Statistical Survey of Type III Radio Bursts at Long Wavelengths Observed by the Solar TErrestrial RElations Observatory (STEREO)/Waves Instruments: Radio Flux Density Variations with Frequency

Krupař, V.; Maksimović, M.; Santolı́k, O.; Kontar, Eduard P.; Cecconi, Baptiste; Hoang, S.; Krupařová, O.; Souček, J; Reid, Hamish; Zaslavsky, A.

doi:10.1007/s11207-014-0522-x

Cited by 36 publications

(43 citation statements)

References 27 publications

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“…The profiles are based on cuts through the spectrogram plots at the times defined in Table 1, which are shown as dotted lines in Figure 5. The intensity profiles are consistent with typical Type III profiles observed at 1 AU (Krupar et al 2014b). It is not immediately apparent why only a small fraction of bursts observed during E02 showed signatures of circular polarization.…”

Section: Polarization Of Type III Stormsupporting

confidence: 85%

Statistics and Polarization of Type III Radio Bursts Observed in the Inner Heliosphere

Pulupa

Bale

Badman

et al. 2020

ApJS

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We present initial results from the Radio Frequency Spectrometer (RFS), the high frequency component of the FIELDS experiment on the Parker Solar Probe (PSP). During the first PSP solar encounter (2018 November), only a few small radio bursts were observed. During the second encounter (2019 April), copious Type III radio bursts occurred, including intervals of radio storms where bursts occurred continuously. In this paper, we present initial observations of the characteristics of Type III radio bursts in the inner heliosphere, calculating occurrence rates, amplitude distributions, and spectral properties of the observed bursts. We also report observations of several bursts during the second encounter which display circular polarization in the right hand polarized sense, with a degree of polarization of 0.15 − 0.38 in the range from 8-12 MHz. The degree of polarization can be explained either by depolarization of initially 100% polarized o-mode emission, or by direct generation of emission in the o and x-mode simultaneously. Direct in situ observations in future PSP encounters could provide data which can distinguish these mechanisms.

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Section: Polarization Of Type III Stormsupporting

confidence: 85%

Statistics and Polarization of Type III Radio Bursts Observed in the Inner Heliosphere

Pulupa

Bale

Badman

et al. 2020

ApJS

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“…3 and 4 of Krupar et al (2014). We obtained flux values of about 4 × 10 −18 Wm −2 Hz −1 and 0.9 × 10 −18 Wm −2 Hz −1 for SWAVES A and B, respectively; compared to the flux distribution derived from 152 bursts by Krupar et al (2014), our event is near the average, which at 1 MHz is about 2.5 × 10 −18 Wm −2 Hz −1 . …”

Section: Radio Observationsmentioning

confidence: 51%

A tiny event producing an interplanetary type III burst

Alissandrakis

Nindos

Patsourakos

et al. 2015

A&A

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Aims. We investigate the conditions under which small-scale energy release events in the low corona gave rise to strong interplanetary (IP) type III bursts. Methods. We analyzed observations of three tiny events, detected by the Nançay Radio Heliograph (NRH), two of which produced IP type III bursts. We took advantage of the NRH positioning information and of the high cadence of AIA/SDO data to identify the associated extreme-UV (EUV) emissions. We measured positions and time profiles of the metric and EUV sources. Results. We found that the EUV events that produced IP type III bursts were located near a coronal hole boundary, while the one that did not was located in a closed magnetic field region. In all three cases tiny flaring loops were involved, without any associated mass eruption. In the best observed case, the radio emission at the highest frequency (435 MHz) was displaced by ∼55 with respect to the small flaring loop. The metric type III emission shows a complex structure in space and in time, indicative of multiple electron beams, despite the low intensity of the events. From the combined analysis of dynamic spectra and NRH images, we derived the electron beam velocity as well as the height, ambient plasma temperature, and density at the level of formation of the 160 MHz emission. From the analysis of the differential emission measure derived from the AIA images, we found that the first evidence of energy release was at the footpoints, and this was followed by the development of flaring loops and subsequent cooling. Conclusions. Even small energy release events can accelerate enough electrons to give rise to powerful IP type III bursts. The proximity of the electron acceleration site to open magnetic field lines facilitates the escape of the electrons into the interplanetary space. The offset between the site of energy release and the metric type III location warrants further investigation.

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“…The Sittler & Guhathakurta (1999) density model suggests that 1 MHz -where the slope changes between STEREO and PSP -corresponds to a radial distance of ∼ 8 R (the fundamental component) or ∼ 14 R (the harmonic component), where the solar wind speed typically exceeds the Alfvén speed, and the solar wind become superalfvénic -the solar wind is no longer in contact with the Sun since Alfvén waves can- not travel back to the Sun Type III burst properties change around 1 MHz as the ambient plasma evolves significantly. Moreover, type III bursts statistically exhibit also a maximum of power spectral density around 1 MHz (Krupar et al 2014b). Furthermore, it is also possible that we rather observe the fundamental component below 1 MHz, while the harmonic component is dominant above 1 MHz.…”

Section: Discussion and Summarymentioning

confidence: 96%

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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Statistical Survey of Type III Radio Bursts at Long Wavelengths Observed by the Solar TErrestrial RElations Observatory (STEREO)/Waves Instruments: Radio Flux Density Variations with Frequency

Cited by 36 publications

References 27 publications

Statistics and Polarization of Type III Radio Bursts Observed in the Inner Heliosphere

Statistics and Polarization of Type III Radio Bursts Observed in the Inner Heliosphere

A tiny event producing an interplanetary type III burst

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

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