SIDC Weekly Bulletin

:Issued: 2017 Jun 20 1307 UTC
:Product: documentation at http://www.sidc.be/products/bul
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# SIDC Weekly bulletin on Solar and Geomagnetic activity             #
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WEEK 859 from 2017 Jun 12
SOLAR ACTIVITY
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During this week solar flaring activity was very low with no C-class, and
only 12 low B-class flares reported. Accordingly there was no wide CMEs
observed this week. 

Three large coronal holes were observed this week. 
First one was the large equatorial coronal hole which reached the central
meridian in the morning of June 13. 
Two large coronal holes, one on the north and one on the south solar
hemisphere, reached central meridian almost simultaneously, in the evening
of June 14.
GEOMAGNETIC ACTIVITY
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During the first two days of the week (June 12 and 13) somewhat enhanced
solar wind speed was observed, associated with the small equatorial coronal
hole which reached central meridian on June 08. 

The in situ observations indicated arrival of the fast solar wind
(associated with the large equatorial coronal hole which has reached the
central meridian in the morning of June 13), in the morning of June 16. 
At about 03:00 UT, sudden increase of the interplanetary magnetic field
(IMF) and the density increase was observed, soon followed with the change
of the phi angle. The strong oscillations of the IMF and its Bz component
were followed by sudden increase of the solar wind speed, density and
temperature marking the interaction region between the slow and fast solar
wind. The maximum of the solar wind speed of about 600 km/s was reached in
the evening of June 16.

Starting from about midday of June 17, the solar wind speed began to
increase simultaneously with the temperature, and with the density decrease
indicating arrival of the fast solar wind associated with two large coronal
holes (one on the north and one on the south solar hemisphere) which
reached central meridian in the evening of June 14. Although it was
difficult to distinguish which of the two coronal holes is associated with
this increase of the solar wind speed, it seems more probably that this was
the coronal hole on the north solar hemisphere.
At the end of the week Earth was still within the fast solar wind with the
speed of about 540 km/s.

During this week geomagnetic conditions were mostly quiet to unsettled,
except the interval of active to minor storm conditions reported on June 16
and early morning of June 17 (associated with the fast solar wind).
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DAILY INDICES
DATE           RC   EISN  10CM   Ak   BKG    M   X
2017 Jun 12   000    000   075   010   A7.2   0   0   
2017 Jun 13   011    012   075   009   A6.2   0   0   
2017 Jun 14   011    012   074   008   A6.3   0   0   
2017 Jun 15   035    032   077   006   A7.0   0   0   
2017 Jun 16   034    031   074   030   A5.5   0   0   
2017 Jun 17   ///    032   075   021   A5.6   0   0   
2017 Jun 18   ///    031   075   014   A5.9   0   0   
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# RC   : Sunspot index (Wolf Number) from Catania Observatory (Italy)
# EISN : Estimated International Sunspot Number
# 10cm : 10.7 cm  radioflux (DRAO, Canada)
# Ak   : Ak Index Wingst (Germany)
# BKG  : Background GOES X-ray level (NOAA, USA)
# M,X  : Number of X-ray flares in M and X class, see below (NOAA, USA)
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NOTICEABLE EVENTS SUMMARY
DAY BEGIN MAX  END  LOC    XRAY OP  10CM Catania/NOAA RADIO_BURST_TYPES 
NONE
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