[Propagation+Space Weather] The W1AW Weekly Propagation Report - 2021 Apr 23 23:07 UTC

[nw7us@sunspotwatch.com]

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The following is the weekly propagation bulletin from W1AW / ARRL (posting on 20210423 23:07 UTC):

QST de W1AW Propagation Forecast Bulletin 17 ARLP017 >From Tad Cook, K7RA Seattle, WA April 23, 2021 To all radio amateurs

SB PROP ARL ARLP017 ARLP017 Propagation de K7RA

Four new sunspots emerged this week, and were visible every day.

And in this week's bulletin a large amount of useful material from W3LPL.

Spaceweather.com issued a warning on April 22: 'A CME is heading for Earth and it could spark a geomagnetic storm when it arrives on April 25th. NOAA forecasters say moderately strong G2-class storms are possible, which means auroras could dip into northern-tier US states from Maine to Washington.'

Average daily sunspot number surged from 7 to 35.1, while average daily solar flux increased from 75 to 78.

Due to seemingly constant solar wind, average planetary A index rose from 5.1 to 16.4, and average daily middle latitude A index went from 4.1 to 13.

Predicted solar flux is 84 on April 23-24, 82 on April 25-27, 80 on April 28, 78 on April 29-30, 68 on May 1-2, 78 on May 3, 72 on May 4-9, 75 on May 10-15, 78 on May 16, 75 on May 17-18, 72 on May 19, 70 on May 20-23 and 68 on May 24-29.

Predicted planetary A index is 10, 8, 25 and 12 on April 23-26, 5 on April 27 through May 3, 15 on May 4, 5 again on May 5-7, 8 on May 8, 5 on May 9-10, then 8, 12, 20, 30, 15, 12 and 8 on May 11-17, 5 on May 18-19, then 8, 12 and 5 on May 20-22.

Geomagnetic activity forecast for the period April 23 to May 18, 2021 from F.K. Janda, OK1HH.

'Geomagnetic field will be: quiet on: May 1-3, 5, 18 quiet to unsettled on: April 28-30, May 6-11, 17 quiet to active on: April 26, May 12 unsettled to active: April 27, May 16, 18 active to disturbed: April 23, (24-25,) May (4,) 13-14, (15)

'Solar wind will intensify on: April 23-25, (then irregularly between April 26-May 1), May 3-5, (6-7, 10-11, 16,) 17-18, (18).

'Remarks: - Parenthesis means lower probability of activity enhancement. - Contradictory indications significantly reduce the accuracy of the forecast.'

Frank Donovan, W3LPL wrote:

'The significant increase in Solar Cycle 25 activity we've long anticipated may have begun on April 19th. As a result 30 and 20 meter night time propagation and 17 and 15 meter daytime propagation is likely to be enhanced through at least April 26th.

'The solar flux index (SFI) is likely to remain at 85 or higher through at least April 26th due to two active regions containing a total of 16 sunspots:

'http://www.spaceweatherlive.com/images/SDO/SDO_HMIIF_1024.jpg

'Two additional active solar regions on the far side of the Sun are expected to rotate into view later this week possibly increasing the SFI and extending enhanced propagation through at least late April:

'https://www.solarham.net/farside.htm

'See my article in May QST: 'What to Expect During the Rising Years of Solar Cycle 25.''

Frank also wrote that new sunspots are fading faster than he hoped, but the steady trend of increasing sunspots should soon sustain the solar flux above 80.

Frank then sent this additional useful content:

'Long distance propagation forecast for Thursday and Friday, April 22-23 from Frank Donovan, W3LPL.

'My propagation forecast derived from today's NOAA/SWPC web pages is published five days a week (M-F) in the Daily DX.

'Propagation at low and mid-latitudes is likely to be normal through Friday. Propagation crossing the auroral oval and polar regions is likely to be mostly normal with below normal intervals through Friday.

'Today's latest planetary Kp Index, updated every three hours:

'https://services.swpc.noaa.gov/images/planetary-k-index.gif

'N0NBH's current HF Band Conditions, updated regularly:

'http://www.hamqsl.com/solar.html

'The solar flux index (SFI) is likely to be about 78 through Friday.

