HELIOS no. 58        08.Nov. 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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ACTIVE REGIONS IN SOLAR CYCLE 23
compared to cycles 20-21-22

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Extracts from Preliminary Report and Forecast, SEL, Boulder, CO. USA:

SWO PRF 1249
10 August 1999
Space Weather Highlights
02 - 08 Aug 1999
Solar activity ranged from low to high levels. The week began with activity at high levels due to an X1/1B flare at 02/2128UT from Region 8647 (S18, L=242, class/area Eao/350 on 04 August) with an associated 570 SFU Tenflare and Type II radio sweep. This region was also responsible for the week's second major flare, an M6/1N flare at 04/0557UT accompanied by a 230 SFU Tenflare and a weak Type II radio sweep. Region 8647 was part of a complex of closely-spaced, interacting regions that included Region 8645 (S26, L=242, class/area Fao/620 on 30 July). Region 8645 was of moderate size and magnetic complexity and produced a few low-level M-class flares during its passage. A few low-level M-class flares occurred within the 8645/8647 region complex as it crossed the west limb during 05 - 07 August. Region 8651 (N25, L=204, class/area Fki/1370 on 02 August), which produced a major flare on 29 July (see PRF #1248), remained a large group of moderate magnetic complexity. It produced a few subflares as it gradually decayed through the period before quietly crossing the west
limb on 08 August.

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SWO PRF 1250
17 August 1999
Space Weather Highlights
09 - 15 Aug 1999
Solar activity ranged from very low to low levels. Isolated C-class flares occurred through the period, most of which were produced by Region 8662 (S16, L=086, class/area Fai/290 on 10 August). This region was of moderate size and magnetic complexity and showed gradual development during 09 - 10 August, then slowly dissipated during the rest of the period.
Real-time solar wind data were available from the Advanced Composition Explorer (ACE) spacecraft for most of the period. Coronal hole effects were evident on 15 August with increased velocities and increased IMF Bz variability with maximum southerly deflections to minus 14 nT (GSM).

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SWO PRF 1251
24 August 1999
Space Weather Highlights
16 - 22 Aug 1999
Solar activity ranged from low to high levels. Activity was at low levels through 18 August with a few long-duration C-class flares detected. Activity increased to moderate levels on 19 August by virtue of an isolated M1/1N flare at 19/1205UT from Region 8672 (N15, L=347, class/area Cro/040 on 19 August). Activity rose to high levels on 20 August as Region 8674 (S25, L=247, class/area Dko/490 on 22 August) produced an impulsive M9/1N flare at 20/2308UT with an associated Type II radio sweep and 480 SFU Tenflare. This region produced another major flare on 21 August, an impulsive M5/1N at 21/2214UT accompanied by a 250 SFU Tenflare. Activity dropped to low levels on 22August with a few C-class flares from Region 8674 including a C5/SN flare at 22/1412UT with Types II and IV radio sweeps. Active levels are also expected around 12 - 16 September. Otherwise, quiet to unsettled levels are expected.

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SWO PRF 1252
31 August 1999
Space Weather Highlights
23 - 29 Aug 1999
Solar activity ranged from low to high levels. Region 8674 (S24, L=246, class/area Fkc/770 on 27 August) produced two major flares and isolated M-class flares. Significant development occurred within the intermediate and trailer portions of the group during 26 - 28 August, which included the formation of two delta magnetic configurations. The first major flare was an M5/2N at 27/1307UT with relatively modest discrete radio emission. The second was an X1/2N at 28/1805UT associated with a 1000 SFU Tenflare and a Type II radio sweep with an estimated shock velocity of 600 km/sec.
Activity dropped to low levels on the last day of the period as Region 8674 entered a period of slow decay. Region 8681 (N21, L=207, class/area Dai/220 on 29 August) emerged rapidly on 28 August, then continued to grow through the rest of the period while producing occasional subflares.

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SWO PRF 1253
07 Sept 1999
Space Weather Highlights
30 Aug - 05 Sep1999
Solar activity ranged from low to moderate levels. Activity reached moderate levels during the first day of the period due to an M3/2B flare at 30/1805UT with an associated Type II radio sweep from Region 8681 (N21, L=207, class/area Dai/280 on 30 August). Region 8681 emerged rapidly on 28 August and continued to grow through 30 August, then showed gradual decay during the rest of the period. Activity declined to low levels on 31 August and remained so during the remaining days with most active centers either stable or declining. Also noteworthy was a precipitous drop in the daily 10.7 cm solar radio flux, which fell from 218 to 112 SFU during the summary period.

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SWO PRF 1254
14 Sept 1999
Space Weather Highlights
06-12 September 1999
Solar activity ranged from very low to moderate levels. Region 8690 (N13, L=119, class/area Dso/050 on 08 September) produced an M1/1B flare at 08/1217UT. This was the only moderate activity during the period. Activity for the rest of the period was very low to low. Region 8690 produced most the activity, however regions 8692 (S27, L=009, class/area Eao/270 on 12 September) and 8699 (N21, L=003, class/area Dro/030 on 12 September) showed rapid growth and increased magnetic complexity at the end of the period.

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SWO PRF 1255
21 Sept 1999
Space Weather Highlights
13-19 September 1999
Solar activity was predominately low with a single moderate event occurring during the period. Region 8690 (N16, L=025, class/area Eao/310 on 17 September) produced an M1/SF flare at 17/0120UT. A partial-halo Coronal Mass Ejection (CME) was observed by the LASCO/SOHO spacecraft following a 50-degree disappearing solar filament (DSF) that occurred 16/1508-1615UT. Region 8699 (N23, L=003, class/area Eso/170 on 19 September) Showed rapid growth at the beginning of the period, and then stabilized for the remainder, producing minor c-class subflares. The other region of note was Region 8700 (N12, L=290, class/area Dri/070 on 19 September) which developed a mixed polarity sunspot group and produced numerous c-class flares.

