First hard X-ray imaging results by Solar Orbiter STIX

Massa, Paolo; Battaglia, Andrea F.; Volpara, Anna; Collier, Hannah; Hurford, Gordon J.; Kuhar, Matej; Perracchione, Emma; Garbarino, Sara; Massone, Anna Maria; Benvenuto, Federico; Schuller, Frederic; Warmuth, Alexander; Dickson, Ewan C. M.; Xiao, Hualin; Maloney, Shane A.; Ryan, Daniel F.; Piana, Michele; Krucker, Säm

doi:10.48550/arxiv.2202.09334

Cited by 2 publications

(2 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…STIX is an indirect imaging system that reconstructs images from a set of 30 visibilities. For the analysis presented here, the calibration as of January 2022 has been used, which provides good calibration for 24 subcollimators with angular resolutions ranging from 14 up to 180 (for details we refer to Massa et al 2022). The images shown in this paper are reconstructed using the CLEAN algorithm (Högbom 1974) adapted for STIX with a clean beam size of 16.5 FWHM.…”

Section: Instrumentationmentioning

confidence: 99%

The relativistic solar particle event on 28 October 2021: Evidence of particle acceleration within and escape from the solar corona

Klein

Musset

Vilmer

et al. 2022

A&A

Self Cite

View full text Add to dashboard Cite

Aims. We analyse particle, radio, and X-ray observations during the first relativistic proton event of solar cycle 25 detected on Earth. The aim is to gain insight into the relationship between relativistic solar particles detected in space and the processes of acceleration and propagation in solar eruptive events. Methods. To this end, we used ground-based neutron monitor measurements of relativistic nucleons and space-borne measurements of electrons with similar speed to determine the arrival times of the first particles at 1 AU and to infer their solar release times. We compared the release times with the time histories of non-thermal electrons in the solar atmosphere and their escape to interplanetary space, as traced by radio spectra and X-ray light curves and images. Results. Non-thermal electrons in the corona are found to be accelerated in different regions. Some are confined in closed magnetic structures expanding during the course of the event. Three episodes of electron escape to the interplanetary space are revealed by groups of decametric-to-kilometric type III bursts. The first group appears on the low-frequency side of a type II burst produced by a coronal shock wave. The two latter groups are accompanied at higher frequencies by bursts with rapid drifts to both lower and higher frequencies (forward- or reverse-drifting bursts). They are produced by electron beams that propagate both sunward and anti-sunward. The first relativistic electrons and nucleons observed near Earth are released with the third group of type III bursts, more than ten minutes after the first signatures of non-thermal electrons and of the formation of the shock wave in the corona. Although the eruptive active region is near the central meridian, several tens of degrees east of the footpoint of the nominal Parker spiral to the Earth, the kilometric spectrum of the type III bursts and the in situ detection of Langmuir waves demonstrate a direct magnetic connection between the L1 Lagrange point and the field lines onto which the electron beams are released at the Sun. Conclusions. We interpret the forward- and reverse-drifting radio bursts as evidence of reconnection between the closed expanding magnetic structures of an erupting flux rope and ambient open magnetic field lines. We discuss the origin of relativistic particles near the Earth across two scenarios: (1) acceleration at the CME-driven shock as it intercepts interplanetary magnetic field lines rooted in the western solar hemisphere and (2) an alternative where the relativistic particles are initially confined in the erupting magnetic fields and get access to the open field lines to the Earth through these reconnection events.

show abstract

Section: Instrumentationmentioning

confidence: 99%

The relativistic solar particle event on 28 October 2021: Evidence of particle acceleration within and escape from the solar corona

Klein

Musset

Vilmer

et al. 2022

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…In the case of radio astronomy, interpolation in the visibility space and application of inverse Fourier transform are sufficient to obtain reliable images of the radio source (Arras et al 2021). In the RHESSI and even more in the STIX frameworks, more sophisticated mathematics based on regularization theory for ill-posed problems is needed to reduce the ambiguity induced by such a sparse sampling of the data space (Massa et al 2022;Perracchione et al 2021;Massa et al 2020;Massone et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Forward-fitting STIX visibilities

Volpara¹,

Massa²,

Perracchione³

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

Aims.To determine to what extent the problem of forward fitting visibilities measured by the Spectrometer/Telescope Imaging X-rays (STIX) on-board Solar Orbiter is more challenging with respect to the same problem in the case of previous hard X-ray solar imaging missions; to identify an effective optimization scheme for parametric imaging for STIX.Methods. This paper introduces a Particle Swarm Optimization (PSO) algorithm for forward fitting STIX visibilities and compares its effectiveness with respect to the standard simplex-based optimization algorithm used so far for the analysis of visibilities measured by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). This comparison is made by considering experimental visibilities measured by both RHESSI and STIX, and synthetic visibilities generated by accounting for the STIX signal formation model.Results. We found out that the parametric imaging approach based on PSO is as reliable as the one based on the simplex method in the case of RHESSI visibilities. However, PSO is significantly more robust when applied to STIX simulated and experimental visibilities.Conclusions. Standard deterministic optimization is not effective enough for forward-fitting the few visibilities sampled by STIX in the angular frequency plane. Therefore a more sofisticated optimization scheme must be introduced for parametric imaging in the case of the Solar Orbiter X-ray telescope. The forward-fitting routine based on PSO we introduced in this paper proved to be significantly robust and reliable, and could be considered as an effective candidate tool for parametric imaging in the STIX context.

show abstract

First hard X-ray imaging results by Solar Orbiter STIX

Cited by 2 publications

References 21 publications

The relativistic solar particle event on 28 October 2021: Evidence of particle acceleration within and escape from the solar corona

The relativistic solar particle event on 28 October 2021: Evidence of particle acceleration within and escape from the solar corona

Forward-fitting STIX visibilities

Contact Info

Product

Resources

About