Energetics of small electron acceleration episodes in the solar corona from radio noise storm observations

James, Tomin; Subramanian, Prasad

doi:10.1093/mnras/sty1216

Cited by 13 publications

(7 citation statements)

References 37 publications

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“…Assuming Ω = 0.15 steradians (Steinberg et al 1974), τ ≈ 3 at 80 MHz (Ramesh 2005b), and an efficiency (η) of ≈10 −10 for the type I burst emission process (Subramanian & Becker 2004), we find E ≈ 8.1×10 22 erg. This is consistent with the reports that ∼10 21 -10 23 ergs are needed for a single type I burst (James & Subramanian 2018). We also calculated the energy using the relation E = n th (n/n th )VE m (see for e.g.…”

Section: Analysis and Resultssupporting

confidence: 89%

Radio, X-ray and extreme-ultraviolet observations of weak energy releases in the `quiet' Sun

Ramesh,

Kathiravan,

Mithun

et al. 2021

Preprint

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We analyzed ground-based low frequency (<100 MHz) radio spectral and imaging data of the solar corona obtained with the facilities in the Gauribidanur observatory during the same time as the very weak soft X-ray flares (sub A-class, flux <10 −7 Wm −2 in the 1 -8 Å wavelength range) from the 'quiet' Sun observed with the X-ray Solar Monitor (XSM) onboard Chandrayaan-2 during the recent solar minimum. Non-thermal type I radio burst activity were noticed in close temporal association with the X-ray events. The estimated brightness temperature (T b ) of the bursts at a typical frequency like 80 MHz is ≈3×10 5 K. Extreme-ultraviolet (EUV) observations at 94 Å with the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) revealed a brightening close to the same location and time as the type I radio bursts. As far as we know reports of simultaneous observations of X-ray and/or EUV counterpart to weak transient radio emission at low frequencies from the 'quiet' Sun in particular are rare. Considering this and the fact that low frequency radio observations are sensitive to weak energy releases in the solar atmosphere, the results indicate that coordinated observations of similar events would be useful to understand transient activities in the 'quiet' Sun.

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Section: Analysis and Resultssupporting

confidence: 89%

Radio, X-ray and extreme-ultraviolet observations of weak energy releases in the `quiet' Sun

Ramesh,

Kathiravan,

Mithun

et al. 2021

Preprint

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“…The remaining 150 type III bursts were not associated with any flare. These 150 bursts were probably due to weak energy releases in the solar atmosphere reported earlier in the literature (for example, Ramesh et al (2010Ramesh et al ( , 2013; Saint-Hilaire, Vilmer, and Kerdraon (2013); Sasikumar Raja and Ramesh (2013b); Mugundhan, Hariharan, and Ramesh (2017); James, Subramanian, and Kontar (2017); James and Subramanian (2018); Sharma, Oberoi, and Arjunwadkar (2018)). We also find that 75% of the type III bursts in our list were observed below 200 MHz (left panel of Figure 5).…”

Section: Preliminary Analysis Of Type III Burstsmentioning

confidence: 73%

Automated Detection of Solar Radio Bursts Using a Statistical Method

et al. 2019

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Radio bursts from the solar corona can provide clues to forecast space weather hazards. After recent technology advancements, regular monitoring of radio bursts has increased and large observational data sets are produced. Hence, manual identification and classification of them is a challenging task. In this paper, we describe an algorithm to automatically identify radio bursts from dynamic solar radio spectrograms using a novel statistical method. We used e-CALLISTO radio spectrometer data observed at Gauribidanur observatory near Bangalore in India during 2013 -2014. We have studied the classifier performance using the receiver operating characteristics. Further, we studied type III bursts observed in the year 2014 and found that 75% of the observed bursts were below 200 MHz. Our analysis shows that the positions of the flare sites which are associated with the type III bursts with upper frequency cut-off 200 MHz

