HELIOS no. 51        06.May 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. 
Comments?   Post them!

Solar Cycle #23, though starting very slow and about 30% behind the last cycle, has surprised with strong groups and activity anything from low to high.  It is thrilling!
In March we saw a CV-top of nearly 124.  Then, on the 8th of April the mean CV was nearly 146, and on the 24th the mean was down to 3!  Flux-values (Penticton, Canada) was 141 on the 8th and 140 on the 9th April, and 133 on the 5th May!
THE 08April-FLUX-VALUE OF 141 WAS THE HIGHEST SINCE 2nd January 1994!!!
At the turning of April/May activity grew rapidly again, and a couple of groups have produced both X-type and M-type x-ray flares!
The following regions had large x-ray flares:
Region 8183: N22 290 M-flare 19Mar
Region 8185: S24 233 M-flares 22, 26 and 27Mar 650 mvh class FKC on 24Mar
Region 8194: S18 035 M-flare 05Apr
Region 8210: S17 140 X-flare 02May
M-flares 29Apr, 01 and 03May, a total of 13 class C x-ray flares.
The X-type X1.1-flare lasted for 2 hours and 13 minutes!  This region had a mvh of 420 at this date and was class EKI and also responsible for the mass ejection resulting in a strong aurora that has been reported in the USA and Canada and was also seen in Norway in the very early hours of 03May!
The graph below shows the solar CV-activity over the last two months. This graph
will be repeated for every issue of Helios Newsletter from now on.

See also the graphs on the Index page.

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Latest solar news referred from NOAA/SWO of Boulder, Colorado, USA:
(from SWO 1174 thru 1183)

SWO PRF 1174 03 March 1998:
Space Weather Highlights
23 February – 01 March 1998
Solar activity was very low to low. A weak Type IV radio sweep was detected at 23/0017UT and was probably related to activity within old Region 8156 (S25, L = 033, class/area Eki/520 on 16 February), a day behind the west limb at the time. A 19-degree filament disappeared from location N22W06 during 23/2058-2155UT. A mostly west-directed coronal mass ejection was associated with the filament disappearance. Flare activity rose to low levels on 01 March as Region 8171 displayed dramatic growth in spot count and, to a lesser extent, magnetic complexity. A faint, partial-halo CME was detected by the SOHO/LASCO instrument around midday 28 February.

***

SWO PRF 1175 10 March 1998:
Space Weather Highlights
02 – 08 March 1998
Space Weather Highlights
23 February – 01 March 1998
Solar activity was low. Region 8171 (S24, L = 234, class/area Eki/660 on 05 March) produced isolated C-class subflares before crossing the west limb early on 07 March. Isolated, optically uncorrelated C-class X-ray flares occurred during the rest of the period.

***

SWO PRF 1176 17 March 1998:
Space Weather Highlights
09 – 15 March 1998
Solar activity ranged from very low to moderate. Region 8179 (S22, L = 032, class/area Ekc/800 on16 March) produced three M-class flares: an M1/1F at 15/1616UT, an M1/1B at 15/1920UT, and an M2/SF at 15/2146UT. There were minor discrete radio emissions associated with the latter two flares. The SOHO/LASCO instrument detected a partial-halo coronal mass ejection (CME) departing the southeast limb around the time of the 15/1920UT M1/SF flare. Region 8179 produced the M-class flares during a period of dramatic growth that began late on 13 March and continued through the end of the period.

***

SWO PRF 1177 24 March 1998:
Space Weather Highlights
16 – 22 March 1998
Solar activity ranged from low to moderate. Region 8179 (S22, L = 032, class/area Ekc/800 on 16 March) reached maturity as a moderately complex E-type on 16 March after a period of dramatic growth that began late on 13 March. Thereafter, the region produced C-class subflares while slowly decaying, then crossed the west limb 22 March. Four low-level M-class flares occurred: an M1 at 16/0106UT with no optical association, an M1 at 8/1112UT, also with no optical association; an M1/1N at 19/0127UT from Region 8183 (N22, L = 290, class/area Cro/080 on 19 March); and an M1/1N at 22/0700UT from Region 8185 (S24, L = 233, class/area Fki/350 on 22 March). The last flare was accompanied by a Type II radio sweep and minor centimetric radio bursts. Region 8185 appeared to stabilize as a moderately complex F-type by the end of the period. A number of coronal mass ejections were seen in the SOHO/LASCO images.

