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Daily bulletin on solar and geomagnetic activity from the SIDC

Emesso: 2021 Jul 24 1242 UTC

SIDC Forecast

Brillamenti solari

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

Geomagnetism

Quiet (A<20 and K<4)

Protoni solari

Quiet

	10cm flux	Ap
24 Jul 2021	086	005
25 Jul 2021	084	004
26 Jul 2021	084	004

Bulletin

Solar activity was at low levels with two C-class flares detected over the past 24 hours. Catania sunspot group 17/NOAA 2842 has now rotated behind the west limb, but is responsible for a C1.5 class flare with peak time 02:06 UTC. Catania sunspot group 20/NOAA 2845 has remained quiet and also rotated behind the west limb. Catania sunspot group 24/NOAA 2849 has remained magnetically simple with alpha type configuration. Nevertheless, it has produced a long C4.3 flare (start time 23:54 UTC, end time, 01:02 UTC, peak time 00:33 UTC). Catania sunspot group 22/NOAA 2846 (beta) Catania sunspot group 20/NOAA 2847 (alpha) have remained stable and Catania sunspot group 21/NOAA 2848 has decreased its complexity to magnetic type alpha. The X-ray flaring activity for the next 24 hours is expected to be at very low to low levels with a 50% probability for C-class flaring.

At 00:36 UTC this morning (July 24th) an eastward coronal mass ejection (CME) has left the Sun from the south-east quadrant around S20E40 following the long-duration C4.3-class flare produced by Catania sunspot group 24/NOAA 2849. While the bulk of the CME is not Earth-directed, a wide- spread dimming and a coronal wave suggest minor possibility of a geo- effective glancing blow. Based on the currently available STEREO/COR2 data a glancing blow will not arrive until late at night on July 28th. Further analysis on the data is required to better estimate the arrival probability. No other Earth-directed CMEs were detected in the available coronagraph imagery.

The greater than 10 MeV proton flux was at nominal levels in the past 24 hours and is expected to remain so in the next 24 hours. The greater than 2MeV electron flux remained under the 1000 pfu threshold and is expected to remain so. The 24h electron fluence was at nominal levels and is expected to remain in the next 24 hours.

Over the past 24 hours the solar wind activity (ACE and DSCOVR) was low. The solar wind speed remained under 400 km/s. The total magnetic field was weak in the range of 2 to 6.3 nT. The north-south (Bz) component was very weak with values between -3.8 to +4.5 nT. The interplanetary magnetic field remained predominantly in the positive sector directed away from the Sun.

The geomagnetic conditions over the past 24 hours were mostly quiet with short isolated unsettled periods. Mostly quiet geomagnetic conditions are expected for the next 24 hours with possible isolated unsettled periods. A mid-lattitude extension of the positive polarity northern polar coronal hole (CH) has now crossed the central meridian and is expected to become geo-effective in the early morning of July 27th leading to active geomagnetic conditions with a possibility for a minor storm later during the day.

Today's estimated international sunspot number (ISN): 029, based on 13 stations.

Solar indices for 23 Jul 2021

Wolf number Catania	070
10cm solar flux	087
AK Chambon La Forêt	010
AK Wingst	006
Estimated Ap	004
Estimated international sunspot number	054 - Based on 27 stations

Noticeable events summary

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

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