Sensing the Earth’s low ionosphere during solar flares using VLF signals and goes solar X-ray data

Kolarski, Aleksandra; Grubor, Davorka

doi:10.1016/j.asr.2014.02.022

Cited by 33 publications

(21 citation statements)

References 28 publications

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“…As noted above, VLF phase changes during solar flares will produce a phase increase (Pant, 1993), while VLF amplitude changes can involve increases, decreases, or both (Kolarski & Grubor, 2014;Žigman et al, 2007). Even for very large flares with monotonically increasing X-ray fluxes, the amplitude need not be monotonically increasing, as seen in Figure 10 here and in Figure 10 of Thomson and Clilverd (2001).…”

Section: Discussionmentioning

confidence: 90%

Developing a Nowcasting Capability for X‐Class Solar Flares Using VLF Radiowave Propagation Changes.

et al. 2019

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A technique for analyzing very low frequency (VLF) radiowave signals is investigated in order to achieve rapid, real-time detection of large solar flares, through the monitoring of changes in VLF radio signal propagation conditions. The reliability of the use of VLF phase and amplitude perturbations to determine the X-ray fluxes involved during 10 large solar flare events (>X1) is examined. Linear regression analysis of signals from the NPM transmitter in Hawaii, received at Arrival Heights, Scott Base, Antarctica, over the years 2011-2015 shows that VLF phase perturbations during large solar flares have a 1.5-3 times lower mean square error when modeling the long wavelength X-ray fluxes than the equivalent short wavelength fluxes. The use of VLF amplitude observations to determine long or short wavelength X-ray flux levels have a 4-10 times higher mean square error than when using VLF phase. Normalized linear regression analysis identifies VLF phase as the most important parameter in the regression, followed by solar zenith angle at the midpoint of the propagation path, then the initial solar X-ray flux level (from 5 min before the impact of the solar flare), with F10.7 cm flux from the day beforehand providing the least important contribution. Transmitter phase measurements are more difficult to undertake than amplitude. However, networks of VLF receivers already exist which include the high quality phase capability required for such a nowcasting product. Such narrowband VLF data can be a redundant source of flare monitoring if satellite data is not available.

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Section: Discussionmentioning

confidence: 90%

Developing a Nowcasting Capability for X‐Class Solar Flares Using VLF Radiowave Propagation Changes.

et al. 2019

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“…A propagation model such as the long wavelength propagation capability (LWPC) code (Ferguson, ) is then used to estimate ionospheric waveguide parameters that most closely match observations. Many have used VLF transmitters and LWPC to infer simplified ionospheric parameters during solar flares (Dahlgren et al, ; Grubor et al, ; Kolarski & Grubor, ; McRae & Thomson, ; Singh et al, ; Šulić & Srećković, ; Thomson & Clilverd, ; Thomson et al, ). Current VLF remote sensing techniques nearly always use this approach.…”

Section: Introductionmentioning

confidence: 99%

Spatial and Temporal Ionospheric Monitoring Using Broadband Sferic Measurements

et al. 2018

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The D region of the ionosphere (60–90 km altitude) is highly variable on timescales from fractions of a second to many hours, and on spatial scales up to many hundreds of kilometers. Very low frequency (VLF) and low‐frequency (LF) (3–30 kHz and 30–300 kHz) radio waves are guided to global distances by reflections from the ground and the D region. Therefore, information about its current state is encoded in received VLF/LF signals. VLF transmitters have been used in the past for D region studies, with ionospheric disturbances manifesting as perturbations in amplitude and/or phase. The return stroke of lightning is an impulsive VLF radiator, but unlike VLF transmitters, lightning events are distributed broadly in space allowing for much greater spatial coverage of the D region compared to VLF transmitter‐based remote sensing in addition to the broadband spectral advantage over the narrowband transmitters. The challenge is that individual lightning‐generated waveforms, or “sferics,” vary due to the lightning current parameters and uncertainty in the time/location information, in addition to D region ionospheric variability. These factors make it difficult to utilize the VLF/LF emissions from lightning in a straightforward manner. We describe a technique to recover the time domain and amplitude/phase spectra for both Bϕ and Br with high fidelity and consider the utility of our technique with ambient and varied ionospheric conditions. We demonstrate a technique to simulate sferics and infer a parameterized ionosphere with the Wait and Spies parameters (h ′ and β) offering all of the tools needed for a global measurement.

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“…As noted above, when SID is strong enough, we can use a comparison with independent detections of different processes and link it to some event. One of the most important sudden perturbers of the ionospheric D-region plasma is the solar X-ray flare [34,35,36,37] and here we will explain the main characteristics of SID on the example of this phenomenon occurred on March 24, 2011. In Fig.…”

Section: Detection Of Strong Sidsmentioning

confidence: 99%

Diagnostics of plasma in the ionospheric D-region: detection and study of different ionospheric disturbance types

2017

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Here we discuss our recent investigations of the ionospheric plasma by using very low and low frequency (VLF/LF) radio waves. We give a review of how to detect different low ionospheric reactions (sudden ionospheric disturbances) to various terrestrial and extra-terrestrial events, show their classification according to intensity and time duration, and present some methods for their detections in time and frequency domains. Investigations of detection in time domain are carried out for intensive long-lasting perturbations induced by solar X-ray flares and for short-lasting perturbations caused by gamma ray bursts. We also analyze time variations of signals used in the low ionospheric monitoring after earthquake events. In addition, we describe a procedure for the detection of acoustic and gravity waves from the VLF/LF signal analysis in frequency domain. The research of the low ionospheric plasma is based on data collected by the VLF/LF receivers located in Belgrade, Serbia.PACS. 52.25.Jm Ionization of plasmas -94.20.Bb Wave propagation -94.20.de D region -92.60.hh Acoustic gravity waves, tides, and compressional waves

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Sensing the Earth’s low ionosphere during solar flares using VLF signals and goes solar X-ray data

Cited by 33 publications

References 28 publications

Developing a Nowcasting Capability for X‐Class Solar Flares Using VLF Radiowave Propagation Changes.

Developing a Nowcasting Capability for X‐Class Solar Flares Using VLF Radiowave Propagation Changes.

Spatial and Temporal Ionospheric Monitoring Using Broadband Sferic Measurements

Diagnostics of plasma in the ionospheric D-region: detection and study of different ionospheric disturbance types

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