@proceedings {873, title = {Reexamining the Characteristics of Flare-Driven Doppler Flash using multipoint HF Observations}, year = {2024}, month = {03/2024}, publisher = {HamSCI}, address = {Cleveland, OH}, abstract = {

Sudden enhancement in the ionospheric electron density following a solar flare causes disruption in the transionospheric high frequency (HF: 3-30 MHz) communications, commonly referred to as Shortwave Fadeout (SWF). This disruption is also recorded as a sudden enhancement in Doppler frequency in the received HF signal, referred to as Doppler Flash. This phenomenon was recorded and reported by the SuperDARN HF radar network. Previous investigations have suggested that among various phases of flare-driven SWFs observed by HF radars Doppler Flash is the first to observe, and there are no significant trends in Doppler Flash with location, operating frequency, or flare intensity. Recent development showed that Doppler observations from the distributed HamSCI Personal Space Weather Station (PSWS) can provide insight into the physics behind changes in phase path length of the trans ionospheric radio signals. Unlike SuperDARN, HamSCI PSWS can record the full phase of the Doppler Flash, provide an edge to revisit the characterization study and compare with existing dataset. In this study, we demonstrate how HamSCI observations can be used to infer flare-driven changes in ionospheric properties. We found: (1) HamSCI PSWS has higher dynamic range than SuperDARN during flare making it less susceptible to SWF, thus it can record the full Doppler Flash; (2) data from HamSCI PSWS shows a strong function trend with flare strength, operating frequency, and location on the Earth; and (3) HF rays traveling longer distances experienced statistically higher Doppler. We understand that, while instantaneous Doppler realized by the HF signal is proportional to the rate of change in solar irradiance, the total Doppler realized is proportional to the total flare-deposited energy in the ionosphere.

}, author = {Shibaji Chakraborty and Kristina V. Collins and Nathaniel A. Frissell and J. Michael Ruohoniemi and Joseph B. H. Baker} } @proceedings {729, title = {The potential of HamSCI Doppler Observations for inferring Solar Flare Effects on the Ionosphere}, year = {2023}, month = {03/2023}, publisher = {HamSCI}, address = {Scranton, PA}, abstract = {

A solar flare is a space weather event that causes a transient in the ionospheric system at sub-auroral, middle, and lower latitudes, commonly known as the solar flare effect (SFE). Sudden enhancement in high-frequency (HF) absorption is a well-known impact of solar flare-driven Short-Wave Fadeout (SWF). Less understood, is a perturbation of the radio wave frequency as it traverses the lower ionosphere in the early stages of SWF, also known as the Doppler flash. SuperDARN radar network is typically used to study the Doppler flash. Previous investigations have suggested two possible sources that might contribute to the manifestation of Doppler flash: first, enhancements of plasma density in the D and lower E-regions; second, the lowering of the reflection point in the F-region. HamSCI is a platform that publicizes and promotes scientific research and understanding through amateur radio activities in the HF band. Studies have shown that solar flare-driven HF absorption can affect amateur radio signal strength. Recent development showed that the HamSCI Doppler observations can provide insight into the physics behind changes in phase path length of the trans ionospheric radio signals. In this study, we will demonstrate how HamSCI Doppler observations can be used to infer flare-driven changes in the ionospheric properties and associated Doppler flash. Furthermore, if successful the study will also quantify Doppler flash recorded in HamSCI as a function of flare strength, flare location on the solar disk, operating frequency, and location on the Earth. Upon successful quantification of Doppler flash, we will compare its properties with previous studies that used SuperDARN observations.

