Viewing archive of Wednesday, 20 July 2016

Daily bulletin on solar and geomagnetic activity from the SIDC

Issued: 2016 Jul 20 1230 UTC

SIDC Forecast

Solar flares

C-class flares expected, (probability >=50%)

Geomagnetism

Minor storm expected (A>=30 or K=5)

Solar protons

Quiet

	10cm flux	Ap
20 Jul 2016	106	023
21 Jul 2016	106	026
22 Jul 2016	105	018

Bulletin

The strongest event of the period was a C4.2 flare south of NOAA 2567, peaking at 03:17UT. A total of 5 C-class flares was recorded, mainly over the inversion line between sunspot groups NOAA 2565 and 2567. Both regions display some group filaments, and NOAA 2567's main spot gained sunspot area to its north. A 20-degrees long filament disappearance was observed southeast of NOAA 2567 between 20 and 23UT on 19 July. No earth- directed coronal mass ejections (CMEs) have been observed in the currently available coronagraphic imagery.

Further C-class flaring is expected, with a chance on an isolated M-class flare.

A shock in the solar wind speed (ACE) was observed on 19 July at 23:05UT, jumping from about 320 km/s to 450 km/s. Bz was mostly positive ( strong +34 nT around 01UT), but with important negative excursions around 23:15UT (-12 nT), between 01UT and 03UT (-15 nT), and a brief but strong dip to -28 nT at 00:22UT. The latter coincided with the expected sector boundary crossing as the direction of the interplanetary magnetic field changed from away to towards the Sun. Since 03UT, solar wind speed has been varying in the 500-600 km/s range, with Bz steady between mostly -3 and +3 nT.

The source of the disturbance is currently believed to be the much earlier than expected (a full day ahead) arrival of a complex series of faint and apparently slow CMEs that departed from the Sun shortly before noon on 17 July.

Minor geomagnetic storming has been observed in the Kp index during the 21-24UT, 00-03UT and 03-06UT intervals. At Dourbes, minor storming was observed from 01-04UT. Dst reached values of only -26 nT (07UT).

Mostly unsettled to active geomagnetic conditions are expected in the wake of the CMEs and in response to the high speed stream of the negative northern coronal hole. Another minor storming episode is possible today and on 21 July.

Today's estimated international sunspot number (ISN): 060, based on 22 stations.

Solar indices for 19 Jul 2016

Wolf number Catania	086
10cm solar flux	101
AK Chambon La Forêt	027
AK Wingst	011
Estimated Ap	010
Estimated international sunspot number	064 - Based on 34 stations

Noticeable events summary

Provided by the Solar Influences Data analysis Center© - SIDC - Processed by SpaceWeatherLive

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