HELIOS no. 56
03.May 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.
Comments? Post them!
SOLAR CYCLE 23 IS FALLING BACK ON SOLAR CYCLE 22
The above graphics show the falling back in both Solar Flux 10,7 cm and in CV.
By the end of April 99, cycle 23 had beeen set back by about 35% in smoothed 6-rotation
Flux,
and at the same time, CV was set back about 49%.
Preliminary predictions (Malde, Apr.99) estimating cycle 23 to be equivalent to cycle
20,
perhaps lower. Predicted: Smoothed 24-wk. Solar Flux 164 in June 2000.
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Extracts from Preliminary Report and Forecast, SEL,
Boulder, CO. USA:
SWO PRF 1222 02 February 1999
02 February 1999
Space Weather Highlights
25-31 January 1999
Solar activity ranged from very low to moderate. Activity reached moderate levels on 25
January due to an M2/SN flare at 25/0056UT from Region 8444 (N19, L = 233, class/area
Dso/100 on 25 January), which showed slight growth prior to the flare. This region also
produced a long-duration C3/SF at 25/0012UT with a Type II radio sweep. Activity dropped
to very low to low levels for the rest of the week with occasional B- and C-class
subfolders from a variety of small sunspot groups.
Real-time solar wind data were available from the Advanced Composition Explorer (ACE)
spacecraft during most of the period. A few minor changes were detected in the solar wind
flow on 27 January including a velocity increase from 330 to 450 km/sec, a density
enhancement which peaked at 17 p/cc, and southerly IMF Bz variations to minus 08 nT (GSM).
Phi data indicated that Earth was within an away solar sector (positive polarity, phi
angle near 135 degrees) during the period.
The proton enhancement at geo-synchronous altitude that followed the M5 flare of 20
January
returned to background levels on 27 January. Proton fluxes remained at background levels
for the rest of the period.
***
SWO PRF 1223 09 February 1999
09 February 1999
Space Weather Highlights
01-07 February 1999
Solar activity ranged from very low to low levels. Isolated, small c-class events
occurred, most of which were not optically correlated. The 06 February 10.7 cm radio flux
reading (99.0) was the lowest since last July. A few large, high-latitude filaments
disappeared from the southern hemisphere during 05 - 06 February.
Real-time solar wind data were available from the Advanced Composition Explorer (ACE)
spacecraft during most of the period. Phi data indicated a shift to a toward solar sector
(negative polarity, phi angle near 315 degrees) on 03 February. We remained within a
toward sector for the rest of the period.
Particle densities at >10 MeV were enhanced on 03 - 04 February and peaked at 18 p/cc.
IMF Bz hovered around zero in the plus to minus 08 nT (GSM) range during most of the
period. However, Bz became more variable on 04 February with maximum southerly deflections
to minus 12 nT. No significant velocity changes were detected during the period.
***
SWO PRF 1224 16 February 1999
16 February 1999
Space Weather Highlights
08-14 February 1999
Solar activity increased to low to moderate levels. Region 8457 (N16, L = 276, class/area
Eki/660 on 13 February), which was the return of old AR 8440, produced two low-level
M-class flares during a period of slow growth. The first was an M1/SF at 12/0325UT with
associated Type II and IV radio sweeps. The second was a long-duration M1/SF at 14/1045UT.
Region 8457 stabilized late in the period. C-class subflares occurred daily from a number
of small regions. The daily 10.7 cm solar radio flux rose steeply during the period and
reached a peak of 205 SFU on 14 February, which was the highest reading to date of Cycle
23.
Real-time solar wind data were available from the Advanced Composition Explorer (ACE)
spacecraft during most of the period. Phi data indicated a shift to an away (positive
polarity) solar sector on 11 February. Earth remained within an away sector for the rest
of the period. Significant changes were detected in the solar wind flow during 11 - 12
February as velocities increased from 330 - 590 km/sec and densities dropped to 02 to 04
p/cc. IMF Bz became more variable during this period as well and ranged from plus to minus
20 nT (GSM). These changes appeared due, at least for the most part, to the effects of a
high-speed coronal hole windstream.
***
SWO PRF 1225 23 February 1999
23 February 1999
Space Weather Highlights
15-21 February 1999
Solar activity was low during most of the period. However, activity briefly rose to
moderate levels on 16 and 21 February by virtue of isolated, low-level M-class flares.