***

SWO PRF 1178 31 March 1998:
Space Weather Highlights
23 – 29 March 1998
Solar activity was low to moderate. There were three M-class X-ray bursts: an optically unassociated M2 at 23/0309UT, an M1/2B flare at 26/1259UT, and a long-duration M2/3N flare at 27/2227UT. The latter two flares were produced by Region 8185 (S25, L = 233, class/area Fkc/650 on 24 March), a moderately complex group that was in slow decline during the period. The long-duration M2/3N flare was notable in that it was associated with a Type II radio sweep and a halo-type coronal mass ejection (CME). A 27-degree filament disappeared from the northwest quadrant beginning 28/1826UT. There was evidence of continuing activity from old Region 8179, now nine days behind the southwest limb. CMEs observed on 25 and 29 March were associated with old Region 8179 based upon space-based X-ray and coronal images. A few optically unassociated Types II and IV radio sweeps may have been produced by the region as well.

***

SWO PRF 1179 07 April 1998:
Space Weather Highlights
30 March – 05 April 1998
Solar activity was low to moderate. Old Region 8179 (S22, L = 032, class/area Ekc/800 on 16 March) returned to the visible disk early on 04 April and was assigned SWO region number 8194. It produced a long-duration M1/SF flare at 05/1639UT as it crossed the east limb. Extremely intense coronal emissions were detected above the southeast limb prior to its arrival and signaled the continued potency of the region, which is situated within a band of historically active longitudes. There was also evidence the region produced coronal mass ejections while on the far side of the disk, another signal the region would be productive upon its return. Region 8195 (S26, L = 036, class/area Axx/030 on 05 April) rotated into view just to the southeast of 8194. Both regions shared a common inversion line and appeared to be part of an emerging region complex. Region 8190 (S20, L = 141, class/area Eai/230 on 01 April) was in a period of moderate growth during 31 March - 01 April and produced C-class subflares. A Type IV radio sweep occurred at 31/0252UT and a Type II radio sweep occurred at 31/0551UT; both were associated with flare activity in Region 8190. This region stabilized on 03 April, then gradually decayed.

***

SWO PRF 1180 14 April 1998:
Space Weather Highlights
06 – 12 April 1998
Activity declined from moderate to very low levels. Region 8195 (S27, L = 027, class/area Cso/060 on 07 April) produced an M1/2F flare at 06/1648UT. This region was one of a complex of regions that rotated into view on 04 April (see SWO PRF 1179). Activity dropped to low levels during 07 - 11 April with isolated C-class subflares observed. Activity declined to very low levels on 12 April.

A sudden impulse (12 nT) was detected by the Boulder USGS magnetometer at 07/1750UT, but was followed by unsettled levels.

***

SWO PRF 1181 21 April 1998:
Space Weather Highlights
13 – 19 April 1998
Solar activity was at very low to low levels. A few B- and C-class subflares occurred. Region 8194 (S18, L = 035, class/area Dso/310 on 07 April) rotated out of view on 18 April.

A solar proton event began on 20 April and was in progress at issue time.
The greater than 2 MeV electron flux at geosynchronous altitude reached high levels during 14 - 16 April, then declined to normal levels for the rest of the period.

***

SWO PRF 1182 28 April 1998:
Space Weather Highlights
20 – 26 April 1998
Solar activity increased to high levels. The week began with activity at moderate levels due to a long-duration M1 X-ray flare detected at 20/1021UT. The source was likely old Region 8194, about two days behind the southwest limb at the time of the flare. An eruptive prominence and a Type II radio sweep accompanied the flare. Activity rose to high levels on 23 April due to an X1 X-ray flare at 23/0555UT. A type IV radio sweep and 430 SFU Tenflare were associated the flare. The source appeared to be old Region 8190, about a day behind the southeast limb at the time of the flare. Old Region 8190 began to rotate into view on 24 April and was numbered as Region 8210 (S17, L = 139, class/area Dso/230 on 25 April).
Region 8210 produced isolated C-class flares during the remainder of the period. Despite the X-class activity, Region 8210 was unimpressive in size, but was becoming magnetically complex by the end of the period.

