Solar Terrestrial Activity Report

Last major update issued on January 14, 2025 at 06:05 UT.
Reports from November 27, 2024 onwards will be updated when time allows. Archived SDO HMI imagery is available and production of STAR images will resume starting January 14.

Recent activity

The geomagnetic field was at quiet to active levels on January 13 as a high speed stream associated with CH1266 became the dominant solar wind source (after 03 UT). Solar wind speed at SOHO ranged between 381 and 489 km/sec, averaging 421 km/sec (+34 km/sec compared to the previous day). The high latitude magnetometer at Andenes recorded quiet to major 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 159.7 - decreasing 10.3 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 190.99. In comparison SC24 peaked on June 28, 2014 at 145.50 while SC23 peaked on February 23, 2002 at 198.15. Current SC25 peak: 191.44 on July 8, 2024 (given a base solar flux level of 65, this is +57.07% compared to the SC24 peak and -5.04% compared to the SC23 peak). The Potsdam WDC planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 9.5). Three hour interval K indices: 42122222 (planetary), 32133322 (Boulder), 63221344 (Andenes).

The background x-ray flux is at the class C1 level (GOES 18).

AR 13947 [N11W80] produced a few C flares and was mostly unchanged as the spot group rotated to the northwest limb.
AR 13950 [S18W59] decayed slowly and quietly.
AR 13953 [N21W84] rotated partly out of view and was quiet.
AR 13956 [N06W16] decayed slowly and quietly with the trailing penumbra fragmenting into smaller penumbrae.
AR 13957 [N21W53] decayed slowly and quietly.
AR 13959 [N18E60] was mostly quiet and stable. New spots emerged late on January 13 and early on January 14.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
T172 [S17W29] was quiet and stable.
T178 [N17E25] reemerged with a tiny spot.
T183 [S12W79] developed slowly and was mostly quiet. SWPC assigned AR 13960 to this spot group on January 13, 2 days after the first spots were observed. C1 flares: C1.7 @ 00:30 UT
New region T187 [S09E81] rotated partly into view.
New region T188 [N00E15] emerged with tiny spots.
New region T189 [S18E09] was observed with tiny spots in an old plage area.
New region T190 [N08E22] emerged with tiny spots.

C2+ flares

C1 flares: C1.4 @ 07:40, C1.6 @ 09:03, C1.7 @ 09:28, C1.4 @ 16:51, C1.5 @ 18:50, C1.6 @ 21:29, C1.5 @ 23:11 UT

Coronal mass ejections (CMEs)

January 11-13: 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 small negative polarity northern hemisphere coronal hole (CH1266) rotated across the central meridian on January 10-11.

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 active on January 13-15 due to effects from CH1266 with a chance of minor storm intervals.

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 30 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.