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Product: Daily Forecast of Geomagnetic Activity
Issued: 2023 September 21 05:52UTC
Prepared by the Athens Space Weather Forecasting Center
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1. Solar activity
Solar activity was decreasing stable during the past 24 hours.
Solar Flux (10.7 cm) measured on 20.09.2023 at 20:00 UTC was 156 sfu.
The background X-Ray flux is at the class B1.1 level.
The geomagnetic field was at quiet to active levels on September 20.
A M8.2 class solar flare erupted on September 20 at 14:19 UT (peak time) from AR3435 and a radioblackout (R2) was observed.
No obviously Earth directed CMEs were observed in available LASCO imagery.
The Kp index now is at unsettled levels with Kp=3.

2. Solar Wind Geomagnetic Activity
Solar Wind speed from ACE: 427 km/s.
Solar Wind speed from STEREO A: 400 km/s.
Solar Wind speed from STEREO B: - km/s.
The southward component Bz is: 1 nT north.

3. Solar Energetic Particle Events
Protons and electrons are quiet.

4. Coronal Holes
An equatorial coronal hole (CH1175) was Earth facing on September 19.

5. Geophysical Activity Forecast
The geomagnetic field is expected to be at quiet to unsettled levels on September 21 and 23 and at quiet to active levels on September 22 due to effect from coronal hole (CH1175) high speed stream.

Date Estimated Ap index Expected geom. storm
2023.09.21 08 -
2023.09.22 12 -
2023.09.23 10 -

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Athens Space Weather Forecasting Center
Physics Department, National & Kapodistrian University of Athens
Athens Neutron Monitor Station A.NE.MO.S
Tel.: +30 210 727 6901
email: spaceweather@phys.uoa.gr
URL: http://spaceweather.phys.uoa.gr
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