Interplanetary Type III Bursts and Electron Density Fluctuations in the Solar Wind

Krupař, V.; Maksimović, M.; Kontar, Eduard P.; Zaslavsky, A.; Santolı́k, O.; Souček, J; Krupařová, O.; Eastwood, J. P.; Szabó, Á.

doi:10.3847/1538-4357/aab60f

Cited by 52 publications

(96 citation statements)

References 37 publications

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“…For time scales corresponding to the effective turbulence scale length in our Monte Carlo simulation technique we obtained = 0.07 and = 0.06 for the perihelions #1 and #2, respectively. It is in a very good agreement with relative density fluctuations = 0.06 − 0.07 predicted by Krupar et al (2018). While type III bursts have been been observed for almost 70 years, a proper model to explain their obscure properties is still missing.…”

Section: Density Fluctuationssupporting

confidence: 85%

“…The obtained relation can be described by power-law type with a spectral index of −0.55 ± 0.01 for radial distances from 2.4 R up to 13.9 R . We note that STEREO results between 125 kHz and 1 MHz (i.e., from 8.4 R up to 45.1 R ) suggest nearly constant relative density fluctuations = 0.06 − 0.07 at the effective turbulence scale length (Krupar et al 2018).…”

Section: Monte Carlo Simulationsmentioning

confidence: 71%

“…Using the power-law model we obtain a spectral index β PSP of −0.60 ± 0.01. Recently, Krupar et al (2018) performed a similar analysis of 152 type III bursts between 125 kHz and 1 MHz observed by the STEREO spacecraft located at 1 au. The obtained spectral index is about twice smaller than for PSP (β STEREO = −1.21 ± 0.01).…”

Section: Discussion and Summarymentioning

confidence: 99%

“…Finally, we have compared predicted relative density fluctuations by STEREO (Krupar et al 2018), and the measured ones by PSP/SWEAP during the perihelions #1 and #2. Specifically, we use density and velocity measurements based on the proton moments from the SPC Faraday cup.…”

Section: Density Fluctuationsmentioning

confidence: 99%

“…Note, however, that predicted relative density fluctuations are based on an assumption that we primarily observe the fundamental component of type III bursts only as the used Monte Carlo technique does not perform well for the harmonic component (Krupar et al 2018).…”

mentioning

confidence: 98%

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Density Fluctuations in the Solar Wind Based on Type III Radio Bursts Observed by Parker Solar Probe

Krupař

Szabó

Maksimović

et al. 2020

ApJS

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Radio waves are strongly scattered in the solar wind, so that their apparent sources seem to be considerably larger and shifted than the actual ones. Since the scattering depends on the spectrum of density turbulence, better understanding of the radio wave propagation provides indirect information on the relative density fluctuations = δn / n at the effective turbulence scale length. Here, we have analyzed 30 type III bursts detected by Parker Solar Probe (PSP). For the first time, we have retrieved type III burst decay times τ d between 1 MHz and 10 MHz thanks to an unparalleled temporal resolution of PSP. We observed a significant deviation in a power-law slope for frequencies above 1 MHz when compared to previous measurements below 1 MHz by the twin-spacecraft Solar TErrestrial RElations Observatory (STEREO) mission. We note that altitudes of radio bursts generated at 1 MHz roughly coincide with an expected location of the Alfvén point, where the solar wind becomes super-Alfvénic. By comparing PSP observations and Monte Carlo simulations we predict relative density fluctuations at the effective turbulence scale length at radial distances between 2.5 R and 14 R to range from 0.22 and 0.09. Finally, we calculated relative density fluctuations measured in situ by PSP at a radial distance from the Sun of 35.7 R during the perihelion #1, and the perihelion #2 to be 0.07 and 0.06, respectively. It is in a very good agreement with previous STEREO predictions ( = 0.06 − 0.07) obtained by remote measurements of radio sources generated at this radial distance.

