Solar activity was at low levels with seven numbered active regions

on the disk.

The largest event of the period was a C3.7 flare on March 25 from

Region 4400. Region 4403, which was numbered last period, is the

suspected source of several flares observed beyond the limb prior to

its rotation onto the disk. Due to its proximity to the northeast

limb, foreshortening continues to prevent a definitive

characterization of its complexity and extent.

The remaining disk regions exhibited varying degrees of decay and

evolution. Region 4397 has dissipated into a small unipolar group,

while Region 4398 underwent penumbral decay. Region 4399 remained

largely stable, though it continues to fluctuate between a unipolar

and bipolar state due to the short-lived trailing spots. Significant

internal changes were noted in the more complex groups: Region 4400

experienced extensive reconfiguration and flux emergence, and gained

a gamma configuration. Similarly, Region 4401 exhibited persistent

flux emergence and an expansion of penumbral area in its trailing

spots. Region 4402 showed a decline in its leader spot cluster.

No Earth-directed coronal mass ejections (CMEs) were observed in

available coronagraph imagery. Solar activity is expected to be low

with a chance for M-class (R1-R2/minor-moderate) flares through March

28.

For the first several hours of the reporting period, solar wind

parameters reflected the continued waning influence of a negative

polarity coronal hole high-speed stream (-CH HSS). During this time,

solar wind speed decreased from approximately 550 km/s to 515 km/s.

On March 25, a transient CME began its passage through the near-Earth

environment. Accompanied by a rise in solar wind speed to a peak of

633 km/s. Solar wind parameters are expected to remain mildly

enhanced as current influences diminish. Additional enhancements are

anticipated on March 26, following the arrival of another component

of the March 22 CME. Following this passage, a gradual return to a

nominal, slow-speed regime is forecast through March 28.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's

Ionosphere,  March 26, 2026, by F. K. Janda, OK1HH:

Solar activity declined during the first half of March. Despite

preliminary forecasts of a subsequent increase, it not only remained

low for another week, but observations also showed no signs of an

impending rise. Eventually, however, solar activity did begin to

rise, while the power flux of solar radio noise at a wavelength of

10.7 cm (abbreviated as solar flux) rose to the level seen in early

February.

The increase in geomagnetic activity also came as a surprise.

Although it initially recurred as expected after 27 days (i.e., March

13–14), the next recurrence not only came later, but the disturbance

lasted twice as long as expected, while was particularly intense on

March 22 (reaching G3 instead of the anticipated G1–G2). However,

given the presence of large coronal holes No. 31 and 33 in the center

of the solar disk—that is, facing Earth—the intensity of the

disturbance may not have been a surprise.

Similarly, regarding future developments, it can be assumed that the

next geomagnetic disturbance will occur later, and the same applies

to the expected increase in solar activity; however, this will still

be during the third decade of April, when we can expect the first

occurrences of the sporadic E layer in the mid-latitudes of the

Earth’s northern hemisphere. This, combined with the expected

increase in daily MUF values, should improve DX signal propagation on

the upper shortwave bands

The Predicted Planetary A Index for March 28 to April 3 is 5, 8, 15,

10, 5, 5, 18 with a mean of 9.4. The Predicted Planetary K Index is

2, 3, 4, 3, 2, 2, 5 with a mean of 3. 10.7 centimeter flux is 130,

128, 125, 125, 130, 120, 120 with a mean of 125.4.

For more information concerning shortwave radio propagation, see
http://www.arrl.org/propagation and the ARRL Technical Information
Service web page at, http://arrl.org/propagation-of-rf-signals. For
an explanation of numbers used in this bulletin, see
http://arrl.org/the-sun-the-earth-the-ionosphere . Information and
tutorials on propagation can be found at, http://k9la.us/ .

Also, check this:

https://bit.ly/3Rc8Njt

"Understanding Solar Indices" from September 2002 QST.