'Three active regions containing a total of 17 mostly tiny sunspots are having minimal effects on HF propagation.

'We are exiting the most disturbed weeks of the March-April geomagnetic storm season when the Earth is passing through the part of the interplanetary magnetic field (IMF) with the most frequent, longest duration southward oriented IMF. Approximately twice as many brief minor and moderate geomagnetic storms occur during March and April compared to the quieter IMF during June and July. Brief minor to moderate geomagnetic storms may be triggered with little warning when the IMF rotates to a southward orientation and persists for several hours coincident with the effects of Earth directed coronal hole high speed streams and coronal mass ejection (CME) enhancements in the solar wind.

'160 and 80 meter short path propagation from North America to VK/ZL is likely to be normal through Friday. 80 and 40 meter short path propagation to south Asia is likely to be mostly normal at about 0030Z Friday. 80 and 40 meter short path propagation from North America to east Asia after about 0900Z is likely to be mostly normal with below normal intervals through Friday.

'30 meter propagation through the auroral ovals and across polar regions is likely to be mostly normal with below normal intervals through Friday. 30 meter propagation is always significantly degraded within a few hours of local noon because of E-region blanketing of long distance F2 propagation. 30 meter night time propagation is likely to improve slightly through Friday due to solar flux index of 78.

'20 meter daytime and evening propagation through the auroral ovals and across polar regions is likely to be mostly normal with below normal intervals through Friday. 20 meter northern trans-polar propagation within a few hours of sunrise and sunset will steadily improve with gradually increasing electron density in the polar F2 region through June. 20 meter night time long distance propagation in the northern hemisphere is likely to improve slightly through Friday due to solar flux index of 78.

'17 and 15 meter daytime long distance propagation in the northern hemisphere is likely to improve slightly through Friday due to solar flux of 78. 12 and 10 meter daytime long distance propagation is likely to be mostly unreliable and limited to propagation from North America to Southern Africa, South Atlantic, South America and South Pacific regions.

'Geomagnetic disturbances caused by coronal hole high speed streams are likely to remain mostly brief, minor and less frequent through at least late 2021. The north-south (Bz) component of the IMF plays a crucial role in triggering brief minor to moderate geomagnetic storms when it persists in a southward orientation (-Bz) with enhanced field strength for several hours coincident with the effects of Earth directed coronal hole high speed stream or CME enhancements in the solar wind.

'IMF field strength, solar wind speed near Earth and geomagnetic activity are likely to be at close to background levels through Friday with a possible enhancement late Friday due to coronal hole high speed stream effects. There is a slight possibility that an M-Class solar flare may cause a brief sudden ionospheric disturbance and short-wave fadeout on the Sun facing side of the Earth late Thursday.

'Geomagnetic storms and Earth directed CMEs strong enough to affect HF propagation are not likely through Friday.

'Mid latitude northern hemisphere sunset is now 32 minutes later and daylength is 81 minutes longer than it was on the March 20th.

'Daylength is increasing by two minutes per day which is steadily lengthening the duration of common daylight between distant locations in the northern hemisphere. Solar elevation in the northern polar region is increasing about three degrees per week, steadily improving 20 meter northern trans-polar propagation through June.

'Today's Penticton 10.7 cm solar flux index updated at 1700Z, 2000Z and 2300Z daily:

'https://bit.ly/2Qq0jIH

'Today's three-day GFZ Planetary K Index forecast updated every three hours:

'https://bit.ly/3noJqdH

'Today's SIDC Daily Bulletin on Solar and Geomagnetic Activity updated at 1230Z daily:

'http://sidc.oma.be/products/meu/

'Today's SWPC Solar Activity Forecast Discussion updated at 0030Z and 1230Z daily:

'https://www.swpc.noaa.gov/products/forecast-discussion

'Today's Australian Space Forecast Centre Summary and Forecast updated at 2330Z daily:

'https://www.sws.bom.gov.au/Space_Weather/1/1 'Perhaps the most useful HF propagation pages for DXers can be found at: http://dx.qsl.net/propagation and http://www.solarham.net

'The April 2021 NASA solar flux index forecast for Solar Cycle 25 has been published, mostly advancing the date for solar maximum to 2024. The SFI represented by the 50% percentile (green line) is similar to Solar Cycle 24. A double peaked solar cycle -- similar to recent Solar Cycles 23 and 24 -- could delay solar maximum by a year or more:

'https://go.nasa.gov/2RYl2DW

'Slightly updated wording to W3LPL's May QST article, unconstrained by QST page limits and reflecting NASA's predicted solar maximum in 2024:

'If the SFI persists below 90 through December 2021, then propagation should improve gradually until a solar maximum weaker than Cycle 24's arrives in 2024.