Region 8458 (S22, L = 270, class/area Dko/660 on 11 February) produced a long-duration
M3/SF flare at 16/0312UT with associated Type II and IV radio sweeps. This region also
produced two C-class flares on 20 February associated with radio sweeps. Region 8462 (N20,
L = 266, class/area Dao/170 on 17 February) produced an M1/1F flare at 16/0016UT and an
M1/SF 21/1345UT. A decreasing trend began late in the period as historically active solar
longitudes began to depart the visible disk.
Real-time solar wind data were available from the Advanced Composition Explorer (ACE)
spacecraft during most of the period. Two transient (CME) structures passed the spacecraft
during the period.
The first, preceded by a relatively weak shock, passed the spacecraft around 17/0500UT
accompanied by a modest velocity increase, enhanced particle densities, and a period of
southward IMF Bz (maximum southerly deflections to minus 14 nT (GSM)). The second CME,
preceded by a much stronger shock, passed the spacecraft about 18/0200UT accompanied by a
velocity increase from 400 to 700 km/sec, increased particle densities, and strong,
sustained southward IMF BZ (maximum southerly deflections to minus 28 nT). This CME
passage resulted in a major geomagnetic storm. Phi data indicated that Earth was within an
away (positive
polarity) solar sector during most of the period.
***
SWO PRF 1226 02 March 1999
02 March 1999
Space Weather Highlights
22-28 February 1999
Solar activity was low during most of the period, but rose to high levels on 28 February.
Region
8471(N29, L = 100, class/area Eao/120 on 28 February) produced an impulsive M6/2B
parallel-ribbon flare at 28/1638UT with moderate discrete radio emission. This flare
followed a period of minor growth in the region.
Real-time solar wind data were available from the Advanced Composition Explorer (ACE)
spacecraft during most of the period. Earth was within an away (positive polarity) solar
sector during most of the period, but the sector shifted to toward (negative polarity) on
the last day of the period. Solar wind velocities ranged from 320 - 460 km/sec. IMF Bz
hovered around zero in the plus to minus 06 nT (GSM) range during most days, but was more
variable on 25 and 28 February with maximum southerly deflections to minus 10 nT. Particle
densities were enhanced on 24 and 27 - 28 February with peaks near 20 p/cc.
***
SWO PRF 1227 09 March 1999
09 March 1999
Space Weather Highlights
01-07 March 1999
Solar activity was low throughout the period. Isolated C-class flares occurred each day
from a few small- to medium-sized regions, typically during periods of minor growth within
these regions. A 38-degree, high latitude filament disappeared from the southeast quadrant
on 05 March.
Real-time solar wind data were available from the Advanced Composition Explorer (ACE)
spacecraft during most of the period. It appeared that Earth was under the influence of a
high-speed coronal hole windstream during most of the period. Velocities were elevated
during the period with peaks near 600 km/sec noted on 02 and 05 March. Particle densities
were enhanced on 01 March preceding the onset of coronal hole effects reaching a peak of
50 p/cc, then declined to a range of 02 - 05 p/cc for most of the rest of the period. The
Earth was in a toward (negative polarity) solar sector during most of the week. IMF Bz
varied from plus 16 to minus 10 nT (GSM) on 01 March, then hovered around zero in the plus
to minus 07 nT range for the rest of the period.
***
SWO PRF 1228 16 March 1999
16 March 1999
Space Weather Highlights
08-14 March 1999
Solar activity varied from low to moderate levels. The week began with activity at
moderate levels, by virtue of an isolated M2/SF flare from Region 8484 (S23, L = 259,
class/area Dao/120 on 11 March) at 08/0637UT with an associated Type II radio sweep.
Region 8484 gradually declined through the rest of the period. Activity dropped to low
levels during 09 - 12 March. A 45-degree filament, last seen centered near S53E06,
disappeared on 10 March. Activity increased to moderate levels during 13 - 14 March as
Region 8487 (N17, L = 240, class/area Eai/200 on 15 March) produced three low-level
M-class flares: an M1/SF at 13/2034UT, an M2/1N at 14/0127UT, and an M1/SF at 14/1010UT;
all of which had minor radio emission. SOHO/LASCO images showed a partial-halo CME that
was associated with the 14/1010UT flare. Region 8487 grew slowly as it produced these
flares and showed moderate to strong magnetic gradients near region center. Region 8485
(N23, L = 277, class/area Fki/560 on 14 March) was the largest and most magnetically
complex group on the disk, but produced
only B- and C-class flares.
