Figure 1. Collection of the time-aligned solar vibrant spectra with the IZMIRAN radio observatory (Troitsk, Russia) (a), the AIP radio spectropolarimeter (Tremsdorf, Germany) (b), the Nançay Decametric Array (Nançay, France) (c) on March 17th, 2004. The fundamental (F) and harmonic (H) components of fractured type II bursts are labeled on the NDA spectrogram, where the semitransparent areas show approximate periods of break and bump spectral features. A group of type III bursts is represented. The lower panel is the solar X-ray emission determined by GOES 12 on that day. The C1.6 class flare start/end and peak times are pointed by orange and cyan rushed vertical lines, respectively. The typical time axis is in the variety 09:15 -09:45 UT.
Utilizing the pre-break band-splitting from the type II occasion with spectral break, we computed the magnetic field worth in the lower part of the PS, particularly below its cusp point. Suffering from big uncertainties in determination of the shock speed during the second type II occasion, we obtained the ratio of the magnetic field inside-to-outside (BIN/BOUT) of the FT (see Fig. 3( b)). The variation of the magnetic field gotten from the type II event with spectral break was employed for normalization of the BIN/ BOUT ratio, given that both fractured type II bursts happened within overlapping varieties of heights in the corona (see Fig. 3( c)).
The magnetic fields of the Sun govern the solar corona structure where the solar wind emanates and more speeds up supersonically. Magnetic-field strength values in the solar wind sources are derived from various solar space- and ground-based observations, but, so far not accounting for specific types of radio bursts. Here, we report about radio observations of two “fractured” type II bursts to demonstrate a novel tool for penetrating of magnetic field variations in the solar wind emitters.
Data Analysis and Results
In our research, we have actually acknowledged 2 successive type II solar radio bursts with the specific morphology tape-recorded in meter-decameter radio observations on March 17th, 2004 (see Fig. 1). In both the bursts there is a collection of spectral functions. While the first type II burst has the spectral break, the 2nd type II burst has the spectral bump, and additionally both type II bursts show the band-splitting. The band-splitting analysis allows ones to supply diagnostics of electromagnetic fields in the solar corona (Vršnak et al., 2002). We made a multi-band analysis of observations from Large Angle and Spectrometric Coronagraph Experiment (LASCO) and Extreme ultraviolet Imaging Telescope (EIT) on Solar and Heliospheric Observatory (SOHO) spacecraft, in addition to the Potential-Field Source-Surface (PFSS) design for getting the geometry of magnetic field lines (see Fig. 2).
The joint analysis of spectral and imaging measurements has actually enabled us to unequivocally identify coronal structures in the solar atmosphere accountable for the bursts features in dynamic spectra. It was developed that both “fractured” bursts were produced by the very same shock caused by the coronal mass ejection (CME) after C1.6 class solar flare from the active area (AR) 10572. The last finding must be related to as a novelty, since this designates FTs as coronal structures influencing the propagation of shock waves in the solar corona.
The magnetic fields of the Sun govern the solar corona structure where the solar wind originates and more speeds up supersonically. The precise observational information about the geography, and more significantly, amounts of the coronal magnetic field are pivotal for recognizing the solar wind sources as well as for the Space Weather modeling where these data define initial conditions. Magnetic-field strength worths in the solar wind sources are derived from numerous solar space- and ground-based observations, however, so far not accounting for particular types of radio bursts. Here, we report about radio observations of 2 “fractured” type II bursts to show an unique tool for probing of magnetic field variations in the solar wind emitters.
These outcomes cope with a relevant job in the solar radio astronomy– measurements of magnetic field in the coronal structures in a regular method.
Figure 3. (a) Magnetic-field strength at a lower part of the pseudo-streamer, BPS, particularly listed below its cusp point, as a function of distance from the photosphere. The orange and green lines represent the coronal electromagnetic field designs of Dulk & & McLean (1978) and Gopalswamy (1986 ), respectively. (b) Magnetic-field strength ratios in the FTs limit and within. (c) The absolute magnetic-field worths in the FTs border and within. The dark strong curve represents the approximation of the electromagnetic field values within the distance variety of 1.391-1.459 Rʘ gotten by the assessment of the very first “fractured” type II burst.
Conclusions
Foremost, the magnetic field inside a Feet has actually been determined from radio observations. These results cope with a pertinent task in the solar radio astronomy– measurements of magnetic field in the coronal structures in a routine method. In this connection, the type II bursts, revealing the band-splitting and unique fractured shapes, can be as penetrating signals to get the magnetic-field strength in different coronal structures acting on the solar wind.
Based upon a just recently published post:
A. Koval, M. Karlický, A. Stanislavsky, B. Wang, M. Bárta, and R. Gorgutsa (2021 ). Shock-wave radio penetrating of solar wind sources in coronal magnetic fields, Astrophysical Journal, 923, 2 DOI: 10.3847/ 1538-4357/ ac2f3f.
Referrals.
Kong, X. L., Chen, Y., Li, G. et al., 2012, ApJ, 750, 2.
Feng, S. W., Chen, Y., Kong, X. L. et al., 2013, ApJ, 767, 1.
Vršnak, B., Magdalenić, J., Aurass, H., & & Mann, G., 2002, A&A, 396, 673.
Gopalswamy, N., Thejappa, G., Sastry, C. V., & & Tlamicha, A., 1986, BAICz, 37, 115.
Wang, Y.-M. & & Sheeley, N. R., Jr., 1992, ApJ, 392, 310.
Abbo, L., Lionello, R., Riley, P. & & Wang, Y.-M., 2015, SoPh, 290, 2043.
* Full list of authors: A. Koval, M. Karlický, A. Stanislavsky, B. Wang, M. Bárta, and R. Gorgutsa.
Magnetic field configurations acquired from the PFSS model based on the measurements from the SOHO MDI for the Carrington Rotation 2014. In panels (a-g) field lines are superimposed on SOHO LASCO C2 and SOHO EIT 195 Å images, where the closed field lines are colored in white, while inward (outward) field lines are envisioned in purple (blue), respectively. In panel (h) the SOHO MDI magnetogram at 09:39 UT reveals the magnetic areas of the south (dark color) and north (white color) polarity on the photosphere, where the closed field lines are colored in green, while colors of external (inward) field lines correspond to the ones in panels (a-g).