A Solar Proton Event (SPE) followed the long-duration M1 of 20 April. The greater than 10 MeV proton flux reached event threshold at 20/1400UT, reached a peak of 1700 PFU at 21/1205UT, and ended at 24/1550UT. The greater than 100 MeV proton flux reached event threshold at 20/1710UT, reached a maximum of 7.4 PFU at 21/1255UT, and ended at
22/0430UT (see GOES proton plot, p. 12). A polar cap absorption event (maximum 13dB) occurred in response to the SPE.
The greater than 2 MeV electron flux at geosynchronous altitude reached moderate to high levels during 25 - 26 April.
Otherwise fluxes were at normal levels.
The geomagnetic field was quiet to unsettled during 20 - 23 April. Space-based sensors detected an interplanetary shock passage around 23/1800UT. A field disturbance followed the shock and continued through the rest of the period. Middle latitude stations detected active to minor storm levels during the disturbance, while higher latitudes detected active to major storm levels. It appears the disturbance was due, in part to a favorably positioned extension if the southern crown coronal hole, although the long-duration M1 may have played a part in the early stages.

***

SWO PRF 1183 05 May 1998:
Space Weather Highlights
27 April – 03 May 1998
Solar activity remained at high levels. Region 8210 (S17, L=140, class/area Eki/420 on 02 May) produced three major flares. The first was an X1/2B at 27/0920UT with an associated 950 SFU Tenflare, Type IV radio sweep and a halo-CME. The second flare was an M6/3B at 29/1637UT, accompanied by a Type IV radio sweep and an Earth-directed, halo-CME. The third flare was an X1/3B at 02/1342UT with an associated 1300 SFU Tenflare, Type IV radio sweep, and a partial-halo CME. Region 8210's magnetic structure became increasingly complex before and during the major flare activity, but appeared to be slowly simplifying by the end of the period. Region 8214 (N27, L = 096, class/area Esc/300 on 03 May) grew at a rapid to moderate pace during 01 - 03 May and produced and produced an isolated M-class flare.

A Solar Proton Event (SPE) followed the X1/3B flare of 02 May. The greater than 10 MeV proton flux reached event threshold at 02/1420UT, reached a peak of 150 PFU at 02/1650UT. The greater than 100 MeV proton flux reached event threshold at 02/1405UT, and reached a maximum of 07.6 PFU at 02/1450UT. Both events ended on 03 May. A polar cap absorption event occurred in response to the SPE (estimated maximum absorption 3.7 dB).
The greater than 2 MeV electron flux at geosynchronous altitude was mostly high through 30 April, then declined to normal to moderate levels for most of the rest of the period. However, fluxes briefly rose above event threshold on 02 and 03 May.
The geomagnetic field was quiet to unsettled through 29 April. The Boulder USGS magnetometer detected a sudden impulse (SI) of 31 nT at 30/0933UT, followed by unsettled to active levels. Conditions declined to quiet levels during most of 01 May. A sudden storm commencement (SSC) of 36 nT occurred at 01/2158UT and was followed by minor to severe storm levels for the rest of the period. This activity was likely due to the M6/3B flare of 29 April.

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Space Weather Forecast
06 May 1998 - 01 June 1998
Solar activity is expected to range from low to moderate. Region 8210 is expected to produce isolated M-class flares until its departure on 07 May. There is also a slight chance for another major flare from this region. Region 8214 may produce M-class flares before departing the limb on 10 May.
Region 8210 may produce another solar proton event before departing the west limb on 08 May.
The greater than 2 MeV electron flux at geosynchronous altitude is expected to be at moderate to high levels through 10 May and again during 22 - 25 May. Mostly normal fluxes are expected during the rest of the period.
The geomagnetic field is expected to be at unsettled to minor storm levels through 07 May as the current disturbance runs its course. Active conditions are expected during 21 - 23 May due to a recurrent coronal hole high-speed wind stream. Quiet to unsettled conditions are expected for the rest of the period.

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Helios no. 52 will be issued 01. July 1998

CV-Helios Network 06.May.98