}, author = {Shibaji Chakraborty and Kristina Collins} } @proceedings {700, title = {Viability of Nowcasting Solar Flare-Driven Radio-Blackouts Using SuperDARN HF Radars}, year = {2023}, month = {03/2023}, publisher = {HamSCI}, address = {Scranton, PA}, abstract = {

The first space weather impact of a solar flare is radio blackout across the dayside of the Earth. At a delay of just 8 minutes, the arrival of enhanced X-ray and EUV radiation leads to a dramatic increase in ionization density in the lower ionosphere. Operation of HF systems are often completely suppressed due to anomalous absorption, while many RF systems suffer some degradation. While the onset of blackout is very rapid (~1-minute), the recovery takes tens of minutes to hours. Furthermore, severe solar flares can disrupt emergency HF communications that support humanitarian aid services, including amateur radio and satellite communication systems. Our current monitoring capability is based on modeling the ionospheric impacts based on GOES satellite observations of solar fluxes. We present a technique to characterize radio blackout following solar flares using HF radar. The future extension of this work is to develop an now-casting system to identify and monitor radio blackouts using HF radars currently deployed to support space science research. Networks of such radars operate continuously in the northern and southern hemisphere as part of the SuperDARN collaboration. Recent studies have shown that radio blackout (also known as shortwave fadeout) is easily detected and characterized using radar observations. We will combine real-time observations from the North American suite of SuperDARN radars to specify the occurrence of radio blackouts in near real-time.

}, author = {Shibaji Chakraborty and J. Michael Ruohoniemi and Joseph B. H. Baker} } @proceedings {618, title = {Viability of Nowcasting Solar Flare-Driven Radio-Blackouts Using SuperDARN HF Radars}, year = {2022}, month = {03/2022}, publisher = {HamSCI}, address = {Huntsville, AL}, abstract = {

The first space weather impact of a solar flare is radio blackout across the dayside of the Earth. At a delay of just 8 minutes, the arrival of enhanced X-ray and EUV radiation leads to a dramatic increase in ionization density in the lower ionosphere. Operation of HF systems are often completely suppressed due to anomalous absorption, while many RF systems suffer some degradation. While the onset of blackout is very rapid (1-minute), the recovery takes tens of minutes to hours. Furthermore, severe solar flares can disrupt emergency HF communications that support humanitarian aid services, including amateur radio and satellite communication systems. Our current monitoring capability is based on modeling the ionospheric impacts based on GOES satellite observations of solar fluxes. We present a technique to characterize radio blackout following solar flares using HF radar. The future extension of this work is to develop an now-casting system to identify and monitor radio blackouts using HF radars currently deployed to support space science research. Networks of such radars operate continuously in the northern and southern hemisphere as part of the SuperDARN collaboration. Recent studies have shown that radio blackout (also known as shortwave fadeout) is easily detected and characterized using radar observations. We will combine real-time observations from the North American suite of SuperDARN radars to specify the occurrence of radio blackouts in near real-time.

}, author = {Shibaji Chakraborty and J. Michael Ruohoniemi and Joseph B. H. Baker} } @proceedings {469, title = {Viability of nowcasting solar flare-driven radio-blackouts using SuperDARN HF radars}, year = {2021}, month = {03/2021}, publisher = {HamSCI}, abstract = {

The first space weather impact of a solar flare is radio blackout across the dayside of the Earth. At a delay of just 8 minutes, the arrival of enhanced X-ray and EUV radiation leads to a dramatic increase in ionization density in the lower ionosphere. Operation of HF systems are often completely suppressed due to anomalous absorption, while many RF systems suffer some degradation. While the onset of blackout is very rapid (~ minutes), the recovery takes tens of minutes to hours. Furthermore, severe solar flares can disrupt emergency HF communications that support humanitarian aid services, including amateur radio and satellite communication systems. Our current monitoring capability is based on modeling the ionospheric impacts based on GOES satellite observations of solar fluxes. We present a technique to characterize radio blackout following solar flares using HF radar. The future extension of this work is to develop an early warning system to identify \& monitor radio blackouts using HF radars currently deployed to support space science research. Networks of such radars operate continuously in the northern and southern hemisphere as part of the SuperDARN collaboration. Recent studies have shown that radio blackout (also known as shortwave fadeout) is easily detected and characterized using radar observations. We will combine real-time observations from the North American suite of SuperDARN radars to specify the occurrence of radio blackouts in near real-time. In this study, however, we present investigation and recognition techniques of shortwave fadeouts in SuperDARN HF radar.

}, author = {Shibaji Chakraborty and J. Michael Ruohoniemi and Joseph B. H. Baker} }