HELIOS no. 52        01.July 1998

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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Except from the first week or so, and the last week of May, the solar activity have been determined as very low to low.  We saw some fine groups though, especially Region 8210, by SWO as a DKO-group at 480 mvh on the 5th of May.  Region 8214 reached a nice FKC at 650 mvh on the same date.  CV was 82,0 by 8 observers.  CV was highest on the 7th May with 115,9 (7 obs.).  CV is again in the excess of 100 at the very end of June.
The below graph show the acceleration and retardation according to Malde's P-Index (1988), which is the 12-week average increase/decrease in percentage of CV-24week Smoothed numbers.  This may explain why the activity has decreased somewhat for a while.
The overlay is the Smoothed CV-24week.

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Latest solar news referred from NOAA/SWO of Boulder, Colorado, USA:
(from SWO 1184 thru 1190)

SWO PRF 1184 12 May 1998
12 May 1998
Space Weather Highlights
04-10 May 1998
Solar activity was at moderate to high levels during most of the period. Region 8210 (S17, L = 140, class/area Dko/480 on 05 May) produced major flares on 06 and 09 May. All told, the region produced six major flares between 23 April and 09 May making it the most productive region to date for Cycle 23. The week's first major flare was an X2/2N at 06/0809UT
accompanied by a Type IV radio sweep, moderate centimetric radio bursts and a partial-halo CME. The second major flare was an M7 at 09/0340UT associated with a Type IV sweep and a 210 SFU Tenflare. There was no optical flare associated with the M7, but space-based images indicated 8210 was the source region (1 1/2 days behind the limb at the time of the flare). Region 8210 also produced low-level M-class flares during 05 - 08 May. The most interesting of these was an M2/2N at 05/2346UT associated with Types II and IV radio sweeps and a partial-halo CME. Region 8214 (N27, L= 096, class/area Fkc/650 on 05 May) produced two M-class flares on 07 May during a period of moderate growth, then
stabilized for the rest of the period. Region 8220 (S31, L = 287, class/area Hsx/200 on 10 May) produced an M3/SF flare at 10/1320UT as it crossed the east limb.
Solar wind data were available from the ACE spacecraft during most of the period. Velocities rapidly increased from 480 -840 km/sec on 04 May following an interplanetary shock passage at 04/0229UT (the source was most likely the X1/3B flare of 02 May, see PRF #1183), then gradually decreased to 460 km/sec by 06 May. Velocities increased from 460 - 690 km/sec on 08 May, then gradually declined during the rest of the period. Solar wind particle densities increased to 18 p/cc on04 May, then declined to a range of 02 -05 p/cc for the rest of the period. Bz shifted strongly southward (maximum deflection minus 40 nT (GSM)) early on 04 May following the shock passage mentioned above and was highly variable (plus to minus 20 nT) for the remainder of the day. Bz ranged from plus 12 to minus 08 nT during the remainder of the period. Solar sector orientation was not easily discernible due to high variability during the summary period.
A Solar Proton Event (SPE) followed the X2/2N flare of 06 May. The greater than 10 MeV proton flux reached event threshold at 06/0835UT, reached a peak of 210 PFU at 06/1650UT and ended at 07/0140UT. The greater than 100 MeV proton flux reached event level at 06/0830UT, reached a maximum of 2.9 PFU at 06/0840UT, then dropped below
threshold at 06/1335UT. A greater than 10 MeV proton flux enhancement followed the M7 flare of 09 May. It began near 09/0600UT and ended early 11 May.
The greater than 2 MeV electron flux at geosynchronous altitude was normal on 04 May, but increased to moderate to high levels for the rest of the period.
A geomagnetic storm occurred in the wake of the X1/3B flare of 02 May. An interplanetary shock was detected by the ACE spacecraft at 04/0229UT followed by a sudden storm commencement (SSC) at Earth at 04/0300UT. The magnitude of the SSC was 86 nT, as measured by the Boulder USGS magnetometer. Severe storm levels (K = 8 to 9) occurred during
04/0300 - 0900UT followed by active to major storm levels. The storm ended at 05/0900UT. Activity declined to quiet to unsettled levels during 06 - 07 May. Field activity increased again on 08 May with unsettled to active levels detected at all latitudes. The field returned to quiet to unsettled levels for the balance of the period.