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“…The presence of nonthermal particles in nanoflares is (so far) the most plausible explanation for the emission observed directly and indirectly in other wavelengths. These observations include (a) short-lived UV brightenings observed with the Interface Region Imaging Spectrograph (IRIS) at loop footpoints in nonflaring active regions (e.g., Testa et al 2014Testa et al , 2020, (b) nonthermal radio emission from the quiescent corona (e.g., James & Subramanian 2018;Mondal et al 2020), and (c) multi-wavelength evidence of non-Maxwellian distributions and non-equilibrium ionization in the quiet transition region, corona, and solar wind (e.g., Dudík et al 2017b,a). Nanoflare observations in HXRs can complement our current understanding of the role of nonthermal particle processes in heating the quiescent corona.…”

Section: Introductionmentioning

confidence: 99%

The faintest solar coronal hard X-rays observed with FOXSI

Buitrago-Casas

Glesener

Christe

et al. 2022

A&A

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Context. Solar nanoflares are small impulsive events releasing magnetic energy in the corona. If nanoflares follow the same physics as their larger counterparts, they should emit hard X-rays (HXRs) but with a rather faint intensity. A copious and continuous presence of nanoflares would result in a sustained HXR emission. These nanoflares could deliver enormous amounts of energy into the solar corona, possibly accounting for its high temperatures. To date, there has not been any direct observation of such persistent HXRs from the quiescent Sun. However, the quiet-Sun HXR emission was constrained in 2010 using almost 12 days of quiescent solar offpointing observations by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). These observations set 2σ upper limits at 3.4 × 10 −2 photons s −1 cm −2 keV −1 and 9.5 × 10 −4 photons s −1 cm −2 keV −1 for the 3-6 keV and 6-12 keV energy ranges, respectively. Aims. Observing faint HXR emission is challenging because it demands high sensitivity and dynamic range instruments. The Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket experiment excels in these two attributes when compared with RHESSI. FOXSI completed its second and third successful flights (FOXSI-2 and -3) on December 11, 2014, and September 7, 2018, respectively. This paper aims to constrain the quiet-Sun emission in the 5-10 keV energy range using FOXSI-2 and -3 observations. Methods. To fully characterize the sensitivity of FOXSI, we assessed ghost ray backgrounds generated by sources outside of the field of view via a ray-tracing algorithm. We used a Bayesian approach to provide upper thresholds of quiet-Sun HXR emission and probability distributions for the expected flux when a quiet-Sun HXR source is assumed to exist. Results. We found a FOXSI-2 upper limit of 4.5×10 −2 photons s −1 cm −2 keV −1 with a 2σ confidence level in the 5-10 keV energy range. This limit is the first-ever quiet-Sun upper threshold in HXR reported using ∼ 1 min observations during a period of high solar activity. RHESSI was unable to measure the quiet-Sun emission during active times due to its limited dynamic range. During the FOXSI-3 flight, the Sun exhibited a fairly quiet configuration, displaying only one aged nonflaring active region. Using the entire ∼6.5 minutes of FOXSI-3 data, we report a 2σ upper limit of ∼ 10 −4 photons s −1 cm −2 keV −1 for the 5-10 keV energy range. Conclusions. The FOXSI-3 upper limits on quiet-Sun emission are similar to that previously reported, but FOXSI-3 achieved these results with only 5 min of observations or about 1/2600 less time than RHESSI. A possible future spacecraft using hard X-ray focusing optics like those in the FOXSI concept would allow enough observation time to constrain the current HXR quiet-Sun limits further, or perhaps even make direct detections. This is the first report of quiet-Sun HXR limits from FOXSI and the first science paper using FOXSI-3 observations.

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Energetics of small electron acceleration episodes in the solar corona from radio noise storm observations

Cited by 13 publications

References 37 publications

Radio, X-ray and extreme-ultraviolet observations of weak energy releases in the `quiet' Sun

Radio, X-ray and extreme-ultraviolet observations of weak energy releases in the `quiet' Sun

Automated Detection of Solar Radio Bursts Using a Statistical Method

The faintest solar coronal hard X-rays observed with FOXSI

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