Microwave Negative Bursts as Indications of Reconnection Between Eruptive Filaments and a Large-Scale Coronal Magnetic Environment

Abstract

Low-temperature plasma ejected in solar eruptions can screen active regions as well as quiet solar areas. Absorption phenomena can be observed in microwaves as “negative bursts” and in various spectral domains. We analyze two very different recent events with such phenomena, and present an updated systematic view of solar events associated with negative bursts. Related filament eruptions can be normal, without essential changes of shape and magnetic configuration, and “anomalous.” The latter are characterized by disintegration of an eruptive filament and dispersal of its remnants as a cloud over a large part of the solar disk. Such phenomena can be observed as giant depressions in the He II 304 Å line. One of possible scenarios for an anomalous eruption is proposed in terms of reconnection of the filament's internal magnetic fields with an external large-scale coronal surrounding.

A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. III. Catastrophe of the Eruptive Filament at a Magnetic Null Point and Formation of an Opposite-Handedness CME

“…The center of the flux rope has shifted across B, while plasma (gray) has departed from the flux rope and moves along the outer field B. The scheme in Figure 13 is basically similar to Figure 6 in Grechnev et al (2013). The apparent difference between the schemes is due to different directions of motions of the eruptive filaments through the magnetic null point in the quadrupolar magnetic configuration.…”

“…The complex reconnection of a flux rope with the adjacent field in complex magnetic topology has been also described by, e.g., Lugaz et al (2011), Zuccarello et al (2012), and Masson, Antiochos, and DeVore (2013). Grechnev et al (2008Grechnev et al ( , 2011aGrechnev et al ( , 2013 have found observational evidence of magnetic reconnection between the internal field belonging to the eruptive filament and the preexisting coronal field. This is a phenomenon of plasma dispersal from an eruptive filament over the solar surface that is visible as the disintegration of the filament.…”

Radio, Hard X-Ray, and Gamma-Ray Emissions Associated with a Far-Side Solar Event

“…As a result, both open and closed structures of these domains become filled with energetic particles as well as cool plasma of the pre-eruptive filament. Related schemes containing a single null point were discussed by Gary and Moore (2004), Masson, Antiochos, and DeVore (2013), Meshalkina et al (2009), Grechnev et al (2013b), and Uralov et al (2014. Stretching a large-scale quadrupole into the solar wind might cause disappearance of the null point.…”

Multi-instrument view on solar eruptive events observed with the Siberian Radioheliograph: From detection of small jets up to development of a shock wave and CME

“…As noted in Section 3, multi-frequency observations of microwave depressions provide the basis for plasma diagnostics in erupting structures. Modeling the spectrum of the absorption depths observed at a few frequencies from 1 to 10 GHz allowed estimating parameters of the erupted material responsible for several negative bursts even without images (Grechnev et al, 2008(Grechnev et al, , 2013bKuzmenko et al, 2009;Kuzmenko and Grechnev, 2017). These studies used a flatlayered model of a relatively large absorbing cloud of given height, dimensions, temperature, and density, with a possible stable compact microwave source covered.…”