PSWS Magnetometer Project

Overview

As part of HamSCI Personal Space Weather Station (PSWS) project, magnetometers which measure magnetic field strength and direction, are designed to provide quantitative and qualitative measurements of the geospace environment from the ground for both scientific and operational purposes at a cost that will allow for crowd-sourced data contributions. 

The PSWS magnetometers employ a low-cost, commercial off-the-shelf, magneto-inductive sensor technology to record three-axis magnetic field variations with an adequate field resolution of less (or better) than 10 nT at a 1 Hz sample rate. Data from the PSWS network will combine these magnetometer measurements with high frequency (HF, 3-30 MHz) radio observations to monitor large-scale current systems and ionospheric disturbances due to drivers from both space and the atmosphere. A densely-spaced magnetometer array, once established, will demonstrate their space weather monitoring capability to an unprecedented spatial extent.

The primary goals are 1) to provide the general context of geomagnetic activity during the HF experiments proposed in the PSWS project; 2) to estimate ionospheric currents at mid/high latitudes; 3) to measure space weather-related disturbances (dB/dt) at higher latitudes. 

HF communication is very much affected by the ionospheric conditions which are inarguably associated with the solar and geomagnetic activity. Magnetic field observations provide critical information about such an interaction (#1). As for #2, the proposed densely-spaced magnetometer network can also provide a complementary data set to help infer ionospheric currents over the entire region where the PSWS is located. At present, ground magnetometers for space research are located primarily near/in the auroral regions. The US government-funded magnetometers are sparsely located across the US at mid latitudes. The HamSCI magnetometer network will help increase the spatial resolution of the magnetic field measurements instead of taking on the existing infrastructure which is designed to provide well-calibrated absolute values of geomagnetic fields. 

The higher spatial density is one of the major unique aspects of the PSWS project. Typically, ground magnetic field data are used to infer equivalent current systems (“E x B drift”) in the ionosphere by combining the horizontal fields at multiple locations (e.g. Amm et al., 2002; Kim et al., 2015). At higher latitudes where more geomagnetic L-shells are concentrated, a more densely-spaced sensor network is desired to increase the number of measurement points and thus to avoid interpolations based on an assumption that ionospheric conditions are uniform between the measurement points: we know that this is an oversimplification. While high-latitude (> auroral region), multi-point magnetic fields from a densely-spaced sensor network have reported in a number of papers, mid-latitude observations of geomagnetic fields from a densely-spaced sensor network have never been done. 

Space weather-related events (e.g., geomagnetically induced current or GIC, related to dB/dt) are also target observations, especially at high latitudes (e.g., Alaska) as stated in #3. Measurements of dB/dt with a higher spatial resolution have not been conducted as well. 

The target specifications and performance level of the magnetometer are: a) time-varying field measurements in three axes; b) less than 10 nT resolution at 1 Hz sample rate; and c) ~50-100 mile spacing. 

One can argue that low/mid-performance magnetometers in your backyard may not add any scientific value. The following is the counter-argument:

  • Such a citizen-science level, large-scale, densely spaced magnetic field observations have never been done before. There are still many unsolved questions as to how the magnetosphere and ionosphere respond to solar activity, particularly, in greater details (in terms of spatial scale). 
  • During geomagnetic storms and substorms, magnetic field variations are on order of tens to hundreds of nT, which are well within the observable range of magnetometers that we are planning. 
  • Some geomagnetic field variations are thought to be associated with earthquakes. Although not directly related to “space weather” per se, it is scientifically valuable to investigate geomagnetic field variations during earthquakes using larger scale, densely spaced magnetometer array, in west coast in particular. This may require more sensitive magnetometers if data are to be used as precursor effect. During the earthquake near the epicenter, however, the disturbance level should be discernible with low/mid-performance level magnetometers.

 

RM3100 Magnetometer Manuals:

 

References

Amm, O., Engebretson, M. J., Hughes, T., Newitt, L., Viljanen, A., and Watermann, J., A traveling convection vortex event study: Instantaneous ionospheric equivalent currents, estimation of field-aligned currents, and the role of induced currents, J. Geophys. Res., 107( A11), 1334, doi:10.1029/2002JA009472, 2002.

Kim, H., Clauer, C. R., Engebretson, M. J., Matzka, J., Sibeck, D. G., Singer, H. J., Stolle, C., Weimer, D. R., and Xu, Z. (2015), Conjugate observations of traveling convection vortices associated with transient events at the magnetopause. J. Geophys. Res. Space Physics, 120, 2015– 2035. doi: 10.1002/2014JA020743.