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Re: [dxatlas] 90-day SSN data for HamCAP

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  • Pete Smith
    OK - thanks! Makes sense. 73, Pete
    Message 1 of 17 , Apr 9, 2005
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      OK - thanks! Makes sense.

      73, Pete

      At 12:56 PM 4/9/2005, Alex, VE3NEA wrote:



      > > While we're on the subject, a question I have wondered about -- why do Ham
      > > Cap's charts not have a graduated hour scale on the X axis? Have I missed
      > > an option to turn them on?
      >
      >HamCap is an interactive application. When you move the mouse cursor over
      >the chart, the time and all other parameters of the point under the cursor
      >are displayed on the status bar.
      >
      >I tried to make the HamCap window as small as possible so that it could be
      >used during contesting and DXing when screen space is a valuable resource,
      >so I removed all unnecessary elements form the user interface, including the
      >time scale on the chart.
      >
      >
      >73 Alex VE3NEA
      >
      >
      >
      >
      >
      >
      >Yahoo! Groups Links
      >
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      >
      >
    • Pete Smith
      [With apologies to readers of the VOACAP list, who are joining this in mid-thread, I feel that Bill and I are floundering fairly far out of our depth in this
      Message 2 of 17 , Apr 9, 2005
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        [With apologies to readers of the VOACAP list, who are joining this in
        mid-thread, I feel that Bill and I are floundering fairly far out of our
        depth in this discussion that began on the dxatlas list. The question
        began as what SSN to use in Ham Cap, a simplified front end for
        VOACAP. HamCAP comes with a table of predicted international SSNs, but can
        also link with IonoProbe, which downloads daily SSNs from the SEC. VE3NEA,
        the author of Ham Cap, prefers the SEC numbers, but the variance from the
        international SSns is considerable, with the SEC number typically running
        much higher. Any advice appreciated!]

        Bill, there's some apples and oranges, or something going on
        here. IonoProbe gets its numbers from the Joint USAF/NOAA Solar and
        Geophysical Activity Summary. Here's a sample:

        "SGAS Number 099 Issued at 0245Z on 09 Apr 2005
        This report is compiled from data received at SWO on 08 Apr
        A. Energetic Events
        Begin Max End Rgn Loc Xray Op 245MHz 10cm Sweep
        None
        B. Proton Events: None
        C. Geomagnetic Activity Summary: The geomagnetic field was quiet.
        D. Stratwarm: Not Available
        E. Daily Indices: (real-time preliminary/estimated values)
        10 cm 088 SSN 056 Afr/Ap 005/004 ...."

        Ionoprobe's retrospective record of these reports shows March 12 (chosen
        randomly) with a SSN of 67, versus 42 on the table you cite. March 18 is
        37 versus 25, and so on.

        I have no idea what the explanation is, though I do note that there is
        another table, ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SUNSPOT_NUMBERS/2005
        , which gives the numbers just for this year to date and states that
        "Values are preliminary after Dec 2004."

        There is an interesting explanation of how various sunspot numbers are
        calculated in
        ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SUNSPOT_NUMBERS/sunspot.predict. It
        seems clear from this explanation that the international sunspot number is
        a highly-massaged, worldwide average number that does not become final for
        some months after the date of observation. By contrast, the number cited
        in the SGAS is the SEC's every-six-hour figure, and must be based strictly
        on its own observations. An interesting graph at
        http://www.nwra-az.com/spawx/comp.html speaks to this. To quote from the
        caption:

        " This plot illustrates the differences between the "real" sunspot number
        (SSN), which is calculated from optical observations of the sun, a sunspot
        number derived from the 10.7cm solar radio flux (SSNf), and a sunspot
        number derived from fitting an ionospheric model to ionospheric
        measurements. All of these indices are used as inputs to models of the
        ionosphere for use in communications-performance predictions - this plot
        shows that they don't always agree as to what the SSN should be in that
        particular context.

        Note: The F10.7-derived SSN (SSNf) is calculated from the 10.7cm solar
        radio flux (the Penticton Radio Observatory noon value) using the following
        relationship:

        F10.7 = 63.74 + 0.727*SSNf + 0.000895*SSNf**2

        So, where does this leave us? Where it left me, frankly, is wondering why
        we use sunspot numbers at all, rather than solar flux and A/K indices, or
        at least the SSNf, which would be closer to the values Bill cited than to
        the current high value of optically-observed SSN. On the other hand, Alex
        argues that results from using the lower SSNs seem to run consistently low
        in terms of predicted vs. observed S/R ratio.