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SWO PRF 1185 19 May 1998
19 May 1998
Space Weather Highlights
11-17 May 1998
Solar activity was very low to low. Region 8218 (S21, L = 346, class/area Eac/270 on 16 May)
generated several small C-class events throughout the period, while region 8220 (S28, L = 283,
class/area Dao/120 on 13 May) was responsible for a couple of additional minor C-class flares.
Solar wind data were available from the ACE spacecraft during most of the period. Velocities rapidly increased from 350-650 km/sec on 15-16 May following an interplanetary shock passage at 15/1356UT, then gradually decreased to 420 km/sec on 17 May. Solar wind particle densities increased to 20 p/cc on 15 May, then declined to a range of 1-3 p/cc for the rest of the period. BZ hovered about zero for most of the period 11-15 May, before displaying wide variability in the range +9 to -13 nT following the shock passage on 16 May. Bz ranged from +5 to -5 nT on 17 May.
There were no significant proton enhancements observed at geosynchronous altitude.
The greater than 2 MeV electron flux at geosynchronous altitude was moderate to high during the
period 11-13 May, mostly high on 14-15 May, and back in the moderate to high range on 16-17 May.
The geomagnetic field was mostly quiet to unsettled throughout the period, with occasional isolated periods of active conditions. A small sudden impulse was detected on ground magnetometers (about 6 nT on the Boulder USGS magnetometer) at 15/1453, apparently in response to the passage of the interplanetary shock mentioned above.

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SWO PRF 1186 26 May 1998
26 May 1998
Space Weather Highlights
18-24 May 1998
Solar activity was very low to low. Sunspot regions were unremarkable during the period. Old Region 8210, the source of X-class flares and proton events during its previous rotation (see PRFs 1182 -1184), returned to the visible disk on 22 May as a much-diminished, stable spot group and was numbered as Region 8225 (S19, L = 134, class/area Axx/010 on 25 May). Old Region 8214 (N27, L =096, class/area Fkc/650 on 05 May) began an uneventful passage into view late on 24 May and was assigned SWO region number 8227 (N25, L = 097, class/area Dao/150 on 25 May).
Solar wind data were available from the Advanced Composition Explorer (ACE) spacecraft during most of the period. Solar sector orientation was away (phi angle near 135 degrees) during 18 - 19 May, then shifted to mostly toward orientation for the rest of the period. Bz hovered around zero and ranged from plus to minus 08 nT (GSM). Solar wind particle densities ranged from 01 - 10 p/cc while velocities ranged from 340 - 470 km/sec.
There were no significant proton enhancements observed at geosynchronous altitude.
The greater than 2 MeV electron flux at geosynchronous altitude was moderate to high during 18 - 22 May, then declined to normal to moderate levels for the balance of the period.
The geomagnetic field was quiet to unsettled during most of the summary period. Isolated, short-lived substorms occurred during local nighttime, particularly at high latitudes.

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SWO PRF 1187 02 June 1998
02 June 1998
Space Weather Highlights
25-31 May 1998
Solar activity unexpectedly increased from low to high levels on 29 May as Region 8226 (N18, L =208, class/area Dko/320 on 26 May) produced an M6 flare at 29/0059UT. A minor Tenflare and Types II and IV radio sweeps were detected during the flare. The region displayed minor magnetic complexity prior to the major flare, but was otherwise stable. Region 8224 (S31, L = 248, class/area Bxo/010 on 19 May) produced a long-duration C7 flare on 27 May while rounding the west limb. A well-defined post-flare loop system and a partial-halo CME were associated with the flare, which later proved to be geoeffective (see the geomagnetic activity discussion below). Activity declined to low levels on 30 May following the departure of Regions 8224 and 8226.
Solar wind data were available from the Advanced Composition Explorer (ACE) spacecraft during most of the period. Velocities ranged from 320 - 400 km/sec through 28 May, then increased to 720 km/sec on 29 May. Velocities gradually dropped from 720 - 440 km/sec during the remainder of the period. Particle densities ranged from 02 - 08 p/cc during most of the period. However, densities increased to 22 p/cc late on 26 May. Another smaller increase occurred during 29 - 30 May with densities peaking at 11 p/cc. Solar sector orientation was not readily discernible during the period. Bz hovered about zero and ranged from minus 06 to plus 08 nT (GSM) during most of the period, but became more variable on 29 May and ranged from minus 18 to plus 15 nT.
There were no significant proton enhancements observed at geosynchronous altitude.
The greater than 2 MeV electron flux at geosynchronous altitude was normal to moderate through 30 May, then increased to moderate to high levels on 31 May.
The geomagnetic field was briefly disturbed on 25 May with active to isolated minor storm periods.
The CME associated with the 27 May long-duration C7 flare intercepted the Earth around
29/1700UT. A geomagnetic field disturbance ensued with active to major storm levels detected at all latitudes. The disturbance subsided to quiet to unsettled levels by midday on 30 May.