Real-time solar wind data were available from the Advanced Composition Explorer (ACE)
spacecraft during most of the period. There were two periods of interest. The first was a
CME passage detected during 09 - 10 March with enhanced particle densities and periods of
sustained southward IMF Bz (maximum deflections to minus 12 nT (GSM). The second period of
interest began during the latter half of 14 March as a high-speed coronal hole windstream
began to affect the Earth's field. These effects included a velocity increase from 380 -
630 km/sec and southward IMF Bz deflections to minus 09 nT. An isolated, positive-polarity
northern-hemispheric hole (possibly recurrent) appeared to be the source of the high-speed
stream.
***
SWO PRF 1229 23 March 1999
23 March 1999
Space Weather Highlights
15-21 March 1999
Solar activity varied from very low to high levels. The week began with activity at
moderate levels by virtue of an M1/1N flare from Region 8487 (N17, L = 239, class/area
Eai/200 on 15 March) at 15/0336UT with an associated Type II radio sweep. Activity
increased to high levels on 16 March due to an impulsive M6/2N at 16/2141UT from Region
8485 (N23, L = 277, class/area Fki/610 on 16 March). Region 8485 also produced five
impulsive, low-level M-class flares during 16 - 18 March, all of which were weak in radio
emission. This region was moderate in size and magnetic complexity throughout its disk
passage. Solar activity dropped to very low to low levels after Region 8485 crossed the
west limb on 20 March.
Real-time solar wind data were available from the Advanced Composition Explorer (ACE)
spacecraft during most of the period. Solar wind velocities gradually decreased from a
high of 590 km/sec on 15 March to 300 km/sec by the end of the period. Phi data indicated
that Earth was within an away (positive polarity) solar sector throughout the period.
Particle densities varied from 01 to 10 p/cc. IMF Bz ranged from plus to minus 05 nT (GSM)
during most of the period. However, southward deflections to around minus 10 nT were
observed on 15 and 21 March.
***
SWO PRF 1230 30 March 1999
30 March 1999
Space Weather Highlights
22-28 March 1999
Solar activity was very low during most of the period. All sunspot groups were small,
simply
structured, and stable.
Real-time solar wind data were available from the Advanced Composition Explorer (ACE)
spacecraft for most of the period. There were two periods of interest. The first occurred
as a transient passed the spacecraft late on 25 March with an associated density increase
to 23 p/cc, a minor velocity increase, and southerly IMF Bz deflections to minus 13 nT
(GSM). This transient may have been associated with a partial-halo CME observed on 21
March. The second period of interest occurred late on 28 March as densities increased to
28 p/cc. Earth was within an away (positive polarity) solar sector throughout the period.
***
SWO PRF 1231 06 April 1999
06 April 1999
Space Weather Highlights
29 March - 04 April 1999
Solar activity ranged from very low to high levels. The week began with activity at very
low to low levels with isolated, mostly B-class X-ray flares. Activity increased to
moderate levels on 02 April with an optically uncorrelated M1 at 02/0821UT. Region 8508
(N20, L = 284, class/area Cao/090 on 04 April) rotated into view on 03 April and appeared
to be the return of old Region 8485. Region 8508 lies within a band of active solar
longitudes that have produced episodes of moderate to high activity for the last several
rotations. Activity rose to high levels on the last day of the period as Region 8508
produced an M5/1F flare at 04/0528UT accompanied by a 190 SFU Tenflare and moderate
centimetric radio bursts. A halo-CME may have been associated with this flare as well.
Real-time solar wind data were available from the Advanced Composition Explorer (ACE)
spacecraft for most of the period.
***
SWO PRF 1232 13 April 1999
13 April 1999
Space Weather Highlights
05-11 April 1999
Solar activity ranged from low to moderate levels. Activity briefly rose to moderate
levels on 08 April due to an impulsive M1/SF flare from Region 8508 at 08/1613UT with
minor radio emission. Region 8508 (N21, L = 283, class/area Dai/190 on 08 April), though
relatively small, showed a moderately complex magnetic structure and was the most active
region on the disk during the period. It also produced isolated C-class flares each day.