        It would be interesting to pass this discussion over to the VOACAP list and
        see what the gurus there, particularly including Greg Hand and George Lane,
        think of it. In fact, I have done that, and it will be interesting to see
        what comes of it.

        73, Pete N4ZR



        At 09:12 AM 4/9/2005, bill_w4zv wrote:



        >I wrote:
        >
        > > Maybe the logic of
        > > the calculation has an error somewhere in its data collection.
        >
        >Definitely so. The current 90 day average (1 Jan 05 - 31 Mar 05) is
        >28.4 using this data:
        >
        >ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SUNSPOT_NUMBERS/RIDAILY.PLT
        >
        >I don't have IonoProbe, but it must have a problem if the 47 number
        >Pete quoted for the IonoProbe calculation is correct. Anyhow, now I
        >know what to use and will probably just go with the NOAA forecast
        >which seems to be fairly accurate at this stage of the cycle.
        >
        >73, Bill
        >
        >
        >
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        >
        >Yahoo! Groups Links
        >
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        >
        >
      • bill_w4zv
        ... wondering why ... I agree. Seems like measured solar flux, which supposedly shows the actual effect of sunspots on the ionosphere, would be better. After
        Message 3 of 17 , Apr 10, 2005
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          --- In dxatlas_group@yahoogroups.com, Pete Smith <n4zr@c...> wrote:

          >
          > So, where does this leave us? Where it left me, frankly, is
          wondering why
          > we use sunspot numbers at all, rather than solar flux and A/K indices,

          I agree. Seems like measured solar flux, which supposedly shows the
          actual effect of sunspots on the ionosphere, would be better. After
          all, when there is a large CME, we often can see little effect on the
          ionosphere depending on how it's directed toward Earth, which way Bz
          points, etc. Of course if VOACAP was originally based on SSN's, then
          maybe they should be the input. Hopefully Greg Hand will respond, and
          please post anything of interest here since I am not on that list. No
          model is any better than its input..."Garbage In Garbage Out" as
          someone said.

          73, Bill
        • bill_w4zv
          I wrote: The current 90 day average (1 Jan 05 - 31 Mar 05) is 28.4 using this data: ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SUNSPOT_NUMBERS/RIDAILY.PLT VE3NEA
          Message 4 of 17 , Apr 10, 2005
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            I wrote: The current 90 day average (1 Jan 05 - 31 Mar 05) is
            28.4 using this data:
            ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SUNSPOT_NUMBERS/RIDAILY.PLT

            VE3NEA wrote: These are the RI indices, not daily SSN values.

            Alex, the NOAA site below calls these "Provisional International
            Sunspot Numbers, so what do you mean they are not daily SSN numbers?
            See especially their comments preceded by ***** below:
            ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SUNSPOT_NUMBERS/sunspot.predict

            >The provisional daily Zurich relative sunspot numbers, Rz, were based
            upon
            observations made at Zurich and its two branch stations in Arosa and
            Locarno
            and communicated by M. Waldmeier of the Swiss Federal Observatory.
            Beginning
            January 1, 1981, the Zurich relative sunspot number program is
            replaced by
            the "Sunspot Index Data Center" (c/o Dr. P. Cugnon, 3 av. Circulaire,
            B-1180
            Bruxelles, Belgium).


            ***** The determination of the provisional International Sunspot
            Numbers Ri results from a statistical treatment of the data
            originating from more than twenty-five observing stations. These
            stations constitute an international network, with the Locarno
            (Switzerland) station as the reference station, to guarantee
            continuity with the past Zurich series of Rz.*****

            >The definitive International Sunspot Numbers Ri are evaluated by a
            similar method based on a network of observing stations selected for
            their
            high number of observations, their continuity during the whole year
            and an
            existing series of observations during the last years. Also taken into
            account is the stability of the K monthly factors with reference to the
            Locarno station.

            *****These relative sunspot numbers are now designated Ri
            (International) instead of Rz (Zurich).*****

            It seems to me Ri is exactly what should be used, but am really
            waiting to see what Greg Hand, etc. of VOACAP have to say.

            73, Bill
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