Solar Terrestrial Activity Report

Last major update issued on February 24, 2025 at 05:45 UT.

Recent activity

The geomagnetic field was at quiet to unsettled levels on February 23. Solar wind speed at SOHO ranged between 299 and 359 km/sec, averaging 325 km/sec (+13 km/sec compared to the previous day). The total field of the IMF increased slowly after 14h UT, as did solar wind density a little later in the day, probably due to the approach of a high speed stream associated with CH1273. The high latitude magnetometer at Andenes recorded quiet to minor storm levels. The above 10 MeV proton flux was very close to background levels all day.

Solar flux density measured at 18h UT on 2.8 GHz was 209.4 - increasing 46.9 over the previous solar rotation. The measurement at 20h UT was discarded as it was enhanced by the X2 flare. (Centered 1 year average SF at 1 AU - 183 days ago: 193.47. In comparison SC24 peaked on June 28, 2014 at 145.50 while SC23 peaked on February 23, 2002 at 198.15. Current SC25 peak: 193.47 on August 25, 2024 (subtracting a baseline solar flux level of 65, this is +59.59% compared to the SC24 peak and -3.52% compared to the SC23 peak). The Potsdam WDC planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.0). Three hour interval K indices: 31110013 (planetary), 21111223 (Boulder), 42100015 (Andenes).

The background x-ray flux is at the class C3 level (GOES 18).

At the time of counting spots (see image time), spots were observed in 15 active regions using 2K resolution (SN: 385) and in 12 active regions using 1K resolution (SN: 243) SDO/HMI images.

AR 13993 [N14W57] was quiet and stable.
AR 13996 [S16W44] decayed slowly losing spots and area, particularly in the trailing spot section.
AR 13998 [S12W27] is a large, compact region and produced many C and M flares. The magnetic delta configuration disappeared. Further M class flaring is possible.
AR 13999 [N07W44] decayed slowly and quietly.
AR 14000 [N16W20] displayed signs of decay as the magnetic delta configuration decreased in size. M class flares are still possible.
AR 14002 [N13E07] developed slowly and quietly.
AR 14003 [N10E37] decayed slowly and quietly and could soon become spotless.
AR 14004 [S12E60] decayed slowly and quietly.
AR 14005 [S05E41] decayed slowly and quietly.
AR 14006 [N18E60] was mostly quiet and stable.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S10812 [S13W60] was mostly quiet and stable.
S10814 [S07W83] decayed slowly and quietly. SWPC appears to have moved AR 13991 to this spot group.
S10820 [S09E09] decayed slowly and quietly.
New region S10822 [N17E17] emerged with tiny spots.
New region S10823 [S19E16] was observed with tiny spots in an old plage area.

C2+ flares

Coronal mass ejections (CMEs)

February 21-23: No obviously Earth directed CMEs.

Coronal holes

[Coronal hole history (since October 2002)]
[Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago]

A negative polarity northern hemisphere coronal hole (CH1273) rotated across the central meridian on February 21. A positive polarity southern hemisphere coronal hole (CH1272) may be too far to the south to cause a disturbance. CH1272 will likely rotate across the central meridian on February 22-25 having decayed in the western half on February 22. A recurrent trans equatorial positive polarity coronal hole (CH1271) will likely become Earth facing on February 24-26.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high latitudes is poor to fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be at quiet to active levels on February 24-25 due to effects associated with CH1273. Quiet to unsettled levels are likely on February 26 due to effects from CH1272. Quiet to minor storm levels are likely on February 27-28 due to effects from CH1271 and CH1272.

1) Effects from a coronal hole could reach Earth within the next 5 days. When the high speed stream has arrived the color changes to green.
2) Effects from a CME are likely to be observed at Earth within 96 hours.
3) There is a possibility of either M or X class flares within the next 48 hours.

Green: 0-30% probability, Yellow: 30-70% probability, Red: 70-100% probability.

Active solar regions

(Click on image for 2K resolution). 4K resolution. Compare to the previous day's image. 0.5K image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue is positive.

Data for all officially numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC, all other regions are numbered sequentially as they emerge using the STAR spot number. Comments are my own, as is the STAR spot count (spots observed at or inside a few hours before midnight) and data for regions not numbered by SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers. SWPC data considered to be not sufficiently precise (location, area, classification) are colored red.

Monthly solar cycle data

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz and any corrections applied to that measurement.
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days).
2B) Boulder SN current month average to date.
2C) STAR SDO 1K Wolf number 27 day average.
3) Running average based on the quicklook and definitive Potsdam WDC ap indices. Values in red are based on the definitive international GFZ Potsdam WDC ap indices.
4) Source: WDC-SILSO, Royal Observatory Of Belgium, Brussels

Solar cycles 24-25

Update on the progress of solar cycle 25 as of February 10, 2025

Sunspot activity has been on a slowly decreasing trend since September 2024 (using the mean solar flux over 3 solar rotations as a proxy). The 365 days average ISN has a peak on July 8, 2024, but is still expected to peak in October 2024 due to low sunspot numbers in March and the first half of April 2024. Unless there is an uptick in sunspot activity over the next couple of months, the 365 days average solar flux is likely to peak 1-2% below the peak of solar cycle 23. While the 365d average solar flux peaks of SC23 and SC25 are similar, sunspot numbers will peak significantly lower for SC25 compared to SC23.

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This report has been prepared by Jan Alvestad. It is based on the analysis of data from whatever sources are available at the time the report is prepared. All time references are to Universal Time. Comments and suggestions are always welcome.

SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.