Solar Terrestrial Activity Report

Last major update issued on February 3, 2025 at 06:50 UT.

Recent activity

The geomagnetic field was at quiet to active levels on February 2, mostly under the influence of effects from CH1268. A distinct change was observed near 15:55 UT at ACE as the total IMF field increase and Bz swung northwards. Bz stayed northwards for the remainder of the day. Phi angle changed several times between away and towards sectors after this change. The arrival of the January 30 CME was highly likely the cause of the decrease in geomagnetic disturbance levels. Once the CME has passed the disturbance related to CH1268 should resume. Solar wind speed at SOHO ranged between 542 and 709 km/sec, averaging 604 km/sec (+46 km/sec compared to the previous day). The high latitude magnetometer at Andenes recorded quiet to minor storm levels. The above 10 MeV proton flux was at background levels all day.

Solar flux density measured at 20h UT on 2.8 GHz was 215.7 - increasing 43.8 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 193.08. In comparison SC24 peaked on June 28, 2014 at 145.50 while SC23 peaked on February 23, 2002 at 198.15. Current SC25 peak: 193.08 on August 4, 2024 (given a base solar flux level of 65, this is +59.10% compared to the SC24 peak and -3.81% compared to the SC23 peak). The Potsdam WDC planetary A index was 18 (STAR Ap - based on the mean of three hour interval ap indices: 18.5). Three hour interval K indices: 34434422 (planetary), 24444532 (Boulder), 54434532 (Andenes).

The background x-ray flux is at the class C4 level (GOES 18).

At the time of counting spots (see image time), spots were observed in 17 active regions using 2K resolution (SN: 515) and in 14 active regions using 1K resolution (SN: 312) SDO/HMI images.

AR 13974 [S17W19] was mostly quiet and stable.
AR 13976 [N12E01] decayed further and produced a few C flares.
AR 13977 [N18W01] developed and has significant polarity intermixing as well as two small magnetic delta configurations. The region produced several M flares including one major flare.
AR 13978 [N11E13] decayed slowly and lost the magnetic delta configuration.
AR 13979 [S09W70] gained spots and had a tiny magnetic delta configuration at the end of the day. An M class flare is possible despite the presence of only small and tiny spots.
AR 13980 [S09E22] decayed slowly and quietly.
(AR 13981 has been removed from the SWPC group list due to SWPC using of the same number for two different spot groups, see ARs S10753 and S10759.)
New AR 13982 [N21E18] emerged on January 30 and was numbered by SWPC 3 days later as slow development continued.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S10753 [N05E31] was reinstated due to the confusion caused by SWPC using AR 13981 for two different spot groups. Slow decay was observed on Feb.2.
S10755 [N16E13] displayed signs of decay. The region has polarity intermixing and an M flare is possible.
S10759 [N07E24] displayed impressive growth and has multiple magnetic delta configurations. X class flaring is possible. This is the spot group SWPC currently has as AR 13981.
S10761 [S18E02] was quiet and stable.
S10762 [N11E23] was quiet and stable.
S10763 [N22E47] developed slowly and quietly.
S10764 [N20W16] was quiet and stable.
New region S10765 [N16W56] emerged with tiny spots.
New region S10766 [S19E59] emerged with tiny spots.
New region S10767 [S20E39] was observed with tiny spots in an old plage area.

C2+ flares

Coronal mass ejections (CMEs)

January 31-February 2: 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 large recurrent positive polarity trans equatorial coronal hole (CH1268) was Earth facing on January 28 - February 1. A recurrent negative polarity northern hemipshere coronal hole (CH1269) will likely rotate across the central meridian on February 6-7.

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. Propagation on long distance northeast-southwest paths is poor to fair.

Forecast

The geomagnetic field is expected to be quiet to unsettled on February 3-5 due to CME effects and effects from CH1268.

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 December 30, 2024

Sunspot activity increased again during the second half of December 2024, and this will be the eighth consecutive month with average solar flux above 180. The average solar flux at 1 AU since May 1, 2024 is 205. There is an increasing chance solar cycle 25 could have a higher 1 year solar flux average than solar cycle 23. The above plot displays a projected peak for the ISN 365d smoothed sunspot number on October 12, 2024. All the other smoothed sunspot numbers as well as the smoothed 365d solar flux have projected peaks October 12-15. A sudden decrease in activity during the first months of 2025 could move the SC25 max to sometime between July and October 2024.

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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.