Investigation Objectives

Science Questions

Functional Requirements

Objective 1:

Characterize the ionospheric and geomagnetic response to space weather events with sources both below and above the ionosphere.

•What are the characteristic temporal and spatial scales of magnetic fluctuations in near-Earth space during geomagnetic disturbances?

•How does ionospheric density vary as a function of location, altitude, and time in response to space weather disturbances associated with driving events such as solar flares, geomagnetic storms, substorms, and lower atmosphere perturbations?

•Determine the vector ground magnetic field for identification of geomagnetic disturbances and micropulsations (e.g. ULF variations).

•Receive transmissions from controlled sources (digital_rf-based) or signals of opportunity (e.g., WWV, WWVH, CHU).

Objective 2:

Characterize ionospheric variability and identify its sources during both quiet and disturbed times.

•What are the characteristics (wavelength, period, direction of travel, location, altitude) of traveling ionospheric disturbances (TIDs)?

•What is the location and nature of sources that drive TIDs, such as lower atmosphere winds/tides and upper atmosphere forcing?

•What is the location and nature of ionospheric variability that is not associated with TIDs?

•How do the location and nature of ionospheric variability sources change from quiet to disturbed times?

Make measurements on a minimum of two transmit-receive paths (three stations) with lengths >= ~100 km and with good spatial distribution for good orthogonality properties.

Objective 3:

Determine the impact of space weather events and ionospheric variability on terrestrial HF communications systems.

•What propagation paths are open/closed for given space weather conditions?

•What is the dominant propagation mode (i.e. single hop, double hop, ducting?) for given space weather conditions?

•What are ionospheric variability effects on HF communications signal parameters such as amplitude/phase scintillation, channel fading, and polarization?

Receive swept-frequency sounder signals from appropriate polarized or non-polarized signals of opportunity such as Digisonde or chirp sounders.

Objective 4:

Characterize the diel (day/night) and seasonal variability of the Earth-ionosphere waveguide as well as its response to solar and geomagnetic activity.

How do the Earth-ionosphere waveguide modes vary according to the season and time of day? How do they vary in response to solar flares, gamma ray bursts, and geomagnetic storms?

How do seasonal and diel effects of the Earth-ionosphere waveguide affect VLF wave propagation?

Can D layer electron density be mapped using ground-based VLF wave observations?

How do the influences of the previous question affect propagation and successful copy of VLF amateur transmissions in the 8270 Hz and 5170 Hz bands?

Sounding of the Earth-ionosphere waveguide using lightning sferics and Naval VLF transmitters.

A network of VLF receivers at various latitudes for comparison.

Monitoring various VLF signal attributes, including Naval VLF transmitter amplitude and phase.

Determination of received channel capacity of VLF amateur transmissions.

Objective 5:

Characterize the variability of the magnetosphere’s geometry and configuration during both geomagnetic activity and quiet times.

Does whistler activity correlate to sunspot number and if so, why?

Does the geometry and configuration of the magnetosphere affect whistler duct electron density? If not, is there some other influence?

Does whistler duct electron density vary by latitude during geomagnetic storms and quiet times?

Does the magnetospere's geometry and configuration have an effect on the geographic scale of the whistler's conjugate point reception footprint?

The ability to record whistler activity at various latitudes with a network of VLF receivers.

Determine statistical data of whistler dispersion for whistler duct electron density estimation.

A network of VLF receivers at various latitudes for comparison.

Lightning location network to monitor potential origins of whistlers and use them to estimate the source sferic of the whistler.