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SWO PRF 1256
28 Sept 1999
Space Weather Highlights
20-26 September 1999
Solar activity ranged from very low to low levels. The visible disk was populated by a number of small, simply-structured sunspot groups which produced B- and C-class subflares. The largest flare of the week was a C9/SF at 21/0352UT associated with a weak Type II radio sweep from Region 8706 (N20, L=207, class/area Cso/120 on 20 September).

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SWO PRF 1257
05 October 1999
Space Weather Highlights
27 September - 03 October 1999
Solar activity was low. The visible disk was populated by a number of small, simply-structured sunspot groups which produced B- and C-class subflares. One event of note was an optically uncorrelated, long-duration C3 x-ray flare at 01/0813UT with a Type II radio sweep (est. velocity 600 km/sec).

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SWO PRF 1258
12 October 1999
Space Weather Highlights
04 - 10 October 1999
Solar activity was low. Isolated B- and C-class subflares occurred each day. The disk was populated by numerous small, simply-structured sunspot groups during most of the period. However, Region 8728 (N22, L=318, class/area Dho/340 on 10 October) rotated into view on 08 October, then grew steadily through the rest of the period to become a group of moderate size and magnetic complexity.

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SWO PRF 1259
19 October 1999
Space Weather Highlights
11 - 17 October 1999
Solar activity ranged from low to high levels. Activity was at low levels through 13 October due to occasional C-class subflares, mostly from Region 8731 (N12, L=292, class/area Fkc/1220 on 17 October). Activity rose to high levels on 14 October due to an impulsive X1/1N flare at 14/0900UT from Region 8731 with associated Types II and IV radio sweeps, and a 1000 SFU Tenflare. This flare occurred during a period of rapid growth within Region 8731 which included the development of a magnetic delta configuration near region center. Activity dropped to low levels on 15 October as the region stabilized as a large F-type spot group with a compact spot distribution and a complex magnetic structure. Region 8751 remained large and complex for the remainder of the period, but produced only
occasional c-class subflares.

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SWO PRF 1260
26 October 1999
Space Weather Highlights
18 - 24 October 1999
Solar activity ranged from low to moderate levels. Activity was at low levels through 19 October with isolated C-class subflares. Activity increased to moderate levels on 20 October with an M1/1F flare from Region 8731 (N12, L = 292, class/area Fkc/1220 on 17 October) at 20/0622UT with an associated Type II radio sweep. This large region displayed a mixed polarity structure and was slowly decaying when the M-flare occurred. Activity declined to low levels on 21 October and remained so for the balance of the period. However, Region 8739 (S12, L = 168, class/area Eki/440 on 23 October) grew during the latter half of the period and became moderate in size and magnetic complexity including a magnetic delta configuration near region center.

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SWO PRF 1261
02 November 1999
Space Weather Highlights
25 - 31 October 1999
Solar activity ranged from low to moderate levels. Moderate levels occurred during 25 - 27
October with isolated, low-level M-class flares from Regions 8739 (S12, L = 167, class/area Fkc/800 on 26 October), 8741 (S25, L = 147, class/area Eao/280 on 25 October), and 8737 (S14, L = 235, class/area Eao/370 on 25 October) (see the Energetic Events summary for occurrence times). Activity dropped to low levels on 28 October with occasional C-class subflares observed during the rest of the period.. Region 8739 was the most interesting of the visible regions due to its moderately complex magnetic structure. However, this region began to slowly decay on 28 October and produced isolated C-class subflares during the rest of the period.
Real-time solar wind data were available from the Advanced Composition Explorer (ACE) spacecraft for most of the period. Coronal hole effects were evident on 25 October with velocities as high as 630 km/sec and densities in the 01 to 04 p/cc range. The coronal hole effects subsided on 26 October.
There were periods of sustained southward IMF Bz observed during 27 October and during 28/1200 -29/1200UT. The 27 October period showed maximum southerly deflections to minus 07 nT (GSM) while the 28 - 29 October interval showed deflections to minus 12 nT. There were no remarkable velocity or density changes noted during this period.
No proton events were detected at geosynchronous orbit during the period.
The greater than 2 MeV electron flux dipped to normal to moderate levels on 29 October, but was at moderate to high levels during the rest of the period.
The geomagnetic field was disturbed during 25 October due to coronal hole effects with unsettled to active levels detected at middle latitudes and active to major storm levels at high latitudes. The field was also disturbed during 27 - 29 October with unsettled to minor storm levels at middle latitudes and unsettled to major storm levels at high latitudes. This disturbance was caused by sustained periods of southward IMF Bz.

Space Weather Outlook
03 - 29 November 1999
Solar activity is expected to be at low to moderate levels. Occasional C-class flares are likely. Isolated M-class flares are also possible throughout the period, especially after 07 November when active longitudes are due to return.
No significant proton events are expected at geosynchronous orbit.
The greater than 2 MeV electron flux at geosynchronous altitude is expected to be at moderate to high levels during 07 - 15 and 20 - 23 November. Normal to moderate fluxes are expected during the remaining days.
The geomagnetic field is expected to be at unsettled to active levels during 06 - 13 and 18 - 21
November due to recurrent coronal hole effects. Quiet to unsettled levels are expected during the rest of the period.

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New members since 01.Aug 99:

We wish you all welcome!

Helios no. 59 will be issued 01. Feb. 2000

CV-Helios Network 08 nov 1999