Solar flares are the most energetic phenomena in the solar atmosphere with consequences for space weather through the generation of solar energetic particles and/or CMEs. Despite tremendous advances in understanding their characteristics, the complete physics of their origin and response to plasma in various layers of the solar atmosphere is not developed. Here, we study the characteristics of...
We study the structure and evolution of solar flare ribbons in the chromosphere to infer properties of magnetic reconnection that occurs in the corona. We analyze the imaging observations of the M7.3 SOL2014-04-18T13 flare obtained by IRIS in both the near and far ultraviolet passbands and by SDO/AIA in the 1600A passband. Two flare ribbons are observed to spread away from the magnetic...
A spatio-temporal analysis of IRIS spectra of Mg II, C II, and Si IV ions allows us to study the dynamics and the stratification of the flare atmosphere along the line of sight during magnetic reconnection at the jet base.
Strong asymmetric Mg II and C II line profiles with extended blue wings observed at the reconnection site are interpreted by the presence of two chromospheric...
We present the first results of the SOL2020-May-29T07:13 event study based on simultaneous observations within the 4-8 GHz range by Siberian Radio Heliograph 48 and the spectropolarimeter 4-8 GHz. The microwave (MW) time profiles of the flare demonstrated at least three quasi-periodic bursts. We obtained the spectra for the bursts and defined the position of the MW sources at different...
The GOES/XRS data show low-level soft X-ray emissions prior to a
flare in a "hot onset" precursor of the main flare development
(2021MNRAS.501.1273H). This phenomenon provides clear evidence for
a heating process not identifiable with the impulsive-phase energy
release. The hot onset phase may last for tens of seconds to minutes,
characterized by steady growth of emission measure at...
What role magnetic reconnection plays in the initiation and evolution of the CME eruptions is still not clear. In a recent work by Zhu et al. (2020), we conducted a statistical study of 42 CME-flare events. We found a significant correlation between CME acceleration and flare reconnection in various aspects, suggesting that flare reconnection is key to acceleration of both fast and slow CMEs...
This work examines eleven solar microflares observed in hard x-rays (HXRs) by the Nuclear Spectroscopic Telescope ARray (NuSTAR). HXR emission in solar flares originates from both hot (millions of Kelvin) plasma and nonthermal accelerated particles, both of which are diagnostic of flare energy release. NuSTAR’s direct focusing optics give it a dramatic increase in sensitivity over indirect...
Observations of solar flare ribbons show significant fine structure in the form of wave-like perturbations and spirals. The origin of this structure is not well understood, but one possibility is that it is related to the tearing instability in the flare current sheet. Here we study this connection by constructing an analytical three-dimensional magnetic field representative of an erupting...
Magnetic flux ropes are the centerpiece of solar eruptions. Direct measurements for the magnetic field of flux ropes are crucial for understanding the triggering and energy release processes, yet they remain heretofore elusive. Here we report microwave imaging spectroscopy observations of an M1.4-class solar flare occurred on 2017 September 6, using data obtained by the Expanded Owens Valley...
In March 2024, sounding rockets will be launched in response to a solar flare for the first time. The Hi-C Flare mission will be among the first to take advantage of this new observing campaign, which was instituted by the NASA Sounding Rocket Program Office in response to a 2019 white paper submitted by Winebarger, Glesener, and Reeves. A soft X-Ray radiometer in development at Montana State...
Fast magnetic reconnection is expected to occur in the current sheet region during the solar eruptions, where outflows near the Alfven speed are predicted from the classic flare models. In observations, the dark, finger-shaped plasma downflows (also referred to as SADs) moving toward the flare arcade are believed as the principal observational evidence of such reconnection-driven outflows....
The X1.6 flare observed on 22 October 2014 (SOL2014-10-22T14:28) was among the strongest flares occurred in the magnetically complex, great active region NOAA 12192. It was a confined flare, without an accompanying CME,despite the large amount of released energy.
In our work we attempt to deepen our understanding of the magnetic field configuration of the AR 12192. We analyzed the...
In the standard eruptive flare model, magnetic reconnection originates in a thin current sheet; created by the inflow of oppositely orientated magnetic fields under a rising magnetic flux rope. The current sheet is notoriously difficult to observe directly, primarily due to the small size of the region. However, insights into current sheet dynamics can be revealed by the behaviour of flare...
Quasi-periodic pulsations (QPPs), characterized by periodic variations in flux, are universally observed during solar flares. QPPs are believed to be intimately related to the modulations of the flare energy release or transport processes. However, up to date, there is no conclusive interpretation of their physical nature. Here, we report a C1.8 confined flare on 2016 February 18. During its...
We present high-resolution and multiline spectropolarimetric observations of a C2-class solar flare (SOL2019-05-06T08:47). The rise, peak, and decay phases of the flare were recorded continuously and quasi-simultaneously in the Ca II K line with the CHROMIS instrument and in the Ca II 8542 Å and Fe I 6173 Å lines with the CRISP instrument at the Swedish 1 m Solar Telescope. At the flare...
We report on identification of new three-dimensional reconnection geometries in eruptive solar flares. These involve reconnection of the erupting flux rope either with the surrounding corona (ar-rf reconnection) or with itself (rr-rf), leading to creation of new flux rope field lines and flare loops. In addition, the CME legs are found to drift across the solar surface. The new reconnection...
