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Daily bulletin on solar and geomagnetic activity from the SIDC

Випущено: 2021 Jul 27 1238 UTC

SIDC Forecast

Сонячні спалахи

Quiet conditions (<50% probability of C-class flares)

Geomagnetism

Active conditions expected (A>=20 or K=4)

Сонячні протони

Quiet

	10cm flux	Ap
27 Jul 2021	080	007
28 Jul 2021	080	019
29 Jul 2021	080	007

Bulletin

The solar activity has been quiet over the past 24 hours, with the X-ray flux below C-level. Two sunspot groups are currently visible on the solar disc (Catania sunspot group 22 / NOAA AR-2846, and Catania sunspot group 23 / NOAA AR-2847). They have not produced any significant flare. The solar activity is expected to remain mostly low levels over the next 24 hours with possible C-class flare.

A relatively slow coronal mass ejection was observed on July 26 around 17:00 UTC in SOHO/LASCO-C2 chronograph images. It is associated with a coronal dimming near the Catania sunspot group 23 (NOAA AR-2847) located around -35 degrees and longitude -02 degrees. At most, a glancing blow may be observed in the solar wind parameters near Earth on July 29 around noon (+/-12 hours). Another nice and large coronal dimming was observed on July 27 from 01:55 UTC to 03:25 UTC close to the disc centre (latitude -11 degrees and longitude -20 degree), which is associated with a filament eruption. The associated coronal mass ejection is observed in SOHO/LASCO-C2 coronagraphe images on July 27 around 03:24 with a projected speed of 388 km/s. The true speed of this coronal mass ejection is estimated to be around 1100 km/s, and its arrival on Earth is estimated tomorrow on July 28 around 17:00 (+/-6 hours).

The greater than 10 MeV proton flux was at nominal levels over the past 24 hours and is expected to remain so for the next 24 hours. The greater than 2 MeV electron flux was below the 1000 pfu threshold in the past 24 hours and is expected to remain so during the next 24 hours. The 24h electron fluence was at normal levels in the last 24 hours and is expected to stay at normal levels for the next 24 hours.

The solar wind parameters (as observed by ACE and DSCOVR) show an ambient background and slow solar wind speed regime. The solar wind speed ranged from 289 km/s to 331 km/s. The interplanetary magnetic field magnitude was below 6.0 nT, and Bz components varied between -2.6 nT and 2.8 nT. The high-speed streams associated with the mid-latitude extension of the positive polarity northern polar Coronal Hole, that has crossed the central meridian on July 24th is expected to enhance the solar wind condition later today on July 27 and persist for several days. The solar wind may also be temporarily enhanced on July 28 due to a glancing blow from the eastward coronal mass ejection driven by the C4.3 flare on July 24 that is expected to arrive to Earth with a relatively low probability.

The geomagnetic conditions were quiet over the past 24 hours. The conditions are expected to remain quiet until Earth remains in slow solar wind speed regime. Then, the conditions are expected to be unsettled to active with the arrival of the high-speed streams associated with northern polar Coronal Hole later today in July 27-28.

Today's estimated international sunspot number (ISN): 022, based on 13 stations.

Solar indices for 26 Jul 2021

Wolf number Catania	027
10cm solar flux	081
AK Chambon La Forêt	006
AK Wingst	004
Estimated Ap	004
Estimated international sunspot number	031 - Based on 25 stations

Noticeable events summary

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

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