[TangerineSDR] Notes from PSWS / TangerineSDR call of 03-30-2020

Tue Mar 31 09:29:29 EDT 2020

Hi all,

Also, I mentioned last night the Guide for Magnetic Measurements and Observatory Practice from IAGA (International Association of Geomagnetism and Aeronomy). Here is the link:

http://www.iaga-aiga.org/data/uploads/pdf/guides/iaga-guide-observatories.pdf

IAGA publishes a number of guides that may be of interest. Here is the complete list:

http://www.iaga-aiga.org/publications/guides/

The IAGA guide is a bit old (1996). So here the current technical reference from intermagnet.org: https://intermagnet.org/publications/intermag_4-6.pdf

I think the IAGA guide is a bit “friendlier” and perhaps more comprehensive, but it is good to have a more current reference as well.

Also, since this is a ham radio group, it is good to remember that ground magnetometer measurements have a strong connection with radio propagation. Most people here are familiar with the Kp index, which is used as a global indicator of geomagnetic storms. One of the largest effects of a geomagnetic storm is an extended depletion of ionospheric densities, which leads to poor propagation on the higher HF bands. The Kp index actually comes from measurements of a network of 13 ground magnetometer stations located around the globe (but not evenly spaced!). See http://blog.aurorasaurus.org/?p=187 for a nice description. For a more ham radio perspective, see https://www.arrl.org/files/file/Technology/tis/info/pdf/0209038.pdf.

73 de Nathaniel W2NAF

From: TangerineSDR <tangerinesdr-bounces at lists.tapr.org> On Behalf Of Phil Erickson via TangerineSDR
Sent: Monday, March 30, 2020 11:41 PM
To: TAPR TangerineSDR Modular Software Defined Radio <tangerinesdr at lists.tapr.org>
Cc: Phil Erickson <phil.erickson at gmail.com>
Subject: Re: [TangerineSDR] Notes from PSWS / TangerineSDR call of 03-30-2020

Hi all,

  Sorry I missed the call.  There is a typo: the field model is IGRF, not IGRFG.

  IGRF is provided by a series of spherical harmonic coefficients.  These are marked for any 5 year interval either as intermediate (IGRF), definitive (DGRF), or predictive (for the current 5 year interval; uses secular change estimates).  Usually the coefficients come out every 5 years, but the field was changing so fast that the last update came early in 2019 instead of 2020.  A simple code, often in FORTRAN, calculates the field given location and epoch (time).

73

Phil W1PJE

On Mon, Mar 30, 2020 at 10:28 PM Tom McDermott via TangerineSDR <tangerinesdr at lists.tapr.org <mailto:tangerinesdr at lists.tapr.org> > wrote:

Notes from PSWS / TangerineSDR call of 03-30-2020

1. Bill has started posting the PSWS / TangerineSDR software to
https://github.com/AB4EJ-1/TangerineSDR-notes

2. Kp is determined by a network of magnetometers. This is useful
in predicting propagation disturbances. During normal conditions:

  At the poles the vertical component should be about 60,000 nT and the
  horizontal component near zero. At the equator the horizontal component
  should be about 30,000 nT and the vertical component near zero.

3. Discussion on magnetometer calibration: how often do they need to be calibrated, and how would this be accomplished?

4. International Geomagnetic Reference Field (IGRFG) model profile parameters provides long term estimates of magnetic field by lat/long/height and year:
https://ccmc.gsfc.nasa.gov/modelweb/models/igrf_vitmo.php

-- Tom, N5EG

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----
Phil Erickson
phil.erickson at gmail.com <mailto:phil.erickson at gmail.com> 

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