Search results for " Solar corona"

On the Coronal Temperature in Solar Microflares

2020

We present a study of solar imaging and spectral observations of a microflare, focusing on the temperature diagnostics provided by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, and the Extreme-Ultraviolet Imaging Spectrometer (EIS) on board Hinode. Our data analysis, in particular from the emission in the 131 and 94 Å channels, indicates that the heated plasma reaches temperatures of ≿10 MK, at odds with a previous analysis of the same event, and we discuss the reason for the discrepancy. A particularly interesting aspect is the likely presence of the Fe XXIII 263.76 Å line, though weak, in EIS spectra in the early phases of the event, supporting the presen…

Acoustic Wave Properties in Footpoints of Coronal Loops in 3D MHD Simulations

2021

Acoustic waves excited in the photosphere and below might play an integral part in the heating of the solar chromosphere and corona. However, it is yet not fully clear how much of the initially acoustic wave flux reaches the corona and in what form. We investigate the wave propagation, damping, transmission, and conversion in the lower layers of the solar atmosphere using 3D numerical MHD simulations. A model of a gravitationally stratified expanding straight coronal loop, stretching from photosphere to photosphere, is perturbed at one footpoint by an acoustic driver with a period of 370 seconds. For this period acoustic cutoff regions are present below the transition region (TR). About 2% …

Fine structure and dynamic heating from temporal and spatial analysis of a solar active region observed with Solar Dynamics Observatory (SDO)

An outstanding issue in current solar and astrophysical research is that of the heating of the solar corona. How is the corona heated to temperatures of greater than 1 MK when the photosphere below is only 6000 K? One observational approach to addressing this important question is to focus on particular areas in the corona such as active regions (ARs). In a scenario that heating is impulsive and the cross-field spatial scale of the heating is so small, under the resolution of the current instruments, we attempted to narrow the question further to discrete bright magnetic flux tubes, the coronal loops, inside active regions. We investigate the emission variability, heating and substructure o…

Plasma Diagnostics and Magnetic Complexity of a Post-Flare Active Region with Hinode/XRT: Spatial and Temporal Evolution

2012

Flares are localized phenomena in active regions, but the magnetic and plasma responses may propagate to a larger area. In this work we investigate the temporal evolution of a flare in an active region with particular attention to the morphological details, and to the temperature and emission measure diagnostics allowed by Hinode/XRT.

The Space Weather X-Ray spectrometer for the Helianthus sub-L1 mission with solar photonic propulsion

2022

Copyright 2022 Society of Photo‑Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this publication for a fee or for commercial purposes, and modification of the contents of the publication are prohibited. Helianthus is a phase A study of a space weather station with solar photonic propulsion. The scientific payload will be made of: an X-ray spectrometer to detect solar flares; SailCor, a coronagraph with a wide field of view; a plasma analyzer; a magnetometer. The maximum allowed mass for the entire scientific payload shall not exceed 5 kg. The two imaging devices…

Dynamic Temperature Structure of the Corona

2012

The solar corona is heated to million degrees and information about the temperature structure is a key to understand the heating mechanisms. Although it is not easy to measure, the temperature looks to be remarkably steady in the solar corona and in active regions outside of transient events, like flares. On the other hand, there is strong evidence of multi-thermal structures, out of equilibrium for most of the time. Is there a way to obtain a coherent scenario? The secret might be in the fine structuring of the corona, and SDO is providing new and important information on this issue.

Exploring the Solar Wind from Its Source on the Corona into the Inner Heliosphere during the First Solar Orbiter-Parker Solar Probe Quadrature

2021

This Letter addresses the first Solar Orbiter (SO) -- Parker Solar Probe (PSP) quadrature, occurring on January 18, 2021, to investigate the evolution of solar wind from the extended corona to the inner heliosphere. Assuming ballistic propagation, the same plasma volume observed remotely in corona at altitudes between 3.5 and 6.3 solar radii above the solar limb with the Metis coronagraph on SO can be tracked to PSP, orbiting at 0.1 au, thus allowing the local properties of the solar wind to be linked to the coronal source region from where it originated. Thanks to the close approach of PSP to the Sun and the simultaneous Metis observation of the solar corona, the flow-aligned magnetic fiel…