Region 8506 (S26, L = 002, class/area Dao/290 on 05 April) developed a beta-gamma-delta
magnetic structure early in the period and produced isolated B-and C-class subflares.
However, it began to decay on 07 April, then ceased to be a significant flare producer.
Real-time solar wind data were available from the Advanced Composition Explorer (ACE)
spacecraft for most of the period. Coronal hole effects were evident during 05 - 06 and 10
- 11 April with elevated wind velocities and decreased densities. IMF Bz became more
variable on 10 April with southerly excursions to minus 08 nT (GSM), but otherwise hovered
about zero in the plus to minus 05 nT range. Solar sector orientation was variable on 05
April, then became mostly toward (negative polarity) during 06 - 08 April. Orientation
shifted to away (positive polarity) on 09 April and remained so for the balance of the
period.
***
SWO PRF 1233 20 April 1999
20 April 1999
Space Weather Highlights
12-18 April 1999
Solar activity ranged from very low to low levels. The disk was populated by small, simple
sunspot groups, a few of which produced isolated B- and C-class subflares. SOHO/LASCO
images showed two partial-halo CME events during the period. The first occurred around
13/0330UT, the second around 17/0600UT.
Real-time solar wind data were available from the Advanced Composition Explorer (ACE)
spacecraft for most of the period. The 13/0330UT CME mentioned above reached the Earth
near midday on 16 April accompanied by a velocity increase from 380 - 470 km/sec,
southward IMF Bz deflections to minus 13 nT (GSM), and a brief particle density increase
to 68 p/cc. Earth was within an away solar sector (positive polarity) during the period.
***
SWO PRF 1234 27 April 1999
27 April 1999
Space Weather Highlights
19-25 April 1999
Solar activity ranged from very low to low levels. The disk was populated by small, simple
sunspot groups, a few of which produced isolated B- and C-class subflares. A large coronal
mass ejection (CME) occurred around midday on 24 April. Space-based images indicated that
the CME was a "back side" event, i.e. originating on the backside of the Sun,
directed away from Earth. A solar proton event was associated with the CME (see the
discussion below). It appeared that old Region 8517 (N22, L = 210, class/area Dso/100 on
20 April), two and a half days behind the west limb at the time, may have been the source
of the CME.
Real-time solar wind data were available from the Advanced Composition Explorer (ACE)
spacecraft for most of the period. Solar wind velocities, proton temperatures, and IMF Bz
variations increased during 19 - 20 April, likely in response to an isolated,
positive-polarity coronal hole.
A greater than 10 MeV solar proton event at geo-synchronous altitude was associated with
the CME mentioned above. It began at 24/1840UT, reached a maximum of 32 PFU at 25/0055UT,
then dropped below event threshold at 25/1450UT, followed by a gradual decline to
pre-event levels.
The greater than 2 MeV electron flux at geo-synchronous altitude was at normal to moderate
levels.
The geomagnetic field was disturbed during 20 April with active to major storm levels (the
major storm periods were limited to high latitudes). The disturbance appeared to be
coronal-hole related.
Quiet conditions prevailed during the rest of the period.
Space Weather Outlook
28 April - 24 May 1999
Solar activity is expected to be at low to moderate levels. An increasing trend is
expected to begin around 30 April with the return of historically active longitudes.
No significant proton enhancements are expected at geo-synchronous altitude.
The greater than 2 MeV electron flux at geo-synchronous altitude may reach high levels
around 30 April - 04 May. Otherwise, normal to moderate levels are expected.
Geomagnetic field activity is expected to increase to active to minor storm levels during
29 April - 02 May due to recurrent coronal hole effects. Quiet to unsettled conditions are
expected during the rest of the period, barring any Earth-directed CMEs.
***
***
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New members since 01.Feb.99:
CV-Helios
Network New Members |
CV-070 |
GEORG ROBECK |
GERMANY | 15.feb.99 |
CV-071 |
RICO HICKMANN |
GERMANY | 16.feb.99 |
CV-072 |
BHARAT ADUR |
INDIA | 03.apr.99 |
We wish you all welcome!
Helios no. 57 will be issued 01. Aug. 1999
CV-Helios Network 04 mai 1999