• ARLP027 Propagation de K7RA

    From ARRL Web site@21:1/5 to All on Fri Jul 7 20:33:43 2023
    XPost: rec.radio.shortwave, rec.radio.info

    SB PROP @ ARL $ARLP027
    ARLP027 Propagation de K7RA

    ZCZC AP27
    QST de W1AW
    Propagation Forecast Bulletin 27 ARLP027
    From Tad Cook, K7RA
    Seattle, WA July 7, 2023
    To all radio amateurs

    ARLP027 Propagation de K7RA

    The average daily sunspot number for June, 2023 was the highest in
    21 years, according to Spaceweather.com.

    From a July 3 email alert from Spaceweather.com:

    "SUNSPOT COUNTS HIT A 21-YEAR HIGH: It's official: The average
    sunspot number in June 2023 hit a 21-year high. Solar Cycle 25 has
    shot past its predecessor, Solar Cycle 24, and may be on pace to
    rival some of the stronger cycles of the 20th century."

    Could we see another Cycle 19, the biggest in recorded history, even
    back before the birth of radio?

    Not too long ago, we heard that this cycle should peak in summer
    2025. Later that was revised to 2024. Now I am seeing occasional
    references to a cycle peak at the end of this year.

    From my own records, average daily sunspot numbers for April through
    June 2023 were 93.7, 125.8 and 143.9, a nice upward trend.

    Some popular news outlets seem confused by the difference between
    sunspot number and number of sunspots, and have quoted another
    higher average.

    Here is the difference. If they are just counting the total number
    of sunspots for the month, this is far different from average daily
    sunspot numbers. The sunspot number is somewhat subjective, but it
    gets ten points for each sunspot group, and one point for each
    sunspot in those groups.

    But I stand by my numbers. They are all from NOAA and appear at the
    end of each bulletin.

    But they may be referencing International Sunspot Number, which may
    be different from the SESC numbers from NOAA.

    Here is an example of confusing sunspot numbers with number of
    sunspots: https://bit.ly/3NCQCAl

    This one is also confusing, saying there were 163.4 sunspots in
    June. https://bit.ly/3PMu6Ym

    But what does this mean? It could be either 163 or 164 sunspots,
    but not a fractional number, unless it expresses an average. The
    minimum sunspot number is 11. This would be one sunspot group
    containing one spot. They are always whole, not fractional

    There was one new sunspot region (group) on June 30, three more on
    July 1, one more on July 2, another on July 4, and one more on July

    Sunspot and solar flux data again this week did not track together.
    Average daily sunspot number declined from 170 to 126.1, while
    average daily solar flux rose slightly from 160.3 to 164.5.

    Geomagnetic indicators were lower, with average daily planetary A
    index declining from 10.7 to 7.3, and middle latitude averages from
    9.9 to 8.

    Predicted solar flux is 155 on July 7, 150 on July 8 to 10, then 155
    on July 11, 160 on July 12 to 13, 175 on July 14 to 18, 170 on July
    19 to 21, 160 on July 22 and 23, 155 on July 24 and 25, 160 on July
    26 and 27, 165 on July 28 and 29, then 170, 170 and 165 on July 30
    through August 1, 155 on August 2 to 6, then 160, 165 and 170 on
    August 7 to 9, and 175 on August 10 to 14.

    Predicted planetary A index is 5, 12 and 8 on July 7 to 9, 5 on July
    10 and 11, then 20 and 30 on July 12 and 13, 8 on July 14 to 22, 5
    on July 23 to 30, 8 on July 31 through August 1, then 5 on August 2
    to 4, 12 and 8 on August 5 and 6, then 5, 20 and 30 on August 7 to
    9, and 8 on August 10 to 18.

    Note those big numbers are about one solar rotation apart, which is
    about 27.5 days.

    Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
    Ionosphere for July 6, 2023 from F. K. Janda, OK1HH.

    When the current 25th solar cycle began in December 2019, solar
    astronomers thought it would be a weak cycle similar to its
    immediate predecessor, solar cycle 24. But now we have a twenty-one
    year peak. And we expect a continued increase for about two more

    The misfortune is that ongoing global changes are reducing the
    ionization rate of the ionosphere. Yet the current conditions for
    shortwave or decameter wave propagation do not match the amount of
    solar activity - they are worse.

    But that's not all. Not only is solar cycle 25 likely to rival some
    of the more powerful cycles of the 20th century, but we're likely to
    see even more powerful solar flares and magnetic storms. History
    repeats itself cyclically, and we need only think of the great
    Halloween storm of 2003, including the strongest solar flare ever
    recorded in X-ray (X45).

    The giant sunspot group AR3354 (only about four times smaller than
    the giant sunspot group of early September 1859) made its last
    appearance on July 2 with an X-class flare. Two days later it

    We won't lose the source of the stronger flares, however - the
    growing AR3359, with its Beta-Gamma magnetic configuration, crossed
    the central meridian toward active western longitudes on July 6 and
    will continue to grow. With its predicted higher activity, we could
    see an increase in the Earth's magnetic field activity as early as
    the middle of next week.

    Tamitha Skov, from July 1. https://youtu.be/HR8mm30oxOQ

    Blackout http://bit.ly/46tTRT8 https://bit.ly/3rhbjdz

    Stormy weekend? https://bit.ly/3pDrT6R

    Send your tips, reports, observations, questions and comments to
    k7ra@arrl.net. When reporting observations, don't forget to tell us
    which mode you were operating.

    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 .

    Also, check this article from September, 2002 QST:


    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 June 29 through July 5, 2023 were 112, 187, 119,
    126, 117, 121, and 101, with a mean of 126.1. 10.7 cm flux was
    162.2, 158.6, 165.5, 170.2, 173.2, 167.2, and 154.6, with a mean of
    164.5. Estimated planetary A indices were 17, 8, 5, 5, 5, 4, and 7,
    with a mean of 7.3. Middle latitude A index was 13, 8, 6, 8, 7, 5,
    and 9, with a mean of 8.

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