Solar Cycle Variations of the Lower Ionosphere Detected by VLF Remote Sensing

Details Solar Cycle Variations of the Lower Ionosphere Detected by VLF Remote Sensing Solar Cycle Variations of the Lower Ionosphere Detected by VLF Remote Sensing

Dec 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmsa51b1231j&link_type=abstract

American Geophysical Union, Fall Meeting 2009, abstract #SA51B-1231

Astronomy and Astrophysics

Astrophysics

[2407] Ionosphere / Auroral Ionosphere, [2487] Ionosphere / Wave Propagation, [2494] Ionosphere / Instruments And Techniques, [7536] Solar Physics, Astrophysics, And Astronomy / Solar Activity Cycle

Scientific paper

Stanford University’s Very Low Frequency (VLF) Beacon transmitter resumed its operations at South Pole Station in February 2009 for the purpose of studying the ionospheric effects of energetic particle precipitation. VLF remote sensing (i.e., the measurement of the amplitude and phase of sub-ionospheric signals) is a sensitive tool for measuring ionospheric conductivity (i.e., electron density and temperature), especially at altitudes below 90 km. Using a 6.25 km dipole antenna, the Beacon transmits a 9 kW, 19.4 kHz signal for one minute out of every fifteen minutes. VLF receivers located at sites throughout Antarctica detect the transmitted signal including Palmer, Rothera, and Commandante Ferraz on the Antarctic Peninsula, SANAE in Queen Maud Land, and the Automated Geophysical Observatories (AGO) located inland. By integrating the signal for its 60-second duration, signal-to-noise ratios of >10 dB are typical at Palmer Station. The amplitude and phase measured at the stations depend on the height and conductivity of the D-region ionosphere along the propagation path and hence on the intensity of solar radiation and the intensity of particle precipitation from the polar cap to the subauroral zone. While there have not been significant precipitation events during this extended solar minimum, the amplitude and phase of the Beacon signal still shows a diurnal variation as the day-night terminator exposes different lengths of the propagation path to enhanced daytime ionization as the Earth rotates. The reduced solar activity has resulted in lower overall nighttime D-layer ionization. This appears as deeper diurnal variations in amplitude of the Beacon signal during solar minimum although the effect on the received phase is less predictable. We show comparisons of the amplitude and phase characteristics of the Beacon signal from 2009 with that from its last operating period during the declining phase of the previous solar cycle from 2004-2005 as well as with a sub-ionospheric model of VLF propagation using different ionospheric profiles.

Affiliated with

Also associated with

No associations

Rating

Solar Cycle Variations of the Lower Ionosphere Detected by VLF Remote Sensing does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Solar Cycle Variations of the Lower Ionosphere Detected by VLF Remote Sensing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Solar Cycle Variations of the Lower Ionosphere Detected by VLF Remote Sensing will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1781073