 February.

The geomagnetic field is expected to be at quiet to unsettled levels during most of the period.
However, active periods are possible during 10 - 11 February.

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