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Section: Density Fluctuationssupporting

confidence: 85%

Section: Monte Carlo Simulationsmentioning

confidence: 71%

Section: Discussion and Summarymentioning

confidence: 99%

Section: Density Fluctuationsmentioning

confidence: 99%

mentioning

confidence: 98%

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Density Fluctuations in the Solar Wind Based on Type III Radio Bursts Observed by Parker Solar Probe

Krupař

Szabó

Maksimović

et al. 2020

ApJS

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Empirical selection of Auroral Kilometric Radiation during a multipoint remote observation with Wind and Cassini

Waters

Jackman

Lamy

et al. 2021

Preprint

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Auroral Kilometric Radiation (AKR) is terrestrial radio emission that originates in particle acceleration regions along magnetic field lines, coinciding with discrete auroral arcs. AKR viewing geometry is complex due to the confinement of the source regions to nightside local times (LTs) and the anisotropy of the beaming pattern, so observations are highly dependent on spacecraft viewing position. We present a novel, empirical technique that selects AKR emission from observations made with the spin-axis aligned antenna of the Wind/WAVES instrument, based on the rapidly varying amplitude of AKR across spacecraft spin timescales. We apply the technique to Wind/WAVES data during 1999 day of year 227-257, when the Cassini spacecraft flew past Earth and provided an opportunity to observe AKR from two remote locations. We examine the AKR flux and power, with observations made from LTs of 1700-0300 hr having an average power up to 10 4 Wsr -1 larger than those on the dayside and an increasing AKR power observed at higher magnetic latitudes. We perform a linear cross-correlation between the Wind AKR power and the spacecraft magnetic latitude, showing positive then negative correlation as Wind travels from the Northern to Southern magnetic hemisphere. Statistically significant diurnal modulations are found in the whole 30-day period and in subsets of the data covering different local time sectors, indicative of a predominantly geometrical effect for remote AKR viewing. The reproduction of well-known features of the AKR verifies the empirical selection and shows the promise of its application to Wind/WAVES observations. Plain Language Summary Auroral Kilometric Radiation (AKR) is naturally occurring radio emission from the Earth's Northern and Southern polar regions, which becomes more intense as the aurora brightens. In this work, we examine data from the Wind spacecraft WAVES instrument from a 30-day interval in 1999 when a second spacecraft, Cassini, was also flying near Earth and measuring the AKR from a different viewpoint. In this work, we select the AKR using an empirical measure of the variability observed by the WAVES instrument, and compare the distribution and time profile of AKR intensity. Comparing measurements of this radio emission from different spacecraft positions help us to understand how the AKR is best viewed and illustrate the constrained beaming of the emission. This information is important for anyone wanting to attempt to interpret measurements of the AKR.

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Visibility and Origin of Compact Interplanetary Radio Type IV Bursts

Sheshvan

Pohjolainen

2018

Sol Phys

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We have analyzed radio type IV bursts in the interplanetary (IP) space at decameter-hectometer (DH) wavelengths to determine their source origin and a reason for the observed directivity. We used radio dynamic spectra from the instruments on three different spacecraft, STEREO-A, Wind, and STEREO-B, which were located approximately 90 degrees apart from each other in 2011-2012, and thus gave a 360 degree view of the Sun. The radio data were compared to white-light and extreme ultraviolet (EUV) observations of flares, EUV waves, and coronal mass ejections (CMEs) in five solar events. We find that the reason that compact and intense DH type IV burst emission is observed from only one spacecraft at a time is the absorption of emission in one direction and that the emission is blocked by the solar disk and dense corona in the other direction. The geometry also makes it possible to observe metric type IV bursts in the low corona from a direction where the higher-located DH type IV emission is not detectable. In the absorbed direction we found streamers, and they were estimated to be the locations of type II bursts, caused by shocks at the CME flanks. The high-density plasma was therefore most probably formed by shockstreamer interaction. In some cases, the type II-emitting region was also capable of stopping later-accelerated electron beams, which were visible as type III bursts that ended near the type II burst lanes.

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Interplanetary Type III Bursts and Electron Density Fluctuations in the Solar Wind

Cited by 52 publications

References 37 publications

Density Fluctuations in the Solar Wind Based on Type III Radio Bursts Observed by Parker Solar Probe

Density Fluctuations in the Solar Wind Based on Type III Radio Bursts Observed by Parker Solar Probe

Empirical selection of Auroral Kilometric Radiation during a multipoint remote observation with Wind and Cassini

Visibility and Origin of Compact Interplanetary Radio Type IV Bursts

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