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SWO PRF 1188 09 June 1998
09 June 1998
Space Weather Highlights
25-31 May 1998
Solar activity was very low to low. Isolated B- and C-class subflares were detected. Most C-class flares were produced by Region 8232 (S19, L = 350, class/area Dko/380 on 05 June). Three moderate-sized filaments disappeared from the southern hemisphere early on 05 June. A partial-halo coronal mass ejection (CME) accompanied the disappearances. An optically uncorrelated Type II radio sweep occurred at 07/0912UT.
Solar wind data were available from the Advanced Composition Explorer (ACE) spacecraft during most of the period. Velocities ranged from 380 - 470 km/sec through 06 June, then increased to 660 km/sec during 07 June. Solar wind particle densities ranged from 02 - 12 p/cc through 04 June.
Densities were enhanced during 05 - 06 June, peaking at 17 p/cc, then dropped to 02 p/cc on 07 June.
Bz ranged from plus 11 nT to minus 11 nT (GSM) during the period. Solar sector orientation was mostly away (phi angle near 135 degrees) through 02 June, then shifted to mostly toward orientation for the remainder of the period.
The greater than 10 MeV proton flux became slightly enhanced beginning 04/2000UT. Fluxes returned to background levels late on 05 June.
The greater than 2 MeV electron flux at geosynchronous altitude was at moderate to high levels during 01 - 02 June, then declined to normal to moderate levels for the remainder of the period.
The geomagnetic field was quiet to unsettled during most of the period. Brief active periods occurred at all latitudes.

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SWO PRF 1189 16 June 1998
16 June 1998
Space Weather Highlights
08-14 June 1998
Solar activity ranged from very low to moderate. Isolated B- and C-class subflares occurred during most of the period. Isolated, long-duration M-class X-ray flares were detected at 11/1027UT and 13/0419UT. The 11/1027UT M1 flare had associated Types II and IV radio sweeps. LASCO/EIT images indicated the flare site was behind the northeast limb. Region 8242 (S22, L = 237, class/area Hsx/140 on 12 June) produced the 13/0419UT M1/1N flare which was accompanied by a Type IV radio sweep. Activity appeared to be on a downward trend by week's end.
Solar wind data were available from the Advanced Composition Explorer (ACE) spacecraft during most of the period. Velocities gradually decreased from 580 - 340 km/sec during the period.
Densities ranged from 02 - 05 p/cc during most of the period. However, a density enhancement
occurred late on 13 June, peaking at 23 p/cc, then returned to pre-enhancement levels by midday on 14 June. Bz hovered around zero in the plus to minus 05 nT range (GSM) during most of the time, but became more variable on 14 June, and reached a maximum southerly deviation of minus 11 nT early in the day. Solar sector orientation was mostly toward (phi angle near 315 degrees) through 09 June, then shifted to away conditions (phi angle near 135 degrees) for the rest of the period.
There were no significant proton enhancements detected at geosynchronous altitude.
The greater than 2 MeV electron flux at geosynchronous altitude was at moderate to high levels
during 08 - 10 June, then declined to normal to moderate levels for the remainder of the period.
The geomagnetic field was quiet to unsettled during most of the period. However, a brief disturbance occurred early 14 June with active to minor storm levels detected at all latitudes.

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SWO PRF 1190 23 June 1998
23 June 1998
Space Weather Highlights
15-21 June 1998
Solar activity was very low to low during most of the period, but increased to moderate levels on 16 June. Old Region 8232 (S21, L = 348, class/area Dko/380 on 05 June) produced a long-duration M1 X-ray flare which peaked at 16/1842UT. The region was a day behind the west limb at the time of the flare. A loop prominence system was associated with the flare. A prominence erupted from the southwest limb on 15 June and was accompanied by a long-duration C1 X-ray flare. A 36-degree filament disappeared from the southeast quadrant on 15 June. Region 8243 (N18, L = 214, class/area Dho/270 on 22 June) produced a C4/1N flare at 20/1430UT with associated Types II and IV radio sweeps.
Solar wind data were available from the Advanced Composition Explorer (ACE) spacecraft during most of the period. Velocities ranged from 300 - 460 km/sec during 15 - 18 June. Velocities increased to 520 km/sec during 19 June then decreased to a range of 400 - 480 km/sec for the remainder of the period. Densities ranged from 01 - 09 p/cc during 15 - 17 June. Densities were slightly enhanced for the remainder of the period and ranged from 02 - 13 p/cc. Bz variations increased during 15 and 19 -21 June with maximum deflections of plus 15 to minus 10 nT (GSM) detected on 19 June. Solar sector orientation was away (phi angle near 135 degrees) during 15 - 17 June, then shifted to toward (phi angle near 315 degrees) for the balance of the period. There were no significant proton enhancements detected at geosynchronous altitude.
The greater than 2 MeV electron flux at geosynchronous altitude increased to moderate levels on 21 June.
The geomagnetic field was quiet to unsettled during most of the period. Brief active to minor storm periods were detected at some high latitude stations.

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Space Weather Forecast
24 June 1998 - 20 July 1998
Solar activity is expected to be low during most of the period.
No 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.
The geomagnetic field is expected to be at quiet to unsettled levels.

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