'If the SFI persists above 110 through December 2021, then propagation should improve rapidly until a solar maximum similar to Cycle 24's arrives in 2024.

'If the SFI persists above 125 through December 2021, then propagation is likely to improve more rapidly until a solar maximum stronger than Cycle 24's arrives in 2024.

'Don't forget to vote for your favorite May QST article here:

'http://www.arrl.org/cover-plaque-poll .'

N4SO recommends an article in the March-April QEX, 'The onset of Solar Cycle 25 and the MGII Index,' by VE6TL.

Jon Jones, N0JK reported an April 20 TEP opening to South America on 6 meters, and sent a long list of stations copied from 2022-2023 UTC, and this report:

'CE6CGX copied me. 10 watts, 1/4 wave whip. Jon N0JK EM28 KS.

'Rx at Tue, 20 Apr 2021 20:25:01 GMT >From N0JK by CE6CGX Loc FF31qp Frequency: 50.314.248 MHz (6m), FT8, -6dB Distance: 8846 km bearing 162 deg'

On April 19 Jon reported that VP8EME in the Falkland Islands was heard on 6 meters by KE8FD and K1TOL around 1800 UTC. 'Looks like the Summer sporadic-E season has begun.'

KA3JAW of Easton, PA reported a long 6 meter opening on April 19, 1435 to 1706 UTC. 'Best DX range was with N5DG (EM20AB) Hempstead, Texas at 1,374 miles.'

And from Cuba:

'Hi, CO7WT, Pavel Milanes here from Camaguey Cuba, FL11bj.

'I like to report a huge opening of 6m band in Saturday 17/April/2020.

'I was calibrating my homebrew 6m transverter to get access to the magic band (Noise generator, SDR, NanoVNA) and out of the blue a digital signal came up for a few seconds on my SDR screen.

'Weird, no antenna is connected, just coax from the tests, then there it is, a mental calculation spotted the 18.313 MHz, aka 50.313 (32.000 MHz XTAL... That's FT8!) a local ham, I think at first, connected my antenna (Cushcraft 3 el 6m yagi) and boom!

'Loud signals from North America and some ones from LU and CE on the side/back of the yagi, Sadly TX side of the transverter is not ready yet.

'I put some pictures on twitter, I will link them here:

'https://twitter.com/co7wt/status/1383490344231202827

'https://twitter.com/co7wt/status/1383526601367818244

'I spotted at least 3 beacons, one from W4 and the other was too unstable to decode properly as they came and go... see the pictures, some of the ones calling on FT8 has signals dancing up and down in a pattern of a few minutes.

'I think on sporadic-E as this is the season.'

If you would like to make a comment or have a tip for our readers, please email the author at, k7ra@arrl.net .

For more information concerning shortwave radio propagation, see http://www.arrl.org/propagation and the ARRL Technical Information Service 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.

An archive of past propagation bulletins is at http://arrl.org/w1aw-bulletins-archive-propagation. More good information and tutorials on propagation are at http://k9la.us/.

Instructions for starting or ending email distribution of ARRL bulletins are at http://arrl.org/bulletins .

Sunspot numbers for April 15 through 21, 2021 were 22, 44, 28, 15, 36, 54, and 47, with a mean of 35.1. 10.7 cm flux was 72, 76.5, 75.3, 78.1, 85.9, 80, and 78, with a mean of 78. Estimated planetary A indices were 13, 19, 29, 16, 18, 13, and 7, with a mean of 16.4. Middle latitude A index was 11, 15, 20, 13, 15, 10, and 7, with a mean of 13.

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