Space weather, week 36 of 2026.
·Week 36 of 2026, August 31, 2026 to September 6, 2026, 7 of 7 days recorded. No day reached storm level; the most disturbed day was August 31, 2026, with the Kp index (0 to 9, storm at 5 and above) peaking at 3.3, unsettled. The Sun let off 3 medium (M-class) and 28 small (C-class) flares over the week.
One section per complete UTC day, written by the daily data run from NOAA's feeds: the planetary Kp index every three hours, the GOES X-ray flare list, NOAA's daily sunspot number and 10.7 cm flux, and hourly solar wind at L1. Nothing here is edited by hand. The record index explains each figure, and the same numbers are in the open data file.
Monday, August 31, 2026
Earth's magnetic field was unsettled: the Kp index, a 0 to 9 scale where 5 and above counts as a geomagnetic storm, peaked at 3.3 in the 03:00 to 06:00 UTC window and averaged 2.4 for the day. Aurora stayed up near the poles. The Sun let off 5 small (C-class) flares; the biggest was C2.6 at 15:16 UTC, too small to notice on Earth. The sunspot count for this day arrives from NOAA the following afternoon and is added on the next run.
Kp through the day, one value per three hours from midnight UTC: 3, 3.3, 3.3, 3.3, 2, 1.7, 1.7, 1.
Tuesday, September 1, 2026
Earth's magnetic field was quiet: the Kp index, a 0 to 9 scale where 5 and above counts as a geomagnetic storm, peaked at 2.7 in the 09:00 to 12:00 UTC window and averaged 1.8 for the day. Aurora stayed up near the poles. The Sun let off 3 small (C-class) flares; the biggest was C5.7 at 21:10 UTC, too small to notice on Earth. The sunspot count for this day arrives from NOAA the following afternoon and is added on the next run.
Kp through the day, one value per three hours from midnight UTC: 1, 1.3, 2, 2.7, 2, 1.7, 1.7, 1.7.
Wednesday, September 2, 2026
Earth's magnetic field was quiet: the Kp index, a 0 to 9 scale where 5 and above counts as a geomagnetic storm, peaked at 2.3 in the 06:00 to 09:00 UTC window and averaged 1.5 for the day. Aurora stayed up near the poles. The Sun let off 1 medium (M-class) and 3 small (C-class) flares; the biggest was M3.0 at 19:20 UTC, enough for a brief shortwave radio fade on the daylit side. The sunspot count for this day arrives from NOAA the following afternoon and is added on the next run.
Kp through the day, one value per three hours from midnight UTC: 0.7, 1, 2.3, 2, 1.7, 1, 1.7, 1.7.
Thursday, September 3, 2026
Earth's magnetic field was quiet: the Kp index, a 0 to 9 scale where 5 and above counts as a geomagnetic storm, peaked at 2.3 in the 00:00 to 03:00 UTC window and averaged 1.5 for the day. Aurora stayed up near the poles. The Sun let off 6 small (C-class) flares; the biggest was C6.9 at 14:46 UTC, too small to notice on Earth. The sunspot count for this day arrives from NOAA the following afternoon and is added on the next run.
Kp through the day, one value per three hours from midnight UTC: 2.3, 1, 0.7, 1, 1.3, 1.7, 2, 1.7.
Friday, September 4, 2026
Earth's magnetic field was quiet: the Kp index, a 0 to 9 scale where 5 and above counts as a geomagnetic storm, peaked at 1.7 in the 09:00 to 12:00 UTC window and averaged 1 for the day. Aurora stayed up near the poles. The Sun let off 1 medium (M-class) and 6 small (C-class) flares; the biggest was M1.2 at 07:53 UTC, enough for a brief shortwave radio fade on the daylit side. The sunspot count for this day arrives from NOAA the following afternoon and is added on the next run. The solar wind, the stream of particles flowing past Earth, averaged 369 km per second, a normal pace, and peaked at 427. Its magnetic field tipped southward for a time (Bz down to -5.3 nT), the direction that feeds storms.
Kp through the day, one value per three hours from midnight UTC: 1.3, 1, 1, 1.7, 1.3, 0.3, 0.7, 0.3.
Saturday, September 5, 2026
Earth's magnetic field was quiet: the Kp index, a 0 to 9 scale where 5 and above counts as a geomagnetic storm, peaked at 2.7 in the 03:00 to 06:00 UTC window and averaged 1.5 for the day. Aurora stayed up near the poles. The Sun let off 1 medium (M-class) and 3 small (C-class) flares; the biggest was M1.0 at 15:18 UTC, enough for a brief shortwave radio fade on the daylit side. The sunspot count for this day arrives from NOAA the following afternoon and is added on the next run. The solar wind, the stream of particles flowing past Earth, averaged 346 km per second, a slow day, and peaked at 389. Its magnetic field tipped southward for a time (Bz down to -5.4 nT), the direction that feeds storms.
Kp through the day, one value per three hours from midnight UTC: 2, 2.7, 2, 2, 1.3, 0.3, 0.3, 1.
Sunday, September 6, 2026
Earth's magnetic field was quiet: the Kp index, a 0 to 9 scale where 5 and above counts as a geomagnetic storm, peaked at 1.7 in the 18:00 to 21:00 UTC window and averaged 1.3 for the day. Aurora stayed up near the poles. The Sun let off 2 small (C-class) flares; the biggest was C5.0 at 10:42 UTC, too small to notice on Earth. The sunspot count for this day arrives from NOAA the following afternoon and is added on the next run. The solar wind, the stream of particles flowing past Earth, averaged 355 km per second, a normal pace, and peaked at 405. Its magnetic field tipped southward for a time (Bz down to -6.2 nT), the direction that feeds storms (23 of 24 hours recorded).
Kp through the day, one value per three hours from midnight UTC: 1.3, 1.3, 1.3, 1.3, 1.3, 0.7, 1.7, 1.7.
What do these numbers mean?
Four things are tracked each day. The Kp index says how disturbed Earth's magnetic field was, on a 0 to 9 scale measured every three hours; 5 and above is a geomagnetic storm, and the higher it goes the farther south the aurora reaches. Flares are sudden flashes on the Sun, sorted by size: C-class is small and harmless, M-class is medium and can briefly fade shortwave radio, X-class is large. The sunspot count is NOAA's daily tally of dark spots, weighted so that groups count more than lone spots; it runs from 0 on a blank Sun to 150 or more near the peak of a solar cycle. The radio output is the Sun's brightness at a 10.7 cm radio wavelength, a second activity gauge that does not depend on counting spots; 70 is quiet, 200 very active. The solar wind is the stream of particles flowing past Earth, measured about 1.5 million km upstream; its speed and the north-south direction of its magnetic field (Bz) decide whether a storm follows, because a southward field lets the wind's energy into Earth's field.